Internet DRAFT - draft-gandhi-shah-teas-assoc-corouted-bidir
draft-gandhi-shah-teas-assoc-corouted-bidir
TEAS Working Group R. Gandhi, Ed.
Internet-Draft Cisco Systems
Intended Status: Standards Track H. Shah
Expires: July 14, 2016 Ciena
Jeremy Whittaker
Verizon
January 11, 2016
RSVP-TE Extensions For Associated Co-routed Bidirectional
Label Switched Paths (LSPs)
draft-gandhi-shah-teas-assoc-corouted-bidir-00
Abstract
In transport networks, there are requirements where reverse
unidirectional LSP of a bidirectional LSP needs to follow the same
path as its forward unidirectional LSP. This document describes how
RSVP Extended ASSOCIATION Object can be used to bind two co-routed
point-to-point unidirectional LSPs into an associated co-routed
bidirectional LSP in single-sided provisioning case. The RSVP
REVERSE_LSP Object is used to enable an endpoint to trigger creation
of the reverse LSP along the same path as the forward LSP.
Fast-reroute procedures to ensure that the traffic flows on the co-
routed path after a failure event are also described.
Status of this Memo
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Copyright and License Notice
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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. Reverse Co-routed Unidirectional LSPs . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Message and Object Definitions . . . . . . . . . . . . . . . . 4
4.1. Extended ASSOCIATION Object . . . . . . . . . . . . . . . 4
5. Signaling Procedure . . . . . . . . . . . . . . . . . . . . . 6
5.1. Co-routed Bidirectional LSP Association . . . . . . . . . 6
5.2. Fast-Reroute For Associated Co-routed Bidirectional LSP . 6
6. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
In transport networks, there are requirements where a reverse LSP of
a bidirectional LSP needs to follow the same path as its forward LSP
[RFC6373].
The 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 into an
associated bidirectional LSP. There are two models described for
provisioning the LSP, single-sided and double-sided. The double-
sided provisioned bidirectional LSPs are not considered in this
document.
The MPLS TP [RFC6370] architecture facilitates the co-routed
bidirectional LSP by using GMPLS extensions to achieve congruent
paths. The RSVP association signaling allows to take advantages of
the 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 fast-reroute mechanisms.
[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 primary LSP path. [GMPLS-FRR] does not define fast-reroute
mechanisms for associated co-routed bidirectional LSPs.
This document describes how Extended ASSOCIATION Object can be used
to bind two reverse co-routed unidirectional LSPs into an associated
co-routed bidirectional LSP in single-sided provisioning case. The
REVERSE_LSP Object is used to enable an endpoint to trigger creation
of the reverse LSP along the same path as the forward LSP. Fast-
reroute procedures to ensure that the traffic flows on the co-routed
path after a failure event are also described.
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 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
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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
For single-sided provisioning, the Traffic Engineering (TE) tunnel is
configured only on one endpoint. 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 information
from the REVERSE_LSP Object and other objects present in the received
Path message [RFC7551]. The reverse LSP thus created may or may not
be congruent.
LSP1 -->
+-----+ +-----+ +-----+
| A +-----------+ C +-----------+ B |
+-----+ +-----+ +-----+
<-- LSP2
Figure 1: An Example of Associated Co-routed Bidirectional LSP
As shown in Figure 1, creation of reverse LSP2 on remote endpoint B
is triggered by LSP1. LSP2 follows the path in the reverse direction
using the EXPLICIT_ROUTE Object (ERO) from the received REVERSE_LSP
Object in LSP1.
For co-routed bidirectional LSP, the originating endpoint A ensures
the reverse LSP follow the same path as the forward LSP by populating
EXPLICIT_ROUTE Object in the REVERSE_LSP Object using the hops
traversed by the forward LSP in the reverse order.
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".
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The Extended Association ID is set by the originating node to the
value specified as following.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | LSP-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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| LSP Source Address |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | LSP-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.
Flags
Bit 0: COROUTED-LSP-FLAG: When set, this flag indicates the
associated bidirectional LSP is co-routed.
Bit 1-15: Not used. Must be set to 0.
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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 MUST add Extended ASSOCIATION Object with
Association Type set to "single-sided associated bidirectional LSP"
and the extended association ID as specified in Section 4.1 of this
document. The COROUTED-LSP-FLAG MUST be set to indicate the nodes on
the LSP path that 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.
As defined in [RFC7551], the remote endpoint simply copies the
content of the received Extended ASSOCIATION Object including the
extended association ID in the reverse LSP 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.
As contents of the Extended ASSOCIATION Object are unique for each
associated co-routed bidirectional LSP, a node can unambiguously
identify the associated LSP pair by matching their Extended
ASSOCIATION Objects. In addition, a node can identify an originating
(forward) LSP by matching the LSP source address with the source
address in the extended association ID.
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 traffic flows on a co-routed
path after a link or node failure. The COROUTED-LSP-FLAG is used by
the PLR nodes to provide fast-reroute protection using associated co-
routed bypass tunnels.
As described in [GMPLS-FRR], BYPASS_ASSIGNMENT subobject in RRO is
used to co-ordinate bypass tunnel assignment between a forward and
reverse direction PLRs. This subobject MUST be added by the forward
direction PLR in the Path message of the originating LSP. The
reverse direction PLR (forward direction LSP MP) simply reflects the
bypass tunnel assignment for the reverse direction LSP on the co-
routed path.
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After a link or node failure, PLRs in both directions trigger fast-
reroute independently using the procedures defined in [RFC4090].
As specified in [GMPLS-FRR], re-corouting procedure can be used to
reroute the traffic in the reverse direction on the co-routed bypass
tunnel path. Reverse direction PLR will assume the role of PRR and
trigger the fast-reroute in the reverse direction on the matching 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
non-supporting nodes. Per [RFC2205], such nodes will ignore the
object but forward it without modification.
This document defines the content of the Extended Association ID for
the Extended ASSOCIATION Object for co-routed bidirectional LSPs.
Operators wishing to use this function SHOULD ensure that it is
supported on the node that is expected to act on the association.
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 informational 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.
[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.
[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., Jin, L., "Extensions to Resource Reservation
Protocol For Fast Reroute of Traffic Engineering GMPLS
LSPs", draft-ietf-teas-gmpls-lsp-fastreroute-03, July
2015.
9.2. Informative References
[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.
[RFC6689] Berger, L., "Usage of The RSVP Association Object", RFC
6689, July 2012.
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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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