PCE Working Group C. Barth
Internet-Draft Juniper Networks
Intended status: Standards Track R. Gandhi
Expires: April 30, 2017 Individual Contributor
B. Wen
Comcast
October 27, 2016
Path Computation Element Communication Protocol Extensions for
Associated Bidirectional Label Switched Paths (LSPs)
draft-barth-pce-association-bidir-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 Multi-Protocol
Label Switching (MPLS) Traffic Engineering (TE) Label Switched Paths
(LSPs) using PCEP.
This document defines Path Computation Element Communication Protocol
(PCEP) extensions for binding two reverse unidirectional RSVP-TE LSPs
into an Associated Bidirectional Label Switched Path (LSP).
Status of This Memo
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Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Key Word Definitions . . . . . . . . . . . . . . . . . . . 3
2.2. Acronyms and Abbreviations . . . . . . . . . . . . . . . . 3
2.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Single-sided Initiation . . . . . . . . . . . . . . . . . 4
3.2. Double-sided Initiation . . . . . . . . . . . . . . . . . 5
3.3. Co-routed Associated Bidirectional LSP . . . . . . . . . . 5
4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 5
4.1. Association Object . . . . . . . . . . . . . . . . . . . . 5
4.2. Bidirectional LSP Association TLV . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. Association Types . . . . . . . . . . . . . . . . . . . . 7
6.2. Bidirectional LSP Association TLV . . . . . . . . . . . . 7
7. Manageability Considerations . . . . . . . . . . . . . . . . . 8
7.1. Control of Function and Policy . . . . . . . . . . . . . . 8
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP) as a
communication mechanism between a Path Computation Client (PCC) and a
Path Control Element (PCE), or between PCE and PCC, that enables
computation of Multi-Protocol Label Switching (MPLS) Traffic
Engineering (TE) Label Switched Paths (LSPs).
[I-D.ietf-pce-stateful-pce] specifies extensions to PCEP to enable
stateful control of MPLS TE LSPs. It describes two modes of
operation - Passive stateful PCE and Active stateful PCE. In this
[I-D.ietf-pce-stateful-pce] document, the focus is on Active stateful
PCE where LSPs are can be provisioned on the PCC and control over
them is delegated to a PCE. Further [I-D.ietf-pce-pce-initiated-lsp]
describes the setup, maintenance and teardown of PCE-initiated LSPs
for the stateful PCE model.
[I-D.ietf-pce-association] 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 [I-D.ietf-pce-stateful-
pce] or a stateless PCE [RFC5440].
The MPLS Transport Profile (MPLS-TP) requirements document [RFC5654]
specifies that MPLS-TP MUST support associated bidirectional point-
to-point LSPs. [RFC7551] specifies RSVP signaling extensions for
binding two reverse unidirectional LSPs into an associated
bidirectional LSP.
This document specifies PCEP extensions for binding two reverse
unidirectional RSVP-TE LSPs into an Associated Bidirectional LSP for
both single-sided and double-sided provisioning.
2. Conventions Used in This Document
2.1. Key Word Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2.2. Acronyms and Abbreviations
LSP: Label Switched Path
LSR: Label Switching Router
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MPLS: Multi-Protocol Label Switching
PCEP: Path Computation Element Communication Protocol
2.3. Terminology
The following terminology is used in this document.
Active Stateful PCE: PCE that uses tunnel state information learned
from PCCs to optimize path computations. Additionally, it actively
updates tunnel parameters in those PCCs that delegated control over
their tunnels to the PCE.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or route
based on a network graph and applying computational constraints.
3. Overview
As shown in Figure 1, two reverse unidirectional LSPs can be
associated to form an associated bidirectional LSP. There are two
methods of initiating the bidirectional LSP association, single-sided
and double-sided as described in the following sections.
LSP1 --> LSP1 --> LSP1 -->
+-----+ +-----+ +-----+ +-----+
| A +-----------+ B +-----------+ C |-----------+ D |
+-----+ +-----+ +-----+ +-----+
<--LSP2 | | <-- LSP2
| |
| |
+-----+ +-----+
+ E +-----------+ F |
+-----+ +-----+
<-- LSP2
Figure 1: An Example of Associated Bidirectional LSP
3.1. Single-sided Initiation
As specified in [RFC7551], in the single-sided provisioning case, the
bidirectional tunnel is signaled only on one ingress LSR of a LSP
tunnel. Both forward and reverse LSPs for this tunnel are initiated
by the PCE with the Association Type set to "Single-sided
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Bidirectional LSP Association" on the originating ingress PCC. The
originating PCC identifies the forward and reverse LSPs in the TLV of
the Association Objects. The originating endpoint uses the signaled
properties for the revere LSP in the RSVP REVERSE_LSP Object
[RFC7551] of the forward LSP Path message. The remote endpoint then
creates the corresponding reverse tunnel and signals the reverse LSP
in response to the received RSVP Path message. The two
unidirectional reverse LSPs on the originating endpoint node are
bound together using the PCEP signaled Association Objects and on the
remote endpoint node by the RSVP signaled Association Objects. As
shown in Figure 1, LSP1 and LSP2 are provisioned on the originating
endpoint A by the PCE peer. The creation of reverse LSP2 on the
remote endpoint D is triggered by the RSVP signaled LSP1.
3.2. Double-sided Initiation
As specified in [RFC7551], in the double-sided provisioning case, the
bidirectional tunnel is provisioned on both endpoint nodes(PCCs) of
the tunnel. The reverse LSPs for this tunnel are initiated by the
PCE peer with Association Type set to "Double-sided Bidirectional LSP
Association" on both ingress PCCs. The two reverse unidirectional
LSPs on both PCCs are bound together by using the PCEP signaled
Association Objects. As shown in Figure 1, LSP1 is provisioned on
the endpoint A and LSP2 is provisioned on the endpoint node D, both
by the PCEP peer.
3.3. Co-routed Associated Bidirectional LSP
In both single-sided and double-sided initiation cases, forward and
reverse LSPs may be co-routed as shown in Figure 2, where both
forward and reverse LSPs follow the same congruent path.
LSP3 --> LSP3 --> LSP3 -->
+-----+ +-----+ +-----+ +-----+
| A +-----------+ B +-----------+ C |-----------+ D |
+-----+ +-----+ +-----+ +-----+
<-- LSP4 <-- LSP4 <-- LSP4
Figure 2: An Example of Co-routed Associated Bidirectional LSP
4. Protocol Extensions
4.1. Association Object
As per [I-D.ietf-pce-association], LSPs are associated by adding them
to a common association group.
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This document defines two new Association Types for the Association
Object as follows:
o Association Type (TBD1) = Single-sided Bidirectional LSP
Association
o Association Type (TBD2) = Double-sided Bidirectional LSP
Association
The Association ID, Association Source, Global Association Source and
Extended Association ID in the Association Object of the
bidirectional LSP are provisioned by the PCE using the procedures
defined in [RFC7551].
4.2. Bidirectional LSP Association TLV
The Bidirectional LSP Association TLV is an optional TLV for use with
the Bidirectional LSP Association Type in the single-sided
provisioning case.
o The Bidirectional LSP Association TLV follows the PCEP TLV format
from [RFC5440].
o The type (16 bits) of the TLV is TBD3, to be assigned by IANA.
o The length is 4 Bytes.
o The value comprises of a single field, the Bidirectional LSP
Association Flags (32 bits), where each bit represents a flag
option.
o If the Bidirectional LSP Association TLV is missing, it means the
LSP is the forward LSP.
o The Bidirectional LSP Association TLV MUST NOT be present more
than once. If it appears more than once, only the first
occurrence is processed and any others MUST be ignored.
The format of the Bidirectional LSP Association TLV is shown in
Figure 3:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bidirectional LSP Association Flags |C|R|F|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Bidirectional LSP Association TLV format
F (FORWARD-LSP, 1 bit) - Indicates whether the LSP associated is the
forward LSP of the bidirectional LSP. If this flag is set, the LSP
is a forward LSP.
R (REVERSE-LSP, 1 bit) - Indicates whether the LSP associated is the
reverse LSP of the bidirectional LSP. If this flag is set, the LSP
is a reverse LSP.
C (Co-ROUTED-LSP, 1 bit) - Indicates whether the bidirectional LSP is
co-routed. If this flag is set, the bidirectional LSP is
co-routed.
5. Security Considerations
This document introduces two new Association Types for the
Association Object, Double-Sided Associated Bidirectional LSP and
Single-Sided Associated Bidirectional LSP. These types, by
themselves, introduce no additional security concerns beyond those
discussed in [RFC5440], [I-D.ietf-pce-stateful-pce] and [I-D.ietf-
pce-association].
6. IANA Considerations
6.1. Association Types
This document defines the following Association Types for the
Association Object defined [I-D.ietf-pce-association].
Value Name Reference
TBD1 Single-sided Bidirectional LSP Association [This I.D.]
TBD2 Double-sided Bidirectional LSP Association [This I.D.]
6.2. Bidirectional LSP Association TLV
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This document defines a new TLV for carrying additional LSP
information for the bidirectional LSP association type as follows:
+--------------------+------------------------+-------------+
| TLV Type Value | TLV Name | Reference |
+--------------------+------------------------+-------------+
| TBD3 | Bidirectional LSP | This |
| | Association TLV | document |
+--------------------+------------------------+-------------+
7. Manageability Considerations
7.1. Control of Function and Policy
An operator MUST be allowed to provision the bidirectional LSP
association parameters at PCEP peers.
8. Acknowledgments
TBA.
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440.
[RFC7551] Zhang, F., Ed., Jing, R., and Gandhi, R., Ed., "RSVP-TE
Extensions for Associated Bidirectional LSPs", RFC 7551,
May 2015.
[I-D.ietf-pce-association] Minei, I., Crabbe, E., Sivabalan, S.,
Ananthakrishnan, H., Zhang, X., and Y. Tanaka, "PCEP
Extensions for Establishing Relationships Between Sets of
LSPs", draft-ietf-pce-association (work in progress).
[I-D.ietf-pce-stateful-pce] Crabbe, E., Minei, I., Medved, J., and
R. Varga, "PCEP Extensions for Stateful PCE", draft-ietf-
pce-stateful-pce (work in progress).
9.2. Informative References
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, September 2009.
[RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module", RFC
7420, December 2014.
[I-D.ietf-pce-pce-initiated-lsp] Crabbe, E., Minei, I., Sivabalan,
S., and R. Varga, "PCEP Extensions for PCE-initiated LSP
Setup in a Stateful PCE Model", draft-ietf-pce-pce-
initiated-lsp (work in progress).
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Authors' Addresses
Colby Barth
Juniper Networks
EMail: cbarth@juniper.net
Rakesh Gandhi
Individual Contributor
EMail: rgandhi.ietf@gmail.com
Bin Wen
Comcast
EMail: Bin_Wen@cable.comcast.com
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