Internet DRAFT - draft-sivabalan-pce-lsp-setup-type
draft-sivabalan-pce-lsp-setup-type
PCE Working Group S. Sivabalan
Internet-Draft J. Medved
Intended status: Standards Track Cisco Systems, Inc.
Expires: January 1, 2015 I. Minei
E. Crabbe
Google, Inc.
R. Varga
Pantheon Technologies SRO
June 30, 2014
Conveying path setup type in PCEP messages
draft-sivabalan-pce-lsp-setup-type-02.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 path
setup methods over a given 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
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 1, 2015.
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Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Path Setup Type TLV . . . . . . . . . . . . . . . . . . . . . 3
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. 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
a path subject to various constraints and optimization criteria from
a PCE. The PCE responds to the PCC with a hop-by-hop path in an
Explicit Route Object (ERO). The PCC uses the ERO 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 a 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.ietf-pce-pce-initiated-lsp] specifies a mechanism allowing a PCE
to dynamically instantiate an LSP on a PCC by sending the ERO and
characteristics of the LSP. The PCC signals the LSP using the ERO
and other attributes sent by the PCE.
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So far, the PCEP protocol and its extensions implicitly assume that
the TE paths are label switched, and are established via the RSVP-TE
protocol. However, other methods of LSP setup are not precluded.
When a new path setup method (other than RSVP-TE) is introduced for
setting up a path, a new capability TLV pertaining to the new path
setup method MAY be advertised when the PCEP session is established.
Such capability TLV MUST be defined in the specification of the new
path setup type. When multiple path setup methods are deployed in a
network, a given PCEP session may have to simultaneously support more
than one path setup types. In this case, the intended path setup
method needs to be either explicitly indicated or implied in the
appropriate PCEP messages (when necessary) so that both the PCC and
the PCE can take the necessary steps to set up the path. This
document introduces a generic TLV called "PATH-SETUP-TYPE TLV" and
specifies the base procedures to facilitate such operational model.
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.
TLV: Type, Length, and Value.
3. Path Setup Type TLV
When a PCEP session is used to set up TE paths using different
methods, the corresponding PCE and PCC must be aware of the path
setup method used. That means, a PCE must be able to specify paths
in the correct format and a PCC must be able take control and take
forwarding plane actions appropriate to the path setup type.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | PST |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: PATH-SETUP-TYPE TLV
PATH-SETUP-TYPE TLV is an optional TLV associated with the RP
([RFC5440]) and the SRP ([I-D.ietf-pce-stateful-pce]) objects. Its
format is shown in the above figure. The type of the TLV is to be
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defined by IANA. The one octet value contains the Path Setup Type
(PST). This document specifies the following PST value:
o PST = 0: Path is setup via RSVP-TE signaling protocol(default).
The absence of the PATH-SETUP-TYPE TLV is equivalent to an PATH-
SETUP-TYPE TLV with an PST value of 0. It is recommended to omit the
TLV in the default case. If the RP or SRP object contains more than
one PATH-SETUP-TYPE TLVs, only the first TLV MUST be processed and
the rest MUST be ignored.
If a PCEP speaker does not recognize the PATH-SETUP-TYPE TLV, it MUST
ignore the TLV in accordance with ([RFC5440]). If a PCEP speaker
recognizes the TLV but does not support the TLV, it MUST send PCErr
with Error-Type = 2 (Capability not supported).
4. Operation
When requesting a path from a PCE using a PCReq message ([RFC5440]),
a PCC MAY include the PATH-SETUP-TYPE TLV in the RP object. If the
PCE is capable of expressing the path in a format appropriate to the
setup method used, it MUST use the appropriate ERO format in the
PCRep message. If the path setup type cannot be inferred from the
ERO or any other object or TLV in the PCRep message, PATH-SETUP-TYPE
TLV may be included in the RP object of the PCRep message.
Regardless of whether PATH-SETUP-TYPE TLV is used or not, if the PCE
does not support the intended path setup type it MUST send PCErr with
Error-Type = TBD (Traffic engineering path setup error) (recommended
value is 21) and Error-Value = 1 (Unsupported path setup type) and
close the PCEP session. If the path setup types corresponding to the
PCReq and PCRep messages do not match, the PCC MUST send a PCErr with
Error-Type = 21 (Traffic engineering path setup error) and Error-
Value = 2 (Mismatched path setup type) and close the PCEP session.
In the case of stateful PCE, if the path setup type cannot be
unambiguously inferred from ERO or any other object or TLV, PATH-
SETUP-TYPE TLV MAY be used in PCRpt and PCUpd messages. If PATH-
SETUP-TYPE TLV is used in PCRpt message, the SRP object MUST be
present even in cases when the SRP-ID-number is the reserved value of
0x00000000. Regardless of whether PATH-SETUP-TYPE TLV is used or
not, if a PCRpt message is triggered due to a PCUpd message (in this
case SRP-ID-number is not equal to 0x00000000), the path setup types
corresponding to the PCRpt and PCUpd messages should match.
Otherwise, the PCE MUST send PCErr with Error-Type = 21 (Traffic
engineering path setup error) and Error-Value = 2 (Mismatched path
setup type) and close the connection.
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In the case of PCE initiated LSPs, a PCE MAY include PATH-SETUP-TYPE
TLV in PCInitiate message if the message does not have any other
means of indicating path setup type. If a PCC does not support the
path setup type associated with the PCInitiate message, the PCC MUST
send PCErr with Error-Type = 21 (Traffic engineering path setup
error) and Error-Value = 1 (Unsupported path setup type) and close
the PCEP session. Similarly, as mentioned above, if the path setup
type cannot be unambiguously inferred from ERO or any other object or
TLV, the PATH-SETUP-TYPE TLV MAY be included in PCRpt messages
triggered by PCInitiate message. Regardless of whether PATH-SETUP-
TYPE TLV is used or not, if a PCRpt message is triggered by a
PCInitiate message, the path setup types corresponding to the PCRpt
and the PCInitiate messages should match. Otherwise, the PCE MUST
send PCErr message with Error-Type = 21 (Traffic engineering path
setup error) and Error-Value = 2 (Mismatched path setup type).
5. Security Considerations
No additional security measure is required.
6. IANA Considerations
IANA is requested to allocate a new TLV type (recommended value is
TBD)for PATH-SETUP-TYPE TLV specified in this document.
This document requests that a registry is created to manage the value
of the path Setup Type field in the PATH-SETUP-TYPE TLV.
Value Description Reference
0 Traffic engineering This document
path is setup using
RSVP signaling
protocol
This document also defines a new Error-Type (recommended 21) and new
Error-Values for the following new error conditions:
Error-Type Meaning
21 Invalid traffic engineering path setup type
Error-value=1: Unsupported path setup type
Error-value=2: Mismatched path setup type
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7. Acknowledgements
We like to thank Marek Zavodsky for valuable comments.
8. Normative References
[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-01 (work in
progress), June 2014.
[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-09 (work in progress), June 2014.
[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
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
USA
Email: inaminei@google.com
Edward Crabbe
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
USA
Email: edc@google.com
Robert Varga
Pantheon Technologies SRO
Mlynske Nivy 56
Bratislava, 821 05
Slovakia
Email: robert.vargad@pantheon.sk
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