< draft-li-pce-sr-bidir-path-03.txt   draft-li-pce-sr-bidir-path-04.txt >
PCE Working Group C. Li PCE Working Group C. Li
Internet-Draft M. Chen Internet-Draft M. Chen
Intended status: Standards Track Huawei Technologies Intended status: Standards Track Huawei Technologies
Expires: September 9, 2019 W. Cheng Expires: September 12, 2019 W. Cheng
China Mobile China Mobile
Z. Li Z. Li
J. Dong J. Dong
Huawei Technologies Huawei Technologies
R. Gandhi R. Gandhi
Cisco Systems, Inc. Cisco Systems, Inc.
March 08, 2019 March 11, 2019
PCEP Extension for Segment Routing (SR) Bidirectional Associated Paths PCEP Extensions for Associated Bidirectional Segment Routing (SR) Paths
draft-li-pce-sr-bidir-path-03 draft-li-pce-sr-bidir-path-04
Abstract Abstract
The Path Computation Element Communication Protocol (PCEP) provides The Path Computation Element Communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Clients (PCCs) requests. computations in response to Path Computation Clients (PCCs) requests.
The Stateful PCE extensions allow stateful control of Multiprotocol The Stateful PCE extensions allow stateful control of Multiprotocol
Label Switching (MPLS) Traffic Engineering (TE) Label Switched Paths Label Switching (MPLS) Traffic Engineering (TE) Label Switched Paths
(LSPs) using PCEP. Furthermore, PCEP can be used for computing paths (LSPs) using PCEP. Furthermore, PCEP can be used for computing paths
in SR networks. in Segment Routing (SR) TE networks.
This document defines PCEP extensions for grouping two reverse This document defines PCEP extensions for grouping two reverse
unidirectional SR Paths into an Associated Bidirectional SR path when unidirectional SR Paths into an Associated Bidirectional SR Path when
using a Stateful PCE for both PCE-Initiated and PCC-Initiated LSPs as using a Stateful PCE for both PCE-Initiated and PCC-Initiated LSPs as
well as when using a Stateless PCE. well as when using a Stateless PCE.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. PCEP Extension for Bidirectional SR Path . . . . . . . . . . 4 3. PCEP Extension for Bidirectional SR Path . . . . . . . . . . . 4
3.1. Double-sided Bidirectional SR Path Association Group 3.1. Double-sided Bidirectional SR Path Association Group
Object . . . . . . . . . . . . . . . . . . . . . . . . . 5 Object . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Bidirectional Flag . . . . . . . . . . . . . . . . . . . . . 5 4. Bidirectional Flag . . . . . . . . . . . . . . . . . . . . . . 6
5. Procedures of Bidirectional Path Computation . . . . . . . . 6 5. Procedures for Associated Bidirectional SR Path Computation . 6
5.1. PCE Initiated SR Paths . . . . . . . . . . . . . . . . . 6 5.1. PCE Initiated Associated Bidirectional SR Paths . . . . . 7
5.2. PCC Initiated SR Paths . . . . . . . . . . . . . . . . . 7 5.2. PCC Initiated Associated Bidirectional SR Paths . . . . . 8
5.3. Error Handling . . . . . . . . . . . . . . . . . . . . . 9 5.3. Error Handling . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6.1. Association Type . . . . . . . . . . . . . . . . . . . . 10 6.1. Association Type . . . . . . . . . . . . . . . . . . . . . 10
6.2. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 10 6.2. PCEP Errors . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1. Normative References . . . . . . . . . . . . . . . . . . 11 10.1. Normative References . . . . . . . . . . . . . . . . . . 12
10.2. Informative References . . . . . . . . . . . . . . . . . 13 10.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
Segment routing (SR) [RFC8402] leverages the source routing and Segment routing (SR) [RFC8402] leverages the source routing and
tunneling paradigms. SR supports to steer packets into an explicit tunneling paradigms. SR supports to steer packets into an explicit
forwarding path at the ingress node. forwarding path at the ingress node.
[RFC5440] describes the Path Computation Element (PCE) Communication [RFC5440] describes the Path Computation Element (PCE) Communication
Protocol (PCEP). PCEP enables the communication between a Path Protocol (PCEP). PCEP enables the communication between a Path
Computation Client (PCC) and a PCE, or between PCE and PCE, for the Computation Client (PCC) and a PCE, or between PCE and PCE, for the
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control of TE LSPs within and across PCEP sessions in compliance with control of TE LSPs within and across PCEP sessions in compliance with
[RFC4657]. It includes mechanisms to effect LSP State [RFC4657]. It includes mechanisms to effect LSP State
Synchronization between PCCs and PCEs, delegation of control over Synchronization between PCCs and PCEs, delegation of control over
LSPs to PCEs, and PCE control of timing and sequence of path LSPs to PCEs, and PCE control of timing and sequence of path
computations within and across PCEP sessions. The model of operation computations within and across PCEP sessions. The model of operation
where LSPs are initiated from the PCE is described in [RFC8281]. where LSPs are initiated from the PCE is described in [RFC8281].
[I-D.ietf-pce-segment-routing] specifies extensions to the Path [I-D.ietf-pce-segment-routing] specifies extensions to the Path
Computation Element Protocol (PCEP) [RFC5440] for SR networks, that Computation Element Protocol (PCEP) [RFC5440] for SR networks, that
allow a stateful PCE to compute and initiate SR-TE paths, as well as allow a stateful PCE to compute and initiate SR-TE paths, as well as
a PCC to request, report or delegate SR paths. a PCC to request, report or delegate SR Paths.
[I-D.negi-pce-segment-routing-ipv6] extend PCEP to support SR for [I-D.ietf-pce-segment-routing-ipv6] extend PCEP to support SR for
IPv6 data plane. IPv6 data plane.
[I-D.ietf-pce-association-group] introduces a generic mechanism to [I-D.ietf-pce-association-group] introduces a generic mechanism to
create a grouping of LSPs which can then be used to define 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 associations between a set of LSPs and/or a set of attributes, for
example primary and secondary LSP associations, and is equally example primary and secondary LSP associations, and is equally
applicable to the active and passive modes of a Stateful PCE applicable to the active and passive modes of a Stateful PCE
[RFC8231] or a stateless PCE [RFC5440]. [RFC8231] or a stateless PCE [RFC5440].
Currently, SR network only supports unidirectional path, but the Currently, SR networks only support unidirectional paths. However,
bidirectional SR path is required in some scenarios, for example, bidirectional SR Paths are required in some networks, for example, in
mobile backhaul transport network. The requirement of SR mobile backhaul transport networks. The requirement of bidirectional
bidirectional path is specified in SR Path is specified in [I-D.ietf-spring-mpls-path-segment].
[I-D.cheng-spring-mpls-path-segment].
[I-D.ietf-pce-association-bidir] defines PCEP extensions for grouping [I-D.ietf-pce-association-bidir] defines PCEP extensions for grouping
two reverse unidirectional MPLS TE LSPs into an Associated two reverse unidirectional MPLS TE LSPs into an Associated
Bidirectional LSP when using a Stateful PCE for both PCE-Initiated Bidirectional LSP when using a Stateful PCE for both PCE-Initiated
and PCC-Initiated LSPs as well as when using a Stateless PCE. and PCC-Initiated LSPs as well as when using a Stateless PCE.
This document extends the bidirectional association to segment This document extends the bidirectional association to segment
routing by specifying PCEP extensions for grouping two reverse routing by specifying PCEP extensions for grouping two reverse
unidirectional SR paths into a bidirectional SR path. unidirectional SR Paths into a bidirectional SR Path.
[I-D.ietf-pce-association-bidir] specify the Double-sided [I-D.ietf-pce-association-bidir] specifies the Double-sided
Bidirectional procedure, where the PCE creates the association and Bidirectional LSP Association procedure, where the PCE creates the
provisions at the both ends, the RSVP-TE does the signaling to the association and provisions at both endpoints, the RSVP-TE does the
egress the status of the forward LSP and the ingress about the signaling to the egress the status of the forward LSP and the ingress
reverse LSP. Thus, the both ends learn both the LSPs forming the about the reverse LSP. Thus, the both endpoints learn the reverse
bidirectional association. In case of SR, to support the LSPs forming the bidirectional LSP association. In case of SR, to
bidirectional use-case, this is done via the PCEP protocol itself as support the bidirectional path use-case, this is done using the PCEP
described in Section 3.1. This is done so that both ends are aware protocol. This is done so that both endpoints are aware of the the
of the Path Segment used by each of the unidirectional LSP, as well unidirectional SR Path, as well as the status and other SR path
as the status, the ERO etc. related information.
[I-D.li-pce-sr-path-segment] defines a procedure for Path Segment in [I-D.li-pce-sr-path-segment] defines a procedure for Path Segment
PCEP for SR by defining the PATH-SEGMENT TLV. The Path Segment can Identifier (PSID) in PCEP for SR using PATH-SEGMENT TLV. The PSID
be a Path Segment in SR-MPLS [I-D.cheng-spring-mpls-path-segment], or can be a Path Segment Identifier in SR-MPLS
a Path Segment in SRv6 [I-D.li-spring-srv6-path-segment], or other [I-D.ietf-spring-mpls-path-segment], or a Path Segment Identifier in
IDs that can identify an SR path. The PATH-SEGMENT TLV SHOULD be SRv6 [I-D.li-spring-srv6-path-segment]. The PSID can be used for an
included for associated bidirectional SR paths. associated bidirectional SR Path for identifying the SR Path.
2. Terminology 2. Terminology
This document makes use of the terms defined in This document makes use of the terms defined in
[I-D.ietf-pce-segment-routing]. The reader is assumed to be familiar [I-D.ietf-pce-segment-routing]. The reader is assumed to be familiar
with the terminology defined in [RFC5440], [RFC8231], [RFC8281], with the terminology defined in [RFC5440], [RFC8231], [RFC8281],
[I-D.ietf-pce-association-group] and [I-D.ietf-pce-association-group] and
[I-D.ietf-pce-association-bidir]. [I-D.ietf-pce-association-bidir].
2.1. Requirements Language 2.1. Requirements Language
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3. PCEP Extension for Bidirectional SR Path 3. PCEP Extension for Bidirectional SR Path
As per [I-D.ietf-pce-association-group], LSPs are associated by As per [I-D.ietf-pce-association-group], LSPs are associated by
adding them to a common association group. adding them to a common association group.
[I-D.ietf-pce-association-bidir] specifies PCEP extensions for [I-D.ietf-pce-association-bidir] specifies PCEP extensions for
grouping two reverse unidirectional MPLS-TE LSPs into an Associated grouping two reverse unidirectional MPLS-TE LSPs into an Associated
Bidirectional LSP for both single-sided and double-sided initiation Bidirectional LSP for both single-sided and double-sided initiation
cases by defining two new Bidirectional LSP Association Groups. cases by defining two new Bidirectional LSP Association Groups.
This document extends the procedure for SR bidirectional associated This document extends the procedure for associated bidirectional SR
paths by defining a new bidirectional association type (i.e. Double- Paths by defining a new bidirectional association group (Double-sided
sided Bidirectional SR Path Association Group). The document further Bidirectional SR Path Association Group). The document further
describes the mechanism of associating two unidirectional SR path describes the mechanism for associating two unidirectional SR Paths
into a bidirectional SR path. [I-D.li-pce-sr-path-segment] defines a into a bidirectional SR Path. [I-D.li-pce-sr-path-segment] defines a
procedure for Path Segment in PCEP for SR by defining the PATH- procedure for communicating Path Segment in PCEP for SR using
SEGMENT TLV. The bidirectional SR path can also use the PATH-SEGMENT PATH-SEGMENT TLV. The bidirectional SR Path can also use the
TLV. PATH-SEGMENT TLV.
Note that a new association type is created by this document to Note that an association group is defined in this document to define
create new procedures applicable to SR-path (and are quite different procedures specific to SR Paths (and the procedures are different
than the RSVP-TE bidirectional association groups). than the RSVP-TE bidirectional association groups defined in
[I-D.ietf-pce-association-bidir]).
3.1. Double-sided Bidirectional SR Path Association Group Object 3.1. Double-sided Bidirectional SR Path Association Group Object
As defined in [I-D.ietf-pce-association-bidir], two LSPs are As defined in [I-D.ietf-pce-association-bidir], two LSPs are
associated as a bidirectional MPLS-TE LSP by a common bidirectional associated as a bidirectional MPLS-TE LSP by a common bidirectional
LSP association group. For associating two SR paths, this document LSP association group. For associating two SR paths, this document
defines a new association group called 'Double-sided Bidirectional SR defines a new association group called 'Double-sided Bidirectional SR
Path Association Group' as follows: Path Association Group' as follows:
o Association Type (TBD1 to be assigned by IANA) = Double-sided o Association Type (TBD1 to be assigned by IANA) = Double-sided
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operator-configured in nature and statically created by the operator operator-configured in nature and statically created by the operator
on the PCEP peers. The paths belonging to this association is on the PCEP peers. The paths belonging to this association is
conveyed via PCEP messages to the PCEP peer. Operator-configured conveyed via PCEP messages to the PCEP peer. Operator-configured
Association Range TLV [I-D.ietf-pce-association-group] MUST NOT be Association Range TLV [I-D.ietf-pce-association-group] MUST NOT be
sent for these Association Types, and MUST be ignored, so that the 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 entire range of association ID can be used for them. The handling of
the Association ID, Association Source, optional Global Association the Association ID, Association Source, optional Global Association
Source and optional Extended Association ID in this association are Source and optional Extended Association ID in this association are
set in the same way as [I-D.ietf-pce-association-bidir]. set in the same way as [I-D.ietf-pce-association-bidir].
A member of the Double-sided Bidirectional SR Path Association Group A member of the 'Double-sided Bidirectional SR Path Association
can take the role of a forward or reverse SR path and follows the Group' can take the role of a forward or reverse SR Path and follow
rules similar to the rules defined in the similar rules defined in [I-D.ietf-pce-association-bidir] for
[I-D.ietf-pce-association-bidir] for LSPs. LSPs.
o An SR path (forward or reverse) can not be part of more than one o An SR Path (forward or reverse) can not be part of more than one
Double-sided Bidirectional SR Path Association Group. 'Double-sided Bidirectional SR Path Association Group'.
o The endpoints of the SR paths in this associations cannot be o The endpoints of the SR Paths in this associations cannot be
different. different.
For describing the SR paths in this association group, such as For describing the SR Paths in this association group, such as
direction and co-routed information, this association group reuses direction and co-routed information, this association group reuses
the Bidirectional LSP Association Group TLV defined in the Bidirectional LSP Association Group TLV defined in
[I-D.ietf-pce-association-bidir]. All fields and processing rules [I-D.ietf-pce-association-bidir]. All fields and processing rules
are as per [I-D.ietf-pce-association-bidir]. are as per [I-D.ietf-pce-association-bidir].
4. Bidirectional Flag 4. Bidirectional Flag
As defined in [RFC5440], the B-flag in RP object MUST be set when the 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 PCC specifies that the path computation request relates to a
bidirectional TE LSP. In this document, the B-flag also MUST be set bidirectional TE LSP. In this document, the B-flag also MUST be set
when the PCC specifies that the path computation request relates to a when the PCC specifies that the path computation request relates to a
bidirectional SR path. When a stateful PCE initiates or updates a bidirectional SR Path. When a stateful PCE initiates or updates a
bidirectional SR paths including LSPs and SR paths, the B-flag in SRP bidirectional 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. object [I-D.ietf-pce-pcep-stateful-pce-gmpls] MAY be set as well.
5. Procedures of Bidirectional Path Computation 5. Procedures for Associated Bidirectional SR Path Computation
Two unidirectional SR paths can be associated by the association Two unidirectional SR Paths can be associated by the association
group object as specified in [I-D.ietf-pce-association-group]. A group object as specified in [I-D.ietf-pce-association-group]. A
bidirectional LSP association group object is defined in bidirectional LSP association group object is defined in
[I-D.ietf-pce-association-bidir] (for MPLS-TE). This documents [I-D.ietf-pce-association-bidir] (for MPLS-TE). This document
extends the mechanism for bidirectional SR paths. Two SR paths can extends these association mechanisms for bidirectional SR Paths. Two
be associated together by including the Bidirectional SR Path SR Paths can be associated together by using the Bidirectional SR
Association Group in the PCEP messages. The PATH-SEGMENT TLV Path Association Group defined in this document for PCEP messages.
[I-D.li-pce-sr-path-segment] SHOULD also be included in the LSP The PATH-SEGMENT TLV [I-D.li-pce-sr-path-segment] SHOULD also be
object for these SR paths to support required use-cases. included in the LSP object for these SR Paths to support required
use-cases.
There is also a need to include the reverse direction path in the For bidirectional SR Paths, there is a need to know the reverse
PCEP messages, so the PCE SHOULD inform the reverse SR path to the direction SR paths. The PCE SHOULD inform the reverse SR Paths to
ingress PCC and vice versa. To achieve this, a PCInitiate message the ingress PCCs and vice versa. To achieve this, a PCInitiate
for the reverse SR path is sent to the ingress PCC and a PCInitiate message for the reverse SR Path is sent to the ingress PCC and a
message for the forward SR path is sent to the egress PCC (with the PCInitiate message for the forward SR Path is sent to the egress PCC
same association group). These PCInitiate message MUST NOT trigger (with the same association group). These PCInitiate message MUST NOT
initiation of SR paths. The information of reverse direction path trigger initiation of SR Paths. The reverse direction SR Path can be
can be used for several scenarios, such as directed BFD used for several use-cases, such as directed BFD
[I-D.ietf-mpls-bfd-directed]. [I-D.ietf-mpls-bfd-directed].
In a bidirectional LSP computaion, a same LSP would be identified via For a bidirectional LSP computation when using both direction LSPs on
2 different PLSP-IDs based on the PCEP session to the ingress or the a node, the same LSP would need to be identified using 2 different
egress. In other words, a LSP will have a PLSP-ID A at the ingress PLSP-IDs based on the PCEP session to the ingress or the egress. In
node while have the PLSP-ID B at the egress node. The PCE could other words, the LSP will have a PLSP-ID A at the ingress node while
maintain the two PLSP-ID for the same LSP. it will have the PLSP-ID B at the egress node. The PCE will maintain
the two PLSP-IDs for the same LSP. For instance, an ingress PCC
For instance, an ingress PCC requests a bidirectional SR path requests a bidirectional SR Path computation, and the PCE computes a
computation, and the PCE compute a forward LSP1 with PLSP-ID 100, and forward LSP1 with PLSP-ID say 100. The reverse LSP2 from the egress
reverse LSP from the egress to the ingress with PLSP-ID 200 allocated to the ingress with PLSP-ID say 200 is allocated by the egress PCC.
by the egress PCC. Since the PLSP-ID space is isolated at each PCC, Since the PLSP-ID space is independent at each PCC, the PLSP-ID
so the PLSP-ID allocated by egress PCC can not be used at the ingress allocated by the egress PCC can not be used for the LSP at the
PCC(PSLD-ID confliction may occur), so the PCE needs to allocate a ingress PCC (PLSP-ID conflict may occur). Hence, the PCE needs to
PLSP-ID for LSP2 from the ingress PCC's PSLP-ID space , such as 101. allocate a PLSP-ID for LSP2 from the ingress PCC's PLSP-ID space ,
It is the same situtaion for LSP1, it has PLSP-ID 100 at the ingress, say 101. Similarly for LSP1, it has PLSP-ID 100 at the ingress, and
and may has PLSP-ID 201 at the egress. may have say PLSP-ID 201 at the egress node.
5.1. PCE Initiated SR Paths 5.1. PCE Initiated Associated Bidirectional SR Paths
As specified in [I-D.ietf-pce-association-group] Bidirectional SR As specified in [I-D.ietf-pce-association-group], Bidirectional SR
Association Group can be created by a Stateful PCE. Path Association Group can be created by a Stateful PCE.
o Stateful PCE can create and update the forward and reverse SR path o Stateful PCE can create and update the forward and reverse SR
independently for Double-sided Bidirectional SR Path Association Paths independently for a 'Double-sided Bidirectional SR Path
Groups. Association Group'.
o Stateful PCE can establish and remove the association relationship o Stateful PCE can establish and remove the association relationship
on a per SR path basis. on a per SR Path basis.
o Stateful PCE can create and update the SR path and the association o Stateful PCE can create and update the SR Path and the association
on a PCC via PCInitiate and PCUpd messages, respectively, using on a PCC via PCInitiate and PCUpd messages, respectively, using
the procedures described in [I-D.ietf-pce-association-group]. the procedures described in [I-D.ietf-pce-association-group].
o The PATH-SEGMENT TLV SHOULD be included for each SR path in the o The PATH-SEGMENT TLV SHOULD be included for each SR Path in the
LSP object. LSP object.
o The opposite direction SR path (LSP2(R) at S, LSP1(R) at D ) o The reverse direction SR Path (LSP2(R) at node S, LSP1(R) at node
SHOULD be informed via PCInitiate message with the matching D) SHOULD be informed by PCE via PCInitiate message with the
association group. matching association group.
+-----+ +-----+
| PCE | | PCE |
+-----+ +-----+
PCUpd/PCInitiate / \ PCUpd/PCInitiate PCInitiate/PCUpd: / \ PCInitiate/PCUpd:
Tunnel 1 (F) / \ Tunnel 2 (R) Tunnel 1 (F) / \ Tunnel 2 (F)
(LSP1 (F), LSP2 (R)) / \ (LSP2 (F), LSP1 (R)) (LSP1 (F), LSP2 (R)) / \ (LSP2 (F), LSP1 (R))
Assoc#1 / \ Assoc#1 Association #1 / \ Association #1
/ \ / \
v v v v
+-----+ LSP1 +-----+ +-----+ LSP1 +-----+
| S |------------>| D | | S |------------>| D |
| |<------------| | | |<------------| |
+-----+ LSP2 +-----+ +-----+ LSP2 +-----+
<no signaling> <no signaling>
Figure 1: PCE-Initiated Double-sided Bidirectional SR Path Figure 1: PCE-Initiated Double-sided Bidirectional SR Path
with Forward and Reverse Direction SR Paths
5.2. PCC Initiated SR Paths 5.2. PCC Initiated Associated Bidirectional SR Paths
As specified in [I-D.ietf-pce-association-group] Bidirectional SR As specified in [I-D.ietf-pce-association-group], Bidirectional SR
Association Group can also be created by a PCC. Path Association Group can also be created by a PCC.
o PCC can create and update the forward and reverse SR paths o PCC can create and update the forward and reverse SR Paths
independently for Double-sided Bidirectional SR Path Association independently for a 'Double-sided Bidirectional SR Path
Groups. Association Group'.
o PCC can establish and remove the association relationship on a per o PCC can establish and remove the association relationship on a per
SR path basis. SR Path basis.
o PCC MUST report the change in the association group of an SR path o PCC MUST report the change in the association group of an SR Path
to PCE(s) via PCRpt message. to PCE(s) via PCRpt message.
o PCC can report the forward and reverse SR paths independently to o PCC can report the forward and reverse SR Paths independently to
PCE(s) via PCRpt message. PCE(s) via PCRpt message.
o PCC can delegate the forward and reverse SR paths independently to o PCC can delegate the forward and reverse SR Paths independently to
a Stateful PCE, where PCE would control the SR paths. a Stateful PCE, where PCE would control the SR Paths.
o Stateful PCE can update the SR paths in the Double-sided o Stateful PCE can update the SR Paths in the 'Double-sided
Bidirectional SR Path Association Group via PCUpd message, using Bidirectional SR Path Association Group' via PCUpd message, using
the procedures described in [I-D.ietf-pce-association-group]. the procedures described in [I-D.ietf-pce-association-group].
o The PATH-SEGMENT TLV MUST be handled as defined in o The PATH-SEGMENT TLV MUST be handled as defined in
[I-D.li-pce-sr-path-segment]. [I-D.li-pce-sr-path-segment].
o The opposite direction SR path (LSP2(R) at S, LSP1(R) at D ) o The reverse direction SR Path (LSP2(R) at node S, LSP1(R) at node
SHOULD be informed via PCInitiate message with the matching D) SHOULD be informed by PCE via PCInitiate message with the
association group. matching association group.
+-----+ +-----+
| PCE | | PCE |
+-----+ +-----+
Reports/Delegates: ^ ^ Reports/Delegates Report/Delegate: ^ ^ Report/Delegate:
Tunnel 1 (F) / \ Tunnel 2 (R) Tunnel 1 (F) / \ Tunnel 2 (F)
(LSP1 (F)) / \ (LSP2 (R)) (LSP1 (F)) / \ (LSP2 (F))
/ \ Association #2 / \ Association #2
/ \ / \
/ \ / \
+-----+ LSP1 +-----+ +-----+ LSP1 +-----+
| S |------------>| D | | S |------------>| D |
| |<------------| | | |<------------| |
+-----+ LSP2 +-----+ +-----+ LSP2 +-----+
<no signaling>
Figure 2a: PCC-Initiated Double-sided Bidirectional SR Path Figure 2a: Step 1: PCC-Initiated Double-sided Bidirectional SR Path
with Forward Direction SR Paths
+-----+ +-----+
| PCE | | PCE |
+-----+ +-----+
PCUpd/PCInitiate / \ PCUpd/PCInitiate PCUpd/PCInitiate: / \ PCUpd/PCInitiate:
Tunnel 1 (F) / \ Tunnel 2 (R) Tunnel 1 (F) / \ Tunnel 2 (F)
(LSP1 (F), LSP2 (R)) / \ (LSP2 (F), LSP1 (R)) (LSP1 (F), LSP2 (R)) / \ (LSP2 (F), LSP1 (R))
Assoc#1 / \ Assoc#1 Association #2 / \ Association #2
/ \ / \
v v v v
+-----+ LSP1 +-----+ +-----+ LSP1 +-----+
| S |------------>| D | | S |------------>| D |
| |<------------| | | |<------------| |
+-----+ LSP2 +-----+ +-----+ LSP2 +-----+
<no signaling>
Figure 2b: PCC-Initiated Double-sided Bidirectional SR Path Figure 2b: Step 2: PCE-Upd/Initiated Double-sided Bidirectional Path
along with opposite direction SR path Along with Reverse Direction SR Paths
5.3. Error Handling 5.3. Error Handling
The error handling as described in section 5.5 of The error handling as described in section 5.5 of
[I-D.ietf-pce-association-bidir] continue to apply. [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 PCEP Path Setup Type (PST) MUST be set to 'TE Path is Setup using
the 'Double-sided Bidirectional SR Path Association Group', in case a Segment Routing' [I-D.ietf-pce-segment-routing] for the LSP belonging
PCEP speaker receives a different PST value, it MUST send an PCErr to the 'Double-sided Bidirectional SR Path Association Group'. In
message with Error-Type = 29 (Early allocation by IANA) (Association case a PCEP speaker receives a different PST value for this
Error) and Error-Value = TBD2 (Bidirectional LSP Association - PST association group, it MUST send a PCErr message with Error-Type = 29
Mismatch). (Early allocation by IANA) (Association Error) and Error-Value = TBD2
(Bidirectional LSP Association - Path Setup Type Mismatch).
6. IANA Considerations 6. IANA Considerations
6.1. Association Type 6.1. Association Type
This document defines a new Association Type for the Association This document defines a new Association Type for the Association
Object defined [I-D.ietf-pce-association-group]. IANA is requested Object defined [I-D.ietf-pce-association-group]. IANA is requested
to make the assignment of a value for the sub-registry "ASSOCIATION 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 Type Field" (to be created in [I-D.ietf-pce-association-group]), as
follows: follows:
Value Name Reference Value Name Reference
------------------------------------------------------------------- -------------------------------------------------------------------
TBD1 Double-sided Bidirectional This document TBD1 Double-sided Bidirectional SR Path This document
SR Path Association Group Association Group
6.2. PCEP Errors 6.2. PCEP Errors
This document defines new Error value for Error Type 29 (Association This document defines new Error value for Error Type 29 (Association
Error). IANA is requested to allocate new Error value within the Error). IANA is requested to allocate new Error value within the
"PCEP-ERROR Object Error Types and Values" sub-registry of the PCEP "PCEP-ERROR Object Error Types and Values" sub-registry of the PCEP
Numbers registry, as follows: Numbers registry, as follows:
Error Type Description Reference Error Type Description Reference
------------------------------------------------------------------- -------------------------------------------------------------------
29 Association Error 29 Association Error
Error value: TBD2 This document Error value: TBD2 This document
Bidirectional LSP Association - PST Mismatch Bidirectional LSP Association -
Path Setup Type Mismatch
7. Security Considerations 7. Security Considerations
The security considerations described in [RFC5440], [RFC8231], The security considerations described in [RFC5440], [RFC8231],
[RFC8281], and [I-D.ietf-pce-segment-routing] apply to the extensions [RFC8281], and [I-D.ietf-pce-segment-routing] apply to the extensions
defined in this document as well. defined in this document as well.
A new Association Type for the Association Object, Double-sided A new Association Type for the Association Object, 'Double-sided
Associated Bidirectional SR Path Association Group is introduced in Associated Bidirectional SR Path Association Group' is introduced in
this document. Additional security considerations related to LSP this document. Additional security considerations related to LSP
associations due to a malicious PCEP speaker is described in associations due to a malicious PCEP speaker is described in
[I-D.ietf-pce-association-group] and apply to this Association Type. [I-D.ietf-pce-association-group] and apply to this Association Type.
Hence, securing the PCEP session using Transport Layer Security (TLS) Hence, securing the PCEP session using Transport Layer Security (TLS)
[RFC8253] is recommended. [RFC8253] is recommended.
8. Contributors 8. Contributors
The following people have substantially contributed to this document: The following people have substantially contributed to this document:
Dhruv Dhody Dhruv Dhody
Huawei Technologies Huawei Technologies
Divyashree Techno Park, Whitefield Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066 Bangalore, Karnataka 560066
India India
Email: dhruv.ietf@gmail.com Email: dhruv.ietf@gmail.com
Quan Xiong Quan Xiong
ZTE Corporation ZTE Corporation
No.6 Huashi Park Rd No.6 Huashi Park Rd
Wuhan, Hubei 430223 Wuhan, Hubei 430223
China China
Email: xiong.quan@zte.com.cn Email: xiong.quan@zte.com.cn
9. Acknowledgments 9. Acknowledgments
Many thanks to Marina's review and professional comments. Many thanks to Marina Fizgeer for detailed review and comments.
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 12, line 19 skipping to change at page 12, line 43
<https://www.rfc-editor.org/info/rfc8281>. <https://www.rfc-editor.org/info/rfc8281>.
[I-D.ietf-pce-association-group] [I-D.ietf-pce-association-group]
Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H., Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
Dhody, D., and Y. Tanaka, "PCEP Extensions for Dhody, D., and Y. Tanaka, "PCEP Extensions for
Establishing Relationships Between Sets of LSPs", draft- Establishing Relationships Between Sets of LSPs", draft-
ietf-pce-association-group-08 (work in progress), March ietf-pce-association-group-08 (work in progress), March
2019. 2019.
[I-D.ietf-pce-association-bidir] [I-D.ietf-pce-association-bidir]
Barth, C., Gandhi, R., and B. Wen, "PCEP Extensions for Gandhi, R., Barth, C., and B. Wen, "PCEP Extensions for
Associated Bidirectional Label Switched Paths (LSPs)", Associated Bidirectional Label Switched Paths (LSPs)",
draft-ietf-pce-association-bidir-02 (work in progress), draft-ietf-pce-association-bidir (work in progress).
November 2018.
[I-D.ietf-pce-pcep-stateful-pce-gmpls] [I-D.ietf-pce-pcep-stateful-pce-gmpls]
Lee, Y., Zhang, F., Casellas, R., Dios, O., and Z. Ali, Lee, Y., Zhang, F., Casellas, R., Dios, O., and Z. Ali,
"Path Computation Element (PCE) Protocol Extensions for "Path Computation Element (PCE) Protocol Extensions for
Stateful PCE Usage in GMPLS-controlled Networks", draft- Stateful PCE Usage in GMPLS-controlled Networks", draft-
ietf-pce-pcep-stateful-pce-gmpls-10 (work in progress), ietf-pce-pcep-stateful-pce-gmpls-10 (work in progress),
March 2019. March 2019.
[I-D.negi-pce-segment-routing-ipv6]
Negi, M., Li, C., Sivabalan, S., and P. Kaladharan, "PCEP
Extensions for Segment Routing leveraging the IPv6 data
plane", draft-negi-pce-segment-routing-ipv6-04 (work in
progress), February 2019.
[I-D.li-pce-sr-path-segment] [I-D.li-pce-sr-path-segment]
Li, C., Chen, M., Dhody, D., Cheng, W., Dong, J., Li, Z., Li, C., Chen, M., Dhody, D., Cheng, W., Dong, J., Li, Z.,
and R. Gandhi, "Path Computation Element Communication and R. Gandhi, "Path Computation Element Communication
Protocol (PCEP) Extension for Path Segment in Segment Protocol (PCEP) Extension for Path Segment in Segment
Routing (SR)", draft-li-pce-sr-path-segment-03 (work in Routing (SR)", draft-li-pce-sr-path-segment (work in
progress), October 2018. progress).
[I-D.ietf-spring-mpls-path-segment]
Cheng, W., Li, H., Chen, M., Gandhi, R., and R. Zigler,
"Path Segment in MPLS Based Segment Routing Network",
draft-ietf-spring-mpls-path-segment (work in progress).
[I-D.li-spring-srv6-path-segment] [I-D.li-spring-srv6-path-segment]
Li, C., Chen, M., Dhody, D., Li, Z., Dong, J., and R. Li, C., Chen, M., Dhody, D., Li, Z., Dong, J., and R.
Gandhi, "Path Segment for SRv6 (Segment Routing in IPv6)", Gandhi, "Path Segment for SRv6 (Segment Routing in IPv6)",
draft-li-spring-srv6-path-segment-00 (work in progress), draft-li-spring-srv6-path-segment-00 (work in progress),
October 2018. October 2018.
10.2. Informative References 10.2. Informative References
[RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
skipping to change at page 13, line 29 skipping to change at page 13, line 47
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[I-D.ietf-pce-segment-routing] [I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing", and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-16 (work in progress), draft-ietf-pce-segment-routing-16 (work in progress),
March 2019. March 2019.
[I-D.ietf-pce-segment-routing-ipv6]
Negi, M., Li, C., Sivabalan, S., and P. Kaladharan, "PCEP
Extensions for Segment Routing leveraging the IPv6 data
plane", draft-ietf-pce-segment-routing-ipv6 (work in
progress).
[I-D.ietf-mpls-bfd-directed] [I-D.ietf-mpls-bfd-directed]
Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen, Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen,
"Bidirectional Forwarding Detection (BFD) Directed Return "Bidirectional Forwarding Detection (BFD) Directed Return
Path", draft-ietf-mpls-bfd-directed-10 (work in progress), Path", draft-ietf-mpls-bfd-directed-10 (work in progress),
September 2018. September 2018.
[I-D.cheng-spring-mpls-path-segment]
Cheng, W., Wang, L., Li, H., Chen, M., Gandhi, R., Zigler,
R., and S. Zhan, "Path Segment in MPLS Based Segment
Routing Network", draft-cheng-spring-mpls-path-segment-03
(work in progress), October 2018.
Authors' Addresses Authors' Addresses
Cheng Li Cheng Li
Huawei Technologies Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd. Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095 Beijing 100095
China China
Email: chengli13@huawei.com Email: chengli13@huawei.com
Mach(Guoyi) Chen Mach(Guoyi) Chen
Huawei Technologies Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd. Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095 Beijing 100095
China China
Email: Mach.chen@huawei.com Email: Mach.chen@huawei.com
Weiqiang Cheng Weiqiang Cheng
China Mobile China Mobile
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