PCEP Extension for Segment Routing (SR) Bi-directional Associated Paths
draft-li-pce-sr-bidir-path-01
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 , Weiqiang Cheng , Zhenbin Li , Jie Dong , Rakesh Gandhi | ||
| Last updated | 2018-09-11 | ||
| Replaced by | draft-ietf-pce-sr-bidir-path, draft-ietf-pce-sr-bidir-path | ||
| RFC stream | (None) | ||
| Formats | |||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
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draft-li-pce-sr-bidir-path-01
PCE Working Group C. Li
Internet-Draft M. Chen
Intended status: Standards Track D. Dhody
Expires: March 16, 2019 Huawei Technologies
W. Cheng
China Mobile
Z. Li
J. Dong
Huawei Technologies
R. Gandhi
Cisco Systems, Inc.
September 12, 2018
PCEP Extension for Segment Routing (SR) Bi-directional Associated Paths
draft-li-pce-sr-bidir-path-01
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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working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://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."
This Internet-Draft will expire on March 16, 2019.
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
(https://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
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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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. PCEP Extension for Bi-directional SR Path . . . . . . . . . . 4
3.1. Double-sided Bidirectional SR Path Association Group
Object . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Bi-directional Flag . . . . . . . . . . . . . . . . . . . . . 5
5. Procedures of Bi-directional Path Computation . . . . . . . . 6
5.1. PCE Initiated SR Paths . . . . . . . . . . . . . . . . . 6
5.2. PCC Initiated SR Paths . . . . . . . . . . . . . . . . . 7
5.3. Error Handling . . . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6.1. Association Type . . . . . . . . . . . . . . . . . . . . 9
6.2. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Segment routing (SR) [RFC8402] leverages the source routing and
tunneling paradigms. SR supports to steer packets into an explicit
forwarding path at the ingress node.
[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].
Currently, SR network only supports uni-directional path, but the
bidirectional SR path is required in some scenarios, for example,
mobile backhaul transport network. The requirement of SR
bidirectional path is specified in
[I-D.cheng-spring-mpls-path-segment].
[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.
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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.ietf-pce-association-bidir] specify the Double-sided
Bidirectional procedure, where the PCE creates the association and
provisions at the both ends, the RSVP-TE does the signaling to the
egress the status of the forward LSP and the ingress about the
reverse LSP. Thus the both ends learn both the LSPs forming the bi-
directional association. In case of SR, to support the bi-
directional use-case, this is done via the PCEP protocol itself as
described in Section 3.1. This is done so that both ends are aware
of the path segment/ID used by each of the uni-directional LSP, as
well as the status, the ERO etc.
[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
in SRv6 [I-D.li-spring-passive-pm-for-srv6-np], or other IDs that can
identify an SR path. The PATH-ID SHOULD 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.
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Note that a new association type is created by this document to
create new procedures applicable to SR-path (and are quite different
to the RSVP-TE bi-directional association groups).
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 (TBD1 to be assigned by IANA) = 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
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
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when the PCC specifies that the path computation request relates to a
bi-directional SR path. 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] may 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] SHOULD 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
(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 SHOULD be included for each SR path in the LSP
object.
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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 +-----+
<no signaling>
Figure 1: PCE-Initiated Double-sided Bidirectional SR Path
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].
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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.
+-----+
| 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. Error Handling
The error handling as described in section 5.5 of
[I-D.ietf-pce-association-bidir] continue to apply.
The Path Setup Type (PST) MUST be set to SR for the LSP belonging to
the 'Double-sided Bidirectional SR Path Association Group', in case a
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PCEP speaker receives a different PST value, it MUST send an PCErr
message with Error-Type = 29 (Early allocation by IANA) (Association
Error) and Error-Value = TBD2 (Bidirectional LSP Association - PST
Mismatch).
6. IANA Considerations
6.1. Association Type
This document adds a new Association Type for the Association Object
defined [I-D.ietf-pce-association-group]. IANA is requested to make
the assignment of a value for the sub-registry "ASSOCIATION Type
Field" (to be created in [I-D.ietf-pce-association-group]), as
follows:
Value Name Reference
-------------------------------------------------------------------
TBD1 Double-sided Bidirectional This document
SR Path Association Group
6.2. PCEP Errors
This document defines new Error value for Error Type 29 (Association
Error). IANA is requested to allocate new Error value within the
"PCEP-ERROR Object Error Types and Values" sub-registry of the PCEP
Numbers registry, as follows:
Error Type Description Reference
-------------------------------------------------------------------
29 Association Error
Error value: TBD2 This document
Bidirectional LSP Association - PST Mismatch
7. Security Considerations
The security considerations described in [RFC5440], [RFC8231],
[RFC8281], and [I-D.ietf-pce-segment-routing] apply to the extensions
defined in this document as well.
A new Association Type for the Association Object, Double-sided
Associated Bidirectional SR Path Association Group are introduced in
this document. Additional security considerations related to LSP
associations due to a malicious PCEP speaker is described in
[I-D.ietf-pce-association-group] and apply to these Association
Types. Hence, securing the PCEP session using Transport Layer
Security (TLS) [RFC8253] is recommended.
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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.
[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.
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[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-ipv6-02 (work
in progress), June 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-01 (work in progress),
August 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>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[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-12 (work in progress), June
2018.
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[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-09 (work in progress),
August 2018.
[I-D.cheng-spring-mpls-path-segment]
Cheng, W., Wang, L., Li, H., Chen, M., Zigler, R., Zhan,
S., and R. Gandhi, "Path Segment in MPLS Based Segment
Routing Network", draft-cheng-spring-mpls-path-segment-02
(work in progress), July 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.
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
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
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Weiqiang Cheng
China Mobile
China
Email: chengweiqiang@chinamobile.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
Rakesh Gandhi
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com
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