draft-ietf-pce-association-diversity-09.txt   draft-ietf-pce-association-diversity-10.txt 
PCE Working Group S. Litkowski PCE Working Group S. Litkowski
Internet-Draft Orange Internet-Draft Orange
Intended status: Standards Track S. Sivabalan Intended status: Standards Track S. Sivabalan
Expires: February 17, 2020 Cisco Systems, Inc. Expires: March 2, 2020 Cisco Systems, Inc.
C. Barth C. Barth
Juniper Networks Juniper Networks
M. Negi M. Negi
Huawei Technologies Huawei Technologies
August 16, 2019 August 30, 2019
Path Computation Element Communication Protocol (PCEP) Extension for LSP Path Computation Element Communication Protocol (PCEP) Extension for LSP
Diversity Constraint Signaling Diversity Constraint Signaling
draft-ietf-pce-association-diversity-09 draft-ietf-pce-association-diversity-10
Abstract Abstract
This document introduces a simple mechanism to associate a group of This document introduces a simple mechanism to associate a group of
Label Switched Paths (LSPs) via an extension to the Path Computation Label Switched Paths (LSPs) via an extension to the Path Computation
Element (PCE) communication Protocol (PCEP) with the purpose of Element (PCE) communication Protocol (PCEP) with the purpose of
computing diverse paths for those LSPs. The proposed extension computing diverse paths for those LSPs. The proposed extension
allows a Path Computation Client (PCC) to advertise to a PCE that a allows a Path Computation Client (PCC) to advertise to a PCE that a
particular LSP belongs to a disjoint-group, thus the PCE knows that particular LSP belongs to a disjoint-group, thus the PCE knows that
the LSPs in the same group need to be disjoint from each other. the LSPs in the same group need to be disjoint from each other.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 17, 2020. This Internet-Draft will expire on March 2, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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implementation should aim to select a path that allows disjointness. implementation should aim to select a path that allows disjointness.
5.6. Disjointness Computation Issues 5.6. Disjointness Computation Issues
There may be some cases where the PCE is not able to provide a set of There may be some cases where the PCE is not able to provide a set of
disjoint paths for one or more LSPs in the association. disjoint paths for one or more LSPs in the association.
When the T flag is set (Strict disjointness requested), if When the T flag is set (Strict disjointness requested), if
disjointness cannot be ensured for one or more LSPs, the PCE MUST disjointness cannot be ensured for one or more LSPs, the PCE MUST
reply to a Path Computation Request (PCReq) with a Path Computation reply to a Path Computation Request (PCReq) with a Path Computation
Reply (PCRep) message containing a NO-PATH object. In case of other Reply (PCRep) message containing a NO-PATH object. In case of PCRpt
PCEP message, the PCE MUST return a PCErr message with Error-Type 26 message, the PCE MUST return a PCErr message with Error-Type 26
"Association Error" and Error-Value 7 "Cannot join the association "Association Error" and Error-Value 7 "Cannot join the association
group". Also, in case of network event leading to an impossible group". Also, in case of network event leading to an impossible
strict disjointness, the PCE MUST send a PCUpd message containing an strict disjointness, the PCE MUST send a PCUpd message containing an
empty ERO to the corresponding PCCs. In addition to the empty ERO empty ERO to the corresponding PCCs. In addition to the empty ERO
Object, the PCE MAY add the NO-PATH-VECTOR TLV ([RFC5440]) in the LSP Object, the PCE MAY add the NO-PATH-VECTOR TLV ([RFC5440]) in the LSP
Object. Object.
This document adds new bits in the NO-PATH-VECTOR TLV: This document adds new bits in the NO-PATH-VECTOR TLV:
bit "TBD7": when set, the PCE indicates that it could not find a bit "TBD7": when set, the PCE indicates that it could not find a
disjoint path for this LSP. disjoint path for this LSP.
bit "TBD8": when set, the PCE indicates that it does not support bit "TBD8": when set, the PCE indicates that it does not support
the requested disjointness computation. the requested disjointness computation.
When the T flag is unset, the PCE is allowed to relax disjointness by When the T flag is unset, the PCE is allowed to relax disjointness by
either applying a requested objective function (Section 5.4) if applying a requested objective function (Section 5.4) if specified.
specified. Otherwise the PCE is allowed to reduce the required level Otherwise, if no objective function is specified, the PCE is allowed
of disjointness (as it deems fit). The actual level of disjointness to reduce the required level of disjointness as it deems fit. The
computed by the PCE can be reported through the DISJOINTNESS-STATUS- actual level of disjointness computed by the PCE can be reported
TLV by setting the appropriate flags in the TLV. While the through the DISJOINTNESS-STATUS-TLV by setting the appropriate flags
DISJOINTNESS-CONFIGURATION-TLV defines the expected level of in the TLV. While the DISJOINTNESS-CONFIGURATION-TLV defines the
disjointness required by configuration, the DISJOINTNESS-STATUS-TLV expected level of disjointness required by configuration, the
defines the actual level of disjointness computed. DISJOINTNESS-STATUS-TLV defines the actual level of disjointness
computed.
There are some cases where the PCE may need to completely relax the There are some cases where the PCE may need to completely relax the
disjointness constraint in order to provide a path to all the LSPs disjointness constraint in order to provide a path to all the LSPs
that are part of the association. A mechanism that allows the PCE to that are part of the association. A mechanism that allows the PCE to
fully relax a constraint is considered by the authors as more global fully relax a constraint is considered by the authors as more global
to PCEP rather than linked to the disjointness use case. As a to PCEP rather than linked to the disjointness use case. As a
consequence, it is considered as out of scope of the document. consequence, it is considered as out of scope of the document.
All LSPs in a particular disjoint group MUST use the same combination All LSPs in a particular disjoint group MUST use the same combination
of T, S, N, L flags in the DISJOINTNESS-CONFIGURATION-TLV. If a PCEP of T, S, N, L flags in the DISJOINTNESS-CONFIGURATION-TLV. If a PCEP
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