draft-ietf-teas-p2mp-loose-path-reopt-00.txt   draft-ietf-teas-p2mp-loose-path-reopt-01.txt 
MPLS Working Group Tarek Saad, Ed. TEAS Working Group Tarek Saad, Ed.
Internet-Draft Rakesh Gandhi, Ed. Internet-Draft Rakesh Gandhi, Ed.
Intended status: Standards Track Zafar Ali Intended status: Standards Track Zafar Ali
Expires: June 11, 2015 Cisco Systems, Inc. Expires: September 2, 2015 Cisco Systems, Inc.
Robert H. Venator Robert H. Venator
Defense Information Systems Agency Defense Information Systems Agency
Yuji Kamite Yuji Kamite
NTT Communications Corporation NTT Communications Corporation
December 8, 2014 March 1, 2015
Extensions to Resource Reservation Protocol For Re-optimization Extensions to Resource Reservation Protocol For Re-optimization
of Loosely Routed Point-to-Multipoint Traffic Engineering LSPs of Loosely Routed Point-to-Multipoint Traffic Engineering LSPs
draft-ietf-teas-p2mp-loose-path-reopt-00 draft-ietf-teas-p2mp-loose-path-reopt-01
Abstract Abstract
For a Traffic Engineered (TE) point-to-multipoint (P2MP) Label For a Traffic Engineered (TE) point-to-multipoint (P2MP) Label
Switched Path (LSP), it is preferable in some cases to re-evaluate Switched Path (LSP), it is preferable in some cases to re-evaluate
and re-optimize the entire P2MP-TE LSP by re-signaling all its and re-optimize the entire P2MP-TE LSP by re-signaling all its
Source-to-Leaf (S2L) sub-LSP(s). Existing mechanisms, a mechanism Source-to-Leaf (S2L) sub-LSP(s). Existing mechanisms, a mechanism
for an ingress Label Switched Router (LSR) to trigger a new path re- for an ingress Label Switched Router (LSR) to trigger a new path re-
evaluation request and a mechanism for a mid-point LSR to notify an evaluation request and a mechanism for a mid-point LSR to notify an
availability of a preferred path, operate on an individual or a sub- availability of a preferred path, operate on an individual or a sub-
group of S2L sub-LSP(s) basis only. group of S2L sub-LSP(s) basis only.
This document defines RSVP-TE signaling extensions to allow an This document defines RSVP-TE signaling extensions to allow an
ingress node of a P2MP-TE LSP to request the re-evaluation of the ingress node of a P2MP-TE LSP to request the re-evaluation of the
entire LSP tree containing one or more S2L sub-LSPs whose paths are entire LSP tree containing one or more S2L sub-LSPs whose paths are
loose (or abstract) hop expanded, and for a mid-point LSR to notify loose (or abstract) hop expanded, and for a mid-point LSR to notify
to the ingress node that a preferable tree exists for the entire to the ingress node that a preferable tree exists for the entire
P2MP-TE LSP. This document also defines markers to indicate P2MP-TE LSP. For re-optimizing a group of S2L sub-LSP(s) in a tree,
beginning and end of a S2L sub-LSP descriptor list when RSVP message an S2L sub-LSP descriptor list can be used to signal one or more S2L
needs to be fragmented due to large number of S2L sub-LSPs when sub-LSPs in an RSVP message. This document defines markers to
performing re-optimization. indicate beginning and end of an S2L sub-LSP descriptor list when the
RSVP message needs to be fragmented due to large number of S2L
sub-LSPs in the message when performing sub-group based re-
optimization.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Existing Mechanism For Re-optimizing Loosely Routed 1.1. Loosely Routed Inter-domain P2MP-TE LSP Tree . . . . . . . 5
P2MP-TE LSP . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Existing Mechanism For Tree-Based P2MP-TE LSP
1.2. Combining Multiple Path Messages for Re-optimization . . . 5 Re-optimization . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3. Existing Mechanism For Sub-Group-Based P2MP-TE LSP
2.1. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 7 Re-optimization . . . . . . . . . . . . . . . . . . . . . 6
2.2. Nomenclatures . . . . . . . . . . . . . . . . . . . . . . 7 2. Conventions Used in This Document . . . . . . . . . . . . . . 7
2.3. Conventions Used in This Document . . . . . . . . . . . . 7 2.1. Key Word Definitions . . . . . . . . . . . . . . . . . . . 7
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Nomenclatures . . . . . . . . . . . . . . . . . . . . . . 8
3. Signaling Procedure For Loosely Routed P2MP-TE LSP 3. Signaling Procedure For Loosely Routed P2MP-TE LSP
Re-optimization . . . . . . . . . . . . . . . . . . . . . . . 8 Re-optimization . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Tree Based Re-optimization . . . . . . . . . . . . . . . . 8 3.1. Tree-Based Re-optimization . . . . . . . . . . . . . . . . 8
3.2. Sub-group Based Re-optimization . . . . . . . . . . . . . 8 3.2. Sub-Group-Based Re-optimization Using Markers . . . . . . 9
4. RSVP Signaling Extensions . . . . . . . . . . . . . . . . . . 9 4. Message and Object Definitions . . . . . . . . . . . . . . . . 10
4.1. P2MP-TE Tree Re-evaluation Request Flag . . . . . . . . . 9 4.1. P2MP-TE Tree Re-evaluation Request Flag . . . . . . . . . 10
4.2. Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 10 4.2. Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 10
4.3. Markers For S2L sub-LSP Descriptor . . . . . . . . . . . . 10 4.3. Markers For S2L sub-LSP Descriptor . . . . . . . . . . . . 11
5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. P2MP-TE Tree Re-evaluation Request Flag . . . . . . . . . 12 7.1. P2MP-TE Tree Re-evaluation Request Flag . . . . . . . . . 12
7.2. Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 12 7.2. Preferable P2MP-TE Tree Exists Path Error Sub-code . . . . 13
7.3. BEGIN and END Markers For S2L sub-LSP Descriptor . . . . . 12 7.3. BEGIN and END Markers For S2L sub-LSP Descriptor . . . . . 13
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . . 14 9.2. Informative References . . . . . . . . . . . . . . . . . . 15
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
This document defines Resource Reservation Protocol - Traffic This document defines Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) [RFC2205] [RFC3209] signaling extensions for Engineering (RSVP-TE) [RFC2205] [RFC3209] signaling extensions for
re-optimizing loosely routed Point-to-Multipoint (P2MP) Traffic re-optimizing loosely routed Point-to-Multipoint (P2MP) Traffic
Engineered (TE) Label Switched Paths (LSPs) [RFC4875] in an Engineered (TE) Label Switched Paths (LSPs) [RFC4875] in an
Multi-Protocol Label Switching (MPLS) and/or Generalized MPLS (GMPLS) Multi-Protocol Label Switching (MPLS) and/or Generalized MPLS (GMPLS)
networks. networks.
skipping to change at page 4, line 31 skipping to change at page 4, line 31
that is not a simple abstract node (that is, an abstract node that that is not a simple abstract node (that is, an abstract node that
identifies more than one node). This is often the case with identifies more than one node). This is often the case with
inter-domain P2MP-TE LSPs where Path Computation Element (PCE) is not inter-domain P2MP-TE LSPs where Path Computation Element (PCE) is not
used [RFC5440]. used [RFC5440].
As per [RFC4875], an ingress node may re-optimize the entire P2MP-TE As per [RFC4875], an ingress node may re-optimize the entire P2MP-TE
LSP by re-signaling all its S2L sub-LSP(s) or may re-optimize LSP by re-signaling all its S2L sub-LSP(s) or may re-optimize
individual or group of S2L sub-LSP(s) i.e. individual or group of individual or group of S2L sub-LSP(s) i.e. individual or group of
destination(s). destination(s).
1.1. Existing Mechanism For Re-optimizing Loosely Routed P2MP-TE LSP
[RFC4736] defines RSVP signaling extensions for re-optimizing loosely [RFC4736] defines RSVP signaling extensions for re-optimizing loosely
routed P2P TE LSP(s) as follows. routed Point-to-Point (P2P) TE LSP(s) as follows:
- A mid-point LSR that expands loose next-hop(s) sends a solicited or o A mid-point LSR that expands loose next-hop(s) sends a solicited
unsolicited PathErr with the Notify error code (25 as defined in or unsolicited PathErr with the Notify error code (25 as defined in
[RFC3209]) with sub-code 6 to indicate "Preferable Path Exists" to [RFC3209]) with sub-code 6 to indicate "Preferable Path Exists" to
the ingress node. the ingress node.
- An ingress node triggers a path re-evaluation request at all o An ingress node triggers a path re-evaluation request at all
mid-point LSR(s) that expands loose next-hop(s) by setting the "Path mid-point LSR(s) that expands loose next-hop(s) by setting the "Path
Re-evaluation Request" flag (0x20) in SESSION_ATTRIBUTES Object in Re-evaluation Request" flag (0x20) in SESSION_ATTRIBUTES Object in
the Path message. the Path message.
- The ingress node upon receiving this PathErr either solicited or o The ingress node upon receiving this PathErr either solicited or
unsolicited initiates re-optimization of the LSP. unsolicited initiates re-optimization of the LSP with a different
LSP-ID.
Following Sections discuss the issues arising when using existing
mechanism defined in [RFC4736] for re-optimizing loosely routed P2MP-
TE LSPs.
1.1. Loosely Routed Inter-domain P2MP-TE LSP Tree
An example of a loosely routed inter-domain P2MP-TE LSP tree is shown
in Figure 1. In this example, the P2MP-TE LSP tree consists of 3 S2L
sub-LSPs, to destinations (i.e. leafs) R10, R11 and R12 from the
ingress node (i.e. source) R1. Nodes R2 and R5 are branch nodes and
nodes ABR3, ABR4, ABR7, ABR8 and ABR9 are area border routers. For
the S2L sub-LSP to destination R10, nodes ABR3, ABR7 and R10 are
defined as loose hops. For the S2L sub-LSP to destination R11, nodes
ABR3, ABR8 and R11 are defined as loose hops. For the S2L sub-LSP to
destination R12, nodes ABR4, ABR9 and R12 are defined as loose hops.
<--area1--><--area0--><-area2->
ABR7---R10
/
/
ABR3---R5
/ \
/ \
R1---R2 ABR8---R11
\
\
ABR4---R6
\
\
ABR9---R12
Figure 1: An Example of Loosely Routed Inter-domain P2MP-TE LSP Tree
1.2. Existing Mechanism For Tree-Based P2MP-TE LSP Re-optimization
[RFC4736] does not define signaling extensions specific for [RFC4736] does not define signaling extensions specific for
re-optimizing entire P2MP-TE LSP tree. Mechanisms defined in re-optimizing entire P2MP-TE LSP tree. Mechanisms defined in
[RFC4736] can be used for signaling the re-optimization of individual [RFC4736] can be used for signaling the re-optimization of individual
or group of S2L sub-LSP(s). However, to use [RFC4736] mechanisms for or group of S2L sub-LSP(s). However, to use [RFC4736] mechanisms for
re-optimizing an entire P2MP-TE LSP tree, an ingress node needs to re-optimizing an entire P2MP-TE LSP tree, an ingress node needs to
send the path re-evaluation requests on all (typically 100s of) S2L send the path re-evaluation requests on all (typically 100s of) S2L
sub-LSPs and the mid-point LSR to notify PathErrs for all S2L sub-LSPs and the mid-point LSR to notify PathErrs for all S2L
sub-LSPs. Such a procedure may lead to the following issues: sub-LSPs. Such procedures may lead to the following issues:
- A mid-point LSR that expands loose next-hop(s) may have to o A mid-point LSR that expands loose next-hop(s) may have to
accumulate the received path re-evaluation request(s) for all S2L accumulate the received path re-evaluation request(s) for all S2L
sub-LSPs (e.g, by using a wait timer) and interpret them as a sub-LSPs (e.g, by using a wait timer) and interpret them as a
re-optimization request for the whole P2MP-TE LSP tree. Otherwise, a re-optimization request for the whole P2MP-TE LSP tree. Otherwise, a
mid-point LSR may prematurely notify "Preferable Path Exists" for one mid-point LSR may prematurely notify "Preferable Path Exists" for one
or a sub-set of S2L sub-LSPs. or a sub-set of S2L sub-LSPs.
- The ingress node that receives (un)solicited PathErr o Similarly, the ingress node may have to heuristically determine
when to perform entire P2MP-TE LSP tree re-optimization versus per
S2L sub-LSP re-optimization, for example, to delay re-optimization
long enough to allow all PathErr(s) to be received. Such procedures
may produce undesired results due to timing related issues.
o The ingress node that receives (un)solicited PathErr
notification(s) for individual S2L sub-LSP(s), may prematurely start notification(s) for individual S2L sub-LSP(s), may prematurely start
re-optimizing the sub-set of S2L sub-LSPs. However, as mentioned in re-optimizing the sub-set of S2L sub-LSPs. However, as mentioned in
[RFC4875] Section 14.2, such sub-group based re-optimization [RFC4875] Section 14.2, such sub-group based re-optimization
procedure may result in data duplication that can be avoided if the procedure may result in data duplication that can be avoided if the
entire P2MP-TE LSP tree is re-optimized using a different LSP-ID, entire P2MP-TE LSP tree is re-optimized using a different LSP-ID,
especially if the ingress node eventually receives PathErr especially if the ingress node eventually receives PathErr
notifications for all S2L sub-LSPs of the P2MP-TE LSP tree. notifications for all S2L sub-LSPs of the P2MP-TE LSP tree.
- The ingress node may have to heuristically determine when to In order to address above mentioned issues and to align re-
perform entire P2MP-TE LSP tree re-optimization versus per S2L sub- optimization of P2MP-TE LSP with P2P LSP [RFC4736], there is a need
LSP re-optimization, for example, to delay re-optimization long for a mechanism to trigger re-optimization of the LSP tree by re-
enough to allow all PathErr(s) to be received. Once all PathErr(s) signaling all S2L sub-LSPs with a different LSP-ID. For this
are received, the ingress node has to accumulate them to see if re- requirement, this document defines RSVP-TE signaling extensions for
optimization of the entire P2MP-TE is necessary. Such procedures may the ingress node to trigger the re-evaluation of the P2MP LSP tree on
produce undesired results due to timing related issues. This may be every hop that has a next-hop defined as a loose or abstract hop for
easily avoided by the RSVP signaling messages defined in this one or more S2L sub-LSP path, and a mid-point LSR to signal to the
document. ingress node that a preferable LSP tree exists (compared to the
current path) or that the whole P2MP-TE LSP must be re-optimized
(because of maintenance required on the TE LSP path).
1.2. Combining Multiple Path Messages for Re-optimization 1.3. Existing Mechanism For Sub-Group-Based P2MP-TE LSP Re-optimization
Based on [RFC4875] (Section 14.2 "Sub-Group-Based Re-Optimization"), Based on [RFC4875] (Section 14.2 "Sub-Group-Based Re-Optimization"),
an ingress node may trigger path re-evaluation requests for a set of an ingress node may trigger path re-evaluation requests using the
S2L sub-LSPs by combining multiple Path messages using S2L sub-LSP procedures defined in [RFC4736] for a set of S2L sub-LSPs and
descriptor list. A mid-point LSR may send a PathErr message combining multiple Path messages using S2L sub-LSP descriptor list.
containing a list of S2L sub-LSPs transiting through the LSR to Similarly, a mid-point LSR may send a PathErr message (with Error
notify the ingress node. This method can alleviate the scale issue code 25, sub-code 6) containing a list of S2L sub-LSPs transiting
associated with sending RSVP messages for individual S2L sub-LSPs. through the LSR using an S2L sub-LSP descriptor list to notify the
This method is useful for re-optimizing a sub-group of S2L sub-LSPs ingress node. This method can be used for re-optimizing a sub-group
within an LSP tree. However, this procedure can lead to following of S2L sub-LSPs within an LSP tree using the same LSP-ID. This
issues: method can alleviate the scale issue associated with sending RSVP
messages for individual S2L sub-LSPs. However, this procedure can
lead to the following issues when used to re-optimize the LSP tree:
- Path message that is intended to carry the path re-evaluation o Path message that is intended to carry the path re-evaluation
request as defined in [RFC4736] with a full list of S2L sub-LSPs in request as defined in [RFC4736] with a full list of S2L sub-LSPs in
S2L sub-LSPs descriptor list will be decomposed at branching LSRs, S2L sub-LSPs descriptor list will be decomposed at branching LSRs,
and only a subset of the S2L sub-LSPs that are routed over the same and only a subset of the S2L sub-LSPs that are routed over the same
next-hop will be added in the descriptor list of the Path message next-hop will be added in the descriptor list of the Path message
propagated to downstream mid-point LSRs. Consequently, when a propagated to downstream mid-point LSRs. Consequently, when a
preferable path exists at such mid-point LSRs, the PathErr can only preferable path exists at such mid-point LSRs, the PathErr can only
include the sub-set of S2L sub-LSPs traversing the LSR. In this include the sub-set of S2L sub-LSPs traversing the LSR. In this
case, at the ingress node there is no way to distinguish which mode case, at the ingress node there is no way to distinguish which mode
of re-optimization to invoke, i.e. sub-group based re-optimization of re-optimization to invoke, i.e. sub-group based re-optimization
using the same LSP-ID or tree based re-optimization using a different using the same LSP-ID or tree based re-optimization using a different
LSP-ID. LSP-ID.
- An LSR may fragment a large RSVP message (when a combined message o An LSR may fragment a large RSVP message (when a combined message
may not be large enough to fit all S2L sub-LSPs). In this case, the may not be large enough to fit all S2L sub-LSPs). In this case, the
ingress node may receive multiple PathErrs with sub-sets of S2L ingress node may receive multiple PathErrs with sub-sets of S2L
sub-LSPs in each (either due to the combined Path message got sub-LSPs in each (either due to the combined Path message got
fragmented or combined PathErr message got fragmented) and would fragmented or combined PathErr message got fragmented) and would
require additional logic to infer to re-optimize the tree (for require additional logic to infer to re-optimize the LSP tree (for
example, waiting for some time to aggregate all possible PathErr example, waiting for some time to aggregate all possible PathErr
messages before taking an action). messages before taking an action).
As discussed in Section 1.1 and Section 1.2 of this document, there In order to address the above mentioned issue due to the RSVP message
is a requirement to align re-optimization of P2MP-TE LSP with P2P LSP fragmentation, this document defines markers to indicate beginning
[RFC4736] to have a mechanism to trigger re-optimization of the LSP and end of an S2L sub-LSP descriptor list when combining large number
tree by re-signaling all S2L sub-LSPs with a different LSP-ID. There of S2L sub-LSPs in an RSVP message.
is also a need to define markers to indicate beginning and end of the
S2L sub-LSP descriptor list when an RSVP message is fragmented due to
large number of S2L sub-LSPs in the message.
This document defines RSVP-TE signaling extensions for the ingress 2. Conventions Used in This Document
node of a P2MP-TE LSP to trigger the re-evaluation of the P2MP LSP
tree on every hop that has a next hop defined as a loose or abstract
hop for one or more S2L sub-LSP path, and a mid-point LSR to signal
to the ingress node that a preferable LSP tree exists (compared to
the current path) or that the whole P2MP-TE LSP must be re-optimized
(because of maintenance required on the TE LSP path). This document
also defines markers to indicate beginning and end of a S2L sub-LSP
descriptor list when RSVP message needs to be fragmented due to large
number of S2L sub-LSPs when performing re-optimization.
2. Terminology 2.1. Key Word Definitions
2.1. Abbreviations 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 [RFC2119].
The reader is assumed to be familiar with the terminology in
[RFC4875] and [RFC4736].
2.2. Abbreviations
ABR: Area Border Router. ABR: Area Border Router.
AS: Autonomous System. AS: Autonomous System.
ERO: Explicit Route Object. ERO: Explicit Route Object.
LSR: Label Switching Router. LSR: Label Switching Router.
TE LSP: Traffic Engineering Label Switched Path. TE LSP: Traffic Engineering Label Switched Path.
TE LSP ingress: Head-end/source of the TE LSP. TE LSP ingress: Head-end/source of the TE LSP.
TE LSP egress: Tail-end/destination of the TE LSP. TE LSP egress: Tail-end/destination of the TE LSP.
2.2. Nomenclatures 2.3. Nomenclatures
Domain: Routing or administrative domain such as an IGP area and an Domain: Routing or administrative domain such as an IGP area and an
autonomous system. autonomous system.
Interior Gateway Protocol Area (IGP Area): OSPF Area or IS-IS level. Interior Gateway Protocol Area (IGP Area): OSPF Area or IS-IS level.
Inter-area TE LSP: A TE LSP whose path transits across at least two Inter-area TE LSP: A TE LSP whose path transits across at least two
different IGP areas. different IGP areas.
Inter-AS MPLS TE LSP: A TE LSP whose path transits across at least Inter-AS MPLS TE LSP: A TE LSP whose path transits across at least
two different Autonomous Systems (ASes) or sub-ASes (BGP two different Autonomous Systems (ASes) or sub-ASes (BGP
confederations). confederations).
S2L sub-LSP: Source-to-leaf sub Label Switched Path. S2L sub-LSP: Source-to-leaf sub Label Switched Path.
2.3. 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 [RFC2119]. The reader
is assumed to be familiar with the terminology in [RFC4875] and
[RFC4736].
3. Signaling Procedure For Loosely Routed P2MP-TE LSP Re-optimization 3. Signaling Procedure For Loosely Routed P2MP-TE LSP Re-optimization
3.1. Tree Based Re-optimization 3.1. Tree-Based Re-optimization
To evaluate an entire P2MP-TE LSP tree on mid-point LSRs that expand To evaluate an entire P2MP-TE LSP tree on mid-point LSRs that expand
loose next-hop(s), an ingress node MAY send a Path message with loose next-hop(s), an ingress node MAY send a Path message with
"P2MP-TE Tree Re-evaluation Request" defined in this document. An "P2MP-TE Tree Re-evaluation Request" defined in this document. The
ingress node SHOULD select one of the S2L sub-LSPs of the P2MP-TE LSP ingress node SHOULD select one of the S2L sub-LSPs of the P2MP-TE LSP
tree transiting a mid-point LSR to trigger the re-evaluation request. tree transiting a mid-point LSR to trigger the re-evaluation request.
The ingress node MAY send a re-evaluation request to each border LSR
on the path of the LSP tree.
A mid-point LSR that expands loose next-hop(s) for one or more S2L A mid-point LSR that expands loose next-hop(s) for one or more S2L
sub-LSP path(s), and that receives a Path message with the "P2MP-TE sub-LSP path(s), and that receives a Path message with the "P2MP-TE
Tree Re-evaluation Request" bit set, SHOULD check for a preferable Tree Re-evaluation Request" bit set:
P2MP-TE LSP tree by re-evaluating all S2L sub-LSP(s) that are
expanded paths of the loose next-hops of the P2MP-TE LSP. If a o The mid-point LSR SHOULD check for a preferable P2MP-TE LSP tree
preferable P2MP-TE LSP tree is found, the mid-point LSR MAY send an by re-evaluating all S2L sub-LSP(s) that are expanded paths of the
RSVP PathErr to the ingress node with Error code 25 (Notify defined loose next-hops of the P2MP-TE LSP.
in [RFC3209] and Error sub-code defined in this document "Preferable
P2MP-TE Tree Exists". The mid-point LSR, in turn, SHOULD not o If a preferable P2MP-TE LSP tree is found, the mid-point LSR MAY
send an RSVP PathErr to the ingress node with Error code 25 (Notify
defined in [RFC3209] and sub-code "Preferable P2MP-TE Tree Exists"
defined in this document. The mid-point LSR, in turn, SHOULD NOT
propagate the "P2MP-TE Tree Re-evaluation Request" bit in subsequent propagate the "P2MP-TE Tree Re-evaluation Request" bit in subsequent
RSVP Path messages sent downstream for the re-evaluated P2MP-TE LSP. RSVP Path messages sent downstream for the re-evaluated P2MP-TE LSP.
o If no preferable tree for P2MP-TE LSP can be found, the
recommended mode is that the mid-point LSR that expands loose next-
hop(s) for one or more S2L sub-LSP path(s) SHOULD propagate the
request downstream by setting the "P2MP-TE Tree Re-evaluation
Request" bit in the LSP_ATTRIBUTES Object of RSVP Path message.
A mid-point LSR MAY send an unsolicited PathErr message with
"Preferable P2MP-TE Tree Exists" PathErr to the ingress node to
notify of a preferred P2MP-TE LSP tree when it determines it exists.
In this case, the mid-point LSR that expands loose next-hop(s) for
one or more S2L sub-LSP path(s) SHOULD select one of the S2L sub-
LSP(s) of the P2MP-TE LSP tree to send this PathErr message to the
ingress node.
The sending of an RSVP PathErr Notify message "Preferable P2MP-TE The sending of an RSVP PathErr Notify message "Preferable P2MP-TE
Tree Exists" to the ingress node SHALL notify the ingress node of the Tree Exists" to the ingress node SHALL notify the ingress node of the
existence of a preferable P2MP-TE LSP tree. In addition, a mid-point existence of a preferable P2MP-TE LSP tree and the ingress node MAY
LSR MAY send an unsolicited PathErr message with "Preferable P2MP-TE trigger re-optimization of the LSP using a different LSP-ID.
Tree Exists" PathErr code 25 to the ingress node to notify of a
preferred the P2MP-TE LSP tree when it determines it exists. In this
case, the mid-point LSR that expands loose next-hop(s) for one or
more S2L sub-LSP path(s) SHOULD select one of the S2L sub-LSP(s) of
the P2MP-TE LSP tree to send this PathErr message to the ingress
node.
If no preferable tree for P2MP-TE LSP can be found, the recommended
mode is that the mid-point LSR that expands loose next-hop(s) for one
or more S2L sub-LSP path(s) SHOULD propagate the request downstream
by setting the "P2MP-TE Tree Re-evaluation Request" bit in the
LSP_ATTRIBUTES Object of RSVP Path message.
3.2. Sub-group Based Re-optimization 3.2. Sub-Group-Based Re-optimization Using Markers
It might be preferable, as per [RFC4875], to re-optimize the entire It might be preferable, as per [RFC4875], to re-optimize the entire
P2MP-TE LSP by re-signaling all of its S2L sub-LSP(s) (Section 14.1, P2MP-TE LSP by re-signaling all of its S2L sub-LSP(s) (Section 14.1,
"Make-before-Break") or to re-optimize individual or group of S2L "Make-before-Break") or to re-optimize individual or group of S2L
sub-LSP(s) i.e. individual or group of destination(s) (Section 14.2 sub-LSP(s) i.e. individual or group of destination(s) (Section 14.2
"Sub-Group-Based Re-Optimization" in [RFC4875]), both using the same "Sub-Group-Based Re-Optimization" in [RFC4875]), both using the same
LSP-ID. For loosely routed S2L sub-LSPs, this can be achieved by LSP-ID. For loosely routed S2L sub-LSPs, this can be achieved by
using the procedures defined in [RFC4736] to re-optimize one or more using the procedures defined in [RFC4736] to re-optimize one or more
S2L sub-LSP(s) of the P2MP-TE LSP. S2L sub-LSP(s) of the P2MP-TE LSP.
An ingress node may trigger path re-evaluation requests for a set of An ingress node may trigger path re-evaluation requests using the
S2L sub-LSPs by combining multiple Path messages using S2L sub-LSP procedures defined in [RFC4736] for a set of S2L sub-LSPs by
descriptor list [RFC4875]. An S2L sub-LSP descriptor list is created combining multiple Path messages using an S2L sub-LSP descriptor list
using a series of S2L_SUB_LSP Objects as defined in [RFC4875]. [RFC4875]. An S2L sub-LSP descriptor list is created using a series
Similarly, a mid-point LSR may send a PathErr message containing a of S2L_SUB_LSP Objects as defined in [RFC4875]. Similarly, a mid-
list of S2L sub-LSPs transiting through the LSR to notify the ingress point LSR may send a PathErr message (with Error code 25, sub-code 6,
node of preferable paths available. Preferable Path Exists) containing a list of S2L sub-LSPs transiting
through the LSR using an S2L sub-LSP descriptor list to notify the
ingress node of preferable paths available.
As per [RFC4875] (Section 5.2.3, "Transit Fragmentation of Path State As per [RFC4875] (Section 5.2.3, "Transit Fragmentation of Path State
Information"), when a Path message is not large enough to fit all S2L Information"), when a Path message is not large enough to fit all S2L
sub-LSPs in the descriptor list, an LSR may fragment the message. In sub-LSPs in the descriptor list, an LSR may fragment the message. In
this case, the LSR MAY add S2L_SUB_LSP_MARKER_BEGIN and this case, the LSR MAY add S2L_SUB_LSP_MARKER_BEGIN and
S2L_SUB_LSP_MARKER_END Objects defined in this document at the S2L_SUB_LSP_MARKER_END Objects defined in this document at the
beginning and at the end of the S2L sub-LSP descriptor list, beginning and at the end of the S2L sub-LSP descriptor list,
respectively. respectively.
Both S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END Objects Both S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END Objects
defined in this document are optional. However, a node MUST add the defined in this document are optional. However, a node MUST add the
S2L_SUB_LSP_MARKER_END Object if it has added S2L_SUB_LSP_MARKER_END Object if it has added
S2L_SUB_LSP_MARKER_BEGIN Object in the S2L sub-LSP descriptor list. S2L_SUB_LSP_MARKER_BEGIN Object in the S2L sub-LSP descriptor list.
A mid-point LSR SHOULD wait to accumulate all S2L sub-LSPs before A mid-point LSR SHOULD wait to accumulate all S2L sub-LSPs before
attempting to re-evaluate preferable path when a Path message for attempting to re-evaluate preferable path when a Path message for
"Path Re-evaluation Request" is received with "Path Re-evaluation Request" is received with
S2L_SUB_LSP_MARKER_BEGIN. An ingress node SHOULD wait to accumulate S2L_SUB_LSP_MARKER_BEGIN Object. An ingress node SHOULD wait to
all S2L sub-LSPs before attempting to trigger re-optimization when a accumulate all S2L sub-LSPs before attempting to trigger
PathErr message with "Preferable Path Exists" is received with re-optimization when a PathErr message with "Preferable Path Exists"
S2L_SUB_LSP_MARKER_BEGIN. is received with S2L_SUB_LSP_MARKER_BEGIN Object.
New objects S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END New objects S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END
defined in this document have a wider applicability than the P2MP-TE defined in this document have a wider applicability other than the
LSP re-optimization but it is outside the scope of this document. P2MP-TE LSP re-optimization but it is outside the scope of this
document.
4. RSVP Signaling Extensions 4. Message and Object Definitions
4.1. P2MP-TE Tree Re-evaluation Request Flag 4.1. P2MP-TE Tree Re-evaluation Request Flag
In order to trigger a tree re-evaluation request, a new flag is In order to trigger a tree re-evaluation request, a new flag is
defined in Attributes Flags TLV of the LSP_ATTRIBUTES Object defined in Attributes Flags TLV of the LSP_ATTRIBUTES Object
[RFC5420] as follows: [RFC5420] as follows:
Bit Number (to be assigned by IANA): P2MP-TE Tree Re-evaluation Bit Number (to be assigned by IANA): P2MP-TE Tree Re-evaluation
Request flag Request flag
skipping to change at page 10, line 23 skipping to change at page 11, line 11
When a preferable path for P2MP-TE LSP tree exists, the mid-point LSR When a preferable path for P2MP-TE LSP tree exists, the mid-point LSR
sends a solicited or unsolicited "Preferable P2MP-TE Tree Exists" sends a solicited or unsolicited "Preferable P2MP-TE Tree Exists"
PathErr notification to the ingress node of the P2MP-TE LSP. PathErr notification to the ingress node of the P2MP-TE LSP.
4.3. Markers For S2L sub-LSP Descriptor 4.3. Markers For S2L sub-LSP Descriptor
An S2L_SUB_LSP Object [RFC4875] identifies a particular S2L sub-LSP An S2L_SUB_LSP Object [RFC4875] identifies a particular S2L sub-LSP
belonging to the P2MP-TE LSP. An S2L sub-LSP descriptor list is belonging to the P2MP-TE LSP. An S2L sub-LSP descriptor list is
created using a series of S2L_SUB_LSP Objects as defined in created using a series of S2L_SUB_LSP Objects as defined in
[RFC4875]. [RFC4875]. In order to indicate the beginning and end of the S2L
sub-LSP descriptor list when the RSVP message needs to be fragmented
In order to indicate the beginning and end of the S2L sub-LSP due to large number of S2L sub-LSPs, the following new types are
descriptor list when the RSVP message needs to be fragmented due to defined for the S2L_SUB_LSP Object [RFC4875].
large number of S2L sub-LSPs, the following new types are defined for
the S2L_SUB_LSP Object [RFC4875].
S2L_SUB_LSP_MARKER_BEGIN : S2L_SUB_LSP_MARKER_BEGIN :
Class-Num 50, C-Type TBA by IANA Class-Num 50, C-Type TBA by IANA
+-----------------+---------------+--------------------------+ +-----------------+---------------+--------------------------+
| Length (4 bytes)| Class_Num 50 | S2L_SUB_LSP_MARKER_BEGIN | | Length (4 bytes)| Class_Num 50 | S2L_SUB_LSP_MARKER_BEGIN |
+-----------------+---------------+--------------------------+ +-----------------+---------------+--------------------------+
S2L_SUB_LSP_MARKER_END : S2L_SUB_LSP_MARKER_END :
skipping to change at page 11, line 25 skipping to change at page 12, line 13
compatibility with non-supporting nodes. Per [RFC2205], nodes not compatibility with non-supporting nodes. Per [RFC2205], nodes not
supporting new S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END supporting new S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END
Objects will ignore them but forward it without modification. Objects will ignore them but forward it without modification.
6. Security Considerations 6. Security Considerations
This document defines a mechanism for a mid-point LSR to notify the This document defines a mechanism for a mid-point LSR to notify the
ingress node of a P2MP-TE LSP of the existence of a preferable tree. ingress node of a P2MP-TE LSP of the existence of a preferable tree.
As per [RFC4736], in the case of a P2MP-TE LSP S2L sub-LSP spanning As per [RFC4736], in the case of a P2MP-TE LSP S2L sub-LSP spanning
multiple domains, it may be desirable for a mid-point LSR to modify multiple domains, it may be desirable for a mid-point LSR to modify
the RSVP PathErr message defined in this document to maintain the RSVP PathErr message defined in this document to preserve
confidentiality across different domains. Furthermore, an ingress confidentiality across domains. Furthermore, an ingress node may
node may decide to ignore this PathErr message coming from a decide to ignore this PathErr message coming from a mid-point LSR
mid-point LSR residing in another domain. Similarly, an mid-point residing in another domain. Similarly, an mid-point LSR may decide
LSR may decide to ignore the tree re-evaluation request originating to ignore the tree re-evaluation request originating from another
from another ingress domain. ingress domain.
7. IANA Considerations 7. IANA Considerations
IANA is requested to administer assignment of new values for IANA is requested to administer assignment of new values for
namespace defined in this document and summarized in this section. namespace defined in this document and summarized in this section.
7.1. P2MP-TE Tree Re-evaluation Request Flag
IANA maintains a name space for RSVP-TE TE parameters "Resource IANA maintains a name space for RSVP-TE TE parameters "Resource
Reservation Protocol-Traffic Engineering (RSVP-TE) Parameters" (see Reservation Protocol-Traffic Engineering (RSVP-TE) Parameters" (see
http://www.iana.org/assignments/rsvp-te-parameters/rsvp-te- http://www.iana.org/assignments/rsvp-te-parameters/rsvp-te-
parameters.xml). From the registries in this name space "Attribute parameters.xml). From the registries in this name space "Attribute
Flags", allocation of new flag is requested (Section 4.1). Flags", allocation of new flag is requested (Section 4.1).
IANA also maintains a name space for RSVP protocol parameters
"Resource Reservation Protocol (RSVP) Parameters" (see
http://www.iana.org/assignments/rsvp-parameters/rsvp-parameters.xml).
From the sub-registry "Sub-Codes - 25 Notify Error" in registry
"Error Codes and Globally-Defined Error Value Sub-Codes", allocation
of a new error code is requested (Section 4.2). Also, from the
sub-registry "Class Types or C-Types 50 S2L_SUB_LSP" in registry
"Class Names, Class Numbers, and Class Types", allocation of new
C-Types is requested (Section 4.3).
7.1. P2MP-TE Tree Re-evaluation Request Flag
The following new flag is defined for the Attributes Flags TLV in the The following new flag is defined for the Attributes Flags TLV in the
LSP_ATTRIBUTES Object [RFC5420]. The numeric value is to be assigned LSP_ATTRIBUTES Object [RFC5420]. The numeric value is to be assigned
by IANA. by IANA.
o P2MP-TE Tree Re-evaluation Request Flag: o P2MP-TE Tree Re-evaluation Request Flag:
+--------+---------------+---------+---------+---------+------------+ +--------+---------------+---------+---------+---------+------------+
| Bit No | Attribute | Carried | Carried | Carried | Reference | | Bit No | Attribute | Carried | Carried | Carried | Reference |
| | Flag Name | in Path | in Resv | in RRO | | | | Flag Name | in Path | in Resv | in RRO | |
+--------+---------------+---------+---------+---------+------------+ +--------+---------------+---------+---------+---------+------------+
| TBA by | P2MP-TE Tree | Yes | No | No | This | | TBA by | P2MP-TE Tree | Yes | No | No | This |
| IANA | Re-evaluation | | | | document | | IANA | Re-evaluation | | | | document |
+--------+---------------+---------+---------+---------+------------+ +--------+---------------+---------+---------+---------+------------+
7.2. Preferable P2MP-TE Tree Exists Path Error Sub-code 7.2. Preferable P2MP-TE Tree Exists Path Error Sub-code
IANA maintains a name space for RSVP protocol parameters "Resource
Reservation Protocol (RSVP) Parameters" (see
http://www.iana.org/assignments/rsvp-parameters/rsvp-parameters.xml).
From the sub-registry "Sub-Codes - 25 Notify Error" in registry
"Error Codes and Globally-Defined Error Value Sub-Codes", allocation
of a new error code is requested (Section 4.2).
As defined in [RFC3209], the Error Code 25 in the ERROR SPEC Object As defined in [RFC3209], the Error Code 25 in the ERROR SPEC Object
corresponds to a Notify Error PathErr. This document adds a new corresponds to a Notify Error PathErr. This document adds a new
sub-code as follows for this PathErr: sub-code for this PathErr as follows:
o Preferable P2MP-TE Tree Exists sub-code: o Preferable P2MP-TE Tree Exists sub-code:
+----------+--------------------+---------+---------+-----------+ +----------+--------------------+---------+---------+-----------+
| Sub-code | Sub-code | PathErr | PathErr | Reference | | Sub-code | Sub-code | PathErr | PathErr | Reference |
| value | Description | Code | Name | | | value | Description | Code | Name | |
+----------+--------------------+---------+---------+-----------+ +----------+--------------------+---------+---------+-----------+
| TBA by | Preferable P2MP-TE | 25 | Notify | This | | TBA by | Preferable P2MP-TE | 25 | Notify | This |
| IANA | Tree Exists | | Error | document | | IANA | Tree Exists | | Error | document |
+----------+--------------------+---------+---------+-----------+ +----------+--------------------+---------+---------+-----------+
7.3. BEGIN and END Markers For S2L sub-LSP Descriptor 7.3. BEGIN and END Markers For S2L sub-LSP Descriptor
IANA maintains a name space for RSVP protocol parameters "Resource
Reservation Protocol (RSVP) Parameters" (see
http://www.iana.org/assignments/rsvp-parameters/rsvp-parameters.xml).
From the sub-registry "Class Types or C-Types 50 S2L_SUB_LSP" in
registry "Class Names, Class Numbers, and Class Types", allocation of
new C-Types is requested (Section 4.3).
As defined in [RFC4875], S2L_SUB_LSP Object is defined with As defined in [RFC4875], S2L_SUB_LSP Object is defined with
Class-Number 50 to identify a particular S2L sub-LSP belonging to the Class-Number 50 to identify a particular S2L sub-LSP belonging to the
P2MP-TE LSP. This document adds two new object types for this object P2MP-TE LSP. This document adds two new object types for this object
as follows: as follows:
o S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END Object types: o S2L_SUB_LSP_MARKER_BEGIN and S2L_SUB_LSP_MARKER_END Object types:
+---------------+---------------------------+-----------------+ +---------------+---------------------------+-----------------+
| C-Type value | Description | Reference | | C-Type value | Description | Reference |
+---------------+---------------------------+-----------------+ +---------------+---------------------------+-----------------+
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