PCEP Extension for Segment Routing (SR) Bi-directional Associated Paths
draft-li-pce-sr-bidir-path-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Cheng Li , Mach Chen , Dhruv Dhody , Zhenbin Li , Jie Dong | ||
| Last updated | 2018-06-20 | ||
| Replaced by | draft-ietf-pce-sr-bidir-path, draft-ietf-pce-sr-bidir-path | ||
| RFC stream | (None) | ||
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| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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| IESG | IESG state | I-D Exists | |
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draft-li-pce-sr-bidir-path-00
PCE Working Group C. Li
Internet-Draft M. Chen
Updates: 8281 (if approved) D. Dhody
Intended status: Standards Track Z. Li
Expires: December 22, 2018 J. Dong
Huawei Technologies
June 20, 2018
PCEP Extension for Segment Routing (SR) Bi-directional Associated Paths
draft-li-pce-sr-bidir-path-00
Abstract
The Path Computation Element Communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Clients (PCCs) requests.
The Stateful PCE extensions allow stateful control of Multiprotocol
Label Switching (MPLS) Traffic Engineering (TE) Label Switched Paths
(LSPs) using PCEP. Furthermore, PCEP can be used for computing paths
in SR networks.
This document defines PCEP extensions for grouping two reverse
unidirectional SR Paths into an Associated Bidirectional SR path when
using a Stateful PCE for both PCE-Initiated and PCC-Initiated LSPs as
well as when using a Stateless PCE.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 22, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. PCEP Extension for Bi-directional SR Path . . . . . . . . . . 4
3.1. Double-sided Bidirectional SR Path Association Group
Object . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Bi-directional Flag . . . . . . . . . . . . . . . . . . . . . 5
5. Procedures of Bi-directional Path Computation . . . . . . . . 5
5.1. PCE Initiated SR Paths . . . . . . . . . . . . . . . . . 6
5.2. PCC Initiated SR Paths . . . . . . . . . . . . . . . . . 7
5.3. Stateless PCE . . . . . . . . . . . . . . . . . . . . . . 8
5.4. Error Handling . . . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Segment routing (SR) [I-D.ietf-spring-segment-routing] leverages the
source routing and tunneling paradigms. SR supports to steer packets
into an explicit forwarding path according to the Segment Routing
Policy ( SR Policy) [I-D.ietf-spring-segment-routing-policy] at the
ingress node.
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However, the SR Policies defined in
[I-D.ietf-spring-segment-routing-policy] only supports uni-
directional SR paths. For supporting bi-directional paths
[I-D.cheng-spring-mpls-path-segment], new SR policies carrying Path
ID and bi-directional path information are defined in
[I-D.li-idr-sr-policy-path-segment-distribution].
[RFC5440] describes the Path Computation Element (PCE) Communication
Protocol (PCEP). PCEP enables the communication between a Path
Computation Client (PCC) and a PCE, or between PCE and PCE, for the
purpose of computation of Multiprotocol Label Switching (MPLS) as
well as Generalzied MPLS (GMPLS) Traffic Engineering Label Switched
Path (TE LSP) characteristics.
[RFC8231] specifies a set of extensions to PCEP to enable stateful
control of TE LSPs within and across PCEP sessions in compliance with
[RFC4657]. It includes mechanisms to effect LSP State
Synchronization between PCCs and PCEs, delegation of control over
LSPs to PCEs, and PCE control of timing and sequence of path
computations within and across PCEP sessions. The model of operation
where LSPs are initiated from the PCE is described in [RFC8281].
[I-D.ietf-pce-segment-routing] specifies extensions to the Path
Computation Element Protocol (PCEP) [RFC5440] for SR networks, that
allow a stateful PCE to compute and initiate SR-TE paths, as well as
a PCC to request, report or delegate SR paths.
[I-D.negi-pce-segment-routing-ipv6] extend PCEP to support SR for
IPv6 data plane.
[I-D.ietf-pce-association-group] introduces a generic mechanism to
create a grouping of LSPs which can then be used to define
associations between a set of LSPs and/or a set of attributes, for
example primary and secondary LSP associations, and is equally
applicable to the active and passive modes of a Stateful PCE
[RFC8231] or a stateless PCE [RFC5440].
[I-D.ietf-pce-association-bidir] defines PCEP extensions for grouping
two reverse unidirectional MPLS TE LSPs into an Associated
Bidirectional LSP when using a Stateful PCE for both PCE-Initiated
and PCC-Initiated LSPs as well as when using a Stateless PCE.
This document extends the bidirectional association to segment
routing by specifying PCEP extensions for grouping two reverse
unidirectional SR paths into a bi-directional SR path.
[I-D.li-pce-sr-path-segment] defines a procedure for path ID in PCEP
for SR by defining the PATH-ID TLV. The path ID can be a path
segment in SR-MPLS [I-D.cheng-spring-mpls-path-segment], or a path ID
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in SRv6 [I-D.li-spring-passive-pm-for-srv6-np], or other IDs that can
identify an SR path. The PATH-ID MUST be included for associated
bidirectional SR paths.
2. Terminology
This memo makes use of the terms defined in
[I-D.ietf-pce-segment-routing]. The reader is assumed to be familiar
with the terminology defined in [RFC5440], [RFC8231], [RFC8281],
[I-D.ietf-pce-association-group] and
[I-D.ietf-pce-association-bidir].
3. PCEP Extension for Bi-directional SR Path
As per [I-D.ietf-pce-association-group], LSPs are associated by
adding them to a common association group.
[I-D.ietf-pce-association-bidir] specifies PCEP extensions for
grouping two reverse unidirectional MPLS-TE LSPs into an Associated
Bidirectional LSP for both single-sided and double-sided initiation
cases by defining two new Bidirectional LSP Association Groups.
This document extends the procedure for SR bidirectional associated
paths by defining a new bidirectional association type (i.e. Double-
sided Bi-directional SR Path Association Group). The document
further describe the mechanism of associating two unidirectional SR
path into a bidirectional SR path. [I-D.li-pce-sr-path-segment]
defines a procedure for path ID in PCEP for SR by defining the PATH-
ID TLV. The bidirectional SR path MUST also use the PATH-ID TLV.
3.1. Double-sided Bidirectional SR Path Association Group Object
As defined in [I-D.ietf-pce-association-bidir], two LSPs are
associated as a bi-directional MPLS-TE LSP by a common bi-directional
LSP association group. For associating two SR paths, this document
defines a new association group called 'Double-sided Bidirectional SR
Path Association Group' as follows:
o Association Type (TBD) = Double-sided Bidirectional SR Path
Association Group
Similar to other bidirectional associations, this Association Type is
operator-configured in nature and statically created by the operator
on the PCEP peers. The paths belonging to this association is
conveyed via PCEP messages to the PCEP peer. Operator-configured
Association Range TLV [I-D.ietf-pce-association-group] MUST NOT be
sent for these Association Types, and MUST be ignored, so that the
entire range of association ID can be used for them. The handling of
the Association ID, Association Source, optional Global Association
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Source and optional Extended Association ID in this association are
set in the same way as [I-D.ietf-pce-association-bidir].
A member of the Double-sided Bi-directional SR Path Association Group
can take the role of a forward or reverse SR path and follows the
rules similar to the rules defined in
[I-D.ietf-pce-association-bidir] for LSPs.
o An SR path (forward or reverse) can not be part of more than one
Double-sided Bi-directional SR Path Association Group.
o The endpoints of the SR paths in this associations cannot be
different.
For describing the SR paths in this association group, such as
direction and co-routed information, this association group reuses
the Bi-directional LSP Association Group TLV defined in
[I-D.ietf-pce-association-bidir]. All fields and processing rules
are as per [I-D.ietf-pce-association-bidir].
4. Bi-directional Flag
As defined in [RFC5440], the B-flag in RP object MUST be set when the
PCC specifies that the path computation request relates to a bi-
directional TE LSP. In this document, the B-flag also MUST be set
when the PCC specifies that the path computation request relates to a
bi-directional SR path. Likely, when a stateful PCE initiates or
updates a bi-directional SR paths including LSPs and SR paths, the
B-flag in SRP object [I-D.ietf-pce-pcep-stateful-pce-gmpls] MUST be
set as well.
5. Procedures of Bi-directional Path Computation
Two uni-directional SR paths can be associated by the association
group object as specified in [I-D.ietf-pce-association-group]. A
bidirectional LSP association group object is defined in
[I-D.ietf-pce-association-bidir] (for MPLS-TE). This documents
extends the mechanism for bidirectional SR paths. Two SR paths can
be associated together by including the Bi-directional SR Path
Association Group in the PCEP messages. The PATH-ID TLV
[I-D.li-pce-sr-path-segment] MUST also be included in the LSP object
for these SR paths.
There is also a need to include the reverse direction path in the
PCEP messages, to do this the PCE SHOULD inform the reverse SR path
to the ingress PCC and vice versa. To achieve this a PCInitiate
message for the reverse SR path is sent to the ingress PCC and a
PCInitiate message for the forward SR path is sent to the egress PCC
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(with the same association group). These PCInitiate message MUST not
trigger initiation of SR paths. The information of reverse direction
path can be used for several scenarios, such as directed BFD
[I-D.ietf-mpls-bfd-directed].
5.1. PCE Initiated SR Paths
As specified in [I-D.ietf-pce-association-group] Bidirectional SR
Association Group can be created by a Stateful PCE.
o Stateful PCE can create and update the forward and reverse SR path
independently for Double-sided Bi-directional SR Path Association
Groups.
o Stateful PCE can establish and remove the association relationship
on a per SR path basis.
o Stateful PCE can create and update the SR path and the association
on a PCC via PCInitiate and PCUpd messages, respectively, using
the procedures described in [I-D.ietf-pce-association-group].
o The Path-ID TLV MUST be included for each SR path in the LSP
object.
o The opposite direction SR path (LSP2(R) at S, LSP1(F) at D )
SHOULD be informed via PCInitiate message with the matching
association group.
+-----+
| PCE |
+-----+
PCUpd/PCInitiate / \ PCUpd/PCInitiate
Tunnel 1 (F) / \ Tunnel 2 (R)
(LSP1 (F), LSP2 (R)) / \ (LSP2 (R), LSP1 (F))
Assoc#1 / \ Assoc#1
/ \
v v
+-----+ LSP1 +-----+
| S |------------>| D |
| |<------------| |
+-----+ LSP2 +-----+
Figure 1: PCE-Initiated Double-sided Bidirectional SR Path
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5.2. PCC Initiated SR Paths
As specified in [I-D.ietf-pce-association-group] Bidirectional SR
Association Group can also be created by a PCC.
o PCC can create and update the forward and reverse SR paths
independently for Double-sided Bi-directional SR Path Association
Groups.
o PCC can establish and remove the association relationship on a per
SR path basis.
o PCC MUST report the change in the association group of an SR path
to PCE(s) via PCRpt message.
o PCC can report the forward and reverse SR paths independently to
PCE(s) via PCRpt message.
o PCC can delegate the forward and reverse SR paths independently to
a Stateful PCE, where PCE would control the SR paths.
o Stateful PCE can update the SR paths in the Double-sided Bi-
directional SR Path Association Group via PCUpd message, using the
procedures described in [I-D.ietf-pce-association-group].
o The Path-ID TLV MUST be handled as defined in
[I-D.li-pce-sr-path-segment].
o The opposite direction SR path (LSP2(R) at S, LSP1(F) at D )
SHOULD be informed via PCInitiate message with the matching
association group.
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+-----+
| PCE |
+-----+
Reports/Delegates: ^ ^ Reports/Delegates
Tunnel 1 (F) / \ Tunnel 2 (R)
(LSP1 (F)) / \ (LSP2 (R))
/ \
/ \
/ \
+-----+ LSP1 +-----+
| S |------------>| D |
| |<------------| |
+-----+ LSP2 +-----+
Figure 2a: PCC-Initiated Double-sided Bidirectional SR Path
+-----+
| PCE |
+-----+
PCUpd/PCInitiate / \ PCUpd/PCInitiate
Tunnel 1 (F) / \ Tunnel 2 (R)
(LSP1 (F), LSP2 (R)) / \ (LSP2 (R), LSP1 (F))
Assoc#1 / \ Assoc#1
/ \
v v
+-----+ LSP1 +-----+
| S |------------>| D |
| |<------------| |
+-----+ LSP2 +-----+
Figure 2b: PCC-Initiated Double-sided Bidirectional SR Path
along with opposite direction SR path
5.3. Stateless PCE
As defined in [I-D.ietf-pce-association-bidir], for a stateless PCE,
it might be useful to associate a path computation request to an
association group, thus enabling it to associate a common set of
configuration parameters or behaviors with the request. A PCC can
request co-routed or non co-routed forward and reverse direction
paths from a stateless PCE for a bidirectional LSP association group.
5.4. Error Handling
The error handling as described in [I-D.ietf-pce-association-bidir]
continue to apply.
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6. IANA Considerations
TBA
7. Security Considerations
TBA
8. Acknowledgments
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
[I-D.ietf-pce-association-group]
Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
Dhody, D., and Y. Tanaka, "PCEP Extensions for
Establishing Relationships Between Sets of LSPs", draft-
ietf-pce-association-group-06 (work in progress), June
2018.
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[I-D.ietf-pce-association-bidir]
Barth, C., Gandhi, R., and B. Wen, "PCEP Extensions for
Associated Bidirectional Label Switched Paths (LSPs)",
draft-ietf-pce-association-bidir-01 (work in progress),
May 2018.
[I-D.ietf-pce-pcep-stateful-pce-gmpls]
Zhang, X., Lee, Y., Zhang, F., Casellas, R., Dios, O., and
Z. Ali, "Path Computation Element (PCE) Protocol
Extensions for Stateful PCE Usage in GMPLS-controlled
Networks", draft-ietf-pce-pcep-stateful-pce-gmpls-08 (work
in progress), February 2018.
[I-D.negi-pce-segment-routing-ipv6]
Negi, M., Kaladharan, P., Dhody, D., and S. Sivabalan,
"PCEP Extensions for Segment Routing leveraging the IPv6
data plane", draft-negi-pce-segment-routing-ipv6-01 (work
in progress), March 2018.
[I-D.li-pce-sr-path-segment]
Li, C., Chen, M., Dong, J., Li, Z., and D. Dhody, "Path
Computation Element Communication Protocol (PCEP)
Extension for Path Identification in Segment Routing
(SR)", draft-li-pce-sr-path-segment-00 (work in progress),
June 2018.
9.2. Informative References
[RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol Generic
Requirements", RFC 4657, DOI 10.17487/RFC4657, September
2006, <https://www.rfc-editor.org/info/rfc4657>.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-11 (work in progress),
November 2017.
[I-D.ietf-mpls-bfd-directed]
Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen,
"Bidirectional Forwarding Detection (BFD) Directed Return
Path", draft-ietf-mpls-bfd-directed-08 (work in progress),
December 2017.
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[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
bogdanov@google.com, b., and P. Mattes, "Segment Routing
Policy Architecture", draft-ietf-spring-segment-routing-
policy-01 (work in progress), June 2018.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018.
[I-D.cheng-spring-mpls-path-segment]
Cheng, W., Wang, L., Li, H., Chen, M., Zigler, R., and S.
Zhan, "Path Segment in MPLS Based Sement Routing Network",
draft-cheng-spring-mpls-path-segment-01 (work in
progress), March 2018.
[I-D.li-spring-passive-pm-for-srv6-np]
Li, C. and M. Chen, "Passive Performance Measurement for
SRv6 Network Programming", draft-li-spring-passive-pm-for-
srv6-np-00 (work in progress), March 2018.
[I-D.li-idr-sr-policy-path-segment-distribution]
Li, C., Chen, M., Dong, J., and Z. Li, "Segment Routing
Policies for Path Segment and Bi-directional Path", draft-
li-idr-sr-policy-path-segment-distribution-00 (work in
progress), April 2018.
Authors' Addresses
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: chengli13@huawei.com
Mach(Guoyi) Chen
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: Mach.chen@huawei.com
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Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Zhenbin Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: jie.dong@huawei.com
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