wdiff draft-ietf-mpls-rsvp-te-p2mp-05.txt draft-ietf-mpls-rsvp-te-p2mp-06.txt

Network Working Group R. Aggarwal (Editor)
Internet Draft Juniper Networks
Expiration Date: November 2006 January 2007
D. Papadimitriou (Editor)
Alcatel

S. Yasukawa (Editor)
NTT
Extensions to RSVP-TE for Point to Multipoint Point-to-Multipoint TE LSPs

draft-ietf-mpls-rsvp-te-p2mp-05.txt

draft-ietf-mpls-rsvp-te-p2mp-06.txt

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Abstract

This document describes extensions to Resource Reservation Protocol -
Traffic Engineering (RSVP-TE) for the setup set up of Traffic Engineered
(TE) point-to-multipoint (P2MP) Label Switched Paths (LSPs) in Multi-
Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
networks. The solution relies on RSVP-TE without requiring a
multicast routing protocol in the Service Provider core. Protocol
elements and procedures for this solution are described.

There can be various applications for P2MP TE LSPs such as IP
multicast. Specification of how such applications will use a P2MP TE
LSP is outside the scope of this document.

Table of Contents

1 Conventions used in this document ..................... 5
2 Terminology ........................................... 5
3 Introduction .......................................... 5
4 Mechanism ............................................. 5 6
4.1 P2MP Tunnels .......................................... 6
4.2 P2MP LSP ............................................. 6
4.3 Sub-Groups ............................................ 6 7
4.4 S2L Sub-LSPs .......................................... 7
4.4.1 Representation of a an S2L Sub-LSP ....................... ...................... 7
4.4.2 S2L Sub-LSPs and Path Messages ........................ 7 8
4.5 Explicit Routing ...................................... 8
5 Path Message .......................................... 10 11
5.1 Path Message Format ................................... 10 11
5.2 Path Message Processing ............................... 11 12
5.2.1 Multiple Path Messages ................................ 12
5.2.2 Multiple S2L Sub-LSPs in one Path message ............. 13
5.2.3 Transit Fragmentation ................................. of Path State Information ....... 15
5.2.4 Control of Branch Fate Sharing ........................ 15 16
5.3 Grafting .............................................. 16
6 Resv Message .......................................... 16 17
6.1 Resv Message Format ................................... 16 17
6.2 Resv Message Processing ............................... 18
6.2.1 Resv Message Throttling ............................... 19
6.3 Record Routing ........................................ 19 Route Recording ....................................... 20
6.3.1 RRO Processing ........................................ 19 20
6.4 Reservation Style ..................................... 19 20
7 PathTear Message ...................................... 20 21
7.1 PathTear Message Format ............................... 20 21
7.2 Pruning ............................................... 20 21
7.2.1 Implicit S2L Sub-LSP Teardown ......................... 20 21
7.2.2 Explicit S2L Sub-LSP Teardown ........................ 21 22
8 Notify and ResvConf Messages .......................... 21 22
8.1 Notify Messages ....................................... 21 22
8.2 ResvConf Messages ..................................... 23 24
9 Refresh Reduction ..................................... 24 25
10 State Management ...................................... 24 25
10.1 Incremental State Update .............................. 24 25
10.2 Combining Multiple Path Messages ...................... 25 26
11 Error Processing ...................................... 26 27
11.1 PathErr Messages ...................................... 26 27
11.2 ResvErr Messages ...................................... 27 28
11.3 Branch Failure Handling ............................... 27 29
12 Admin Status Change ................................... 28 30

13 Label Allocation on LANs with Multiple Downstream Nodes ..28 .30
14 P2MP LSP and Sub-LSP Re-optimization .................. 29 30
14.1 Make-before-break ..................................... 29 30
14.2 Sub-Group Based Re-optimization ....................... 29 31
15 Fast Reroute .......................................... 30 31
15.1 Facility Backup ....................................... 30 32
15.1.1 Link Protection ....................................... 30 32
15.1.2 Node Protection ....................................... 31 32
15.2 One to One one-to-one Backup ..................................... 31 33
16 Support for LSRs that are not P2MP Capable ............ 32 34
17 Reduction in Control Plane Processing with LSP Hierarchy..34 Hierarchy .36
18 P2MP LSP Remerging and Cross-Over ..................... 34 36
18.1 Procedures ............................................ 35 37
18.1.1 Re-Merge Procedures ................................... 36 38
19 New and Updated Message Objects ....................... 38 40
19.1 SESSION Object ........................................ 38 40
19.1.1 P2MP LSP Tunnel IPv4 SESSION Object ................... 38 40
19.1.2 P2MP LSP Tunnel IPv6 SESSION Object ................... 39 41
19.2 SENDER_TEMPLATE object ................................ 39 41
19.2.1 P2MP LSP Tunnel IPv4 SENDER_TEMPLATE Object ........... 40 42
19.2.2 P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object ........... 40 42
19.3 <S2L_SUB_LSP> S2L_SUB_LSP Object .................................. 41 .................................... 43
19.3.1 <S2L_SUB_LSP> S2L_SUB_LSP IPv4 Object ............................. 41 ............................... 44
19.3.2 <S2L_SUB_LSP> S2L_SUB_LSP IPv6 Object ............................. 42 ............................... 44
19.4 FILTER_SPEC Object .................................... 42 44
19.4.1 P2MP LSP_IPv4 FILTER_SPEC Object ...................... 42 44
19.4.2 P2MP LSP_IPv4 LSP_IPv6 FILTER_SPEC Object ...................... 42 45
19.5 P2MP SECONDARY_EXPLICIT_ROUTE Object (SERO) ........... 43 45
19.6 P2MP SECONDARY_RECORD_ROUTE Object (SRRO) ............. 43 45
20 IANA Considerations ................................... 43 45
20.1 New Class Numbers ..................................... 43 45
20.2 New Class Types ....................................... 43 46
20.3 New Error Values ...................................... 44 46
20.4 LSP Attributes Flags .................................. 45 47
21 Security Considerations ............................... 45 47
22 Acknowledgements ...................................... 45 48
23 Appendix .............................................. 45
23.1 Example ............................................... 45
24 References ............................................ 47
24.1 48
23.1 Normative References .................................. 47
24.2 48
23.2 Informative References ................................ 48 49
24 Appendix .............................................. 49
24.1 Example ............................................... 50
25 Author Information .................................... 49 51
25.1 Editor Information .................................... 49 51
25.2 Contributor Information ............................... 49 52
26 Intellectual Property ................................. 52 54
27 Full Copyright Statement .............................. 52 54
28 Acknowledgement ....................................... 53 55

1. Conventions used in this document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].

2. Terminology

This document uses terminologies defined in [RFC3031], [RFC2205],
[RFC3209], [RFC3473] [RFC3473], [RFC4461] and [RFC4461]. [RFC4090].

3. Introduction

[RFC3209] defines a mechanism for setting up P2P TE LSPs point-to-point (P2P)
Traffic Engineered (TE) Label Switched Paths (LSPs) in MPLS Multi-Protocol
Label Switching (MPLS) networks. [RFC3473] defines extensions to
[RFC3209] for setting up P2P TE LSPs in GMPLS Generalized MPLS (GMPLS)
networks. However these specifications do not provide a mechanism
for building P2MP point-to-multipoint (P2MP) TE LSPs.

This document defines extensions to the RSVP-TE protocol [RFC3209],
[RFC3473] to support P2MP TE LSPs satisfying the set of requirements
described in [RFC4461].

This document relies on the semantics of RSVP the Resource Reservation
Protocol (RSVP) that RSVP-TE inherits for building P2MP LSPs. A P2MP
LSP is comprised of multiple S2L sub-
LSPs. source-to-leaf (S2L) sub-LSPs. These S2L
sub-LSPs are set up between the ingress and egress
LSRs egress-LSRs and are
appropriately combined by the branch LSRs using RSVP semantics to
result in a P2MP TE LSP. One Path message may signal one or multiple
S2L sub-LSPs. sub-LSPs for a single P2MP LSP. Hence the S2L sub-LSPs belonging
to a P2MP LSP can be signaled using one Path message or split across
multiple Path messages.

Path computation and P2MP application specific aspects

There are outside various applications for P2MP TE LSPs and the scope of signaling
techniques described in this document.

4. Mechanism

This document describes a can be used, sometimes in
combination with other techniques, to support different applications.

Specification of how applications will use P2MP TE LSPs and how the
paths of P2MP TE LSPs are computed is outside the scope of this
document.

4. Mechanism

This document describes a solution that optimizes data replication by
allowing non-ingress nodes in the network to be replication/branch
nodes. A branch node is an LSR that is capable of replicating replicates the incoming data on two
to one or more outgoing interfaces. The solution relies on RSVP-TE in
the network for setting up a P2MP TE LSP.

The P2MP TE LSP is set up by associating multiple S2L sub-LSPs and
relying on data replication at branch nodes. This is described
further in the following sub-sections by describing P2MP Tunnels and
how they relate to S2L sub-LSPs.

4.1. P2MP Tunnels

The specific aspect related to defining feature of a P2MP TE LSP is the action required at a
branch node, nodes where data replication occurs. Incoming MPLS labeled
data is appropriately replicated to several outgoing interfaces which may have use different labels.
labels for the data.

A P2MP TE Tunnel comprises one or more P2MP LSPs. A P2MP TE Tunnel is
identified by a P2MP SESSION object. This object contains the
identifier of the P2MP Session which includes the P2MP ID, Identifier
(P2MP ID), a tunnel
ID Identifier (Tunnel ID) and an extended tunnel ID.
identifier (Extended Tunnel ID). The P2MP ID is a four octet number
and is unique within the scope of the ingress LSR.

The <P2MP ID, Tunnel ID, Extended Tunnel ID> tuple provides an
identifier for the set of destinations of the P2MP TE Tunnel.

The fields of a the P2MP SESSION object are identical to those of the
SESSION object defined in [RFC3209] except that the Tunnel Endpoint
Address field is replaced by the P2MP Identifier (P2MP ID) ID field. The P2MP ID provides an identifier for the set of destinations of the
P2MP TE Tunnel. SESSION
object is defined in section 19.1

4.2. P2MP LSP

A P2MP LSP is identified by the combination of the P2MP ID, Tunnel
ID, ID
and Extended Tunnel ID that are part of the P2MP SESSION object, and
the tunnel sender address and LSP ID fields of the P2MP
SENDER_TEMPLATE object. The new P2MP SENDER_TEMPLATE object is
defined in section 20.2. 19.2.

4.3. Sub-Groups

As with all other RSVP controlled LSPs, P2MP LSP state is managed
using RSVP messages. While the use of RSVP messages is the same, P2MP
LSP state differs from P2P LSP state in a number of ways. The two most
notable differences are that a A P2MP LSP
comprises multiple S2L Sub-
LSPs Sub-LSPs and that, as a result of this, this it may not be
possible to represent full state in a single IP packet and even more likely that
it can't fit into a single IP packet. It must also
be possible to efficiently add and remove endpoints to and from P2MP
TE LSPs. An additional issue is that the P2MP LSP must also handle
the state "remerge" problem, see [RFC4461]. [RFC4461] and section 18.

These differences in P2MP state are addressed through the addition of
a sub-group identifier (Sub-Group ID) and sub-group originator (Sub-
Group Originator ID) to the SENDER_TEMPLATE and FILTER_SPEC objects.
Taken together the Sub-Group ID and Sub-Group Originator ID are
referred to as the Sub-Group fields.

The Sub-Group fields, together with rest of the SENDER_TEMPLATE and
SESSION objects, are used to represent a portion of a P2MP LSP's
state. This portion of a P2MP LSP's state refers only to signaling
state and not data plane replication or branching. For example, it is
possible for a node to "branch" signaling state for a P2MP LSP, but
to not branch the data associated with the P2MP LSP. Typical
applications for generation and use of multiple subgroups sub-groups are adding
an egress egress, and semantic fragmentation to ensure that a Path message
remains within a single IP packet.

4.4. S2L Sub-LSPs

A P2MP LSP is constituted of one or more S2L sub-LSPs.

4.4.1. Representation of a an S2L Sub-LSP

An S2L sub-LSP exists within the context of a P2MP LSP. Thus it is
identified by the P2MP ID, Tunnel ID, and Extended Tunnel ID that are
part of the P2MP SESSION, the tunnel sender address and LSP ID fields
of the P2MP SENDER_TEMPLATE object, and the S2L sub-LSP destination
address that is part of the <S2L_SUB_LSP> S2L_SUB_LSP object. The <S2L_SUB_LSP> S2L_SUB_LSP
object is defined in section 20.3. 19.3.

An EXPLICIT_ROUTE Object (ERO) or P2MP SECONDARY_EXPLICIT_ROUTE P2MP_SECONDARY_EXPLICIT_ROUTE
Object (SERO) is used to optionally specify the explicit route of a
S2L sub-LSP. Each ERO or SERO that is signaled corresponds to a
particular <S2L_SUB_LSP> S2L_SUB_LSP object. Details of explicit route encoding
are specified in section 4.5. The SECONDARY_EXPLICIT_ROUTE Object is
defined in [RECOVERY], a new P2MP SECONDARY_EXPLICIT_ROUTE Object C-
type is defined in Section 20.5 19.5 and a matching P2MP
SECONDARY_RECORD_ROUTE
P2MP_SECONDARY_RECORD_ROUTE Object C-type is defined in Section 20.6. 19.6.

4.4.2. S2L Sub-LSPs and Path Messages

The mechanism in this document allows a P2MP LSP to be signaled using
one or more Path messages. Each Path message may signal one or more
S2L sub-LSPs. Support for multiple Path messages is desirable as one
Path message may not be large enough to contain all the S2L sub-LSPs;
and they also allow separate manipulation of sub-trees of the P2MP
LSP. The reason for allowing a single Path message, to signal
multiple S2L sub-LSPs, is to optimize the number of control messages
needed to setup set up a P2MP LSP.

4.5. Explicit Routing

When a Path message signals a single S2L sub-LSP (that is, the Path
message is only targeting a single leaf in the P2MP tree), the
EXPLICIT_ROUTE object encodes the path from the ingress LSR to the
egress LSR. egress-LSR. The Path
message also includes the <S2L_SUB_LSP> S2L_SUB_LSP object for the S2L sub-LSP
being signaled. The < [<EXPLICIT_ROUTE>], <S2L_SUB_LSP> > tuple
represents the S2L sub-LSP and is referred to as the sub-LSP
descriptor. The absence of the ERO should be interpreted as
requiring hop-by-hop routing for the sub-LSP based on the S2L sub-LSP
destination address field of the <S2L_SUB_LSP> S2L_SUB_LSP object.

When a Path message signals multiple S2L sub-LSPs the path of the
first S2L sub-LSP, from the ingress LSR to the egress LSR, egress-LSR, is encoded in the ERO. The
first S2L sub-LSP is the one that corresponds to the first <S2L_SUB_LSP>
S2L_SUB_LSP object in the Path message. The S2L sub-LSPs
corresponding to the <S2L_SUB_LSP> S2L_SUB_LSP objects that follow are termed as
subsequent S2L sub-LSPs.

The path of each subsequent S2L sub-LSP is encoded in a P2MP
SECONDARY_EXPLICIT_ROUTE
P2MP_SECONDARY_EXPLICIT_ROUTE object (SERO). The format of the SERO
is the same as an ERO (as defined in [RFC3209]). [RFC3209] and [RFC3473]). Each
subsequent S2L sub-LSP is represented by tuples of the form < [<P2MP
SECONDARY_EXPLICIT_ROUTE>] <S2L_SUB_LSP> >. An SERO for a particular
S2L sub-LSP includes only the path from a certain branch LSR to the
egress egress-
LSR if the path to of that S2L sub-LSP. The branch LSR can be derived from MUST appear as an explicit hop
in the ERO or some other SEROs. SERO. The absence of an SERO should be
interpreted as requiring hop-by-hop routing for that S2L sub-LSP.
Note that the destination address is carried in the S2L sub-LSP
object. The encoding of the SERO and <S2L_SUB_LSP> S2L_SUB_LSP object are described
in detail in section 20. 19.

In order to avoid the potential repetition of path information for
the parts of S2L sub-LSPs that share hops, this information is
deduced from the explicit routes of other S2L sub-LSPs using explicit
route compression in SEROs.

Explicit route compression is illustrated using the following figure. Figure 1.

A
|
|
B
|
|
C----D----E
| | |
| | |
F G H-------I
| |\ |
| | \ |
J K L M
| | | |
| | | |
N O P Q--R

Figure 1. Explicit Route Compression

Figure 1. shows a P2MP LSP with LSR A as the ingress LSR ingress-LSR and six
egress LSRs: (F, N, O, P, Q and R). When all the six S2L sub-LSPs are
signaled in one Path message let us assume that the S2L sub-LSP to
LSR F is the first S2L sub-LSP and the rest are subsequent S2L sub-
LSPs. Following The following encoding is one way for the ingress LSR ingress-LSR A to
encode the S2L sub-LSP explicit routes using compression:

S2L sub-LSP-F: ERO = {B, E, D, C, F}, <S2L_SUB_LSP> object-F
S2L sub-LSP-N: SERO = {D, G, J, N}, <S2L_SUB_LSP> object-N
S2L sub-LSP-O: SERO = {E, H, K, O}, <S2L_SUB_LSP> object-O
S2L sub-LSP-P: SERO = {H, L, P}, <S2L_SUB_LSP> object-P,
S2L sub-LSP-Q: SERO = {H, I, M, Q}, <S2L_SUB_LSP> object-Q,
S2L sub-LSP-R: SERO = {Q, R}, <S2L_SUB_LSP> object-R,

After LSR E processes the incoming Path message from LSR B it sends a
Path message to LSR D with the S2L sub-LSP explicit routes encoded as
follows:

S2L sub-LSP-F: ERO = {D, C, F}, <S2L_SUB_LSP> object-F
S2L sub-LSP-N: SERO = {D, G, J, N}, <S2L_SUB_LSP> object-N
LSR E also sends a Path message to LSR H and following is one way to
encode the S2L sub-LSP explicit routes using compression:

S2L sub-LSP-O: ERO = {H, K, O}, <S2L_SUB_LSP> object-O
S2L sub-LSP-P: SERO = {H, L, P}, S2L_SUB_LSP object-P,
S2L sub-LSP-Q: SERO = {H, I, M, Q}, <S2L_SUB_LSP> object-Q,
S2L sub-LSP-R: SERO = {Q, R}, <S2L_SUB_LSP> object-R,

After LSR H processes the incoming Path message from E it sends a
Path message to LSR K, LSR L and LSR I. The encoding for the Path
message to LSR K is as follows:

S2L sub-LSP-O: ERO = {K, O}, <S2L_SUB_LSP> object-O

The encoding of the Path message sent by LSR H to LSR L is as
follows:

S2L sub-LSP-P: ERO = {L, P}, <S2L_SUB_LSP> object-P,

Following

The following encoding is one way for LSR H to encode the S2L sub-LSP
explicit routes in the Path message sent to LSR I:

S2L sub-LSP-Q: ERO = {I, M, Q}, <S2L_SUB_LSP> object-Q,
S2L sub-LSP-R: SERO = {Q, R}, <S2L_SUB_LSP> object-R,

The explicit route encodings in the Path messages sent by LSRs D and
Q are left as an exercise to for the reader.

This compression mechanism reduces the Path message size. It also
reduces extra processing that can result if explicit routes are
encoded from ingress to egress for each S2L sub-LSP. No assumptions
are placed on the ordering of the subsequent S2L sub-LSPs and hence
on the ordering of the SEROs in the Path message. All LSRs need to
process the ERO corresponding to the first S2L sub-LSP. A An LSR needs
to process a an S2L sub-LSP descriptor for a subsequent S2L sub-LSP
only if the first hop in the corresponding SERO is a local address of
that LSR. The branch LSR that is the first hop of a an SERO propagates
the corresponding S2L sub-LSP downstream.

5. Path Message

5.1. Path Message Format

This section describes modifications made to the Path message format
as specified in [RFC3209] and [RFC3473]. The Path message is enhanced
to signal one or more S2L sub-LSPs. This is done by including the S2L
sub-LSP descriptor list in the Path message as shown below.

<Path Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ...]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
[ <PROTECTION> ]
[ <LABEL_SET> ... ]
[ <SESSION_ATTRIBUTE> ]
[ <NOTIFY_REQUEST> ]
[ <ADMIN_STATUS> ]
[ <POLICY_DATA> ... ]
<sender descriptor>
[<S2L sub-LSP descriptor list>]

Following is the format of the S2L sub-LSP descriptor list.

<S2L sub-LSP descriptor list> ::= <S2L sub-LSP descriptor>
[ <S2L sub-LSP descriptor list> ]

<S2L sub-LSP descriptor> ::= <S2L_SUB_LSP>
[ <P2MP SECONDARY_EXPLICIT_ROUTE> ]

Each LSR MUST use the common objects in the Path message and the S2L
sub-LSP descriptors to process each S2L sub-LSP represented by the
<S2L_SUB_LSP>
S2L_SUB_LSP object and the SECONDARY-/EXPLICIT_ROUTE object
combination.

Per the definition of <S2L sub-LSP descriptor>, each S2L_SUB_LSP
object MAY be followed by a corresponding SERO. The first <S2L_SUB_LSP> object's S2L_SUB_LSP
object is a special case, and its explicit route is specified by the
ERO. Explicit routes of subsequent S2L sub-LSPs are specified by the
corresponding SERO. A SERO corresponds to Therefore, the following <S2L_SUB_LSP>
object. first S2L_SUB_LSP object SHOULD NOT be followed
by an SERO, and if one is present it MUST be ignored.

The RRO in the sender descriptor contains the upstream hops traversed
by the Path message and applies to all the S2L sub-LSPs signaled in
the Path message.

An IF_ID RSVP_HOP object MUST be used on links where there is not a
one-to-one association of a control channel to a data channel
[RFC3471]. An RSVP_HOP object defined in [RFC2205] SHOULD be used
otherwise.

Path message processing is described in the next section.

5.2. Path Message Processing

The ingress-LSR initiates the set up setup of an S2L sub-LSP to each
egress-LSR egress-
LSR that is the a destination of the P2MP LSP. Each S2L sub-LSP is
associated with the same P2MP LSP using common P2MP SESSION object
and <Sender Address, LSP-ID> fields in the P2MP SENDER_TEMPLATE
object. Hence it can be combined with other S2L sub-LSPs to form a
P2MP LSP. Another S2L sub-LSP belonging to the same instance of this
S2L sub-LSP (i.e. the same P2MP LSP) shares SHOULD share resources with
this S2L sub-LSP. The session corresponding to the P2MP TE tunnel is
determined based on the P2MP SESSION object. Each S2L sub-LSP is
identified using the <S2L_SUB_LSP> S2L_SUB_LSP object. Explicit routing for the S2L
sub-LSPs is achieved using the ERO and SEROs.

As mentioned earlier, it is possible to signal S2L sub-LSPs for a
given P2MP LSP in one or more Path messages and a given Path message
can contain one or more S2L sub-LSPs. A An LSR that supports RSVP-TE
signaled P2MP LSPs MUST be able to receive and process multiple Path
messages for the same P2MP LSP and multiple S2L sub-LSPs in one Path
message. This implies that such an LSR MUST be able to receive and
process all objects listed in section 20. 19.

5.2.1. Multiple Path Messages

As described in section 3, 4, either the <EXPLICIT_ROUTE> < [<EXPLICIT_ROUTE>]
<S2L_SUB_LSP> > or the <P2MP SECONDARY_EXPLICIT_ROUTE> < [<P2MP SECONDARY_EXPLICIT_ROUTE>]
<S2L_SUB_LSP> > tuple is used to specify a an S2L sub-LSP. Multiple
Path messages can be used to signal a P2MP LSP. Each Path message can
signal one or more S2L sub-LSPs. If a Path message contains only one
S2L sub-LSP, each LSR along the S2L sub-LSP follows [RFC3209]
procedures for processing the Path message besides the <S2L_SUB_LSP> S2L_SUB_LSP
object processing described in this document.

Processing of Path messages containing more than one S2L sub-LSP is
described in Section 5.2.2.

An ingress LSR may ingress-LSR MAY use multiple Path messages for signaling a P2MP
LSP. This may be because a single Path message may not be large
enough to signal the P2MP LSP. Or it may be while adding leaves to
the P2MP LSP the new leaves are signaled in a new Path message. Or an
ingress LSR MAY choose to break the P2MP tree into separate
manageable P2MP trees. These trees share the same root and may share
the trunk and certain branches. The scope of this management
decomposition of P2MP trees is bounded by a single tree (the P2MP
Tree) and multiple trees with a single leaf each (S2L sub-LSPs). Per
[RFC4461], a P2MP LSP MUST have consistent attributes across all
portions of a tree. This implies that each Path message that is used
to signal a P2MP LSP is signaled using the same signaling attributes
with the exception of the S2L sub-LSP information descriptors and Sub-Group
identifiers.
identifier.

The resulting sub-LSPs from the different Path messages belonging to
the same P2MP LSP SHOULD share labels and resources where they share
hops to prevent multiple copies of the data being sent.

In certain cases a transit LSR may need to generate multiple Path
messages to signal state corresponding to a single received Path
message. For instance ERO expansion may result in an overflow of the
resultant Path message. In this case the message can be decomposed
into multiple Path messages such that each of the messages carry message carries a subset
of the X2L sub-tree carried by the incoming message.

Multiple Path messages generated by an LSR that signal state for the
same P2MP LSP are signaled with the same SESSION object and have the
same <Source address, LSP-ID> in the SENDER_TEMPLATE object. In order
to disambiguate these Path messages a <Sub-Group Originator ID, sub- Sub-
Group ID> tuple is introduced (also referred to as the Sub-Group
field)
fields) and encoded in the SENDER_TEMPLATE object. Multiple Path
messages generated by a an LSR to signal state for the same P2MP LSP
have the same Sub-Group Originator ID and have a different sub-Group
ID. The Sub-Group Originator ID MUST be set to the TE Router ID of
the LSR that originates the Path message. This is either the ingress
LSR or a LSR which re-originates the Path message with its own Sub-
Group Originator ID. Cases when a transit LSR
may change the Sub-
Group Sub-Group Originator ID of an incoming Path message
are described below. The <Sub-Group Sub-Group Originator ID, sub-Group ID> tuple ID is globally unique.
The sub-Group ID space is specific to the Sub-Group Originator ID.
Therefore the combination <Sub-Group Originator ID, sub-Group ID> is
network-wide unique. Also, a router that changes the Sub-Group
originator ID of an incoming Path message MUST use the same value of
the Sub-Group Originator ID for all outgoing Path messages, for a
particular P2MP LSP, and SHOULD not vary it during the life of the
P2MP LSP.

5.2.2. Multiple S2L Sub-LSPs in one Path message

The S2L sub-LSP descriptor list allows the signaling of one or more
S2L sub-LSPs in one Path message. It is possible to signal multiple
<S2L_SUB_LSP> object and ERO/SERO combinations in Each S2L sub-LSP descriptor
describes a single Path
message. Note that these two objects differentiate a S2L sub-LSP.

All LSRs MUST process the ERO corresponding to the first S2L sub-LSP
if the ERO is present. If one or more SEROs are present an ERO MUST
be present. The first S2L sub-LSP MUST be propagated in a Path
message by each LSR along the explicit route specified by the ERO, if
the ERO is present. Else it MUST be propagated using hop-by-hop
routing towards the destination identified by the <S2L_SUB_LSP> S2L_SUB_LSP object.

An LSR MUST process a S2L sub-LSP descriptor for a subsequent S2L sub-
LSP
sub-LSP as follows:

If the <S2L_SUB_LSP> S2L_SUB_LSP object is followed by an SERO, the LSR MUST
check the first hop in the SERO:
- If the first hop of the SERO identifies a local address of the
LSR, and the LSR is also the egress identified by the
<S2L_SUB_LSP>
S2L_SUB_LSP object, the descriptor MUST NOT be propagated
downstream, but the SERO may be used for egress control per
[RFC4003].
- If the first hop of the SERO identifies a local address of the
LSR, and the LSR is not the egress as identified by the
<S2L_SUB_LSP> object
S2L_SUB_LSP object, the S2L sub-LSP descriptor MUST be
included in a Path message sent to the next-hop determined
from the SERO.
- If the first hop of the SERO is not a local address of the LSR LSR,
the S2L sub-LSP descriptor MUST be included in the Path message
sent to the LSR that is the next hop to reach the first hop in
the SERO. This next hop is determined by using the ERO or other
SEROs that encode the path to the SERO's first hop.

If the <S2L_SUB_LSP> S2L_SUB_LSP object is not followed by an SERO, the LSR MUST
examine the <S2L_SUB_LSP> S2L_SUB_LSP object:
- If this LSR is the egress as identified by the
<S2L_SUB_LSP>
S2L_SUB_LSP object, the S2L sub-LSP descriptor MUST
NOT be propagated downstream.
- If this LSR is not the egress as identified by the
<S2L_SUB_LSP>
S2L_SUB_LSP object, the LSR MUST make a routing decision
to determine the next hop towards the egress, and MUST
include the S2L sub-LSP descriptor in a Path message sent
to the next-hop towards the egress. In this case, the LSR
MAY insert an SERO into the S2L sub-LSP descriptor.

Hence a branch LSR MUST only propagate the relevant S2L sub-LSP
descriptors on to each downstream link. A hop. An S2L sub-LSP descriptor list
that is propagated on a downstream link MUST only contain those S2L
sub-LSPs that are routed using that link. hop. This processing MAY result
in a subsequent S2L sub-LSP in an incoming Path message to become becoming the
first S2L sub-LSP in an outgoing Path message.

Note that if one or more SEROs contain loose hops, expansion of such
loose hops MAY result in overflowing the Path message size. Section
5.2.3 describes how signaling of the set of S2L sub-LSPs can be split
in
across more than one Path message.

The RECORD_ROUTE Object (RRO) contains the hops traversed by the Path
message and applies to all the S2L sub-LSPs signaled in the Path
message. A transit LSR MUST append its address in an incoming RRO and
propagate it downstream. A branch LSR MUST form a new RRO for each of
the outgoing Path messages by copying the RRO from the incoming Path
message and appending its address. Each such updated RRO MUST be
formed using the rules in [RFC3209]. [RFC3209] updated by [RFC3473] as
appropriate.

If a an LSR is unable to support a an S2L sub-LSP in a Path message, message (for
example, it is unable to route towards the destination using the
SERO), a PathErr message MUST be sent for the impacted S2L sub-LSP,
and normal processing of the rest of the P2MP LSP SHOULD continue.
The default behavior is that the remainder of the LSP is not impacted
(that is, all other branches are allowed to set up) and the failed
branches are reported in PathErr messages in which the
Path_State_Removed flag MUST NOT be set. However, the ingress LSR ingress-LSR
may set a an LSP Integrity flag to request that if there is a setup
failure on any branch the entire LSP should fail to set up. This is
described further in
section 12. sections 5.2.4 and 11.

5.2.3. Transit Fragmentation of Path State Information

In certain cases a transit LSR may need to generate multiple Path
messages to signal state corresponding to a single received Path
message. For instance ERO expansion may result in an overflow of the
resultant Path message. It is desirable not to rely on RSVP [RFC2205] disallows the use of IP
fragmentation and thus IP fragmentation MUST be avoided in this case.
In order to achieve this, the multiple Path messages generated by the
transit LSR, are signaled with the Sub-Group Originator ID set to the
TE Router ID of the transit LSR and a distinct sub-Group Sub-Group ID for each
Path message. Thus each distinct Path message that is generated by
the transit LSR for the P2MP LSP carries a distinct <Sub-Group
Originator ID, Sub-Group ID> tuple.

When multiple Path messages are used by an ingress or transit node,
each Path message SHOULD be identical with the exception of the S2L
sub-LSP related information descriptor (e.g., SERO), message and hop information
(e.g., INTEGRITY, MESSAGE_ID and RSVP_HOP), and the sub-group fields
of the SENDER_TEMPLATE objects. Except when performing a make-
before-break operation as specified in section 14.1, the tunnel
sender address and LSP ID fields MUST be the same in each message,
and for transit nodes, the same as the values in the received Path
message.

As described above one case in which the Sub-Group Originator ID of a
received Path message is changed is that of fragmentation of a Path
message at a transit fragmentation. node. Another case is when the Sub-Group
Originator ID of a received Path message may be changed in the
outgoing Path message and set to that of the LSR originating the Path
message based on a local policy. For instance a an LSR may decide to
always change the Sub-Group Originator ID while performing ERO
expansion. The Sub-Group ID MUST not be changed if the Sub-Group
Originator ID is not being changed.

5.2.4. Control of Branch Fate Sharing

An ingress LSR ingress-LSR can control the behavior of an LSP if there is a
failure during LSP setup or after an LSP has been established. The
default behavior is that only the branches downstream of the failure
are not established, but the ingress may request 'LSP integrity' such
that any failure anywhere within the LSP tree causes the entire P2MP
LSP to fail.

The ingress LSP may request 'LSP integrity' by setting bit (TBA) TBD of the
Attributes Flags TLV. (RFC Editor, please replace "TBD" with the bit
number allocated by IANA per section 20.4. Please remove this note.)
The bit is set if LSP integrity is required.

It is RECOMMENDED to use the LSP_REQUIRED_ATTRIBUTES Object. Object
[RFC4420].

A branch LSR that supports the Attributes Flags TLV and recognizes
this bit MUST support LSP integrity or reject the LSP setup with a
PathErr message carrying the error "Routing Error"/"Unsupported LSP
Integrity"

5.3. Grafting

The operation of adding egress LSR(s) egress-LSR(s) to an existing P2MP LSP is
termed as grafting. This operation allows egress nodes to join a P2MP
LSP at different points in time.

There are two methods to add S2L sub-LSPs to a P2MP LSP. The first
is to add new S2L sub-LSPs to the P2MP LSP by adding them to an
existing Path message and refreshing the entire Path message. Path
message processing described in section 4 results in adding these S2L
sub-LSPs to the P2MP LSP. Note that as a result of adding one or more
S2L sub-LSPs to a Path message the ERO compression encoding may have
to be recomputed.

The second is to use incremental updates described in section 10.1.
The egress LSRs can be added by signaling only the impacted S2L sub-
LSPs in a new Path message. Hence other S2L sub-LSPs do not have to
be re-signaled.

6. Resv Message

6.1. Resv Message Format

The Resv message follows the [RFC3209] and [RFC3473] format:

The FF flow descriptor and SE filter spec are modified as follows to
identify the S2L sub-LSPs that they correspond to:

<FF flow descriptor> ::= [ <FLOWSPEC> ] <FILTER_SPEC> <LABEL>
[ <RECORD_ROUTE> ]
[ <S2L sub-LSP flow descriptor list> ]

<SE filter spec> ::= <FILTER_SPEC> <LABEL> [ <RECORD_ROUTE> ]
[ <S2L sub-LSP flow descriptor list> ]

<S2L sub-LSP flow descriptor list> ::=
<S2L sub-LSP flow descriptor>
[ <S2L sub-LSP flow descriptor list> ]

<S2L sub-LSP flow descriptor> ::= <S2L_SUB_LSP>
[ <P2MP
SECONDARY_EXPLICIT_ROUTE> <P2MP_SECONDARY_RECORD_ROUTE> ]

FILTER_SPEC is defined in section 20.4. 19.4.

The S2L sub-LSP flow descriptor has the same format as S2L sub-LSP
descriptor in section 4.1 with the difference that a
P2MP_SECONDARY_RECORD_ROUTE object is used in place of a P2MP
SECONDARY_EXPLICIT_ROUTE object. The P2MP_SECONDARY_RECORD_ROUTE
objects follow the same compression mechanism as the P2MP
SECONDARY_EXPLICIT_ROUTE objects. Note that that a Resv message can
signal multiple S2L sub-LSPs that may belong to the same FILTER_SPEC
object or different FILTER_SPEC objects. The same label SHOULD be
allocated if the <Sender Address, LSP-ID> fields of the FILTER_SPEC
object are the same.

However different upstream labels are MUST be allocated if the <Sender Address,
LSP-ID> of the FILTER_SPEC object is different as that implies that
the FILTER_SPEC refers to a different P2MP LSP.

6.2. Resv Message Processing

The egress LSR MUST follow normal RSVP procedures while originating a
Resv message. The format of Resv messages is as defined in Section
6.1. As usual, the Resv message carries the label allocated by the
egress LSR.

A node upstream of the egress node MUST allocate its own label and
pass it upstream in the Resv message upstream. message. The node MAY combine multiple
flow descriptors, from different Resv messages received from
downstream, in one Resv message sent upstream. A Resv message MUST
NOT be sent upstream until at least one Resv message has been
received from a downstream neighbor. When the integrity bit is set in
the LSP_REQUIRED_ATTRIBUTE object, no Resv message MUST NOT be sent
upstream until all Resv messages have been received from the
downstream neighbors.

Each FF flow descriptor or SE filter spec sent upstream in a Resv
message includes a S2L sub-LSP descriptor list. Each such FF flow
descriptor or SE filter spec for the same P2MP LSP (whether on one or
multiple Resv messages) on the same Resv MUST be allocated the same
label, and FF flow descriptors or SE filter specs SHOULD use the same
label across multiple Resv messages.

This label is associated by that node with all the labels received
from downstream Resv messages for that P2MP LSP. Note that a transit
node may become a replication point in the future when a branch is
attached to it. Hence this results in the setup of a P2MP LSP from
the ingress-LSR to the egress LSRs. egress-LSRs.

The ingress LSR ingress-LSR may need to understand when all desired egresses have
been reached. This is achieved using <S2L_SUB_LSP> S2L_SUB_LSP objects.

Each branch node can potentially send one MAY forward a single Resv message upstream for each
received Resv message from a downstream receiver. Note that there may
be a large number of Resv messages at and close to the downstream ingress LSR
for an LSP with many receivers. This MAY A branch LSR SHOULD combine Resv
state from multiple receivers into a single Resv message to be sent
upstream (see section 6.2.1), but note that this may result in
overflowing the Resv message, message particularly when considering that as the number of
messages receivers
downstream of any branch LSR increases as the closer the branch node LSR is closer to the
ingress of LSR. Thus, a branch LSR MAY choose to send more than one Resv
message upstream and partition the P2MP LSP.

Transit nodes Resv state between the messages.

When a transit node set the Sub-Group Originator field in a Path
message it MUST replace the Sub-Group ID fields received in the
FILTER_SPEC objects of any associated Resv messages with the value
that was it originally received in the Sub-Group
ID field fields of the Path
message from the upstream neighbor, when the
node set the Sub-Group Originator field in the associated Path
message. neighbor.

ResvErr messages message generation is unmodified. Nodes propagating a
received ResvErr message MUST use the Sub-Group field values carried
in the corresponding Resv message.

6.2.1. Resv Message Throttling

A branch node may have to send the a revised Resv message being sent upstream
whenever there is a change in a Resv message for a an S2L sub-LSP
received from one of the downstream neighbors. This can result in
excessive Resv messages sent upstream,particularly upstream, particularly when the S2L sub-
LSPs are established for the first time. established. In order to mitigate this situation,
branch nodes can limit their transmission of Resv messages.
Specifically, in the case where the only change being sent in a Resv
message is in one or more SRRO objects, the branch node SHOULD
transmit the Resv message only after a delay time has passed since
the transmission of the previous Resv message for the same session.
This delayed Resv message SHOULD include SRROs for all branches. A
suggested value for the delay time is thirty seconds. Specific
mechanisms for Resv message throttling and delay timer settings are
implementation dependent and are outside the scope of this document.

6.3. Record Routing Route Recording

6.3.1. RRO Processing

A Resv message for a P2P LSP contains a record recorded route per S2L sub-LSP that is being
signaled by the Resv message if the sender node requests ingress
LSR requested route recording by including a an RRO in the original
Path message. The same rule is used during signaling of P2MP LSP i.e. insertion LSPs.
That is, inclusion of the an RRO in the Path message used to signal one
or more S2L sub-LSP sub-LSPs triggers the inclusion of an RRO a recorded route for
each sub-LSP. sub-LSP in the Resv message.

The record recorded route of the first S2L sub-LSP is encoded in the RRO.
Additional RROs recorded routes for the subsequent S2L sub-LSPs are referred to as
encoded in P2MP_SECONDARY_RECORD_ROUTE objects (SRROs). Their format
is specified in section 20.5. 19.5. Each S2L_SUB_LSP object in a Resv is
associated with an RRO or SRRO. The ingress node then receives first S2L_SUB_LSP object (for the RRO and
possibly
first S2L sub-LSP) is associated with the SRRO corresponding to each RRO. Subsequent S2L_SUB_LSP
objects (for subsequent S2L sub-LSP. Each
<S2L_SUB_LSP> object is sub-LSPs) are each followed by an SRRO
that contains the recorded route for that S2L sub-LSP from the RRO/SRRO. leaf
to a branch. The ingress node can then determine use the record route corresponding to a particular S2L
sub-LSP. The RRO and SRROs can be used to construct
determine the end to end
Path end-to-end path for each S2L sub-LSP.

6.4. Reservation Style

Considerations about the reservation style in a Resv message apply as
described in [RFC3209]. The reservation style in the Resv messages
can either be either FF or SE. All P2MP LSPs that belong to the same P2MP
Tunnel MUST be signaled with the same reservation style. Irrespective
of whether the reservation style is FF or SE, the S2L sub-LSPs that
belong to the same P2MP LSP SHOULD share labels where they share
hops. If the S2L sub-LSPs that belong to the same P2MP LSP share
labels then they MUST share resources. The S2L sub-LSPs that belong
to different P2MP LSP MUST NOT share labels. If the reservation style is FF
then S2L sub-LSPs that belong to different P2MP LSP LSPs MUST NOT share resources.
resources or labels. If the reservation style is SE than then S2L sub-LSPs
that belong to different P2MP LSP LSPs and the same P2MP Tunnel SHOULD
share resources where they share hops, but MUST not share labels. labels in
packet environments.

7. PathTear Message

7.1. PathTear Message Format

The format of the PathTear message is as follows:

<PathTear Message> ::= <Common Header> [ <INTEGRITY> ]
[ [ <MESSAGE_ID_ACK> |
<MESSAGE_ID_NACK> ... ]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
[ <sender descriptor> ]
[ <S2L sub-LSP descriptor list> ]

<S2L sub-LSP descriptor list> ::= <S2L_SUB_LSP>
[ <S2L sub-LSP descriptor list> ]

The definition of <sender descriptor> is not changed by this
document.

7.2. Pruning

The operation of removing egress LSR(s) egress-LSR(s) from an existing P2MP LSP is
termed as pruning. This operation allows egress nodes to be removed
from a P2MP LSP at different points in time. This section describes
the mechanisms to perform pruning.

7.2.1. Implicit S2L Sub-LSP Teardown

Implicit teardown uses standard RSVP message processing. Per standard
RSVP processing, a an S2L sub-LSP may be removed from a P2MP TE LSP by
sending a modified message for the Path or Resv message that
previously advertised the S2L sub-LSP. This message MUST list all S2L
sub-LSPs that are not being removed. When using this approach, a node
processing a message that removes a an S2L sub-LSP from a P2MP TE LSP
MUST ensure that the S2L sub-LSP is not included in any other Path
state associated with session before interrupting the data path to
that egress. All other message processing remains unchanged.

When implicit teardown is used to delete one or more S2L sub-LSPs, by
modifying a Path message, a transit LSR may have to generate a
PathTear message downstream to delete one or more of these S2L sub-
LSPs. This can happen if as a result of the implicit deletion of S2L
sub-LSP(s) there are no remaining S2L sub-LSPs to send in the
corresponding Path message downstream.

7.2.2. Explicit S2L Sub-LSP Teardown

Explicit S2L Sub-LSP teardown relies on generating a PathTear message
for the corresponding Path message. The PathTear message is signaled
with the SESSION and SENDER_TEMPLATE objects corresponding to the
P2MP LSP and the <Sub-Group Originator ID, Sub-Group ID> tuple
corresponding to the Path message. This approach SHOULD be used when
all the egresses signaled by a Path message need to be removed from
the P2MP LSP. Other S2L sub-LSPs, from other sub-groups signaled
using other Path messages, are not affected by the PathTear.

A transit LSR that propagates the PathTear message downstream MUST
ensure that it sets the <Sub-Group Originator ID, Sub-Group ID> tuple
in the PathTear message to the values used to generate in the previous Path message that corresponds used
to the set up the S2L sub-LSPs being deleted by it
in the PathTear message. torn down. The transit LSR may need
to generate multiple PathTear messages for an incoming PathTear
message if it had performed transit fragmentation for the
corresponding incoming Path message.

When a P2MP LSP is removed by the ingress, a PathTear message MUST be
generated for each Path message used to signal the P2MP LSP.

8. Notify and ResvConf Messages

8.1. Notify Messages

The Notify Request object and Notify messages message are described in
[RFC3473]. Both object and messages message SHALL be supported for delivery of
upstream and downstream notification. Processing not detailed in this
section MUST comply to [RFC3473].

1. Upstream Notification

If a transit LSR sets the Sub-Group Originator ID in the
SENDER_TEMPLATE object of a Path message to its own address and the
incoming Path message carries a Notify Request object then this LSR
MUST change the Notify node address in the Notify Request object to
its own address in the Path message that it sends.

If this LSR subsequently receives a corresponding Notify message from
a downstream LSR than it MUST:

- send a Notify message upstream toward the Notify
node address that the LSR received in the Path message.
- process the sub-group fields of the SENDER_TEMPLATE
object on the received Notify message, and modify their values
in the Notify message that is forwarded to match the sub-group
field values in the original Path message received from upstream.

The receiver of an (upstream) Notify message MUST identify the state
referenced in this message based on the SESSION and SENDER_TEMPLATE.

2. Downstream Notification

A transit LSR sets the Sub-Group Originator ID in the FILTER_SPEC
object(s) of a Resv message to the value, that was received in the
corresponding Path message. If the incoming Resv message carries a
Notify Request object then then:

- If there is at least another incoming Resv message that carries a
Notify Request object and the LSR merges these Resv messages into a
single Resv message that is sent upstream, the LSR MUST set the
Notify node address in the Notify Request object to its Router ID.

- Else if the value, that was received LSR sets the Sub-Group Originator ID in the
corresponding outgoing
Path message, that corresponds to the received Resv message, to its
own address, the LSR MUST set the Notify node address in the Notify
Request object to its Router ID.

- Else the LSR MUST propagate the Notify Request object unchanged, in
the Resv message that it sends upstream.

If this LSR subsequently receives a corresponding Notify message from
an upstream LSR than then it MUST:
- send a Notify message downstream toward the Notify
node address that the LSR received in the Resv message.
- process the sub-group fields of the FILTER_SPEC object in the
received Notify message, and modify their values in the Notify
message that is forwarded to match the sub-group field values
in the original Path message sent downstream by this LSR.
- send a Notify message downstream toward the Notify
node address that the LSR received in the Resv message.

The receiver of a (downstream) Notify message MUST identify the state
referenced in the message based on the SESSION and FILTER_SPEC
objects.

The consequence of these rules for a P2MP LSP is that an upstream
Notify message generated on a branch will result in a Notify being
delivered to the upstream Notify node address. The receiver of the
Notify message MUST NOT assume that the Notify message applies to all
downstream egresses, but MUST examine the information in the message
to determine to which egresses the message applies.

Downstream Notify messages MUST be replicated at branch LSRs
according to the Notify Request objects received on Resv messages.
Some downstream branches might not request Notify messages, but all
that have requested Notify messages MUST receive them them.

8.2. ResvConf Messages

ResvConf messages are described in [RFC2205]. ResvConf processing in
[RFC3473] and [RFC3209] is taken directly from [RFC2205]. An egress egress-
LSR may MAY include a RESV_CONFIRM object that contains the egress LSR's egress-LSR's
address. The object and message SHALL be supported for the
confirmation of receipt of the Resv message in P2MP TE LSPs.
Processing not detailed in this section MUST comply to [RFC2205].

A transit LSR sets the Sub-Group Originator ID in the FILTER_SPEC
object(s) of a Resv message to the value, that was received in the
corresponding Path message. If any of the incoming Resv messages
corresponding to a single Path message carry a RESV_CONFIRM object
then the LSR MUST include a RESV_CONFIRM object in the corresponding
Resv message that it sends upstream and upstream. If the sub-group originator ID
is its own address then it MUST set the receiver address in the
RESV_CONFIRM object to this addresse, else it MUST propagate the
object unchanged.

A transit LSR sets the Sub-Group Originator ID in the FILTER_SPEC
object(s) of a Resv message to the value that was received in the
corresponding Resv Path message. If this LSR subsequently receives a corresponding ResvConf message
from an upstream LSR than it MUST:
- send incoming Resv message corresponding
to a ResvConf single Path message downstream toward the receiver address that carries a RESV_CONFIRM object then the LSR received in the
MUST include a RESV_CONFIRM object in the corresponding Resv message.
- process the sub-group fields of the FILTER_SPEC object in the
received ResvConf message, and modify their values in the ResvConf message
that is forwarded to match the it sends upstream and:

- If there is at least another incoming Resv message that carries a
RESV_CONFIRM object and the LSR merges these Resv messages into a
single Resv message that is sent upstream, the LSR MUST set the
receiver address in the RESV_CONFIRM object to its Router ID.

- If the LSR sets the Sub-Group Originator ID in the outgoing Path
message, that corresponds to the received Resv message, to its own
address, the LSR MUST set the receiver address in the RESV_CONFIRM
object to its Router ID.

- Else the LSR MUST propagate the RESV_CONFIRM object unchanged, in
the Resv message that it sends upstream.

If this LSR subsequently receives a corresponding ResvConf message
from an upstream LSR than it MUST:
- process the sub-group fields of the FILTER_SPEC object in the
received ResvConf message, and modify their values in the ResvConf
message that is forwarded to match the sub-group field values
in the original Path message sent downstream by this LSR.

- send a ResvConf message downstream toward the receiver address that
the LSR received in the RESV_CONFIRM object in the Resv message.

The receiver of a ResvConf message MUST identify the state referenced
in this message based on the SESSION and FILTER_SPEC objects.

The consequence of these rules for a P2MP LSP is that a ResvConf
message generated at the ingress will result in a ResvConf message
being delivered to the branch and then to the receiver address in the
original RESV_CONFIRM object. The receiver of a ResvConf message MUST
NOT assume that the ResvConf message should be sent to all downstream
egresses, but MUST replicate the message according to the
RESV_CONFIRM objects received in Resv messages. Some downstream
branches might not request ResvConf messages, and ResvConf messages
SHOULD NOT be sent on these branches. All downstream branches that do
requested ResvConf messages MUST be sent such a message.

9. Refresh Reduction

The refresh reduction procedures described in [RFC2961] are equally
applicable to P2MP LSP LSPs described in this document. Refresh reduction
applies to individual messages and the state they install/maintain,
and that continues to be the case for P2MP LSP. LSPs.

10. State Management

State signaled by a P2MP Path message is managed identified by a local
implementation using the <P2MP ID, Tunnel ID, Extended Tunnel ID> as
part of the SESSION object and <Tunnel Sender Address, LSP ID, Sub-
Group Originator ID, Sub-Group ID> as part of the SENDER_TEMPLATE
object.

Additional information signaled in the Path/Resv message is part of
the state created by a local implementation. This includes PHOP/NHOP
and SENDER_TSPEC/FILTER_SPEC object. objects.

10.1. Incremental State Update

RSVP as defined in [RFC2205] and as extended by RSVP-TE [RFC3209] and
GMPLS [RFC3473] uses the same basic approach to state communication
and synchronization, namely full state is sent in each state
advertisement message. Per [RFC2205] Path and Resv messages are
idempotent. Also, [RFC2961] categorizes RSVP messages into two types:
trigger and refresh messages and improves RSVP message handling and
scaling of state refreshes but does not modify the full state
advertisement nature of Path and Resv messages. The full state
advertisement nature of Path and Resv messages has many benefits, but
also has some drawbacks. One notable drawback is when an incremental
modification is being made to a previously advertised state. In this
case, there is the message overhead of sending the full state and the
cost of processing it. It is desirable to overcome this drawback and
add/delete S2L sub-LSPs to a P2MP LSP by incrementally updating the
existing state.

It is possible to use the procedures described in this document to
allow S2L sub-LSPs to be incrementally added or deleted from the P2MP
LSP by allowing a Path or a PathTear message to incrementally change
the existing P2MP LSP Path state.

As described in section 4.2, 5.2, multiple Path messages can be used to
signal a P2MP LSP. The Path messages are distinguished by different
<Sub-Group Originator ID, sub-Group Sub-Group ID> tuples in the SENDER_TEMPLATE
object. In order to perform incremental S2L sub-LSP state addition a
separate Path message with a new sub-Group Sub-Group ID is used to add the new
S2L sub-LSPs, by the ingress LSR. ingress-LSR. The Sub-Group Originator ID MUST be
set to the TE Router ID [RFC3477] of the node that sets the Sub-Group
ID.

This maintains the idempotent nature of RSVP Path messages; avoids
keeping track of individual S2L sub-LSP state expiration and provides
the ability to perform incremental P2MP LSP state updates.

10.2. Combining Multiple Path Messages

There is a tradeoff between the number of Path messages used by the
ingress to maintain the P2MP LSP and the processing imposed by full
state messages when adding S2L sub-LSPs to an existing Path message.
It is possible to combine S2L sub-LSPs previously advertised in
different Path messages in a single Path message in order to reduce
the number of Path messages needed to maintain the P2MP LSP. This can
also be done by a transit node that performed fragmentation and at a
later point is able to combine multiple Path messages that it
generated into a single Path message. This may happen when one or
more S2L sub-LSPs are pruned from the existing Path states.

The new Path message is signaled by the node that is combining
multiple Path messages with all the S2L sub-LSPs that are being
combined in a single Path message. This Path message MAY contain a new
Sub-Group ID field value. values. When a new Path and Resv message that is
signaled for an existing S2L sub-LSP is received by a transit LSR,
state including the new instance of the S2L sub-LSP is created.

The S2L sub-LSP SHOULD continue to be advertised in both the old and
new Path messages until a Resv message listing the S2L sub-LSP and
corresponding to the new Path message is received by the combining
node. Hence until this point state for the S2L sub-LSP SHOULD be
maintained as part of the Path state for both the old and the new
Path message [Section 3.1.3, RFC2205]. At that point the S2L sub-LSP
SHOULD be deleted from the old Path state using the procedures of
section 7.

A Path message with a sub-Group_ID(n) Sub-Group_ID(n) may signal a set of S2L sub-
LSPs that belong partially or entirely to an already existing Sub-
Group_ID(i), the SESSION object and <Sender Tunnel Address, LSP-ID,
Sub-Group Originator ID> being the same. Or it may signal a strictly
non-overlapping new set of S2L sub-LSPs with a strictly higher sub- Sub-
Group_ID value.

1) If sub-Group_ID(i) Sub-Group_ID(i) = sub-Group_ID(n), Sub-Group_ID(n), then either a full refresh
is indicated by the Path message or a an S2L Sub-LSP is added
to/deleted from the group signaled by sub-Group_ID(n) Sub-Group_ID(n)

2) If sub-Group_ID(i) Sub-Group_ID(i) != sub-Group_ID(n), Sub-Group_ID(n), then the Path message is
signaling a set of S2L sub-LSPs that belong partially or entirely to
an already existing Sub-Group_ID(i) or a strictly non-overlapping set
of S2L sub-LSPs.

11. Error Processing

PathErr and ResvErr messages are processed as per RSVP-TE procedures.
Note that an LSR on receiving a PathErr/ResvErr message for a
particular S2L sub-LSP changes the state only for that S2L sub-LSP.
Hence other S2L sub-LSPs are not impacted. If the ingress node
requests the maintenance of the 'LSP integrity', any an error reported
within the on a branch of a P2MP TE
LSP must be reported to (at least) any other
branching nodes belonging to this LSP. Therefore, reception of an
error message for a particular S2L sub-LSP MAY may change the state of any other
S2L sub- LSP sub-LSP of the same P2MP TE LSP. This is explained further in
section 11.3

11.1. PathErr Messages

The PathErr message will include one or more <S2L_SUB_LSP> S2L_SUB_LSP objects. The
resulting modified format for a PathErr message is:

<PathErr Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> |
<MESSAGE_ID_NACK>] ... ]
[ <MESSAGE_ID> ]
<SESSION> <ERROR_SPEC>
[ <ACCEPTABLE_LABEL_SET> ... ]
[ <POLICY_DATA> ... ]
<sender descriptor>
[ <S2L sub-LSP descriptor list> ]

PathErr messages generation is unmodified, but nodes that set the
Sub-Group Originator field and propagate a received PathErr message
upstream MUST replace the Sub-Group fields received in the PathErr
message with the value that was received in the Sub-Group fields of
the Path message from the upstream neighbor. Note the receiver of a
PathErr message is able to identify the errored outgoing Path
message, and outgoing interface, based on the Sub-Group fields
received in the PathErr message. The S2L sub-LSP descriptor list is
defined in section 5.1.

11.2. ResvErr Messages

The ResvErr message will include one or more <S2L_SUB_LSP> S2L_SUB_LSP objects. The
resulting modified format for a ResvErr Message is:

ResvErr messages generation is unmodified, but nodes that set the
Sub-Group Originator field and propagate a received ResvErr message
downstream MUST replace the Sub-Group fields received in the ResvErr
message with the value that was set in the Sub-Group fields of the
Path message sent to the downstream neighbor. Note the receiver of a
ResvErr message is able to identify the errored outgoing Path Resv
message, and outgoing interface, based on the Sub-Group fields
received in the ResvErr message.

11.3. Branch Failure Handling The flow descriptor list is defined
in section 6.1.

11.3. Branch Failure Handling

During setup and during normal operation, PathErr messages may be
received at a branch node. In all cases, a received PathErr message
is first processed per standard processing rules. That is: the
PathErr message is sent hop-by-hop to the ingress/branch LSR for that
Path message. Intermediate nodes until this ingress/branch LSR MAY
inspect this message but take no action upon it. The behavior of a
branch LSR that generates a PathErr message is under the control of
the ingress LSR. ingress-LSR.

The default behavior is that the PathErr message does not have the
Path_State_Removed flag set. However, if the ingress LSR ingress-LSR has set the
LSP integrity flag on the Path message (see LSP_REQUIRED_ATTRIBUTEs
object in section 5.2.4) and if the Path_State_Removed flag is
supported, the LSR generating a PathErr to report the failure of a
branch of the P2MP LSP SHOULD set the Path_State_Removed flag.

A branch LSR that receives a PathErr message during LSP setup with
the Path_State_Removed flag set MUST act according to the wishes of
the
ingress LSR. ingress-LSR. The default behavior is that the branch LSR clears
the Path_State_Removed flag on the PathErr and sends it further
upstream. It does not tear any other branches of the LSP. However,
if the LSP integrity flag is set on the Path message, the branch LSR
MUST send PathTear on all other downstream branches and send the
PathErr message upstream with the Path_State_Removed flag set.

A branch LSR that receives a PathErr message with the
Path_State_Removed flag clear MUST act according to the wishes of the
ingress LSR.
ingress-LSR. The default behavior is that the branch LSR forwards the
PathErr upstream and takes no further action. However, if the LSP
integrity flag is set on the Path message, the branch LSR MUST send
PathTear on all downstream branches and send the PathErr upstream
with the Path_State_Removed flag set (per [RFC3473]).

In all cases, the PathErr message forwarded by a branch LSR MUST
contain the S2L sub-LSP identification and explicit routes of all
branches that are reported by received PathErr messages and all
branches that are explicitly torn by the branch LSR.

12. Admin Status Change

A branch node that receives an ADMIN_STATUS object processes it
normally and also relays the ADMIN_STATUS object in a Path on every
branch. All Path messages may be concurrently sent to the downstream
neighbors.

Downstream nodes process the change in the ADMIN_STATUS object per
[RFC3473], including generation of Resv messages. When the last
received upstream ADMIN_STATUS object had the R bit set, branch nodes
wait for a Resv message with a matching ADMIN_STATUS object to be
received (or a corresponding PathErr or ResvTear messsage) on all
branches before relaying a corresponding Resv message upstream.

13. Label Allocation on LANs with Multiple Downstream Nodes

A sender on branch LSR of a P2MP LSP on an Ethernet LAN uses a different label for sending segment SHOULD send one
copy of the data traffic to each
node per downstream LSR connected on the that LAN for
that belongs to the P2MP LSP. Thus the sender
performs replication. It may be considered desirable on a LAN to use
the same label Procedures for sending preventing MPLS labelled traffic to multiple nodes belonging to
replication in such a case is beyond the
same P2MP LSP, to avoid replication. Procedures for doing scope of this are
for further study. document.

14. P2MP LSP and Sub-LSP Re-optimization

It is possible to change the path used by P2MP LSPs to reach the
destinations of the P2MP Tunnel. There are two methods that can be
used to accomplish this. The first is make-before-break, defined in
[RFC3209], and the second uses the sub-groups defined above.

14.1. Make-before-break

In this case all the S2L sub-LSPs are signaled with a different LSP
ID by the ingress-LSR and follow make-before-break procedure defined
in [RFC3209]. Thus a new P2MP LSP is established. Each S2L sub-LSP is
signaled with a different LSP ID, corresponding to the new P2MP LSP.
After moving traffic to the new P2MP LSP, the ingress can tear down
the old P2MP LSP. This procedure can be used to re-optimize the path
of the entire P2MP LSP or paths to a subset of the destinations of
the P2MP LSP. When modifying just a portion of the P2MP LSP this
approach requires the entire P2MP LSP to be resignaled.

14.2. Sub-Group Based Re-optimization

Any node may initiate re-optimization of a set of S2L sub-LSPs by
using the incremental state update and then, optionally, combining
multiple path messages.

To alter the path taken by a particular set of S2L sub-LSPs the node
initiating the path change initiates one or more separate Path
messages, for the same P2MP LSP, each with a new sub-Group ID. The
generation of these Path messages, each with one or more S2L sub-
LSPs, follows procedures in section 5.2. As is the case in Section
10.2, a particular egress continues to be advertised in both the old
and new Path messages until a Resv message listing the egress and
corresponding to the new Path message is received by the re-
optimizing node. At that point the egress SHOULD be deleted from the
old Path state using the procedures of section 7. Sub-tree re-
optimization is then completed.

Sub-Group based re-optimization may result in transient data
duplication as the new Path messages for a set of S2L sub-LSPs may
transit one or more nodes with the old Path state for the same set of
S2L sub-LSPs.

As is always the case, a node may choose to combine multiple path
messages as described in section 10.2.

15. Fast Reroute

[RFC4090] extensions can be used to perform fast reroute for the
mechanism described in this document when applied within packet
networks. GMPLS introduces other protection techniques that can be
applied to packet and non-packet environments [RECOVERY], but which
are not discussed further in this document. This section only applies
to LSRs that support [RFC4090].

This section uses terminology defined in [RFC4090] and fast reroute
procedures defined in [RFC4090] MUST be followed unless specified
below. The head-end and transit LSRs MUST follow the
SESSION_ATTRIBUTE and FAST_REROUTE object processing as specified in
[RFC4090] for each Path message and S2L sub-LSP of a P2MP LSP. Each
S2L sub-LSP of a P2MP LSP MUST have the same protection
characteristics. The RRO processing MUST apply to SRRO as well unless
modified below.

The sections that follow describe how Fast Reroute may be applied to
P2MP MPLS TE LSPs in all of the principal operational scenarios. This
document does not describe the detailed processing steps for every
imaginable usage case and they may be described in future documents,
as needed.

15.1. Facility Backup

Facility backup can be used for link or node protection of LSRs on
the path of a P2MP LSP. The downstream labels MUST be learned by the
PLR as specified in [RFC4090] from the label corresponding to the S2L
sub-LSP in the RESV message. SERO processing for SEROs signaled in a
backup tunnel MUST follow backup tunnel ERO processing described in
[RFC4090].

15.1.1. Link Protection

If link protection is desired, a bypass tunnel MUST be used to
protect the link between the PLR and next-hop. Thus all S2L sub-LSPs
that use the link MUST SHOULD be protected in the event of link failure.
Note that all such S2L sub-LSPs belonging to a particular instance of
a P2MP tunnel will SHOULD share the same outgoing label on the link
between the PLR and the next-hop. next-hop as per section 5.2.1. This is the
P2MP LSP label on the link. Label stacking is used to send data for
each P2MP LSP into the bypass tunnel. The inner label is the P2MP LSP
label allocated by the next-
hop. next-hop.

During failure failure, Path messages for each S2L sub-LSP, sub-LSP that are
effected, is affected,
MUST be sent to the MP, by the PLR. It is recommended RECOMMENDED that the PLR use
uses the sender template specific template-specific method to identify these Path
messages. Hence the PLR will set the source address in the sender
template to a local PLR address.

The MP MUST use the LSP-ID to identify the corresponding S2L sub-LSPs. sub-
LSPs. The MP MUST not NOT use the <sub-group originator ID, sub-group
ID> while identifying the corresponding S2L sub-LSPs. In order to
further process a an S2L sub-LSP the MP MUST determine the protected
S2L sub-LSP using the LSP-id and the <S2L_SUB_LSP> S2L_SUB_LSP object.

15.1.2. Node Protection

If node protection is desired the PLR MUST SHOULD use one or more P2P
bypass tunnels to protect the set of S2L sub-LSPs that transit the
protected node. Each of these P2P bypass tunnels MUST intersect the
path of the S2L sub-LSPs that they protect on a an LSR that is
downstream from the protected node. This constrains the set of S2L
sub-LSPs being backed backed- up via that bypass tunnel to those S2L sub-LSPs sub-
LSPs that pass through a common downstream MP. This MP is the
destination of the bypass tunnel. The MP MUST allocate the same label to all such S2L sub-LSPs
belonging to a particular P2MP LSP. This is the inner label used
during label stacking by When the PLR when it sends forwards incoming data
for each a P2MP LSP into the bypass tunnel. The tunnel, the outer label is the bypass
tunnel label. label and the inner label is the label allocated by the MP to
the set of S2L sub-LSPs belonging to that P2MP LSP.

After detecting failure of the protected node the PLR MUST send a one
or more Path message messages for each all protected S2L sub-LSP sub-LSPs to the MP of the
protected S2L sub-LSP. It is recommended RECOMMENDED that the PLR use the sender
template specific method to identify these Path messages. Hence the
PLR will set the source address in the sender template to a local PLR
address. The MP MUST use the LSP-ID to identify the corresponding S2L
sub-LSPs. The MP MUST not NOT use the <sub-group originator ID, sub-group
ID> while identifying the corresponding S2L sub-LSPs. sub-LSPs because the sub-
group originator ID might be changed by some LSR that is bypassed by
the bypass tunnel. In order to further process a an S2L sub-LSP the MP
MUST determine the protected S2L sub-LSP using the LSP-id LSP-ID and the <S2L_SUB_LSP>
S2L_SUB_LSP object.

Note that node protection MAY require the PLR to be branch capable in
the data plane as multiple bypass tunnels may be required to backup
the set of S2L sub-LSPs passing through the protected node. If the
PLR is not branch capable, the node protection mechanism described
here is applicable to only those cases where all the S2L sub-LSPs
passing through the protected node also pass through a single MP that
is downstream from the protected node. Procedures for node A PLR MUST set the Node
protection
when flag in the RRO/SRRO as specified in [RFC4090]. If a PLR
is not branch capable and all the protected one or more S2L sub-LSPs are added to a
P2MP tree and these S2L sub-LSPs do not pass through a single transit the existing MP that is
downstream from of the protected
node are for further study. node, then the PLR MUST reset this flag.

It is also to be noted that procedures in this section require P2P bypass
tunnels. Procedures for using P2MP bypass tunnels are for further
study.

15.2. One to One one-to-one Backup

One to one

one-to-one backup as described in [RFC4090] can be used to protect a
particular S2L sub-LSP against link and next-hop failure. Protection
may be used for one or more S2L sub-LSPs between the PLR and the
next-hop. All the S2L sub-LSPs corresponding to the same instance of
the P2MP tunnel, between the PLR and the next-hop SHOULD share the
same P2MP LSP label. label as per section 5.2.1. All or some of these such S2L sub-LSPs may
belonging to a P2MP LSP MUST be protected.

The detour backup S2L sub-LSPs may or may not share labels, depending on traverse different next-hops at the
detour path. PLR.
Thus the set of outgoing labels and next-hops for a P2MP LSP that was
using a single next-hop and label between the PLR and next-hop before
protection, may change once protection is triggerred.

Its This MAY
require a PLR to be branch capable in the data plane. If the PLR is recommended that
not branch capable, the path specific method be used one-to-one backup mechanisms described here
are only applicable to identify
a those cases where all the backup S2L sub-LSP. Hence sub-LSPs
pass through the DETOUR object SHOULD be inserted in same next-hop downstream of the PLR. Procedures for
one-to-one backup Path message. A backup S2L sub-LSP MUST be treated when a PLR is not branch capable and all the backup
S2L sub-LSPs do not pass through the same downstream next-hop are for
further study.

It is recommended that the path specific method be used to identify a
backup S2L sub-LSP. Hence the DETOUR object SHOULD be inserted in the
backup Path message. A backup S2L sub-LSP MUST be treated as
belonging to a different P2MP tunnel instance than the one specified
by the LSP-id. Furthermore multiple backup S2L sub-LSPs MUST be
treated as part of the same P2MP tunnel instance if they have the
same LSP-id LSP-ID and the same DETOUR objects. Note that as specified in
section 4 S2L sub-LSPs between different P2MP tunnel instances use
different labels.

If there is only one S2L sub-LSP in the Path message, the DETOUR
object applies to that sub-LSP. If there are multiple S2L sub-LSPs in
the Path message the DETOUR object applies to all the S2L sub-LSPs.

16. Support for LSRs that are not P2MP Capable

It may be that some LSRs in a network are capable of processing the
P2MP extensions described in this document, but do not support P2MP
branching in the data plane. If such an LSR is requested to become a
branch LSR by a received Path message, it MUST respond with a PathErr
message carrying the Error Code "Routing Error" and Error Value
"Unable to Branch".

Its

It is also conceivable that some LSRs, in a network deploying P2MP
capability, may not support the extensions described in this
document. If a Path message for the establishment of a P2MP LSP
reaches such an LSR it will reject it with a PathErr because it will
not recognize the C-Type of the P2MP SESSION object.

LSRs that do not support the P2MP extensions in this document may be
included as transit LSRs by the use of LSP-stitching [LSP-STITCH] and
LSP-hierarchy [RFC4206]. Note that LSRs that are required to play any
other role in the network (ingress, branch or egress) MUST support
the extensions defined in this document.

The use of LSP-stitching and LSP-hierarchy [RFC4206] allows P2MP LSPs
to be built in such an environment. A P2P LSP segment is signaled
from the last P2MP capable hop upstream of a legacy LSR to the first
P2MP capable hop downstream of it. This assumes that intermediate
legacy LSRs are transit LSRs: they cannot act as P2MP branch points.
Transit LSRs along this LSP segment do not process control plane
messages associated with the P2MP LSP. Furthermore, these transit
LSRs also do not need to have P2MP data plane capabilities as they
only need to process data belonging to the P2P LSP segment. Hence
these transit LSRs do not need to support P2MP MPLS. This P2P LSP
segment is stitched to the incoming P2MP LSP. After the P2P LSP
segment is established the P2MP Path message is sent to the next P2MP
capable LSR as a directed Path message. The next P2MP capable LSR
stitches the P2P LSP segment to the outgoing P2MP LSP.

In packet networks, the S2L sub-LSPs may be nested inside the outer
P2P LSP. Hence label stacking can be used to enable use of the same
LSP segment for multiple P2MP LSP. Stitching and nesting
considerations and procedures are described further in [INT-REG]. [LSP-STITCH]
and [RFC4206].

It may be an overhead for an operator to configure the P2P LSP
segments in advance, when it is desired to support legacy LSRs. It
may be desirable to do this dynamically. The ingress can use IGP
extensions to determine non P2MP capable LSRs [TE-NODE-CAP]. It can use
this information to compute S2L sub-LSP paths such that they avoid these
legacy non-P2MP capable LSRs. The explicit route object of a an S2L
sub-LSP path may contain loose hops if there are legacy LSRs along
the path. The corresponding explicit route contains a list of objects
upto the P2MP capable LSR that is adjacent to a legacy LSR followed
by a loose object with the address of the next P2MP capable LSR. The
P2MP capable LSR expands the loose hop using its TED. When doing this
it determines that the loose hop expansion requires a P2P LSP to
tunnel through the legacy LSR. If such a P2P LSP exists, it uses that
P2P LSP. Else it establishes the P2P LSP. The P2MP Path message is
sent to the next P2MP capable LSR using non-adjacent signaling.

The P2MP capable LSR that initiates the non-adjacent signaling
message to the next P2MP capable LSR may have to employ a fast
detection mechanism such as [BFD] [BFD-MPLS] to the next P2MP capable
LSR. This may be needed for the directed Path message Head-End to
use node protection FRR when the protected node is the directed Path
message tail.

Note that legacy LSRs along a P2P LSP segment cannot perform node
protection of the tail of the P2P LSP segment.

17. Reduction in Control Plane Processing with LSP Hierarchy

It is possible to take advantage of LSP hierarchy [RFC4206] while
setting up P2MP LSP, as described in the previous section, to reduce
control plane processing along transit LSRs that are P2MP capable.
This is applicable only in environments where LSP hierarchy can be
used. Transit LSRs along a P2P LSP segment, being used by a P2MP LSP,
do not process control plane messages associated with the P2MP LSP.
Infact
In fact they are not aware of these messages as they are tunneled
over the P2P LSP segment. This reduces the amount of control plane
processing required on these transit LSRs.

Note that the P2P LSPs can be set up dynamically setup as described in the
previous section or preconfigured. For example in Figure 2, 2 in section
24, PE1 can setup a P2P LSP to P1 and use that as a LSP segment. The
Path messages for PE3 and PE4 can now be tunneled over the LSP
segment. Thus P3 is not aware of the P2MP LSP and does not process
the P2MP control messages.

18. P2MP LSP Remerging and Cross-Over

This section is currently under discussion between the authors and
will be updated in the next revision.

This section details the procedures for detecting and dealing with
re-merge and cross-over. The term re-merge refers to the case of an
ingress or transit node that creates a branch of a P2MP LSP, a re-
merge branch, which intersects the P2MP LSP at another node farther
down the tree. This may occur due to such events as an error in path
calculation, an error in manual configuration, or network topology
changes during the establishment of the P2MP LSP. If the procedures
detailed in this section are not followed, data duplication will
result.

The term cross-over refers to the case of an ingress or transit node
that creates a branch of a P2MP LSP, a cross-over branch, which
intersects the P2MP LSP at another node farther down the tree. It is
unlike re-merge in that at the intersecting node the cross-over
branch has a different outgoing interface as well as a different
incoming interface. This may be necessary in certain combinations of
topology and technology; e.g., in a transparent optical network in
which different wavelengths are required to reach different leaf
nodes.

Normally, a P2MP LSP has a single incoming interface on which all of
the Path messages associated with that data for the P2MP LSP are is received. The incoming interface is
identified by the IF_ID RSVP_HOP Object, if present, and by interface
over which the Path message was received if the IF_ID RSVP_HOP Object
is not present. However, in the case of dynamic LSP re-routing, the
incoming interface may change.

Similarly, in both the re-merge case and cross-over cases, a node
will receive a Path message for a given P2MP LSP on identifying a
different incoming interface, interface for the data, and the node needs to be
able to distinguish between dynamic LSP re-routing and the re-merge/cross-over re-
merge/cross-over cases.

(Make-before-break

Make-before-break represents yet another similar but different case,
in that the incoming interface associated with the make-before-break
P2MP LSP may be different than that associated with the original P2MP
LSP. However, the two P2MP LSPs will be treated as distinct, but
related, LSPs because they will have different LSP ID field values in
their SENDER_TEMPLATE objects.) objects.

18.1. Procedures

When a node receives a Path message, it MUST check whether it has
matching state for the P2MP LSP. Matching state is identified by
comparing the SESSION and SENDER_TEMPLATE objects in the received
Path message with the SESSION and SENDER_TEMPLATE objects of each
locally maintained P2MP LSP Path state. The P2MP ID, Tunnel ID, and
Extended Tunnel ID in the SESSION Object and the sender address and
LSP ID in the SENDER_TEMPLATE object are used for the comparison. If
the node has matching state and the incoming interface for the
received Path message is different than the incoming interface of the
matching P2MP LSP Path state, then the node MUST determine whether it
is dealing with dynamic LSP rerouting or re-merge/cross-over.

Dynamic LSP rerouting is identified by checking whether there is any
intersection between the set of SUB-LSP S2L_SUB_LSP objects associated with
the matching P2MP LSP Path state and the set of SUB-LSP S2L_SUB_LSP objects
in the received Path message. If there is any intersection, then
dynamic re-routing has occurred. If there is no intersection between
the two sets of SUB-LSP S2L_SUB_LSP objects, then either re-merge or cross-over cross-
over has occurred. (Note that in the case of dynamic LSP rerouting,
Path messages for the non-intersecting members of set of SUB-LSPs S2L_SUB_LSPs
associated with the matching P2MP LSP Path state will be received
subsequently on the new incoming interface.)

In order to identify the re-merge case, the node processing the
received Path message MUST identify the outgoing interfaces
associated with the matching P2MP Path state. Re-merge has occurred
if there is any intersection between the set of outgoing interfaces
associated with the matching P2MP LSP Path state and the set of
outgoing interfaces in the received Path message.

18.1.1. Re-Merge Procedures

There are two approaches to dealing with the re-merge case. In the
first, the node detecting the re-merge case, i.e., the re-merge node,
allows the re-merge case to persist but data from all but one
incoming interface is dropped at the re-merge node. In the second,
the re-merge node initiates the removal of the re-merge branch(es)
via signaling. Which approach is used is a matter of local policy. A
node MUST support both approaches and MUST allow user configuration
of which approach is to be used.

When configured to allow a re-merge case to persist, the re-merge
node MUST validate consistency between the objects included in the
received Path message and the matching P2MP LSP Path state. Any
inconsistencies MUST result in an appropriate PathErr message sent to the
previous hop of the received Path message. The Error Code is set to
"Routing Problem" and the Error Value is set to "P2MP Re-Merge
Parameter Mistmatch".

If there are no inconsistencies, the node logically merges, from the
downstream perspective, the control state of incoming Path message
with the matching P2MP LSP Path state. Specifically, procedures
related to processing of messages received from upstream MUST NOT be
modified from the upstream perspective; this includes refresh and
state timeout related processing. In addition to the standard
upstream related procedures, the node MUST ensure that each object
received from upstream is appropriately represented within the set of
Path messages sent downstream. For example, the received <S2L sub-LSP
descriptor list> MUST be included in the set of outgoing Path
messages. If there are any NOTIFY_REQUEST request objects present, then the
procedures defined in Section 8 MUST be followed for both all Path and
Resv messages. Special processing is also required for Resv
processing. Specifically, any Resv message received from downstream
MUST be mapped into an outgoing Resv message that is sent to the
previous hop of the received Path message. In practice, this
translates to decomposing the complete <S2L sub-LSP descriptor list>
into sub-sets that match the incoming Path messages and then
constructing an outgoing Resv message for each incoming Path message.

When configured to allow a re-merge case to persist, the re-merge
node receives data associated with the P2MP LSP on multiple incoming
interfaces, but it may MUST only send the data from one of these
interfaces to its outgoing interfaces, i.e., the node MUST drop data
from all but one incoming interface. This ensures that duplicate
data is not sent on any outgoing interface. The mechanism used to
select the incoming interface to use is implementation specific and
is outside the scope of this document.

When configured to correct the re-merge branch via signaling, the re-
merge node MUST send a PathErr message corresponding to the received
Path message. The PathErr message MUST include all of the objects
normally included in a PathErr message, as well as one or more SUB-
LSP
S2L_SUB_LSP objects from the set of sub-LSPs associated with the
matching P2MP LSP Path state. A minimum of three SUB-LSP S2L_SUB_LSP objects
is RECOMMENDED. This will allow the node that caused the re-merge to
identify the outgoing Path state associated with the valid portion of
the P2MP LSP. The set of SUB-LSP S2L_SUB_LSP objects in the received Path
message MUST also be included. The PathErr message MUST include the
Error Code "Routing Problem" and Error Value of "P2MP Remerge
Detected". The node MAY set the Path_State_Removed flag [RFC3473].
As is always the case, the PathErr message is sent to the previous
hop of the received Path message.

A node that receives a PathErr message that contains the Error Value
"Routing Problem/P2MP Remerge Detected" MUST determine if it is the
node that created the re-merge case. This is done by checking
whether there is any intersection between the set of SUB-LSP S2L_SUB_LSP
objects associated with the matching P2MP LSP Path state and the set
of SUB-
LSP other-branch S2L_SUB_LSP objects in the received PathErr message.
If there is, then the node created the re-merge case. Other-branch
S2L_SUB_LSP objects are those S2L_SUB_LSP objects included, by the
node detecting the re-merge case, in the PathErr message that were
taken from the matching P2MP LSP Path state. Such S2L_SUB_LSP
objects are identifiable as they will not be included in the Path
message associated with the received PathErr message. See Section
11.1 for more details on how such an association is identified.

The node SHOULD remove the re-merge case by moving the SUB-LSP S2L_SUB_LSP
objects included in the Path message associated with the received
PathErr message to the outgoing interface associated with the
matching P2MP LSP Path state. A trigger Path message for the moved
SUB-LSP
S2L_SUB_LSP objects is then sent via that outgoing interface. If the
received PathErr message did not have the Path_State_Removed flag
set, the node SHOULD send a PathTear via the outgoing interface
associated with the re-merge branch.

If use of a new outgoing interface violates one or more SERO
constraint, then a PathErr message containing the associated egresses
and any identified SUB-LSP S2L_SUB_LSP objects SHOULD be generated with the
Error Code "Routing Problem" and Error Value of "ERO Resulted in
Remerge".

The only case where this process will fail is when all the listed
SUB-LSP
S2L_SUB_LSP objects are deleted prior to the PathErr message
propagating to the ingress. In this case, the whole process will be
corrected on the next (refresh or trigger) transmission of the
offending Path message.

19. New and Updated Message Objects

This section presents the RSVP object formats as modified by this
document.

19.1. SESSION Object

A P2MP LSP SESSION object is used. This object uses the existing
SESSION C-Num. New C-Types are defined to accommodate a logical P2MP
destination identifier of the P2MP Tunnel. This SESSION object has a
similar structure as the existing point to point RSVP-TE SESSION
object. However the destination address is set to the P2MP ID
instead of the unicast Tunnel Endpoint address. All S2L sub-LSPs that
are part of the same P2MP LSP share the same SESSION object. This
SESSION object identifies the P2MP Tunnel.

The combination of the SESSION object, the SENDER_TEMPLATE object and
the <S2L_SUB_LSP> S2L_SUB_LSP object, identifies each S2L sub-LSP. This follows the
existing P2P RSVP-TE notion of using the SESSION object for
identifying a P2P Tunnel which in turn can contain multiple LSPs,
each distinguished by a unique SENDER_TEMPLATE object.

19.1.1. P2MP LSP Tunnel IPv4 SESSION Object

Class = SESSION, P2MP_LSP_TUNNEL_IPv4 C-Type = 13

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2MP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

P2MP ID

A 32-bit identifier used in the SESSION object that remains
constant over the life of the P2MP tunnel. It encodes the
P2MP ID and identifies Identifier that is unique within the set of destinations scope of the P2MP
Tunnel. Ingress
LSR.

Tunnel ID

A 16-bit identifier used in the SESSION object that remains
constant over the life of the P2MP tunnel.

Extended Tunnel ID

A 32-bit identifier used in the SESSION object that remains
constant over the life of the P2MP tunnel. Normally set to
all zeros. Ingress nodes LSRs
that wish to narrow the scope of have a
SESSION to globally unique identifier for the ingress-PID pair may P2MP tunnel
SHOULD place their IPv4 tunnel sender address
here as here. A combination of
this address, P2MP ID and Tunnel ID provides a globally unique
identifier [RFC3209]. for the P2MP tunnel.

19.1.2. P2MP LSP Tunnel IPv6 SESSION Object

This is same as the P2MP IPv4 LSP SESSION Object with the difference
that the extended tunnel ID may be set to a 16 byte identifier
[RFC3209].

Class = SESSION, P2MP_LSP_TUNNEL_IPv4 C-Type = 14

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2MP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID (16 bytes) |
| |
| ....... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

19.2. SENDER_TEMPLATE object

The SENDER_TEMPLATE object contains the ingress-LSR source address.
The LSP ID can be can be changed to allow a sender to share resources with
itself. Thus multiple instances of the P2MP tunnel can be created,
each with a different LSP ID. The instances can share resources with
each other, but use different labels. other. The S2L sub-LSPs corresponding to a particular instance
use the same LSP ID.

As described in section 4.2 it is necessary to distinguish different
Path messages that are used to signal state for the same P2MP LSP by
using a <Sub-Group ID Originator ID, Sub-Group ID> tuple. The
SENDER_TEMPLATE object is modified to carry this information as shown
below.

19.2.1. P2MP LSP Tunnel IPv4 SENDER_TEMPLATE Object

Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv4 C-Type = 12

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 tunnel sender address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Group Originator ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Sub-Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

IPv4 tunnel sender address
See [RFC3209] [RFC3209].

Sub-Group Originator ID
The Sub-Group Originator ID is set to the TE Router ID of
the LSR that originates the Path message. This is either the
ingress LSR
ingress-LSR or a an LSR which re-originates the Path message
with its own Sub-Group Originator ID.

Sub-Group ID
An identifier of a Path message used to differentiate
multiple Path messages that signal state for the same P2MP
LSP. This may be seen as identifying a group of one or more
egress nodes targeted by this Path message.

LSP ID
See [RFC3209]

19.2.2. P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object

Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv6 C-Type = 13

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| IPv6 tunnel sender address |
+ +
| (16 bytes) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| Sub-Group Originator ID |
+ +
| (16 bytes) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Sub-Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

IPv6 tunnel sender address
See [RFC3209] [RFC3209].

Sub-Group Originator ID
The Sub-Group Originator ID is set to the IPv6 TE Router ID
of the LSR that originates the Path message. This is either
the ingress LSR ingress-LSR or a an LSR which re-originates the Path
message with its own Sub-Group Originator ID.

Sub-Group ID
As above in section 19.2.1.

LSP ID
See [RFC3209]

19.3. <S2L_SUB_LSP> S2L_SUB_LSP Object

A new <S2L_SUB_LSP> S2L_SUB_LSP object identifies a particular S2L sub-LSP belonging to
the P2MP LSP.

19.3.1. <S2L_SUB_LSP> S2L_SUB_LSP IPv4 Object

SUB_LSP

S2L_SUB_LSP Class = 50, S2L_SUB_LSP_IPv4 C-Type = 1

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 S2L Sub-LSP destination address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

IPv4 Sub-LSP destination address

IPv4 address of the S2L sub-LSP destination.

19.3.2. <S2L_SUB_LSP> S2L_SUB_LSP IPv6 Object

SUB_LSP

S2L_SUB_LSP Class = 50, S2L_SUB_LSP_IPv6 C-Type = 2

This is same as the S2L IPv4 Sub-LSP object, with the difference that
the destination address is a 16 byte IPv6 address.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 S2L Sub-LSP destination address (16 bytes) |
| .... |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

19.4. FILTER_SPEC Object

The FILTER_SPEC object is canonical to the P2MP SENDER_TEMPLATE
object.

19.4.1. P2MP LSP_IPv4 FILTER_SPEC Object

Class = FILTER SPEC, P2MP LSP_IPv4 C-Type = 12

The format of the P2MP LSP_IPv4 FILTER_SPEC object is identical to
the P2MP LSP_IPv4 SENDER_TEMPLATE object.

19.4.2. P2MP LSP_IPv4 LSP_IPv6 FILTER_SPEC Object

Class = FILTER SPEC, P2MP LSP_IPv6 C-Type = 13

The format of the P2MP LSP_IPv6 FILTER_SPEC object is identical to
the P2MP LSP_IPv6 SENDER_TEMPLATE object.

19.5. P2MP SECONDARY_EXPLICIT_ROUTE Object (SERO)

The P2MP SECONDARY_EXPLICIT_ROUTE Object (SERO) is defined as
identical to the ERO. The class of the P2MP SERO is the same as the
SERO defined in [RECOVERY]. The P2MP SERO uses a new C-Type = 2. The
sub-objects are identical to those defined for the ERO.

19.6. P2MP SECONDARY_RECORD_ROUTE Object (SRRO)

The P2MP SECONDARY_RECORD_ROUTE Object (SRRO) is defined as identical
to the ERO. The class of the P2MP SRRO is the same as the SRRO
defined in [RECOVERY]. The P2MP SRRO uses a new C-Type = 2. The sub-
objects are identical to those defined for the RRO.

20. IANA Considerations

20.1. New Class Numbers

IANA is requested to assign the following Class Numbers for the new
object classes introduced. The Class Types for each of them are to be
assigned via standards action. The sub-object types for the P2MP
SECONDARY_EXPLICIT_ROUTE and P2MP_SECONDARY_RECORD_ROUTE follow the
same IANA considerations as those of the ERO and RRO [RFC3209].

50 Class Name = SUB_LSP

C-Type
1 S2L_SUB_LSP_IPv4 C-Type
2 S2L_SUB_LSP_IPv6 C-Type

20.2. New Class Types

IANA is requested to assign the following C-Type values:

Class Name = SESSION

C-Type
13 P2MP_LSP_IPv4 C-Type
14 P2MP_LSP_IPv6 C-Type

Class Name = SENDER_TEMPLATE

C-Type
12 P2MP_LSP_IPv4 C-Type
13 P2MP_LSP_IPv6 C-Type

Class Name = FILTER_SPEC

C-Type
12 P2MP LSP_IPv4 C-Type
13 P2MP LSP_IPv6 C-Type

Class Name = SECONDARY_EXPLICIT_ROUTE

C-Type
2 P2MP SECONDARY_EXPLICIT_ROUTE C-Type

Class Name = SECONDARY_RECORD_ROUTE

C-Type
2 P2MP_SECONDARY_RECORD_ROUTE C-Type

20.3. New Error Values

Four new Error Values are defined for use with the Error Code
"Routing Problem". IANA is requested to assign values.

The Error Value "Unable to Branch" indicates that a P2MP branch
cannot be formed by the reporting LSR. IANA is requested to assign
value 23 to this Error Value.

The Error Value "Unsupported LSP Integrity" indicates that a P2MP
branch does not support the requested LSP integrity function. IANA is
requested to assign value 24 to this Error Value.

The Error Value "P2MP Remerge Detected" indicates that a node has
detected remerge. IANA is requested to assign value 25 to this Error
Value.

The Error Value "P2MP Re-Merge Parameter Mismatch" is described in
section 18. IANA is requested to assign value 26 to this Error Value.

The Error Value "ERO Resulted in Remerge" is described in section 18.
IANA is requested to assign value 27 to this Error Value.

20.4. LSP Attributes Flags

IANA has been asked to manage the space of flags in the Attibutes
Flags TLV carried in the LSP_REQUIRED_ATTRIBUTES Object [LSP-ATTR]. [RFC4420].
This document defines a new flag as follows:

Suggested Bit Number: 3
Meaning: LSP Integrity Required
Used in Attributes Flags on Path: Yes
Used in Attributes Flags on Resv: No
Used in Attributes Flags on RRO: No
Referenced Section of this Doc: 10 5.2.4

21. Security Considerations

This

In principle this document does not introduce any new security issues. The
security issues
above those identified in [RFC3209] [RFC3209], [RFC3473] and [RFC4206].
[RFC2205] specifies the message integrity mechanisms for hop-by-hop
RSVP signaling. These mechanisms apply to the hop-by-hop P2MP RSVP-
TE signaling in this document. Further [RFC3473] and [RFC4206]
specify the security mechanisms for non hop-by-hop RSVP-TE signaling.
These mechanisms apply to the non hop-by-hop P2MP RSVP-TE signaling
specified in this document, particularly in sections 16 and 17.

An administration may wish to limit the domain over which P2MP TE
tunnels can be established. This can be accomplished by setting
filters on various ports to deny action on a RSVP path message with a
SESSION object of type P2MP_LSP_IPv4 or P2MP_LSP_IPv6.

The ingress LSR of a P2MP TE LSP, determines the leaves of the P2MP
TE LSP based on the application of the P2MP TE LSP. The specification
of how such applications will use a P2MP TE LSP is outside the scope
of this document. However these applications SHOULD provide
mechanisms to ensure that unauthorized leaves are still
relevant. not added to the
P2MP TE LSP.

22. Acknowledgements

This document is the product of many people. The contributors are
listed in Section 27.2.

Thanks to Yakov Rekhter, Der-Hwa Gan, Arthi Ayyanger and Nischal
Sheth for their suggestions and comments. Thanks also to Dino
Farninacci and Benjamin Niven for his their comments.

23. Appendix References

23.1. Example

Following is one example of setting up a P2MP LSP using the
procedures described in this document.

Source 1 (S1)
|
PE1
| |
|L5 |
P3 |
| |
L3 |L1 |L2
R2----PE3--P1 P2---PE2--Receiver 1 (R1)
| L4
PE5----PE4----R3
|
|
R4

Figure 2.

The mechanism is explained using Figure 2. PE1 is the ingress-LSR.
PE2, PE3 and PE4 are Egress-LSRs.

a) PE1 learns that PE2, PE3 and PE4 are interested in joining a P2MP
tree with a P2MP ID of P2MP ID1. We assume that PE1 learns of the
egress-LSRs at different points.

b) PE1 computes the P2P path to reach PE2.

c) PE1 establishes the S2L sub-LSP to PE2 along <PE1, P2, PE2>

d) PE1 computes the P2P path to reach PE3 when it discovers PE3. This
path is computed to share the same links where possible with the sub-
LSP to PE2 as they belong to the same P2MP session.

e) PE1 establishes the S2L sub-LSP to PE3 along <PE1, P3, P1, PE3>

f) PE1 computes the P2P path to reach PE4 when it discovers PE4. This
path is computed to share the same links where possible with the sub-
LSPs to PE2 and PE3 as they belong to the same P2MP session.

g) PE1 signals the Path message for PE4 sub-LSP along <PE1, P3, P1,
PE4>

e) P1 receives a Resv message from PE4 with label L4. It had
previously received a Resv message from PE3 with label L3. It had
allocated a label L1 for the sub-LSP to PE3. It uses the same label
and sends the Resv messages to P3. Note that it may send only one
Resv message with multiple flow descriptors in the flow descriptor
list. If this is the case and FF style is used, the FF flow
descriptor will contain the S2L sub-LSP descriptor list with two
entries: one for PE4 and the other for PE3. For SE style, the SE
filter spec will contain this S2L sub-LSP descriptor list. P1 also
creates a label mapping of (L1 -> {L3, L4}). P3 uses the existing
label L5 and sends the Resv message to PE1, with label L5. It reuses
the label mapping of {L5 -> L1}.

24. References

24.1. Normative References

[RFC4206] K. Kompella, Y. Rekhter, "LSP Hierarchy with Generalized
MPLS TE" [RFC4206]

[LSP-ATTR] A. Farrel, et. al. , "Encoding Normative References

[RFC4206] K. Kompella, Y. Rekhter, "LSP Hierarchy with Generalized
MPLS TE" [RFC4206]

[RFC4420] A. Farrel, et. al. , "Encoding of
Attributes for Multiprotocol Label Switching (MPLS)
Label Switched Path (LSP) Establishment Using RSVP-TE",
draft-ietf-mpls-rsvpte-attributes-05.txt, March 2004,
work in progress.
RFC 4420, February 2006.

[RFC3209] D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan,
G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
RFC3209, December 2001, work in progress.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997, work in
progress.

[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S. and
S. Jamin, "Resource ReSerVation Protocol (RSVP)
-- Version 1, Functional Specification", RFC 2205,
September 1997, work in progress.

[RFC3471] Lou Berger, et al., "Generalized MPLS - Signaling
Functional Description", RFC 3471, January 2003, work in
progress.

[RFC3473] L. Berger et.al., "Generalized MPLS Signaling - RSVP-TE
Extensions", RFC 3473, January 2003, work in progress.

[RFC2961] L. Berger, D. Gan, G. Swallow, P. Pan, F. Tommasi,
S. Molendini, "RSVP Refresh Overhead Reduction Extensions"
,
Extensons", RFC 2961, April 2001, work in progress.

[RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001,
work in progress.

[RFC4090] P. Pan, G. Swallow, A. Atlas (Editors), "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", work in progress.

[RFC3477] K. Kompella, Y. Rekther, "Signalling Unnumbered Links in
Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", work in progress.

[RFC4461] S. Yasukawa, Editor "Signaling Requirements for
Point-to-Multipoint Traffic Engineered MPLS LSPs", RFC4461.

[RECOVERY] "GMPLS Based Segment Recovery",
draft-ietf-ccamp-gmpls-segment-recovery-02.txt

24.2.

23.2. Informative References

[BFD] D. Katz, D. Ward, "Bidirectional Forwarding Detection",
draft-ietf-bfd-02.txt,
draft-ietf-bfd-base-05.txt, work in progress.

[BFD-MPLS] R. Aggarwal, K. Kompella, T. Nadeau, G. Swallow, "BFD for
MPLS LSPs", draft-ietf-bfd-mpls-01.txt, LSPs", draft-ietf-bfd-mpls-02.txt, work in progress.

[LSP-STITCH] A. Ayyanger, J.P. Vasseur, "Label Switched Path
Stitching with Generalized MPLS Traffic Engineering",
work in progress.

[IPR-1] Bradner, S., "IETF Rights in Contributions", BCP 78,
RFC 3667, February 2004, progress

[TE-NODE-CAP] JP Vasseur, JL Le Roux, et al. "Routing extensions for
discovery of Traffic Engineering Node Capabilities",
draft-ietf-ccamp-te-node-cap-01.txt, June 2006,
work in progress.

[IPR-2] Bradner, S., Ed., "Intellectual Property Rights progress

[RFC4003] L. Berger, "GMPLS Signaling Procedure for Egress
Control", February, 2005.

24. Appendix

24.1. Example

Following is one example of setting up a P2MP LSP using the
procedures described in IETF
Technology", BCP 79, RFC 3668, February 2004, work this document.

Source 1 (S1)
|
PE1
| |
|L5 |
P3 |
| |
L3 |L1 |L2
R2----PE3--P1 P2---PE2--Receiver 1 (R1)
| L4
PE5----PE4----R3
|
|
R4

Figure 2.

The mechanism is explained using Figure 2. PE1 is the ingress-LSR.
PE2, PE3 and PE4 are Egress-LSRs.

a) PE1 learns that PE2, PE3 and PE4 are interested in
progress.

[INT-REG] A. Farrel, J.P. Vasseur, joining a P2MP
tree with a P2MP ID of P2MP ID1. We assume that PE1 learns of the
egress-LSRs at different points in time.

b) PE1 computes the P2P path to reach PE2.

c) PE1 establishes the S2L sub-LSP to PE2 along <PE1, P2, PE2>

d) PE1 computes the P2P path to reach PE3 when it discovers PE3. This
path is computed to share the same links where possible with the sub-
LSP to PE2 as they belong to the same P2MP session.

e) PE1 establishes the S2L sub-LSP to PE3 along <PE1, P3, P1, PE3>

f) PE1 computes the P2P path to reach PE4 when it discovers PE4. This
path is computed to share the same links where possible with the sub-
LSPs to PE2 and A. Ayyangar, "A Framework for
Inter-Domain MPLS Traffic Engineering",
draft-ietf-ccamp-inter-domain-framework-04.txt, work in
progress.

[RFC2209] R. Braden, L. Zhang, "Resource Reservation Protocol (RSVP)
Version 1 Message Processing Rules", RFC 2209, work in
progress.

[LSP-STITCH] A. Ayyanger, J.P. Vasseur, "Label Switched PE3 as they belong to the same P2MP session.

g) PE1 signals the Path
Stitching message for PE4 sub-LSP along <PE1, P3, P1,
PE4>
e) P1 receives a Resv message from PE4 with Generalized MPLS Traffic Engineering",
work in progress

[TE-NODE-CAP] JP Vasseur, JL Le Roux, et al. "Routing extensions label L4. It had
previously received a Resv message from PE3 with label L3. It had
allocated a label L1 for
discovery of Traffic Engineering Node Capabilities",
draft-vasseur-ccamp-te-node-cap-00.txt, February 2005,
work the sub-LSP to PE3. It uses the same label
and sends the Resv messages to P3. Note that it may send only one
Resv message with multiple flow descriptors in progress

[RFC4003] L. Berger, "GMPLS Signaling Procedure the flow descriptor
list. If this is the case and FF style is used, the FF flow
descriptor will contain the S2L sub-LSP descriptor list with two
entries: one for Egress
Control", February, 2005. PE4 and the other for PE3. For SE style, the SE
filter spec will contain this S2L sub-LSP descriptor list. P1 also
creates a label mapping of (L1 -> {L3, L4}). P3 uses the existing
label L5 and sends the Resv message to PE1, with label L5. It reuses
the label mapping of {L5 -> L1}.

25. Author Information

25.1. Editor Information

Rahul Aggarwal
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Email: rahul@juniper.net

Seisho Yasukawa
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 4769
EMail: yasukawa.seisho@lab.ntt.co.jp

Dimitri Papadimitriou
Alcatel
Francis Wellesplein 1,
B-2018 Antwerpen, Belgium
Phone: +32 3 240-8491
Email: Dimitri.Papadimitriou@alcatel.be

25.2. Contributor Information

John Drake
Boeing
Email: john.E.Drake2@boeing.com

Alan Kullberg
Motorola Computer Group
120 Turnpike Road 1st Floor
Southborough, MA 01772
EMail: alan.kullberg@motorola.com

Lou Berger
Movaz Networks, Inc.
7926 Jones Branch Drive
Suite 615
McLean VA, 22102
Phone: +1 703 847-1801
LabN Consulting, L.L.C.
EMail: lberger@movaz.com lberger@labn.net

Liming Wei
Redback Networks
350 Holger Way
San Jose, CA 95134
Email: lwei@redback.com

George Apostolopoulos
Redback Networks
350 Holger Way
San Jose, CA 95134
Email: georgeap@redback.com

Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
Email: kireeti@juniper.net

George Swallow
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough , MA - 01719
USA
Email: swallow@cisco.com

JP Vasseur
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough , MA - 01719
USA
Email: jpv@cisco.com
Dean Cheng
Cisco Systems Inc.
170 W Tasman Dr.
San Jose, CA 95134
Phone 408 527 0677
Email: dcheng@cisco.com

Markus Jork
Avici Systems
101 Billerica Avenue
N. Billerica, MA 01862
Phone: +1 978 964 2142
EMail: mjork@avici.com

Hisashi Kojima
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 6070
EMail: kojima.hisashi@lab.ntt.co.jp

Andrew G. Malis
Tellabs
2730 Orchard Parkway
San Jose, CA 95134
Phone: +1 408 383 7223
Email: Andy.Malis@tellabs.com

Koji Sugisono
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 2605
EMail: sugisono.koji@lab.ntt.co.jp

Masanori Uga
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 4804
EMail: uga.masanori@lab.ntt.co.jp

Igor Bryskin
Movaz Networks, Inc.
7926 Jones Branch Drive
Suite 615
McLean VA, 22102
ibryskin@movaz.com
Adrian Farrel
Old Dog Consulting
Phone: +44 0 1978 860944
EMail: adrian@olddog.co.uk

Jean-Louis Le Roux
France Telecom
2, avenue Pierre-Marzin
22307 Lannion Cedex
France
E-mail: jeanlouis.leroux@francetelecom.com

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28. Acknowledgement

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