PCE Working Group S. Sivabalan
Internet-Draft J. Medved
Intended status: Standards Track Cisco Systems, Inc.
Expires: April 07, 2014 I. Minei
Juniper Networks, Inc.
R. Varga
Pantheon Technologies SRO
E. Crabbe
Google, Inc.
October 04, 2013
LSP setup method in PCEP messages
draft-sivabalan-pce-lsp-setup-type-00.txt
Abstract
A path computation element can compute traffic engineering paths (TE
paths) through a network that are subject to various constraints.
Currently, TE paths are label switched paths (LSPs) which are set up
using the RSVP-TE signaling protocol. However, other TE path setup
methods are possible within the PCE architecture. This document
proposes an extension to PCEP to allow support for different LSP
setup methods over a single PCEP session.
Requirements Language
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].
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://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 April 07, 2014.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LSP Setup Type TLV . . . . . . . . . . . . . . . . . . . . . 3
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP) for
communication between a Path Computation Client (PCC) and a Path
Control Element (PCE) or between one a pair of PCEs. A PCC requests
from a PCE the computation of a path subject to various constraints
and optimization criteria. The PCE responds to the PCC with a hop-
by-hop path in an ER object. The PCC uses the ERO object to set up
the path in the network.
[I-D.ietf-pce-stateful-pce] specifies extensions to PCEP that allow a
PCC to delegate its LSPs to the PCE. The PCE can then update the
state of LSPs delegated to it. In particular, the PCE may modify the
path of an LSP by sending a new ERO. The PCC uses this ERO to re-
route the LSP in a make-before-break fashion.
[I-D.crabbe-pce-pce-initiated-lsp] specifies a mechanism allowing a
PCE to dynamically instantiate LSPs on a PCC by sending the path and
characteristics of the LSP. The PCC signals the LSP using the ERO
(and other attributes) sent by the PCE.
So far, the PCEP protocol and its extensions implicitly assume that
the TE paths are label-switched paths (LSPs), which are established
via the RSVP-TE protocol. However, other methods of LSP setup are
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not precluded. Most recently, Segment Routing has emerged as another
technology for setting up source-routed TE paths. Other methods for
setting up TE paths are possible in the future.
[I-D.sivabalan-pce-segment-routing] specifies the ERO format for LSPs
set up using SR (SR-ERO). However, it should be noted that when the
LSP setup method over a given PCEP session is not the RSVP-TE
signaling protocol, a new capability MUST be advertised when the PCEP
session is established. A given PCEP session can be used to compute,
initiate, and maintain LSPs which are set up using different setup
methods. To facilitate this, the intended LSP setup method needs to
be indicated in the appropriate PCEP messages, and the path of the
LSP needs to be encoded in a format that is appropriate for the setup
type. This document defines a new TLV called "LSP-SETUP-TYPE TLV"
for this purpose.
2. Terminology
The following terminologies are used in this document:
ERO: Explicit Route Object.
LSR: Label Switching Router.
PCC: Path Computation Client.
PCE: Path Computation Element
PCEP: Path Computation Element Protocol.
SR: Segment Routing.
SR-ERO: Segment Routed Explicit Route Object.
TLV: Type, Length, and Value.
3. LSP Setup Type TLV
A PCC can simultaneously support setting up LSPs using different
methods. To enable meaningful interaction with a PCE, the PCE must
encode the LSP path in a format that is appropriate for the setup
method used. To do so, the PCE must be made aware of the setup
method used by the PCC for a particular LSP.
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP-ST | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: LSP-SETUP-TYPE TLV
LSP-SETUP-TYPE TLV is an optional TLV for use in the RP ([RFC5440])
and SRP ([I-D.ietf-pce-stateful-pce]) objects. Its format is shown
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in the above figure. The type of the TLV is to be defined by IANA.
The one octet value contains the LSP Setup Type (LSP-ST). This
document specifies the following LSP-ST values:
o ST = 0: LSP is setup via RSVP-TE signaling protocol(default).
o ST = 1: LSP is setup via Segment Routing.
In the absence of this TLV, RSVP-TE is assumed as the setup method.
If an RP or SRP object contains more than one LSP-SETUP-TYPE TLV,
only the first TLV MUST be processed and the rest MUST be ignored.
4. Operation
When requesting the computation of a path from a PCE using a PCReq
message ([RFC5440]), a PCC MAY include the LSP-SETUP-TYPE TLV in the
RP object. If the PCE is capable of expressing the LSP path in a
format appropriate for the setup method used, it MUST use the
appropriate ERO format in the PCRep message. If the PCE does not
support the intended LSP establishment type, but it does recognize
the LSP-SETUP-TYPE TLV, it MUST send PCErr with Error-Type = TBD (LSP
setup error) (recommended value is 19) and Error-Value = 1
(Unsupported LSP setup type,) and close the PCEP session. If an LSP
setup type specified in PCRep message does not match that of the
PCReq message, the PCC MUST send a PCErr with Error-Type = 19 (LSP
setup error) and Error-Value = 2 (Mismatched LSP setup type) and
close the PCEP session.
In the case of stateful PCE, a PCC MUST report the setup type of all
LSPs in PCRpt messages both in the synchronization phase and in
subsequent updates. The absence of the LSP-SETUP-TYPE TLV is
equivalent to an LSP_SETUP-TYPE TLV with an LSP-ST value of 0 (RSVP-
TE), and it is recommended to omit including it when this is the
case. If the LSP-SETUP-TYPE TLV needs to be included, the SRP object
MUST be present even in cases when the SRP-ID-number is the reserved
value of 0x00000000. A PCRpt message whose SRP-ID-number is not
equal to 0x00000000 MUST match the path-type of the PCUpd message
that triggered its generation. Otherwise, the PCE MUST send PCErr
with Error-Type = 19 (LSP setup error) and Error-Value = 2
(Mismatched LSP setup type) and close the connection.
In the case of PCE initiated LSPs, if a PCC does not support the
path-type specified in PCInitiate message, the PCC MUST send PCErr
with Error-Type = 19 (LSP setup error) and Error-Value = 1
(Unsupported LSP setup type) and close the PCEP session. The path-
type in PCRpt messages generated as a result of a PCUpd or PCInitiate
message MUST match the path-type of the message that triggered it.
Otherwise, the PCE MUST send PCErr with Error-Type = 19 (LSP setup
error) and Error-Value = 2 (Mismatched LSP setup type). For LSPs
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that are not setup up using RSVP-TE signaling protocol, the path-type
MUST be included in the SRP object, and the SRP object MUST be
included even if the SRP-ID-number is the reserved value of
0x00000000.
If a PCEP speaker does not support LSP-SETUP-TYPE TLV, it MUST send
PCErr with Error-Type = 3 (Unknown Object) and Error-Value = 3
(Unsupported TLV).
5. IANA Considerations
IANA is requested to allocate a new TLV type (recommended value is
TBD)for LSP-SETUP-TYPE TLV specified in this document.
This document requests that a registry is created to manage the value
of the LSP Setup Type field in the LSP-SETUP-TYPE TLV.
Value Description Reference
0 LSP is setup using RSVP signaling protocol This document
1 LSP is Segment Routed This document
Table 1
This document also defines a new Error-Type (recommended 19) and new
Error-Values for the following new error conditions:
Error-Type Meaning
19 Invalid LSP setup type
Error-value=1: Unsupported LSP setup type
Error-value=2: Mismatched LSP setup type
This document also defines a new Error-Value for the existing Error-
Type 3 (Unknown Object):
Error-Type Meaning
3 Unknown Object
Error-value=3: Unsupported TLV
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6. Normative References
[I-D.crabbe-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-crabbe-pce-pce-initiated-lsp-02 (work in
progress), July 2013.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-06 (work in progress), August 2013.
[I-D.sivabalan-pce-segment-routing]
Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E., and
R. Raszuk, "PCEP Extensions for Segment Routing", draft-
sivabalan-pce-segment-routing-01 (work in progress), July
2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
Authors' Addresses
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
Jan Medved
Cisco Systems, Inc.
170 West Tasman Dr.
San Jose, CA 95134
USA
Email: jmedved@cisco.com
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Ina Minei
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: ina@juniper.net
Robert Varga
Pantheon Technologies SRO
Mlynske Nivy 56
Bratislava, 821 05
Slovakia
Email: robert.vargad@pantheon.sk
Edward Crabbe
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
USA
Email: edc@google.com
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