TEAS Working Group R. Gandhi, Ed.
Internet-Draft Cisco Systems
Intended Status: Standards Track H. Shah
Expires: August 18, 2017 Ciena
Jeremy Whittaker
Verizon
February 14, 2017
Fast Reroute Procedures For Associated Co-routed Bidirectional
Label Switched Paths (LSPs)
draft-gandhishah-teas-assoc-corouted-bidir-03
Abstract
Resource Reservation Protocol (RSVP) association signaling can be
used to bind two unidirectional LSPs into an associated bidirectional
LSP. In packet transport networks, there are requirements where the
reverse unidirectional LSP of an associated bidirectional LSP needs
to follow the same path as its forward unidirectional LSP. In
addition, the associated bidirectional LSP needs to maintain
co-routed-ness even after a failure event in the network. This
document describes fast reroute procedures for associated
bidirectional LSPs that ensure the traffic flows on a co-routed path
after a failure event for single-sided provisioning model.
Status of this Memo
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Key Word Definitions . . . . . . . . . . . . . . . . . . . 3
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2.1. Reverse Co-routed Unidirectional LSPs . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Co-routed Bidirectional LSP Association . . . . . . . . . 4
3.2. Fast Reroute Bypass Tunnel Assignment . . . . . . . . . . 5
4. Signaling Procedure . . . . . . . . . . . . . . . . . . . . . 6
4.1. Co-routed Bidirectional LSP Association . . . . . . . . . 6
4.2. Fast Reroute For Associated Co-routed Bidirectional LSP . 7
5. Message and Object Definitions . . . . . . . . . . . . . . . . 7
5.1. Extended ASSOCIATION Object . . . . . . . . . . . . . . . 7
6. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
The Resource Reservation Protocol (RSVP) (Extended) ASSOCIATION
Object is specified in [RFC6780] which can be used generically to
associate (G)Multi-Protocol Label Switching (MPLS) Label Switched
Paths (LSPs). [RFC7551] defines mechanisms for binding two point-to-
point unidirectional LSPs [RFC3209] into an associated bidirectional
LSP. There are two models described in [RFC7551] for provisioning an
associated bidirectional LSP, single-sided and double-sided. In this
document, only the single-sided provisioned associated bidirectional
LSPs are considered for co-routed-ness.
The MPLS Transport Profile (TP) [RFC6370] architecture facilitates
the co-routed bidirectional LSP by using the GMPLS extensions
[RFC3473] to achieve congruent paths. However, the RSVP association
signaling allows to enable co-routed bidirectional LSPs without
having to deploy GMPLS extensions in the existing networks. The
association signaling also allows to take advantage of the existing
Traffic Engineering (TE) mechanisms in the network.
In packet transport networks, there are requirements where the
reverse LSP of an associated bidirectional LSP needs to follow the
same path as its forward LSP [RFC6373]. In addition, the associated
bidirectional LSP needs to maintain co-routed-ness even after a
failure event in the network.
[GMPLS-FRR] defines fast reroute procedure for GMPLS signaled LSPs to
co-ordinate bypass tunnel assignments in the forward and reverse
directions. The mechanisms defined in [GMPLS-FRR] can be used for
fast reroute of the associated bidirectional LSPs.
This document describes fast reroute procedures for associated
co-routed bidirectional LSPs to ensure the traffic flows on the
co-routed path in the forward and reverse direction of the LSP after
a failure event.
2. Conventions Used in This Document
2.1. Key Word Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2.2. Terminology
The reader is assumed to be familiar with the terminology in
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[RFC2205], [RFC3209], [RFC7551], and [RFC4090].
2.2.1. Reverse Co-routed Unidirectional LSPs
Two reverse unidirectional point-to-point (P2P) LSPs are setup in the
opposite directions between a pair of source and destination nodes to
form an associated bidirectional LSP. A reverse unidirectional LSP
originates on the same node where the forward unidirectional LSP
terminates, and it terminates on the same node where the forward
unidirectional LSP originates. A reverse co-routed unidirectional
LSP traverses along the same path of the forward direction
unidirectional LSP in the opposite direction.
3. Overview
As specified in [RFC7551], in the single-sided provisioning case, the
RSVP TE tunnel is configured only on one endpoint node. An LSP for
this tunnel is initiated by the originating endpoint with (Extended)
ASSOCIATION Object containing Association Type set to "single-sided
associated bidirectional LSP" and REVERSE_LSP Object inserted in the
Path message. The remote endpoint then creates the corresponding
reverse TE tunnel and signals the reverse LSP in response using the
information from the REVERSE_LSP Object and other objects present in
the received Path message. The reverse LSP thus created may or may
not be congruent and follow the same path as its forward LSP.
The single-sided associated co-routed bidirectional LSP signaled
using the mechanisms defined in [RFC7551] requires solutions for the
following issues for fast reroute to ensure co-routed-ness.
3.1. Co-routed Bidirectional LSP Association
Multiple forward and reverse LSPs of a bidirectional LSP may be
present at mid-point nodes with identical (Extended) ASSOCIATION
Objects. For example, this can occur while RSVP states are timing
out after fast reroute, or during recovery phase in RSVP graceful
restart. This creates an ambiguity at mid-point nodes to identify
the correct associated LSP pair for fast reroute bypass assignment.
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LSP3 --> LSP3 -->
LSP1 --> LSP1 --> LSP1 -->
+-----+ +-----+ +-----+ +-----+
| A +-----------+ B +-----------+ C +-----------+ D |
+-----+ +--+--+ +--+--+ +-----+
<-- LSP2 | <-- LSP2 | <-- LSP2
<-- LSP4 | | <-- LSP4
| |
| LSP3 --> |
+--+--+ +--+--+
| E +-----------+ F |
+-----+ +-----+
<-- LSP4
Figure 1: Multiple LSPs with Matching (Extended) ASSOCIATION Object
As shown in Figure 1, LSP1 and LSP2 are an associated co-routed LSP
pair, similarly LSP3 and LSP4 are an associated co-routed LSP pair,
both pairs belong to the same associated bidirectional LSP and carry
identical (Extended) ASSOCIATION Objects. In this example, mid-point
nodes B and C may mistakenly associate LSP1 with non co-routed
reverse LSP4 instead of co-routed reverse LSP3 due to the matching
(Extended) ASSOCIATION Objects.
3.2. Fast Reroute Bypass Tunnel Assignment
In order to ensure that the traffic flows on the co-routed path after
a link or node failure on the LSP path, the mid-point Point of Local
Repair (PLR) nodes need to assign correct bidirectional co-routed
bypass tunnels for fast reroute. Such bypass assignment requires
co-ordination between the forward and reverse direction PLR nodes
when more than one bypass tunnels are present on a node.
+-----+ +-----+
| G +-----------+ H |
+--+--+ +--+--+
| |
| |
LSP1 --> | LSP1 --> | LSP1 -->
+-----+ +--+--+ +--+--+ +-----+
| A +-----------+ B +-----------+ C +-----------+ D |
+-----+ +--+--+ +--+--+ +-----+
<-- LSP2 | <-- LSP2 | <-- LSP2
| |
| |
+--+--+ +--+--+
| E +-----------+ F |
+-----+ +-----+
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Figure 2: Multiple Bidirectional Bypass Tunnels
As shown in Figure 2, there are two bypass tunnels available, one on
path B-G-H-C and other on path B-E-F-C. In order to ensure co-
routed-ness, the mid-point PLR nodes B and C need to co-ordinate
bypass tunnel assignment to ensure that traffic in both directions
flow through either on path B-G-H-C or path B-E-F-C, after the link
B-C failure.
4. Signaling Procedure
4.1. Co-routed Bidirectional LSP Association
In order to ensure co-routed-ness, Extended ASSOCIATION Object is
used in the RSVP Path message using the procedures defined in
[RFC7551] as following.
o The originating head-end node MUST add Extended ASSOCIATION Object
with Association Type set to "single-sided associated
bidirectional LSP" and unique Extended Association ID for each
associated forward and reverse LSP pair forming the bidirectional
LSP. As an example, a node MAY set the Extended Association ID to
the values specified in Section 5.1 of this document. As
specified in [RFC7551], the remote endpoint copies the contents of
the received Extended ASSOCIATION Object including the Extended
Association ID in the RSVP Path message of the reverse LSP's
Extended ASSOCIATION Object.
o The originating head-end node MUST add an EXPLICIT_ROUTE Object
(ERO) in the REVERSE_LSP Object by using the hops traversed by the
forward LSP in the reverse order to ensure that reverse LSP
follows the same path as forward direction LSP in the opposite
direction. As specified in [RFC7551], the remote endpoint builds
the ERO of the reverse LSP using the ERO from the received
REVERSE_LSP Object of the forward LSP.
o When an ERO contains one or more loose next-hop(s), the
originating head-end MUST add RECORD_ROUTE Object (RRO) in the
Path message of the forward LSP to record the hops traversed by
the LSP. The remote endpoint SHOULD use the recorded hops from
the RRO in the forward LSP to expand the loose next-hop(s), to
ensure that the reverse LSP follows the same path as the forward
LSP.
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4.2. Fast Reroute For Associated Co-routed Bidirectional LSP
The mechanisms defined in [GMPLS-FRR] can be used for associated
co-routed bidirectional LSP to ensure the traffic flows on a
co-routed path in the forward and reverse directions after a link or
node failure as following.
o As described in [GMPLS-FRR], BYPASS_ASSIGNMENT subobject is
signaled in the RRO of the Path message to co-ordinate bypass
tunnel assignment between the forward and reverse direction PLR
nodes. A BYPASS_ASSIGNMENT subobject MUST be added by the forward
direction PLR node in the Path message of the originating LSP to
indicate the bypass tunnel assigned.
o The forward direction PLR node always initiates the bypass tunnel
assignment for the originating LSP. The reverse direction PLR
(forward direction LSP Merge Point (MP)) node simply reflects the
bypass tunnel assignment for the reverse direction LSP.
o After a link or node failure, the PLR nodes in both forward and
reverse directions trigger fast reroute independently using the
procedures defined in [RFC4090].
o When using a node protection bypass tunnel, asymmetry of paths can
occur in the forward and reverse directions of the bidirectional
LSP after a link failure [GMPLS-FRR]. This is corrected using the
re-corouting procedure defined in [GMPLS-FRR]. Unlike GMPLS LSPs,
the asymmetry of paths does not result in RSVP soft-state time-out
with the associated bidirectional LSPs.
5. Message and Object Definitions
5.1. Extended ASSOCIATION Object
The Extended Association ID in the Extended ASSOCIATION Object can be
set by the originating node to the value specified as following when
the associated bidirectional LSP is co-routed.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 LSP Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
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: Variable Length ID :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IPv4 Extended Association ID
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| IPv6 LSP Source Address |
+ +
| (16 bytes) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: Variable Length ID :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: IPv6 Extended Association ID
LSP Source Address
IPv4/IPv6 source address of the originating LSP.
LSP-ID
16-bits LSP-ID of the originating LSP.
Variable Length ID
Variable length ID inserted by the originating node of the
Associated co-routed bidirectional LSP.
6. Compatibility
This document describes the procedures for fast reroute for
associated co-routed bidirectional LSPs. Operators wishing to use
this function SHOULD ensure that it is supported on the nodes on the
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LSP path.
7. Security Considerations
This document uses signaling mechanisms defined in [RFC7551] and
[GMPLS-FRR] and does not introduce any additional security
considerations other than already covered in [RFC7551], [GMPLS-FRR]
and the MPLS/GMPLS security framework [RFC5920].
8. IANA Considerations
This document does not make any request for IANA action.
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
May 2005.
[RFC6780] Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP
Association Object Extensions", RFC 6780, October 2012.
[RFC7551] Zhang, F., Ed., Jing, R., and Gandhi, R., Ed., "RSVP-TE
Extensions for Associated Bidirectional LSPs", RFC 7551,
May 2015.
[GMPLS-FRR] Taillon, M., Saad, T., Ed., Gandhi, R., Ed., Ali, Z.,
Bhatia, M., "Extensions to Resource Reservation Protocol
For Fast Reroute of Traffic Engineering GMPLS LSPs",
draft-ietf-teas-gmpls-lsp-fastreroute, work in progress.
9.2. Informative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.
[RFC6373] Andersson, L., Berger, L., Fang, L., Bitar, N., and E.
Gray, "MPLS Transport Profile (MPLS-TP) Control Plane
Framework", RFC 6373, September 2011.
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Authors' Addresses
Rakesh Gandhi (editor)
Cisco Systems, Inc.
EMail: rgandhi@cisco.com
Himanshu Shah
Ciena
EMail: hshah@ciena.com
Jeremy Whittaker
Verizon
EMail: jeremy.whittaker@verizon.com
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