TEAS Working Group R. Gandhi, Ed.
Internet-Draft Cisco Systems
Intended Status: Standards Track H. Shah
Expires: March 14, 2017 Ciena
Jeremy Whittaker
Verizon
September 10, 2016
Fast Reroute Procedures For Associated Co-routed Bidirectional
Label Switched Paths (LSPs)
draft-gandhishah-teas-assoc-corouted-bidir-02
Abstract
In packet transport networks, there are requirements where reverse
unidirectional LSP of a bidirectional LSP needs to follow the same
path as its forward unidirectional LSP. The bidirectional LSP needs
to maintain co-routed-ness even after a failure event in the network.
This document describes RSVP signaling to unambiguously bind two co-
routed point-to-point LSPs into an associated co-routed bidirectional
LSP. Fast-reroute procedures are defined to ensure that the traffic
flows on the co-routed path after a failure event.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
Gandhi, et al. Expires March 14, 2017 [Page 1]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Key Word Definitions . . . . . . . . . . . . . . . . . . . 3
2.2. Reverse Co-routed Unidirectional LSPs . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Message and Object Definitions . . . . . . . . . . . . . . . . 6
4.1. Extended ASSOCIATION Object . . . . . . . . . . . . . . . 6
5. Signaling Procedure . . . . . . . . . . . . . . . . . . . . . 7
5.1. Co-routed Bidirectional LSP Association . . . . . . . . . 7
5.2. Fast-Reroute For Associated Co-routed Bidirectional LSP . 8
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
Gandhi, et al. Expires March 14, 2017 [Page 2]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
1. Introduction
In packet transport networks, there are requirements where a reverse
Multi-Protocol Label Switching (MPLS) Label Switched Path (LSP) of a
bidirectional LSP needs to follow the same path as its forward LSP
[RFC6373]. The bidirectional LSP needs to maintain co-routed-ness
even after a failure event in the network.
The Resource Reservation Protocol (RSVP) Extended ASSOCIATION Object
is specified in [RFC6780] which can be used generically to associate
(G)MPLS LSPs. [RFC7551] defines mechanisms for binding two point-to-
point unidirectional LSPs [RFC3209] into an associated bidirectional
LSP. There are two models described for provisioning the
bidirectional LSP, single-sided and double-sided. Only the single-
sided provisioned bidirectional LSPs are considered in this document
for providing fast-reroute for the co-routed bidirectional LSPs.
The MPLS Transport Profile (TP) [RFC6370] architecture facilitates
the co-routed bidirectional LSP by using 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.
[GMPLS-FRR] defines fast-reroute procedures for GMPLS signaled LSPs
to ensure traffic flows on a co-routed path after a failure event on
the LSP path. [GMPLS-FRR] defined fast-reroute mechanisms are
equally applicable to the associated co-routed bidirectional LSPs.
This document describes how Extended ASSOCIATION Object can be used
to unambiguously bind two reverse co-routed unidirectional LSPs into
an associated co-routed bidirectional LSP in the single-sided
provisioning case. Fast-reroute procedures are defined to ensure the
traffic flows on the co-routed path 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. Reverse Co-routed Unidirectional LSPs
Two reverse unidirectional point-to-point (P2P) LSPs are setup in the
Gandhi, et al. Expires March 14, 2017 [Page 3]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
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 Traffic Engineering (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.
LSP1 --> LSP1 --> LSP1 -->
+-----+ +-----+ +-----+ +-----+
| A +-----------+ B +-----------+ C |-----------+ D |
+-----+ +-----+ +-----+ +-----+
<-- LSP2 <-- LSP2 <-- LSP2
Figure 1a: An Example of Associated Co-routed Bidirectional LSP
As shown in Figure 1a, LSP1 is provisioned on the originating
endpoint A. The creation of reverse LSP2 on the remote endpoint D is
triggered by the LSP1. LSP2 follows the path in the reverse
direction using the EXPLICIT_ROUTE Object (ERO) from the received
REVERSE_LSP Object in the Path message of LSP1 [RFC7551].
For co-routed bidirectional LSP, the originating endpoint A can
ensure that the reverse LSP follows the same path as the forward LSP
(e.g. A-B-C-D) by populating the ERO in the REVERSE_LSP Object using
the hops traversed by the forward LSP in the reverse order (e.g. D-C-
B-A).
For fast-reroute, the associated co-routed bidirectional LSP signaled
using mechanisms defined in [RFC7551] requires solutions for the
following issues:
Gandhi, et al. Expires March 14, 2017 [Page 4]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
o Multiple forward and reverse LSPs of a bidirectional LSP may be
present at mid-point nodes with identical Extended ASSOCIATION
Objects. As examples, this can happen while RSVP states are timing
out, during recovery phase in RSVP graceful restart, etc. This
creates an ambiguity at mid-point nodes to identify the correct
associated LSP pair that can lead to undesirable fast-reroute bypass
assignment.
As shown in Figure 1b, 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.
In order to ensure co-routed-ness, the mid-point nodes must
unambiguously identify the correct matching co-routed associated
forward and reverse LSP pair. To ensure this, the Extended
ASSOCIATION Object needs to be unique per associated co-routed
forward and reverse LSP pair.
LSP3 --> LSP3 -->
LSP1 --> LSP1 --> LSP1 -->
+-----+ +-----+ +-----+ +-----+
| A +-----------+ B +-----------+ C |-----------+ D |
+-----+ +-----+ +-----+ +-----+
<--LSP2 | <-- LSP2 | <-- LSP2
<--LSP4 | | <-- LSP4
| |
| LSP3 --> |
+-----+ +-----+
+ E +-----------+ F |
+-----+ +-----+
<-- LSP4
Figure 1b: Example of LSPs with matching Extended ASSOCIATION Objects
o The ERO for the reverse LSP signaled by the originating endpoint
may contain loose next-hop(s) in case of loosely routed LSPs (e.g.
inter-domain LSPs). For co-routed bidirectional LSP, the mid-point
and endpoint nodes need to ensure that the loose next-hop expansion
for the reverse LSP is on the co-routed path as its forward LSP. To
achieve this, the expanding node may require the recorded path of the
forward LSP.
o In order to ensure that the traffic flows on the co-routed path
Gandhi, et al. Expires March 14, 2017 [Page 5]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
after a link or node failure on the LSP path, the mid-point Point of
Local Repair (PLR) nodes need to identify the correct matching pair
and know that it is co-routed. This way PLR nodes can assign
bidirectional co-routed bypass tunnels for fast-reroute. Such bypass
assignment requires co-ordination between the forward and reverse
direction PLR nodes.
4. Message and Object Definitions
4.1. Extended ASSOCIATION Object
The Extended ASSOCIATION Object is populated using the rules defined
in [RFC7551] for the Association Type "single-sided associated
bidirectional LSP".
The Extended Association ID is 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: Variable Length Extended ID :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IPv4 Extended Association ID 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| IPv6 LSP Source Address |
+ +
| (16 bytes) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Gandhi, et al. Expires March 14, 2017 [Page 6]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
| Reserved | LSP-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: Variable Length Extended ID :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IPv6 Extended Association ID Format
LSP Source Address
IPv4/IPv6 source address of the originating LSP.
LSP-ID
16-bits LSP-ID of the originating LSP.
Variable Length Extended ID
Variable length Extended ID inserted by the originating node of
the Associated co-routed bidirectional LSP.
5. Signaling Procedure
5.1. Co-routed Bidirectional LSP Association
In general, the processing rules for the Extended ASSOCIATION Object
as specified in [RFC6780] and [RFC7551] are followed for co-routed
bidirectional LSP association.
The originating head-end node MUST add Extended ASSOCIATION Object
with Association Type set to "single-sided associated bidirectional
LSP" and the Extended Association ID set to the values specified in
Section 4.1 of this document in the RSVP Path message. The Extended
Association ID thus added allows to identify each associated LSP pair
of the associated co-routed bidirectional LSP. The presence of
Extended Association ID in this format indicates the nodes on the LSP
path that the bidirectional LSP is co-routed. In addition, the
originating head-end node MUST add 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. When the ERO
contains one or more loose next-hop(s), the originating endpoint MUST
add RECORD_ROUTE Object (RRO) in the Path message of the forward LSP
to record the hops traversed by the LSP.
Gandhi, et al. Expires March 14, 2017 [Page 7]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
As defined in [RFC7551], the remote endpoint simply copies the
contents of the received Extended ASSOCIATION Object including the
Extended Association ID in the Path message of the reverse LSP's
Extended ASSOCIATION Object. In addition, the remote endpoint builds
the ERO of the reverse LSP using the ERO from the received
REVERSE_LSP Object of the forward LSP. If ERO contains one or more
loose next-hop(s), 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.
As contents of the Extended ASSOCIATION Objects are unique for each
associated LSP pair of the associated co-routed bidirectional LSP, a
mid-point node can unambiguously identify the associated LSP pair by
matching their Extended ASSOCIATION Objects. When a mid-point node
needs to expand the loose next-hop in the ERO, it SHOULD use the
recorded hops from the RRO in the forward LSP to ensure that the
reverse LSP is co-routed and follows the same path as its forward
LSP.
5.2. Fast-Reroute For Associated Co-routed Bidirectional LSP
The procedures defined in [GMPLS-FRR] are used for associated
co-routed bidirectional LSP to ensure that the traffic flows on a
co-routed path after a link or node failure.
As described in [GMPLS-FRR], BYPASS_ASSIGNMENT subobject in the RRO
is signaled to co-ordinate bypass tunnel assignment between its
forward and reverse direction PLR nodes. This subobject MUST be
added by the forward direction PLR node in the Path message of the
originating LSP. 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
on the co-routed path.
After a link or node failure, PLR nodes in both directions trigger
fast-reroute independently using the procedures defined in [RFC4090].
As specified in [GMPLS-FRR], reverse direction PLR node triggers the
fast-reroute in the reverse direction on the matching associated co-
routed bypass tunnel to ensure that both traffic and RSVP signaling
flow on the co-routed path after the failure.
6. Compatibility
The Extended ASSOCIATION Object has been defined in [RFC6780], with
class number in the form 11bbbbbb, which ensures compatibility with
Gandhi, et al. Expires March 14, 2017 [Page 8]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
non-supporting nodes. Per [RFC2205], such nodes will ignore the
object but forward it without modification.
This document defines 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 LSP path. The
Extended Association ID defined in this document is backwards
compatible with the functions defined in [RFC7551] and [RFC6780].
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].
Using the Extended Association ID in the intercepted signalling
message, a node may be able to get additional information of the LSP
such as co-routed type and the originating node. This is judged to
be a very minor security risk as this information is already
available by other means.
8. IANA Considerations
This document does not make any request for IANA action.
Gandhi, et al. Expires March 14, 2017 [Page 9]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
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.,
"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.
Gandhi, et al. Expires March 14, 2017 [Page 10]
Internet-Draft FRR For Co-routed Bidirectional LSP September 10, 2016
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
Gandhi, et al. Expires March 14, 2017 [Page 11]