wdiff draft-ietf-mpls-ldp-p2mp-02.txt draft-ietf-mpls-ldp-p2mp-03.txt

Network Working Group I. Minei (Editor)
Internet-Draft K. Kompella
Intended status: Standards Track Juniper Networks
Expires: December 3, 2006 January 10, 2008 I. Wijnands (Editor)
B. Thomas
Cisco Systems, Inc.
July 9, 2007

Label Distribution Protocol Extensions for Point-to-Multipoint and
Multipoint-to-Multipoint Label Switched Paths
draft-ietf-mpls-ldp-p2mp-02
draft-ietf-mpls-ldp-p2mp-03

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Abstract

This document describes extensions to the Label Distribution Protocol
(LDP) for the setup of point to multi-point (P2MP) and multipoint-to-
multipoint (MP2MP) Label Switched Paths (LSPs) in Multi-Protocol
Label Switching (MPLS) networks. The solution relies on LDP without
requiring a multicast routing protocol in the network. Protocol
elements and procedures for this solution are described for building
such LSPs in a receiver-initiated manner. There can be various
applications for P2MP/MP2MP LSPs, for example IP multicast or support
for multicast in BGP/MPLS L3VPNs. Specification of how such
applications can use a LDP signaled P2MP/MP2MP LSP is outside the
scope of this document.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
1.1. Conventions used in this document . . . . . . . . . . . . 3 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 4
2. Setting up P2MP LSPs with LDP . . . . . . . . . . . . . . . . 4 5
2.1. Support for P2MP LSP setup with LDP . . . . . . . . . . . 5
2.2. The P2MP FEC Element . . . . . . . . . . . . . . . . . . . 4
2.2. 6
2.3. The LDP MP Opaque Value Element . . . . . . . . . . . . . 6
2.2.1. 7
2.3.1. The Generic LSP Identifier . . . . . . . . . . . . . . 6
2.3. 8
2.4. Using the P2MP FEC Element . . . . . . . . . . . . . . . . 7
2.3.1. 8
2.4.1. Label Map . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2. 9
2.4.2. Label Withdraw . . . . . . . . . . . . . . . . . . . . 9 11
3. Shared Trees . . . . . . . . . . . . . . . . . . . . . . . . . 10 11
4. Setting up MP2MP LSPs with LDP . . . . . . . . . . . . . . . . 11 12
4.1. Support for MP2MP LSP setup with LDP . . . . . . . . . . . 13
4.2. The MP2MP downstream and upstream FEC elements. Elements. . . . . . 11
4.2. 13
4.3. Using the MP2MP FEC elements Elements . . . . . . . . . . . . . . . 11
4.2.1. 14
4.3.1. MP2MP Label Map upstream and downstream . . . . . . . 13
4.2.2. 15
4.3.2. MP2MP Label Withdraw . . . . . . . . . . . . . . . . . 15 17
5. Upstream label allocation on Ethernet networks The LDP MP Status TLV . . . . . . . . 16
6. Root node redundancy for MP2MP LSPs . . . . . . . . . . . . 18
5.1. The LDP MP Status Value Element . . . 16
6.1. Root node redundancy procedure . . . . . . . . . . 19
5.2. LDP Messages containing LDP MP Status messages . . . . . . 16
7. Make before break 20
5.2.1. LDP MP Status sent in LDP notification messages . . . 20
5.2.2. LDP MP Status TLV in Label Mapping Message . . . . . . 20
6. Upstream label allocation on a LAN . . . . . . . . . . . . . 17
7.1. Protocol event . 21
6.1. LDP Multipoint-to-Multipoint on a LAN . . . . . . . . . . 21
6.1.1. MP2MP downstream forwarding . . . . . . . . . . . 18
8. Security Considerations . . 21
6.1.2. MP2MP upstream forwarding . . . . . . . . . . . . . . 22
7. Root node redundancy . . . 18
9. IANA considerations . . . . . . . . . . . . . . . . . . 22
7.1. Root node redundancy - procedures for P2MP LSPs . . . 18
10. Acknowledgments . . 23
7.2. Root node redundancy - procedures for MP2MP LSPs . . . . . 23
8. Make Before Break (MBB) . . . . . . . . . . . . . . . . 19
11. Contributing authors . . . 24
8.1. MBB overview . . . . . . . . . . . . . . . . . . 19
12. References . . . . . 24
8.2. The MBB Status code . . . . . . . . . . . . . . . . . . . 25
8.3. The MBB capability . . 21
12.1. Normative References . . . . . . . . . . . . . . . . . . 26
8.4. The MBB procedures . 21
12.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . 26
8.4.1. Terminology . . . . . . . . . . . . . . . . . . . . . 26
8.4.2. Accepting elements . . 21
Intellectual Property and Copyright Statements . . . . . . . . . . 23

1. Introduction

The LDP protocol is described in [1]. It defines mechanisms . . . . . . 27
8.4.3. Procedures for
setting up point-to-point upstream LSR change . . . . . . . . . . 27
8.4.4. Receiving a Label Map with MBB status code . . . . . . 28
8.4.5. Receiving a Notification with MBB status code . . . . 28
8.4.6. Node operation for MP2MP LSPs . . . . . . . . . . . . 29
9. Security Considerations . . . . . . . . . . . . . . . . . . . 29
10. IANA considerations . . . . . . . . . . . . . . . . . . . . . 29
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30
12. Contributing authors . . . . . . . . . . . . . . . . . . . . . 30
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
13.1. Normative References . . . . . . . . . . . . . . . . . . . 32
13.2. Informative References . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
Intellectual Property and Copyright Statements . . . . . . . . . . 34

1. Introduction

The LDP protocol is described in [1]. It defines mechanisms for
setting up point-to-point (P2P) and multipoint-to-point (MP2P) LSPs multipoint-to-point (MP2P) LSPs
in the network. This document describes extensions to LDP for
setting up point-to-multipoint (P2MP) and multipoint-to-multipoint
(MP2MP) LSPs. These are collectively referred to as multipoint LSPs
(MP LSPs). A P2MP LSP allows traffic from a single root (or ingress)
node to be delivered to a number of leaf (or egress) nodes. A MP2MP
LSP allows traffic from multiple ingress nodes to be delivered to
multiple egress nodes. Only a single copy of the packet will be sent
on any link traversed by the MP LSP (see note at end of
Section 2.4.1). This is accomplished without the use of a multicast
protocol in the network. There can be several MP LSPs rooted at a
given ingress node, each with its own identifier.

The solution assumes that the leaf nodes of the MP LSP know the root
node and identifier of the MP LSP to which they belong. The
mechanisms for the distribution of this information are outside the
scope of this document. The specification of how an application can
use a MP LSP signaled by LDP is also outside the scope of this
document.

Interested readers may also wish to peruse the requirements draft [9]
and other documents [8] and [10].

1.1. 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 [2].

1.2. Terminology

The following terminology is taken from [9].

P2P LSP: An LSP that has one Ingress LSR and one Egress LSR.

P2MP LSP: An LSP that has one Ingress LSR and one or more Egress
LSRs.

MP2P LSP: An LSP that has one or more Ingress LSRs and one unique
Egress LSR.

MP2MP LSP: An LSP that connects a set of leaf nodes, acting
indifferently as ingress or egress.

MP LSP: A multipoint LSP, either a P2MP or an MP2MP LSP.

Ingress LSR: Source of the P2MP LSP, also referred to as root node.

Egress LSR: One of potentially many destinations of an LSP, also
referred to as leaf node in the case of P2MP and MP2MP LSPs.

Transit LSR: An LSR that has one or more directly connected
downstream LSRs.

Bud LSR: An LSR that is an egress but also has one or more directly
connected downstream LSRs.

2. Setting up P2MP LSPs with LDP

A P2MP LSP consists of a single root node, zero or more transit nodes
and one or more leaf nodes. Leaf nodes initiate P2MP LSP setup and
tear-down. Leaf nodes also install forwarding state to deliver the
traffic received on a P2MP LSP to wherever it needs to go; how this
is done is outside the scope of this document. Transit nodes install
MPLS forwarding state and propagate the P2MP LSP setup (and tear-
down) toward the root. The root node installs forwarding state to
map traffic into the P2MP LSP; how the root node determines which
traffic should go over the P2MP LSP is outside the scope of this
document.

2.1. Support for P2MP LSP setup with LDP

Support for the setup of P2MP LSPs is advertised using LDP
capabilities as defined in [6]. An implementation supporting the
P2MP procedures specified in this document MUST implement the
procedures for Capability Parameters in Initialization Messages.

A new Capability Parameter TLV is defined, the P2MP Capability.
Following is the format of the P2MP Capability Parameter.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| P2MP Capability (TBD IANA) | Length (= 1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Reserved |
+-+-+-+-+-+-+-+-+

The P2MP Capability TLV MUST be supported in the LDP Initialization
Message. Advertisement of the P2MP Capability indicates support of
the procedures for P2MP LSP setup detailed in this document. If the
peer has not advertised the corresponding capability, then no label
messages using the P2MP FEC Element should be sent to the peer.

2.2. The P2MP FEC Element

For the setup of a P2MP LSP with LDP, we define one new protocol
entity, the P2MP FEC Element to be used as a FEC Element in the FEC
TLV. Note that the P2MP FEC Element does not necessarily identify
the traffic that must be mapped to the LSP, so from that point of
view, the use of the term FEC is a misnomer. The description of the
P2MP FEC Element follows.

The P2MP FEC Element consists of the address of the root of the P2MP
LSP and an opaque value. The opaque value consists of one or more
LDP MP Opaque Value Elements. The opaque value is unique within the
context of the root node. The combination of (Root Node Address,
Opaque Value) uniquely identifies a P2MP LSP within the MPLS network.

The P2MP FEC Element is encoded as follows:

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 Type (TBD)| Address Family | Address Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Root Node Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Length | Opaque Value ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ ~
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: The type of the P2MP FEC Element is to be assigned by IANA.

Address Family: Two octet quantity containing a value from ADDRESS
FAMILY NUMBERS in [3] that encodes the address family for the Root
LSR Address.

Address Length: Length of the Root LSR Address in octets.

Root Node Address: A host address encoded according to the Address
Family field.

Opaque Length: The length of the Opaque Value, in octets.

Opaque Value: One or more MP Opaque Value elements, uniquely
identifying the P2MP LSP in the context of the Root Node. This is
described in the next section.

If the Address Family is IPv4, the Address Length MUST be 4; if the
Address Family is IPv6, the Address Length MUST be 16. No other
Address Lengths are defined at present.

If the Address Length doesn't match the defined length for the
Address Family, the receiver SHOULD abort processing the message
containing the FEC Element, and send an "Unknown FEC" Notification
message to its LDP peer signaling an error.

If a FEC TLV contains a P2MP FEC Element, the P2MP FEC Element MUST
be the only FEC Element in the FEC TLV.

2.3. The LDP MP Opaque Value Element

The LDP MP Opaque Value Element is used in the P2MP and MP2MP FEC
Elements defined in subsequent sections. It carries information that
is meaningful to leaf (and bud) LSRs, but need not be interpreted by
non-leaf LSRs.

The LDP MP Opaque Value Element is encoded as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type(TBD) | Length | Value ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ~
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type: The type of the LDP MP Opaque Value Element is to be assigned
by IANA.

Length: The length of the Value field, in octets.

Value: String of Length octets, to be interpreted as specified by
the Type field.

2.3.1. The Generic LSP Identifier

The generic LSP identifier is a type of Opaque Value Element encoded
as follows:

Type: 1 (to be assigned by IANA)

Length: 4

Value: A 32bit integer, unique in the context of the root, as
identified by the root's address.

This type of Opaque Value Element is recommended when mapping of
traffic to LSPs is non-algorithmic, and done by means outside LDP.

2.4. Using the P2MP FEC Element

This section defines the rules for the processing and propagation of
the P2MP FEC Element. The following notation is used in the
processing rules:

1. P2MP FEC Element <X, Y>: a FEC Element with Root Node Address X
and Opaque Value Y.

2. P2MP Label Map <X, Y, L>: a Label Map message with a FEC TLV with
a single P2MP FEC Element <X, Y> and Label TLV with label L.

3. P2MP Label Withdraw <X, Y, L>: a Label Withdraw message with a
FEC TLV with a single P2MP FEC Element <X, Y> and Label TLV with
label L.

4. P2MP LSP <X, Y> (or simply <X, Y>): a P2MP LSP with Root Node
Address X and Opaque Value Y.

5. The notation L' -> {<I1, L1> <I2, L2> ..., <In, Ln>} on LSR X
means that on receiving a packet with label L', X makes n copies
of the packet. For copy i of the packet, X swaps L' with Li and
sends it out over interface Ii.

The procedures below are organized by the role which the node plays
in the P2MP LSP. Node Z knows that it is a leaf node by a discovery
process which is outside the scope of this document. During the
course of protocol operation, the root node recognizes its role
because it owns the Root Node Address. A transit node is any node
(other than the root node) that receives a P2MP Label Map message
(i.e., one that has leaf nodes downstream of it).

Note that a transit node (and indeed the root node) may also be a
leaf node.

2.4.1. Label Map

The following lists procedures for generating and processing P2MP
Label Map messages for nodes that participate in a P2MP LSP. An LSR
should apply those procedures that apply to it, based on its role in
the P2MP LSP.

For the approach described here we use downstream assigned labels.
On Ethernet networks this may be less optimal, see Section 6.

2.4.1.1. Determining one's 'upstream LSR'

A node Z that is part of P2MP LSP <X, Y> determines the LDP peer U
which lies on the best path from Z to the root node X. If there are
more than one such LDP peers, only one of them is picked. U is Z's
"Upstream LSR" for <X, Y>.

When there are several candidate upstream LSRs, the LSR MAY select
one upstream LSR using the following procedure:

1. The candidate upstream LSRs are numbered from lower to higher IP
address

2. The following hash is performed: H = (Sum Opaque value) modulo N,
where N is the number of candidate upstream LSRs

3. The selected upstream LSR U is the LSR that has the number H.

This allows for load balancing of a set of LSPs among a set of
candidate upstream LSRs, while ensuring that on a LAN interface a
single upstream LSR is selected.

2.4.1.2. Leaf Operation

A leaf node Z of P2MP LSP <X, Y> determines its upstream LSR U for
<X, Y> as per Section 2.4.1.1, allocates a label L, and sends a P2MP
Label Map <X, Y, L> to U.

2.4.1.3. Transit Node operation

Suppose a transit node Z receives a P2MP Label Map <X, Y, L> from LDP
peer T. Z checks whether it already has state for <X, Y>. If not, Z
allocates a label L', and installs state to swap L' with L over
interface I associated with peer T. Z also determines its upstream
LSR U for <X, Y> as per Section 2.4.1.1, and sends a P2MP Label Map
<X, Y, L'> to U.

If Z already has state for <X, Y>, then Z does not send a Label Map
message for P2MP LSP <X, Y>. All that Z needs to do in this case is
update its forwarding state. Assuming its old forwarding state was
L'-> {<I1, L1> <I2, L2> ..., <In, Ln>}, its new forwarding state
becomes L'-> {<I1, L1> <I2, L2> ..., <In, Ln>, <I, L>}.

2.4.1.4. Root Node Operation

Suppose the root node Z receives a P2MP Label Map <X, Y, L> from peer
T. Z checks whether it already has forwarding state for <X, Y>. If
not, Z creates forwarding state to push label L onto the traffic that
Z wants to forward over the P2MP LSP (how this traffic is determined
is outside the scope of this document).

If Z already has forwarding state for <X, Y>, then Z adds "push label
L, send over interface I" to the nexthop, where I is the interface
associated with peer T.

2.4.2. Label Withdraw

The following lists procedures for generating and processing P2MP
Label Withdraw messages for nodes that participate in a P2MP LSP. An
LSR should apply those procedures that apply to it, based on its role
in the P2MP LSP.

2.4.2.1. Leaf Operation

If a leaf node Z discovers (by means outside the scope of this
document) that it is no longer a leaf of the P2MP LSP, it SHOULD send
a Label Withdraw <X, Y, L> to its upstream LSR U for <X, Y>, where L
is the label it had previously advertised to U for <X, Y>.

2.4.2.2. Transit Node Operation

If a transit node Z receives a Label Withdraw message <X, Y, L> from
a node W, it deletes label L from its forwarding state, and sends a
Label Release message with label L to W.

If deleting L from Z's forwarding state for P2MP LSP <X, Y> results
in no state remaining for <X, Y>, then Z propagates the network. This document describes extensions Label
Withdraw for <X, Y>, to LDP its upstream T, by sending a Label Withdraw
<X, Y, L1> where L1 is the label Z had previously advertised to T for
setting up point-to-multipoint (P2MP) and multipoint-to-multipoint
(MP2MP) LSPs. These
<X, Y>.

2.4.2.3. Root Node Operation

The procedure when the root node of a P2MP LSP receives a Label
Withdraw message are collectively referred to the same as multipoint LSPs
(MP LSPs). for transit nodes, except that it
would not propagate the Label Withdraw upstream (as it has no
upstream).

2.4.2.4. Upstream LSR change

If, for a given node Z participating in a P2MP LSP <X, Y>, the
upstream LSR changes, say from U to U', then Z MUST update its
forwarding state by deleting the state for label L, allocating a new
label, L', for <X,Y>, and installing the forwarding state for L'. In
addition Z MUST send a Label Map <X, Y, L'> to U' and send a Label
Withdraw <X, Y, L> to U.

3. Shared Trees

The mechanism described above shows how to build a tree with a single
root and multiple leaves, i.e., a P2MP LSP. One can use essentially
the same mechanism to build Shared Trees with LDP. A P2MP LSP allows Shared Tree can
be used by a group of routers that want to multicast traffic from among
themselves, i.e., each node is both a single root (or ingress) node to be delivered to (when it sources
traffic) and a number of leaf (or egress) nodes. node (when any other member of the group sources
traffic). A MP2MP
LSP allows traffic from multiple ingress nodes to be delivered Shared Tree offers similar functionality to
multiple egress nodes. Only a single copy of the packet will be sent
on any link traversed by MP2MP LSP,
but the MP LSP (see note at end of
Section 2.3.1). This underlying multicasting mechanism uses a P2MP LSP. One
example where a Shared Tree is accomplished without the use useful is video-conferencing. Another
is Virtual Private LAN Service (VPLS) [7], where for some types of
traffic, each device participating in a multicast
protocol VPLS must send packets to
every other device in the network. There can be several MP LSPs that VPLS.

One way to build a Shared Tree is to build an LDP P2MP LSP rooted at
a
given ingress node, each with its own identifier.

The solution assumes that common point, the leaf nodes of Shared Root (SR), and whose leaves are all the MP LSP know
members of the root
node and identifier group. Each member of the MP LSP Shared Tree unicasts
traffic to which they belong. The
mechanisms the SR (using, for example, the distribution MP2P LSP created by the
unicast LDP FEC advertised by the SR); the SR then splices this
traffic into the LDP P2MP LSP. The SR may be (but need not be) a
member of this information are outside the
scope multicast group.

A major advantage of this document. The specification of how an application can
use a MP LSP signaled by LDP approach is also outside that no further protocol
mechanisms beyond the scope of this
document.

Interested readers may also wish one already described are needed to peruse set up a
Shared Tree. Furthermore, a Shared Tree is very efficient in terms
of the requirement draft [4]
and other documents [8] and [9].

1.1. Conventions used multicast state in this document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", the network, and "OPTIONAL" is reasonably efficient in this
document are
terms of the bandwidth required to be interpreted as described in RFC 2119 [2].

1.2. Terminology

The following terminology send traffic.

A property of this approach is taken from [4].

P2P LSP: An LSP that has one Ingress LSR and one Egress LSR.

P2MP LSP: An LSP that has one Ingress LSR a sender will receive its own
packets as part of the multicast; thus a sender must be prepared to
recognize and one or more Egress
LSRs.

MP2P LSP: A LSP discard packets that it itself has one or more Ingress LSRs and one unique
Egress LSR.

MP2MP LSP: A LSP that connects a set of leaf nodes, acting
indifferently as ingress or egress.

MP LSP: A multipoint LSP, either sent. For a P2MP or an MP2MP LSP.

Ingress LSR: Source number
of applications (for example, VPLS), this requirement is easy to
meet. Another consideration is the P2MP LSP, also referred various techniques that can be
used to as root node.

Egress LSR: One of potentially many destinations of an LSP, also
referred splice unicast LDP MP2P LSPs to as leaf node in the case of LDP P2MP and MP2MP LSPs.

Transit LSR: An LSR that has one or more directly connected
downstream LSRs.

Bud LSR: An LSR that is an egress but also has one or more directly
connected downstream LSRs.

2. LSP; these will
be described in a later revision.

4. Setting up P2MP MP2MP LSPs with LDP

An MP2MP LSP is much like a P2MP LSP in that it consists of a single
root node, zero or more transit nodes and one or more leaf nodes. Leaf nodes initiate P2MP LSP setup and
tear-down. Leaf nodes also install forwarding state to deliver the
traffic received on a P2MP LSP to wherever it needs to go; how this
is done is outside LSRs
acting equally as Ingress or Egress LSR. A leaf node participates in
the scope setup of this document. Transit nodes install
MPLS forwarding state and propagate the P2MP an MP2MP LSP setup (and tear-
down) toward the root. The root node installs forwarding state to
map traffic into the P2MP LSP; how the root node determines by establishing both a downstream LSP,
which
traffic should go over the P2MP LSP is outside the scope of this
document.

For the setup of much like a P2MP LSP with LDP, we define one new protocol
entity, from the P2MP FEC Element to be root, and an upstream LSP
which is used in the FEC TLV. The
description of the P2MP FEC Element follows.

2.1. The P2MP FEC Element

The P2MP FEC Element consists of to send traffic toward the address of root and other leaf nodes.
Transit nodes support the root of setup by propagating the P2MP upstream and
downstream LSP setup toward the root and an opaque value. The opaque value consists of one or more
LDP MP Opaque Value Elements. The opaque value is unique within installing the
context necessary
MPLS forwarding state. The transmission of packets from the root node. The combination
node of (Root Node Address,
Opaque Value) uniquely identifies a P2MP MP2MP LSP within the MPLS network.

The P2MP FEC element is encoded as follows:

Type: The type of to the P2MP FEC element receivers is identical to be assigned by IANA.

Address Family: Two octet quantity containing that for a value P2MP
LSP. Traffic from ADDRESS
FAMILY NUMBERS in [3] that encodes a leaf node follows the address family for upstream LSP toward the Root
LSR Address.

Address Length: Length of
root node and branches downward along the Root LSR Address in octets.

Root Node Address: A host address encoded according downstream LSP as required
to reach other leaf nodes. Mapping traffic to the Address
Family field.

Opaque Length: The length of the Opaque Value, in octets.

Opaque Value: One or more MP Opaque Value elements, uniquely
identifying the P2MP MP2MP LSP in may
happen at any leaf node. How that mapping is established is outside
the context scope of the Root Node. This this document.

Due to how a MP2MP LSP is
described in the next section.

If the Address Family built a leaf LSR that is IPv4, the Address Length MUST be 4; if sending packets on
the
Address Family MP2MP LSP does not receive its own packets. There is IPv6, the Address Length MUST be 16. No other
Address Lengths are defined at present.

If also no
additional mechanism needed on the Address Length doesn't root or transit LSR to match the defined length for the
Address Family, the receiver SHOULD abort processing the message
containing the FEC Element, and send an "Unknown FEC" Notification
message
upstream traffic to its LDP peer signaling an error.

If the downstream forwarding state. Packets that
are forwarded over a FEC TLV contains MP2MP LSP will not traverse a P2MP FEC Element, the P2MP FEC Element MUST
be link more than
once, with the only FEC Element exception of LAN links which are discussed in the FEC TLV.

2.2. The LDP MP Opaque Value Element

The
Section 4.3.1

4.1. Support for MP2MP LSP setup with LDP MP Opaque Value Element

Support for the setup of MP2MP LSPs is used advertised using LDP
capabilities as defined in [6]. An implementation supporting the P2MP and
MP2MP FEC
elements defined procedures specified in subsequent sections. It carries information that this document MUST implement the
procedures for Capability Parameters in Initialization Messages.

A new Capability Parameter TLV is meaningful to leaf (and bud) LSRs, but need not be interpreted by
non-leaf LSRs.

The LDP MP Opaque Value Element defined, the MP2MP Capability.
Following is encoded as follows: the format of the MP2MP Capability Parameter.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type(TBD)
|1|0| MP2MP Capability (TBD IANA) | Length (= 1) | Value ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ~
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Reserved |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type:
+-+-+-+-+-+-+-+-+

The type of MP2MP Capability TLV MUST be supported in the LDP MP Opaque Value Element is to be assigned
by IANA.

Length: The length Initialization
Message. Advertisement of the Value field, in octets.

Value: String MP2MP Capability indicates support of Length octets, to be interpreted as specified by
the Type field.

2.2.1. The Generic procedures for MP2MP LSP Identifier setup detailed in this document. If the
peer has not advertised the corresponding capability, then no label
messages using the MP2MP upstream and downstream FEC Elements should
be sent to the peer.

4.2. The generic LSP identifier is a type MP2MP downstream and upstream FEC Elements.

For the setup of Opaque Value Element encoded
as follows:

Type: 1 (to a MP2MP LSP with LDP we define 2 new protocol
entities, the MP2MP downstream FEC and upstream FEC Element. Both
elements will be assigned by IANA)
Length: 4

Value: A 32bit integer, unique used as FEC Elements in the context of FEC TLV. Note that the root, as
identified by
MP2MP FEC Elements do not necessarily identify the root's address.

This type traffic that must
be mapped to the LSP, so from that point of opaque value element view, the use of the term
FEC is recommended when mapping a misnomer. The description of
traffic to LSPs the MP2MP FEC Elements follow.

The structure, encoding and error handling for the MP2MP downstream
and upstream FEC Elements are the same as for the P2MP FEC Element
described in Section 2.2. The difference is non-algorithmic, that two new FEC types
are used: MP2MP downstream type (TBD) and done by means outside LDP.

2.3. Using MP2MP upstream type (TBD).

If a FEC TLV contains an MP2MP FEC Element, the P2MP MP2MP FEC Element
MUST be the only FEC Element in the FEC TLV.

4.3. Using the MP2MP FEC Elements

This section defines the rules for the processing and propagation of
the P2MP MP2MP FEC Element. Elements. The following notation is used in the
processing rules:

1. P2MP MP2MP downstream LSP <X, Y> (or simply downstream <X, Y>): an
MP2MP LSP downstream path with root node address X and opaque
value Y.

2. MP2MP upstream LSP <X, Y, D> (or simply upstream <X, Y, D>): a
MP2MP LSP upstream path for downstream node D with root node
address X and opaque value Y.

3. MP2MP downstream FEC Element <X, Y>: a FEC Element with Root Node Address root node
address X and Opaque Value Y.

2. P2MP opaque value Y used for a downstream MP2MP LSP.

4. MP2MP upstream FEC Element <X, Y>: a FEC Element with root node
address X and opaque value Y used for an upstream MP2MP LSP.

5. MP2MP Label Map downstream <X, Y, L>: a A Label Map message with a
FEC TLV with a single P2MP MP2MP downstream FEC Element <X, Y> and Label
label TLV with label L.

3. P2MP

6. MP2MP Label Map upstream <X, Y, Lu>: A Label Map message with a
FEC TLV with a single MP2MP upstream FEC Element <X, Y> and label
TLV with label Lu.

7. MP2MP Label Withdraw downstream <X, Y, L>: a Label Withdraw
message with a FEC TLV with a single P2MP MP2MP downstream FEC Element
<X, Y> and Label label TLV with label L.

4. P2MP LSP <X, Y> (or simply

8. MP2MP Label Withdraw upstream <X, Y>): Y, Lu>: a P2MP LSP Label Withdraw
message with Root Node
Address X and Opaque Value Y.

5. The notation L' -> {<I1, L1> <I2, L2> ..., <In, Ln>} on LSR X
means that on receiving a packet with label L', X makes n copies
of the packet. For copy i of the packet, X swaps L' FEC TLV with Li a single MP2MP upstream FEC Element
<X, Y> and
sends it out over interface Ii. label TLV with label Lu.

The procedures below are organized by the role which the node plays
in the P2MP MP2MP LSP. Node Z knows that it is a leaf node by a discovery
process which is outside the scope of this document. During the
course of the protocol operation, the root node recognizes its role
because it owns the Root Node Address. root node address. A transit node is any node
(other than then the root node) that receives a P2MP MP2MP Label Map message
(i.e., one that has leaf nodes downstream of it).

Note that a transit node (and indeed the root node) may also be a
leaf node.

2.3.1. node and the root node does not have to be an ingress LSR or
leaf of the MP2MP LSP.

4.3.1. MP2MP Label Map upstream and downstream

The following lists procedures for generating and processing P2MP MP2MP
Label Map messages for nodes that participate in a P2MP MP2MP LSP. An LSR
should apply those procedures that apply to it, based on its role in
the P2MP MP2MP LSP.

For the approach described here we use downstream assigned labels.
On Ethernet networks this if there are several receivers for a
MP2MP LSP on a LAN, packets are replicated over the LAN. This may
not be less optimal, optimal; optimizing this case is for further study, see Section 5.

2.3.1.1. [4].

4.3.1.1. Determining one's 'upstream LSR'

A node Z that is part of P2MP LSP <X, Y> determines upstream MP2MP LSR

Determining the upstream LDP peer U
which lies on the best path from Z to the root node X. If there are
more than one such LDP peers, only one of them is picked. U is Z's
"Upstream LSR" for a MP2MP LSP <X, Y>.

When there are several candidate upstream LSRs, the LSR MAY select
one upstream LSR using the following procedure:

1. The candidate upstream LSRs are numbered from lower to higher IP
address

2. The following hash is performed: H = (Sum Opaque value) modulo N,
where N is the number of candidate upstream LSRs

3. The selected upstream LSR U is the LSR that has Y> follows
the number H.

This allows procedure for load balancing of a set of LSPs among a set of
candidate upstream LSRs, while ensuring that on P2MP LSP described in Section 2.4.1.1.

4.3.1.2. Determining one's downstream MP2MP LSR

A LDP peer U which receives a LAN interface MP2MP Label Map downstream from a
single upstream LSR is selected.

2.3.1.2. Leaf Operation LDP
peer D will treat D as downstream MP2MP LSR.

4.3.1.3. MP2MP leaf node operation

A leaf node Z of P2MP a MP2MP LSP <X, Y> determines its upstream LSR U for
<X, Y> as per Section 2.3.1.1, 4.3.1.1, allocates a label L, and sends a P2MP MP2MP
Label Map downstream <X, Y, L> to U.

2.3.1.3. Transit Node operation

Suppose a

Leaf node Z expects an MP2MP Label Map upstream <X, Y, Lu> from node
U in response to the MP2MP Label Map downstream it sent to node U. Z
checks whether it already has forwarding state for upstream <X, Y>.
If not, Z creates forwarding state to push label Lu onto the traffic
that Z wants to forward over the MP2MP LSP. How it determines what
traffic to forward on this MP2MP LSP is outside the scope of this
document.

4.3.1.4. MP2MP transit node operation

When node Z receives a P2MP MP2MP Label Map downstream <X, Y, L> from LDP peer T. Z
D associated with interface I, it checks whether it already has forwarding
state for downstream <X, Y>. If not, Z allocates a label L', L' and
installs downstream forwarding state to swap label L' with label L
over interface I associated with peer T. I. Z also determines its upstream LSR U for <X, Y> as
per Section 2.3.1.1, 4.3.1.1, and sends a P2MP MP2MP Label Map downstream <X, Y,
L'> to U.

If Z already has forwarding state for downstream <X, Y>, then Z does not send a Label Map
message for P2MP LSP <X, Y>. All all that Z
needs to do in this case is update its forwarding state. Assuming its old
forwarding state was L'-> {<I1, L1> <I2, L2> ..., <In, Ln>}, its new
forwarding state becomes L'-> {<I1, L1> <I2, L2> ..., <In, Ln>, <I,
L>}.

2.3.1.4. Root

Node Operation

Suppose the root node Z receives a P2MP Label Map <X, Y, L> from peer
T. Z checks whether it already has forwarding state for upstream <X, Y>. Y,
D>. If it does, then no further action needs to happen. If it does
not, Z it allocates a label Lu and creates forwarding state to push a new label L onto the traffic that
Z wants to forward over the P2MP LSP (how this traffic is determined
is outside the scope of this document).

If Z already has swap for Lu from
the label swap(s) from the forwarding state for downstream <X, Y>, then Z adds "push label
L, send over interface I" to the nexthop, where I is
omitting the swap on interface
associated with peer T.

2.3.2. Label Withdraw

The following lists procedures for generating and processing P2MP
Label Withdraw messages I for nodes that participate in a P2MP LSP. An
LSR should apply those procedures that apply node D. This allows upstream
traffic to it, based on its role
in follow the MP2MP tree down to other node(s) except the P2MP LSP.

2.3.2.1. Leaf Operation

If a leaf
node from which Z discovers (by means outside the scope of this
document) that it is no longer a leaf of received the P2MP LSP, it SHOULD send
a MP2MP Label Withdraw Map downstream <X, Y, L> to its upstream L>.
Node Z determines the downstream MP2MP LSR U for as per Section 4.3.1.2,
and sends a MP2MP Label Map upstream <X, Y>, where L
is the label it had previously advertised Y, Lu> to U for <X, Y>.

2.3.2.2. node D.

Transit Node Operation

If a transit node Z receives will also receive a MP2MP Label Withdraw message Map upstream <X, Y, L> from
a node W, it deletes label L from its forwarding state, and sends a
Lu> in response to the MP2MP Label Release message Map downstream sent to node U
associated with interface Iu. Node Z will add label L swap Lu over
interface Iu to W.

If deleting L from Z's the forwarding state for P2MP LSP <X, Y> results
in no state remaining for <X, Y>, then Z propagates the Label
Withdraw for <X, Y>, to its upstream T, by sending a Label Withdraw upstream <X, Y, L1> where L1 is the label Z had previously advertised D>. This allows
packets to T for
<X, Y>.

2.3.2.3. Root Node Operation

The procedure when go up the tree towards the root node.

4.3.1.5. MP2MP root node of operation

4.3.1.5.1. Root node is also a P2MP LSP leaf

Suppose root/leaf node Z receives a MP2MP Label
Withdraw message are the same as Map downstream <X, Y,
L> from node D associated with interface I. Z checks whether it
already has forwarding state downstream <X, Y>. If not, Z creates
forwarding state for transit nodes, except downstream to push label L on traffic that it
would not propagate Z
wants to forward down the Label Withdraw upstream (as MP2MP LSP. How it determines what traffic
to forward on this MP2MP LSP is outside the scope of this document.
If Z already has no
upstream).

2.3.2.4. Upstream LSR change

If, forwarding state for a given node Z participating in a P2MP LSP downstream <X, Y>, then Z will
add the
upstream LSR changes, say from U label push for L over interface I to U', then it.

Node Z MUST update its checks if it has forwarding state by deleting the state for label L, allocating upstream <X, Y, D>. If
not, Z allocates a new
label, L', for <X,Y>, label Lu and installing creates upstream forwarding state to
push Lu with the label push(s) from the forwarding state for L'. In
addition Z MUST send a Label Map downstream
<X, Y, L'> Y>, except the push on interface I for node D. This allows
upstream traffic to U' go down the MP2MP to other node(s), except the
node from which the traffic was received. Node Z determines the
downstream MP2MP LSR as per section Section 4.3.1.2, and send sends a
MP2MP Label
Withdraw Map upstream <X, Y, L> to U.

3. Shared Trees

The mechanism described above shows how Lu> to build a node D. Since Z is the root of
the tree with Z will not send a single
root MP2MP downstream map and multiple leaves, i.e., a P2MP LSP. One can use essentially
the same mechanism to build Shared Trees with LDP. A Shared Tree can
be used by will not receive
a group of routers that want to multicast traffic among
themselves, i.e., each MP2MP upstream map.

4.3.1.5.2. Root node is both a root node (when it sources
traffic) and not a leaf node (when any other member of

Suppose the group sources
traffic). A Shared Tree offers similar functionality to root node Z receives a MP2MP LSP,
but the underlying multicasting mechanism uses a P2MP LSP. One
example where a Shared Tree is useful is video-conferencing. Another
is Virtual Private LAN Service (VPLS) [7], where Label Map downstream <X, Y,
L> from node D associated with interface I. Z checks whether it
already has forwarding state for some types of
traffic, each device participating in a VPLS must send packets to
every other device in that VPLS.

One way to build a Shared Tree is to build an LDP P2MP LSP rooted at
a common point, the Shared Root (SR), downstream <X, Y>. If not, Z
creates downstream forwarding state and whose leaves are all the
members of the group. Each member of the Shared Tree unicasts
traffic installs a outgoing label L
over interface I. If Z already has forwarding state for downstream
<X, Y>, then Z will add label L over interface I to the SR (using, existing
state.

Node Z checks if it has forwarding state for example, the MP2P LSP created by upstream <X, Y, D>. If
not, Z allocates a label Lu and creates forwarding state to swap Lu
with the
unicast LDP FEC advertised by label swap(s) from the SR); forwarding state downstream <X, Y>,
except the SR then splices this swap for node D. This allows upstream traffic into to go down
the LDP P2MP LSP. The SR may be (but need not be) a
member of MP2MP to other node(s), except the multicast group.

A major advantage of this approach node is that no further protocol
mechanisms beyond was received from.
Root node Z determines the one already described are needed to set up a
Shared Tree. Furthermore, downstream MP2MP LSR D as per
Section 4.3.1.2, and sends a Shared Tree MP2MP Label Map upstream <X, Y, Lu> to
it. Since Z is very efficient in terms
of the multicast state in the network, and is reasonably efficient in
terms root of the bandwidth required to tree Z will not send traffic.

A property of this approach is that a sender MP2MP
downstream map and will not receive a MP2MP upstream map.

4.3.2. MP2MP Label Withdraw

The following lists procedures for generating and processing MP2MP
Label Withdraw messages for nodes that participate in a MP2MP LSP.
An LSR should apply those procedures that apply to it, based on its own
packets as part
role in the MP2MP LSP.

4.3.2.1. MP2MP leaf operation

If a leaf node Z discovers (by means outside the scope of the multicast; thus a sender must be prepared to
recognize and discard packets this
document) that it itself has sent. For is no longer a number leaf of applications (for example, VPLS), this requirement is easy the MP2MP LSP, it SHOULD
send a downstream Label Withdraw <X, Y, L> to
meet. Another consideration its upstream LSR U for
<X, Y>, where L is the various techniques that can be
used label it had previously advertised to splice unicast LDP MP2P LSPs U for
<X,Y>.

Leaf node Z expects the upstream router U to respond by sending a
downstream label release for L and a upstream Label Withdraw for <X,
Y, Lu> to remove Lu from the LDP P2MP LSP; these upstream state. Node Z will
be described in remove
label Lu from its upstream state and send a later revision.

4. Setting up MP2MP LSPs label release message
with LDP

An label Lu to U.

4.3.2.2. MP2MP LSP is much like a P2MP LSP in that it consists of transit node operation

If a single
root node, zero or more transit nodes and one or more leaf LSRs
acting equally as Ingress or Egress LSR. A leaf node participates in
the setup of an MP2MP LSP by establishing both Z receives a downstream LSP,
which is much like a P2MP LSP label withdraw message <X,
Y, L> from the root, node D, it deletes label L from its forwarding state
downstream <X, Y> and an from all its upstream LSP
which is used states for <X, Y>. Node
Z sends a label release message with label L to send traffic toward the root and other leaf nodes.
Transit nodes support D. Since node D is no
longer part of the setup by propagating downstream forwarding state, Z cleans up the
forwarding state upstream <X, Y, D> and sends a upstream Label
Withdraw for <X, Y, Lu> to D.

If deleting L from Z's forwarding state for downstream LSP setup toward <X, Y> results
in no state remaining for <X, Y>, then Z propagates the Label
Withdraw <X, Y, L> to its upstream node U for <X,Y>.

4.3.2.3. MP2MP root and installing the necessary
MPLS forwarding state. node operation

The transmission of packets from procedure when the root node of a MP2MP LSP to the receivers is identical to that for a P2MP
LSP. Traffic from receives a leaf node follows label
withdraw message is the upstream LSP toward same as for transit nodes, except that the
root node and branches downward along the downstream LSP as required
to reach other leaf nodes. Mapping traffic to would not propagate the Label Withdraw upstream (as it has
no upstream).

4.3.2.4. MP2MP LSP may
happen at any leaf node. How that mapping is established is outside Upstream LSR change

The procedure for changing the scope of this document.

Due to how a MP2MP LSP is built a leaf upstream LSR that is sending packets on the MP2MP LSP does not receive its own packets. There same as documented
in Section 2.4.2.4, except it is also no
additional mechanism needed on the root or transit LSR to match
upstream traffic applied to the downstream forwarding state. Packets that
are forwarded over a MP2MP LSP will not traverse a link more than
once, with FECs, using the exception of LAN links which are discussed
procedures described in Section 4.2.1

For the setup of 4.3.1 through Section 4.3.2.3.

5. The LDP MP Status TLV

An LDP MP capable router MAY use an LDP MP Status TLV to indicate
additional status for a MP2MP MP LSP with LDP we define 2 new protocol
entities, the MP2MP downstream FEC and to its remote peers. This includes
signaling to peers that are either upstream FEC element. Both
elements will be used in or downstream of the FEC TLV. LDP
MP capable router. The description value of the MP2MP
elements follow.

4.1. The MP2MP downstream LDP MP status TLV will remain
opaque to LDP and upstream FEC MAY encode one or more status elements.

The structure, encoding and error handling for the MP2MP downstream
and upstream FEC elements are the same LDP MP Status TLV is encoded as for follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| LDP MP Status Type(TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
~ ~
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

LDP MP Status Type: The LDP MP Status Type to be assigned by IANA.

Length: Length of the P2MP FEC element
described LDP MP Status Value in Section 2.1. octets.

Value: One or more LDP MP Status Value elements.

5.1. The LDP MP Status Value Element

The LDP MP Status Value Element that is included in the LDP MP Status
TLV Value has the following encoding.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type: The difference is that two new FEC types
are used: MP2MP downstream type (TBD) and MP2MP upstream type (TBD).

If a FEC TLV contains an MP2MP FEC Element, of the MP2MP FEC LDP MP Status Value Element
MUST is to be assigned
by IANA.

Length: The length of the only FEC Element Value field, in the FEC TLV.

4.2. Using the MP2MP FEC elements

This section defines the rules for the processing and propagation octets.

Value: String of Length octets, to be interpreted as specified by
the MP2MP FEC elements. Type field.

5.2. LDP Messages containing LDP MP Status messages

The following notation is used LDP MP status message may appear either in the
processing rules:

1. MP2MP downstream LSP <X, Y> (or simply downstream <X, Y>): an
MP2MP LSP downstream path with root node address X and opaque
value Y.

2. MP2MP upstream LSP <X, Y, D> (or simply upstream <X, Y, D>): a
MP2MP LSP upstream path for downstream node D label mapping
message or a LDP notification message.

5.2.1. LDP MP Status sent in LDP notification messages

An LDP MP status TLV sent in a notification message must be
accompanied with root node
address X and opaque value Y.

3. MP2MP downstream FEC element <X, Y>: a Status TLV. The general format of the
Notification Message with an LDP MP status TLV is:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Notification (0x0001) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LDP MP Status TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional LDP MP FEC element with root node
address X and opaque value Y TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Label TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Status TLV status code is used for a downstream MP2MP LSP.

4. MP2MP upstream FEC element <X, Y>: a FEC element with root node
address X to indicate that LDP MP status TLV
and opaque value Y used for an upstream MP2MP LSP.

5. additional information follows in the Notification message's
"optional parameter" section. Depending on the actual contents of
the LDP MP status TLV, an LDP P2MP or MP2MP Label Map downstream <X, Y, L>: A Label Map message with a FEC TLV with a single MP2MP downstream FEC element <X, Y> and
label TLV with label L.

6. MP2MP Label Map upstream <X, Y, Lu>: A Label Map message with a
FEC TLV with a single MP2MP upstream FEC element <X, Y> may
also be present to provide context to the LDP MP Status TLV. (NOTE:
Status Code is pending IANA assignment).

Since the notification does not refer to any particular message, the
Message Id and label Message Type fields are set to 0.

5.2.2. LDP MP Status TLV with label Lu.

7. MP2MP in Label Withdraw downstream <X, Y, L>: a Mapping Message

An example of the Label Withdraw Mapping Message defined in RFC3036 is shown
below to illustrate the message with a FEC an Optional LDP MP Status TLV with a single MP2MP downstream
present.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Label Mapping (0x0400) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FEC element
<X, Y> and label TLV with label L.

8. MP2MP Label Withdraw upstream <X, Y, Lu>: a |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Withdraw
message with a FEC TLV with a single MP2MP upstream FEC element
<X, Y> and label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional LDP MP Status TLV with |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional Optional Parameters |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6. Upstream label Lu.

The procedures below are organized by the role which the node plays
in the MP2MP LSP. Node Z knows that it is allocation on a leaf node by LAN

On a discovery
process which is outside the scope of this document. During LAN the
course upstream LSR will send a copy of the protocol operation, the root node recognizes its role
because it owns the root node address. A transit node packet to each
receiver individually. If there is any node
(other more then the root node) that receives a MP2MP Label Map message
(i.e., one that has leaf nodes downstream of it).

Note that a transit node (and indeed receiver on the root node) may also be a
leaf node and LAN
we don't take full benefit of the root node does not have to be an ingress LSR or
leaf multi-access capability of the MP2MP LSP.

4.2.1. MP2MP Label Map upstream and downstream

The following lists procedures for generating and processing MP2MP
Label Map messages for nodes that participate in a MP2MP LSP. An LSR
should apply those procedures that apply to it, based on its role in
network. We may optimize the MP2MP LSP.

For bandwidth consumption on the approach described here if there are several receivers for a
MP2MP LSP LAN and
replication overhead on a LAN, packets are replicated over the LAN. This may
not be optimal; optimizing this case is for further study, see [5].

4.2.1.1. Determining one's upstream MP2MP LSR

Determining the by using upstream label
allocation [4]. Procedures on how to distribute upstream labels
using LDP peer U for is documented in [5].

6.1. LDP Multipoint-to-Multipoint on a MP2MP LSP <X, Y> follows
the LAN

The procedure for to allocate a P2MP LSP described context label on a LAN is defined in Section 2.3.1.1.

4.2.1.2. Determining one's downstream MP2MP [4].
That procedure results in each LSR

A LDP peer U which receives on a MP2MP Label Map downstream from given LAN having a LDP
peer D will treat D context
label which, on that LAN, can be used to identify itself uniquely.
Each LSR advertises its context label as downstream MP2MP LSR.

4.2.1.3. MP2MP leaf node operation

A leaf node Z an upstream-assigned label,
following the procedures of [5]. Any LSR for which the LAN is a
downstream link on some P2MP or MP2MP LSP <X, Y> determines its upstream will allocate an upstream-
assigned label identifying that LSP. When the LSR U for
<X, Y> as per Section 4.2.1.1, allocates forwards a packet
downstream on one of those LSPs, the packet's top label L, must be the
LSR's context label, and sends a MP2MP
Label Map downstream <X, Y, L> to U.

Leaf node Z expects an MP2MP Label Map upstream <X, Y, Lu> from node
U in response to the MP2MP Label Map downstream it sent to node U. Z
checks whether it already has forwarding state for upstream <X, Y>.
If not, Z creates forwarding state to push packet's second label Lu onto is the label
identifying the LSP. We will call the top label the "upstream LSR
label" and the traffic
that Z wants to forward over second label the "LSP label".

6.1.1. MP2MP LSP. How it determines what
traffic to forward on this downstream forwarding

The downstream path of a MP2MP LSP is outside the scope of this
document.

4.2.1.4. MP2MP transit node operation

When node Z receives much like a MP2MP Label Map downstream <X, Y, L> from peer
D associated with interface I, it checks whether it has forwarding
state normal P2MP LSP, so
we will use the same procedures as defined in [5]. A label request
for downstream <X, Y>. If not, Z allocates a LSP label L' and
installs downstream forwarding state is send to swap label L' with the upstream LSR. The label L
over interface I. Z also determines its mapping that
is received from the upstream LSR U contains the LSP label for <X, Y> as
per Section 4.2.1.1, the
MP2MP FEC and sends a the upstream LSR context label. The MP2MP Label Map downstream <X, Y,
L'>
path (corresponding to U.

If Z already has the LSP label) will be installed the context
specific forwarding state for downstream <X, Y>, all that Z
needs table corresponding to do is update its forwarding state. Assuming its old the upstream LSR label.
Packets sent by the upstream router can be forwarded downstream using
this forwarding state was L'-> {<I1, L1> <I2, L2> ..., <In, Ln>}, its new based on a two label lookup.

6.1.2. MP2MP upstream forwarding state becomes L'-> {<I1, L1> <I2, L2> ..., <In, Ln>, <I,
L>}.

Node Z checks whether it already

A MP2MP LSP also has an upstream forwarding state path. Upstream packets
need to be forwarded in the direction of the root and downstream on
any node on the LAN that has a downstream interface for the LSP. For
a given MP2MP LSP on a given LAN, exactly one LSR is considered to be
the upstream <X, Y,
D>. LSR. If an LSR on the LAN receives a packet from one of
its downstream interfaces for the LSP, and if it does, then no further action needs to happen. If it does
not, forward the
packet onto the LAN, it allocates a ensures that the packet's top label Lu and creates a new is the
context label swap for Lu from of the upstream LSR, and that its second label swap(s) from is the forwarding state downstream <X, Y>,
omitting
LSP label that was assigned by the swap on interface I for node D. This allows upstream
traffic to follow LSR.

Other LSRs receiving the MP2MP tree down packet will not be able to other node(s) except tell whether the
node
packet really came from which Z received the MP2MP Label Map downstream <X, Y, L>.
Node Z determines upstream router, but that makes no
difference in the downstream MP2MP processing of the packet. The upstream LSR as per Section 4.2.1.2, will
see its own upstream LSR in the label, and sends this will enable it to
determine that the packet is traveling upstream.

7. Root node redundancy

The root node is a single point of failure for an MP LSP, whether
this is P2MP or MP2MP. The problem is particularly severe for MP2MP Label Map upstream <X, Y, Lu> to
LSPs. In the case of MP2MP LSPs, all leaf nodes must use the same
root node D.

Transit to set up the MP2MP LSP, because otherwise the traffic
sourced by some leafs is not received by others. Because the root
node Z will also receive is the single point of failure for an MP LSP, we need a fast and
efficient mechanism to recover from a MP2MP Label Map upstream <X, Y,
Lu> root node failure.

An MP LSP is uniquely identified in response to the MP2MP Label Map downstream sent to node U
associated with interface Iu. Node Z will add label swap Lu over
interface Iu to network by the forwarding state upstream <X, Y, D>. This allows
packets to go up opaque value
and the tree towards root node address. It is likely that the root node.

4.2.1.5. MP2MP node for an MP
LSP is defined statically. The root node operation

4.2.1.5.1. Root address may be configured
on each leaf statically or learned using a dynamic protocol. How
leafs learn about the root node is also a leaf out of the scope of this document.

Suppose root/leaf that for the same opaque value we define two (or more) root
node Z receives addresses and we build a tree to each root using the same opaque
value. Effectively these will be treated as different MP LSPs in the
network. Once the trees are built, the procedures differ for P2MP
and MP2MP Label Map downstream <X, Y,
L> from LSPs. The different procedures are explained in the
sections below.

7.1. Root node D associated with interface I. Z checks whether it
already has forwarding state downstream <X, Y>. If not, Z creates
forwarding state redundancy - procedures for downstream P2MP LSPs

Since all leafs have set up P2MP LSPs to push label L all the roots, they are
prepared to receive packets on either one of these LSPs. However,
only one of the roots should be forwarding traffic at any given time,
for the following reasons: 1) to achieve bandwidth savings in the
network and 2) to ensure that the receiving leafs don't receive
duplicate packets (since one cannot assume that Z
wants to forward down the MP2MP LSP. How it determines what traffic receiving leafs
are able to forward on this MP2MP LSP discard duplicates). How the roots determine which one
is the active sender is outside the scope of this document.
If Z already has forwarding state for downstream <X, Y>, then Z will
add the label push

7.2. Root node redundancy - procedures for L over interface I MP2MP LSPs

Since all leafs have set up an MP2MP LSP to it.

Node Z checks if it has forwarding state each one of the root
nodes for upstream <X, Y, D>. If
not, Z allocates this opaque value, a label Lu and creates upstream forwarding state sending leaf may pick either of the
two (or more) MP2MP LSPs to
push Lu with forward a packet on. The leaf nodes
receive the label push(s) from packet on one of the forwarding state downstream
<X, Y>, except MP2MP LSPs. The client of the push MP2MP
LSP does not care on interface I which MP2MP LSP the packet is received, as long
as they are for node D. This allows
upstream traffic to go down the same opaque value. The sending leaf MUST only
forward a packet on one MP2MP LSP at a given point in time. The
receiving leafs are unable to other node(s), except discard duplicate packets because they
accept on all LSPs. Using all the
node from which available MP2MP LSPs we can
implement redundancy using the traffic was received. Node Z determines following procedures.

A sending leaf selects a single root node out of the
downstream MP2MP LSR as per section Section 4.2.1.2, available roots
for a given opaque value. A good strategy MAY be to look at the
unicast routing table and sends select a
MP2MP Label Map upstream <X, Y, Lu> to node D. Since Z root that is closest in terms of
the unicast metric. As soon as the root address of the tree Z will not send a MP2MP downstream map and will not receive
a MP2MP upstream map.

4.2.1.5.2. Root active root
disappears from the unicast routing table (or becomes less
attractive) due to root node is not a or link failure, the leaf

Suppose can select a
new best root address and start forwarding to it directly. If
multiple root nodes have the same unicast metric, the highest root
node Z receives addresses MAY be selected, or per session load balancing MAY be
done over the root nodes.

All leafs participating in a MP2MP Label Map dowbstream <X, Y,
L> from node D associated with interface I. Z checks whether it
already has forwarding state LSP MUST join to all the available
root nodes for downstream <X, Y>. If not, Z
creates downstream forwarding state and installs a outgoing label L
over interface I. If Z already has forwarding state for downstream
<X, Y>, then Z will add label L over interface I to given opaque value. Since the existing
state.

Node Z checks if sending leaf may pick
any MP2MP LSP, it has forwarding state must be prepared to receive on it.

The advantage of pre-building multiple MP2MP LSPs for upstream <X, Y, D>. If
not, Z allocates a label Lu and creates forwarding state to swap Lu
with the label swap(s) single opaque
value is that convergence from a root node failure happens as fast as
the forwarding state downstream <X, Y>,
except the swap unicast routing protocol is able to notify. There is no need for node D. This allows upstream traffic
an additional protocol to go down
the MP2MP advertise to other node(s), except the leaf nodes which root node
is was received from.
Root node Z determines the downstream active root. The root selection is a local leaf policy that
does not need to be coordinated with other leafs. The disadvantage
of pre-building multiple MP2MP LSPs is that more label resources are
used, depending on how many root nodes are defined.

8. Make Before Break (MBB)

An LSR D selects as per
Section 4.2.1.2, and sends a MP2MP Label Map its upstream <X, Y, Lu> to
it. Since Z LSR for a MP LSP the LSR that is its
next hop to the root of the tree Z will not send a MP2MP
downstream map and will not receive LSP. When the best path to reach the
root changes the LSR must choose a MP2MP new upstream map.

4.2.2. MP2MP Label Withdraw

The following lists procedures for generating LSR. Sections
Section 2.4.2.4 and processing MP2MP
Label Withdraw messages for nodes that participate Section 4.3.2.4 describe these procedures.

When the best path to the root changes the LSP may be broken
temporarily resulting in packet loss until the LSP "reconverges" to a MP2MP LSP.
An
new upstream LSR. The goal of MBB when this happens is to keep the
duration of packet loss as short as possible. In addition, there are
scenarios where the best path from the LSR should apply those procedures that apply to it, based on its
role in the MP2MP LSP.

4.2.2.1. MP2MP leaf operation

If root changes but
the LSP continues to forward packets to the prevous next hop to the
root. That may occur when a link comes up or routing metrics change.
In such a leaf node Z discovers (by means outside case a new LSP should be established before the scope of this
document) that it old LSP is no longer a leaf of
removed to limit the MP2MP LSP, it SHOULD
send duration of packet loss. The procedures
described below deal with both scenarios in a downstream Label Withdraw <X, Y, L> to its upstream way that an LSR U for
<X, Y>, where L is the label it had previously advertised does
not need to U for
<X,Y>.

Leaf node Z expects know which of the events described above caused its
upstream router U for an MBB LSP to respond by sending change.

This MBB procedures are an optional extension to the MP LSP building
procedures described in this draft.

8.1. MBB overview

The MBB procedues use additional LDP signaling.

Suppose some event causes a downstream label release for L and LSR-D to select a new upstream Label Withdraw
LSR-U for <X,
Y, Lu> to remove Lu from the upstream state. Node Z will remove
label Lu from its upstream state and send a label release message
with label Lu FEC-A. The new LSR-U may already be forwarding packets for
FEC-A; that is, to U.

4.2.2.2. MP2MP transit node operation

If a transit node Z downstream LSR's other than LSR-D. After LSR-U
receives a downstream label withdraw message <X,
Y, L> for FEC-A from node D, LSR-D, it deletes label L from its forwarding state
downstream <X, Y> and will notify LSR-D when it
knows that the LSP for FEC-A has been established from all the root to
itself. When LSR-D receives this MBB notification it will change its upstream states
next hop for <X, Y>. Node
Z sends a label release message with label L the LSP root to D. Since node D LSR-U.

The assumption is no
longer part of that if LSR-U has received an MBB notification from
its upstream router for the downstream FEC-A LSP and has installed forwarding state, Z cleans up
state the LSP it is capable of forwarding state upstream <X, Y, D> packets on the LSP. At
that point LSR-U should signal LSR-D by means of an MBB notification
that it has become part of the tree identified by FEC-A and sends a upstream Label
Withdraw for <X, Y, Lu> that
LSR-D should initiate its switchover to D.

If deleting L from Z's forwarding state the LSP.

At LSR-U the LSP for downstream <X, Y> results FEC-A may be in 1 of 3 states.

1. There is no state remaining for <X, Y>, then Z propagates FEC-A.

2. State for FEC-A exists and LSR-U is waiting for MBB notification
that the LSP from the root to it exists.

3. State for FEC-A exists and the MBB notification has been
received.

After LSR-U receives LSR-D's Label
Withdraw <X, Y, L> Mapping message for FEC-A LSR-U
MUST NOT reply with an MBB notification to LSR-D until its upstream node U state for <X,Y>.

4.2.2.3. MP2MP root node operation

The procedure when
the root node LSP is state #3 above. If the state of a MP2MP the LSP receives a label
withdraw message at LSR-U is state
#1 or #2, LSR-U should remember receipt of the same as Label Mapping message
from LSR-D while waiting for an MBB notification from its upstream
LSR for transit nodes, except that the
root node would not propagate LSP. When LSR-U receives the Label Withdraw MBB notification from its
upstream (as LSR it has
no upstream).

4.2.2.4. MP2MP Upstream transitions to LSP state #3 and sends an MBB
notification to LSR-D.

8.2. The MBB Status code

As noted in Section 8.1, the procedures to establish an MBB MP LSP
are different from those to establish normal MP LSPs.

When a downstream LSR change

The procedure sends a Label Mapping message for changing the MP LSP to its
upstream LSR is the same as documented
in Section 2.3.2.4, except it is applied MAY include an LDP MP Status TLV that carries a MBB
Status Code to MP2MP FECs, using the indicate MBB procedures described in Section 4.2.1 through Section 4.2.2.3.

5. Upstream label allocation on Ethernet networks

On Ethernet networks apply to the LSP. This new
MBB Status Code MAY also appear in an LDP Notification message used
by an upstream LSR will send a copy of the packet to each receiver individually. If there is more then one receiver on
the Ethernet we don't take full benefit of the multi-access
capability of signal LSP state #3 to the network. We may optimize downstream LSR; that
is, that the bandwidth consumption
on upstream LSR's state for the Ethernet LSP exists and replication overhead on the that it has
received notification from its upstream LSR by using
upstream label allocation [5]. Procedures on how to distribute
upstream labels using LDP that the LSP is documented in [6].

6. Root node redundancy for MP2MP LSPs

MP2MP leaf nodes must use the same root node to setup state
#3.

The MBB Status is a type of the MP2MP LSP.
Otherwise there will LDP MP Status Value Element as
described in Section 5.1. It is encoded as follows:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBB Type = 1 | Length = 1 | Status code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

MBB Type: Type 1 (to be partitioned MP2MP LSP and traffic sourced by
some leafs is not received assigned by others. Having a single root node for
a MP2MP LSP IANA)

Length: 1

Status code: 1 = MBB request
2 = MBB ack

8.3. The MBB capability

An LSR MAY advertise that it is a single point capable of failure, which is not preferred. We
need a fast and efficient mechanism to recover from a root node
failure.

6.1. Root node redundancy procedure

It is likely that handling MBB LSPs using
the root node for a MP2MP LSP is capability advertisement as defined
statically. in [6]. The root node address may be configured on each leaf
statically or learned using a dynamic protocol. How MP2MP leafs
learn about the root node is out of LDP MP MBB
capability has the scope of this document. A
MP2MP LSP following format:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0| LDP MP MBB Capability | Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Reserved |
+-+-+-+-+-+-+-+-+

Note: LDP MP MBB Capability (Pending IANA assignment)

If an LSR has not advertised that it is uniquely identified by MBB capable, its LDP peers
MUST NOT send it messages which include MBB parameters. If an LSR
receives a opaque value Label Mapping message with a MBB parameter from downstream
LSR-D and the root node
address. Suppose its upstream LSR-U has not advertised that for it is MBB
capable, the same opaque value we define two root
node addresses and we build a tree LSR MUST send an MBB notification immediatly to each root using the same opaque
value. Effectively these LSR-U
(see Section Section 8.4). If this happens an MBB MP LSP will not be treated as different MP2MP LSPs in
the network. Since all leafs have setup
established, but normal a MP2MP MP LSP to each one of
the root nodes for this opaque value, a sending leaf may pick either
of will be the two result.

8.4. The MBB procedures

8.4.1. Terminology

1. MBB LSP <X, Y>: A P2MP or MP2MP LSPs Make Before Break (MBB) LSP entry
with Root Node Address X and Opaque Value Y.

2. A(N, L): An Accepting element that consists of an upstream
Neighbor N and Local label L. This LSR assigned label L to forward
neighbor N for a packet on. The leaf nodes will
receive the packet on one of specific MBB LSP. For an active element the MP2MP LSPs,
corresponding Label is stored in the client label forwarding database.

3. iA(N, L): An inactive Accepting element that consists of the MP2MP
LSP does not care on which MP2MP LSP the packet was received from, as
long as they are an
upstream neighbor N and local Label L. This LSR assigned label L
to neighbor N for the same opaque value. The sending leaf MUST
only forward a packet on one MP2MP LSP at a given point specific MBB LSP. For an inactive element
the corresponding Label is not stored in time. The
receiving leafs are unable to discard duplicate packets because they
accept on both LSPs. Using both these MP2MP LSPs we can implement
redundancy using the following procedures. label forwarding
database.

4. F(N, L): A sending leaf selects a single root node out Forwarding state that consists of the available roots downstream Neighbor
N and Label L. This LSR is sending label packets with label L to
neighbor N for a given opaque value. specific FEC.

5. F'(N, L): A good strategy MAY be Forwarding state that has been marked for sending a
MBB Notification message to look at the
unicast routing table Neighbor N with Label L.

6. MBB Notification <X, Y, L>: A LDP notification message with a MP
LSP <X, Y>, Label L and select MBB Status code 2.

7. MBB Label Map <X, Y, L>: A P2MP Label Map or MP2MP Label Map
downstream with a root FEC element <X, Y>, Label L and MBB Status code
1.

8.4.2. Accepting elements

An accepting element represents a specific label value L that is closest according in
terms of unicast metric. As soon as the root address of our active
root disappears from the unicast routing table (or becomes less
attractive) due has
been advertised to root node or link failure we can select a new best
root address neighbor N for a MBB LSP <X, Y> and start forwarding to it directly. If multiple root
nodes is a
candidate for accepting labels switched packets on. An LSR can have the same unicast metric, the highest root node addresses
MAY be selected, or we MAY do per session load balancing over the
root nodes.

All leafs participating in
two accepting elements for a MP2MP specific MBB LSP <X, Y> LSP, only one of
them MUST join to all be active. An active element is the available
root nodes element for a given opaque value. Since which the sending leaf may pick
any MP2MP LSP, it must be prepared to receive on it.

The advantage of pre-building multiple MP2MP LSPs for a single opaque
label value has been installed in the label forwarding database. An
inactive accepting element is that we can converge from created after a root node failure as fast as the
unicast routing protocol new upstream LSR is able to notify us. There
chosen and is no need for
an additional protocol to advertise pending to replace the leaf nodes which root node
is active element in the label
forwarding database. Inactive elements only exist temporarily while
switching to a new upstream LSR. Once the switch has been completed
only one active root. The root selection element remains. During network convergence it is a local leaf policy
possible that
does not need to be coordinated with an inactive accepting element is created while an other leafs. The disadvantage
inactive accepting element is pending. If that we are using more happens the older
inactive accepting element MUST be replaced with an newer inactive
element. If an accepting element is removed a Label Withdraw has to
be send for label resources depending on how many root
nodes are defined.

7. Make before break

An L to neighbor N for <X, Y>.

8.4.3. Procedures for upstream LSR is chosen based on the best path change

Suppose a node Z has a MBB LSP <X, Y> with an active accepting
element A(N1, L1). Due to reach the root of
the MP LSP. When the a routing change it detects a new best
path to reach the for root changes it needs to
choose X and selects a new upstream LSR. Section 2.3.2.4 LSR N2. Node Z allocates
a new local label L2 and Section 4.2.2.4
describes these procedures. When the best path to the root changes
the LSP may be broken creates an inactive accepting element iA(N2,
L2). Node Z sends MBB Label Map <X, Y, L2>to N2 and packet forwarding is interrupted, in that
case it needs to converge waits for the
new upstream LSR N2 to respond with a MBB Notification for <X, Y,
L2>. During this transition phase there are two accepting elements,
the element A(N1, L1) still accepting packets from N1 over label L1
and the new inactive element iA(N2, L2).

While waiting for the MBB Notification from upstream LSR ASAP. There are also
scenarios where the best path changed, but the LSP N2, it is still
forwarding packets. That happens when links come up or routing
metrics are changed. In
possible that case it would like an other transition occurs due to build a routing change.
Suppose the new LSP
before it breaks upstream LSR is N3. An inactive element iA(N3, L3)
is created and the old LSP inactive element iA(N2, L2) MUST be removed.
A label withdraw MUST be sent to minimize the traffic interruption. N2 for <X, Y, L2&gt. The approuch described below deals with both scenarios and does not
require LDP to know which of MBB
Notification for <X, Y, L2> from N2 will be ignored because the events above caused
inactive element is removed.

It is possible that the MBB Notification from upstream
router to change. The approuch below LSR is an optional extention never
received due to link or node failure. To prevent waiting
indefinitely for the MBB Notification a timeout SHOULD be applied.
As soon as the timer expires, the
MP LSP building procedures described in this draft.

7.1. Protocol event

An approach is to use additional signaling in LDP. Section 8.4.5 are
applied as if a MBB Notification was received for the inactive
element.

8.4.4. Receiving a Label Map with MBB status code

Suppose node Z has state for a
downstream LSR-D is changing to MBB LSP <X, Y> and receives a MBB
Label Map <X, Y, L2> from N2. A new upstream LSR-U for FEC-A, this
LSR-U may already be forwarding packets for this FEC-A. Based on the
existence of state for FEC-A, LSR-U F(N2, L2) will send a notification to the
LSR-D
be added to initiate the switchover. The assumption is that MP LSP if our
upstream LSR-U has state for the FEC-A and it has received a
notification from its upstream router, then did not already exist. If this LSR MBB LSP
has an active accepting element or node Z is forwarding
packets for this FEC-A and it can send the root of the MBB LSP
a MBB notification back to
initiate the switchover. You could say there <X, Y, L2)> is an explicit
notification send to tell the LSR node N2. If node Z has an
inactive accepting element it became part of marks the tree identified by
FEC-A. LSR-D can be in 3 different states.

1. There no Forwarding state for as <X, Y,
F'(N2, L2)>.

8.4.5. Receiving a given FEC-A.

2. State for FEC-A Notification with MBB status code

Suppose node Z receives a MBB Notification <X, Y, L> from N. If node
Z has just been created and is waiting for
notification.

3. State state for FEC-A exists MBB LSP <X, Y> and notification an inactive accepting element
iA(N, L) that matches with N and L, we activate this accepting
element and install label L in the label forwarding database. If an
other active accepting was received.

Suppose LSR-D sends a present it will be removed from the label mapping
forwarding database.

If this MBB LSP <X, Y> also has Forwarding states marked for FEC-A to LSR-U. LSR-U must
only reply with a notification sending
MBB Notifications, like <X, Y, F'(N2, L2)>, MBB Notifications are
send to LSR-D if it is in state #3 as
described above. these downstream LSRs. If LSR-U node Z receives a MBB Notification
for an accepting element that is in state 1 not inactive or 2, it should remember it
has received a label mapping from LSR-D which does not match the
Label value and Neighbor address, the MBB notification is waiting ignored.

8.4.6. Node operation for MP2MP LSPs

The procedures described above apply to the downstream path of a
notification. As soon
MP2MP LSP. The upstream path of the MP2MP is setup as LSR-U received normal without
including a notification from its
upstream LSR it can move to state #3 and trigger notifications MBB Status code. If the MBB procedures apply to its a MP2MP
downstream LSR's that requested it. More details will be added FEC element, the upstream path to a node N is only
installed in the next revision label forwarding database if node N is part of the
active accepting element. If node N is part of an inactive accepting
element, the draft.

8. upstream path is installed when this inactive accepting
element is activated.

9. Security Considerations

The same security considerations apply as for the base LDP
specification, as described in [1].

10. IANA considerations

This document creates a new name space (the LDP MP Opaque Value
Element type) that is to be managed by IANA. Also, this IANA, and the allocation of
the value 1 for the type of Generic LSP Identifier.

This document requires allocation of three new LDP FEC element Element types:

1. the P2MP
type, FEC type - requested value 0x04

2. the MP2MP-up and FEC type - requested value 0x05

3. the MP2MP-down types.

10. FEC type - requested value 0x06

This document requires the assignment of three new code points for
three new Capability Parameter TLVs, corresponding to the
advertisement of the P2MP, MP2MP and MBB capabilities. The values
requested are:

P2MP Capability Parameter - requested value 0x0508

MP2MP Capability Parameter - requested value 0x0509

MBB Capability Parameter - requested value 0x050A

This document requires the assignment of a LDP Status TLV code to
indicate a LDP MP Status TLV is following in the Notification
message. The value requested is:

LDP MP status - requested value 0x0000002C

This document requires the assigment of a new code point for a LDP MP
Status TLV. The value requested is:

LDP MP Status TLV Type - requested value 0x096D

This document creates a new name space (the LDP MP Status Value
Element type) that is to be managed by IANA, and the allocation of
the value 1 for the type of MBB Status.

11. Acknowledgments

The authors would like to thank the following individuals for their
review and contribution: Nischal Sheth, Yakov Rekhter, Rahul
Aggarwal, Arjen Boers, Eric Rosen, Nidhi Bhaskar, Toerless Eckert and Eckert,
George Swallow.

11. Swallow, Jin Lizhong and Vanson Lim.

12. Contributing authors

Below is a list of the contributing authors in alphabetical order:

Shane Amante
Level 3 Communications, LLC
1025 Eldorado Blvd
Broomfield, CO 80021
US
Email: Shane.Amante@Level3.com

Luyuan Fang
AT&T
200 Laurel Avenue, Room C2-3B35
Middletown, NJ 07748
Cisco Systems
300 Beaver Brook Road
Boxborough, MA 01719
US
Email: luyuanfang@att.com lufang@cisco.com

Hitoshi Fukuda
NTT Communications Corporation
1-1-6, Uchisaiwai-cho, Chiyoda-ku
Tokyo 100-8019,
Japan
Email: hitoshi.fukuda@ntt.com
Yuji Kamite
NTT Communications Corporation
Tokyo Opera City Tower
3-20-2 Nishi Shinjuku, Shinjuku-ku,
Tokyo 163-1421,
Japan
Email: y.kamite@ntt.com

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

Ina Minei
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: ina@juniper.net

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

Bob Thomas
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough, MA, 01719
E-mail: rhthomas@cisco.com

Lei Wang
Telenor
Snaroyveien 30
Fornebu 1331
Norway
Email: lei.wang@telenor.com
IJsbrand Wijnands
Cisco Systems, Inc.
De kleetlaan 6a
1831 Diegem
Belgium
E-mail: ice@cisco.com

12.

13. References

12.1.

13.1. Normative References

[1] Andersson, L., Doolan, P., Feldman, N., Fredette, A., and B.
Thomas, "LDP Specification", RFC 3036, January 2001.

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

[3] Reynolds, J. and J. Postel, J., "Assigned Numbers", Numbers: RFC 1700 is Replaced by an On-
line Database", RFC 1700,
October 1994. 3232, January 2002.

[4] Roux, J., "Requirements for point-to-multipoint extensions to
the Label Distribution Protocol",
draft-leroux-mpls-mp-ldp-reqs-03 (work in progress),
February 2006.

[5] Aggarwal, R., "MPLS Upstream Label Assignment and Context
Specific Label Space", draft-raggarwa-mpls-upstream-label-01 draft-ietf-mpls-upstream-label-02 (work
in progress), October 2005.

[6] March 2007.

[5] Aggarwal, R. and J. Roux, "MPLS Upstream Label Assignment for
RSVP-TE and
LDP", draft-raggarwa-mpls-rsvp-ldp-upstream-00 draft-ietf-mpls-ldp-upstream-01 (work in progress), July 2005.

12.2.
March 2007.

[6] Thomas, B., "LDP Capabilities",
draft-ietf-mpls-ldp-capabilities-00 (work in progress),
May 2007.

13.2. Informative References

[7] Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual
Private Networks (L2VPNs)", draft-ietf-l2vpn-l2-framework-05
(work in progress), June 2004. RFC 4664, September 2006.

[8] Aggarwal, R., Papadimitriou, D., and S. Yasukawa, "Extensions
to RSVP-TE Resource Reservation Protocol - Traffic Engineering
(RSVP-TE) for Point-to-Multipoint TE
LSPs", draft-ietf-mpls-rsvp-te-p2mp-06 Label Switched Paths
(LSPs)", RFC 4875, May 2007.

[9] Roux, J., "Requirements for Point-To-Multipoint Extensions to
the Label Distribution Protocol",
draft-ietf-mpls-mp-ldp-reqs-02 (work in progress),
August 2006.

[9] March 2007.

[10] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP VPNs",
draft-ietf-l3vpn-2547bis-mcast-02
draft-ietf-l3vpn-2547bis-mcast-00 (work in progress),
June 2006. 2005.

Authors' Addresses

Ina Minei
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US

Email: ina@juniper.net

Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US

Email: kireeti@juniper.net

IJsbrand Wijnands
Cisco Systems, Inc.
De kleetlaan 6a
Diegem 1831
Belgium

Email: ice@cisco.com

Bob Thomas
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough 01719
US

Email: rhthomas@cisco.com

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