PCE Working Group A. Tokar
Internet-Draft S. Sivabalan
Intended status: Standards Track Cisco Systems, Inc.
Expires: January 1, 2020 M. Negi
Huawei Technologies
June 30, 2019
Carrying SID Algorithm information in PCE-based Networks.
draft-tokar-pce-sid-algo-00
Abstract
The Algorithm associated with a prefix Segment-ID (SID) defines the
path computation Algorithm used by Interior Gateway Protocols (IGPs).
This information is available to controllers such as the Path
Computation Element (PCE) via topology learning. This document
proposes an approach for informing headend routers regarding the
Algorithm associated with each prefix SID used in PCE-computed paths.
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 https://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 January 1, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
Tokar, et al. Expires January 1, 2020 [Page 1]
Internet-Draft SID Algorithm in PCEP June 2019
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. SR ERO NAI Extensions . . . . . . . . . . . . . . . . . . . . 3
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6.1. PCEP SR-ERO NAI Types . . . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
A PCE can compute SR-TE paths using prefix SIDs with different
Algorithms depending on the use-case, constraints, etc. While this
information is available on the PCE, there is no method of conveying
this information to the headend router.
Similarly, the headend can also compute SR-TE paths using different
Algorithms, and this information also needs to be conveyed to the PCE
for collection or troubleshooting purposes. In addition, in the case
of multiple (redundant) PCEs, when the headend receives a path from
the primary PCE, it needs to be able to report the complete path
information - including the Algorithm - to the backup PCE so that in
HA scenarios, the backup PCE can verify the prefix SIDs
appropriately.
Refer to [I-D.ietf-ospf-segment-routing-extensions] and
[I-D.ietf-isis-segment-routing-extensions] for details about the
prefix SID Algorithm.
This document introduces two new NAI types for the SR-ERO subobject,
which is defined in [I-D.ietf-pce-segment-routing].
Tokar, et al. Expires January 1, 2020 [Page 2]
Internet-Draft SID Algorithm in PCEP June 2019
2. Terminology
The following terminologies are used in this document:
ERO: Explicit Route Object
IGP: Interior Gateway Protocol
NAI: Node or Adjacency Identifier.
PCE: Path Computation Element
PCEP: Path Computation Element Protocol.
SID: Segment Identifier.
SR: Segment Routing.
SR-TE: Segment Routing Traffic Engineering.
3. SR ERO NAI Extensions
The SR-ERO subobject encoding is extended with additional NAI types.
The following new NAI types (NT) are defined:
o NT=TBD1: The NAI is an IPv4 node ID with Algorithm.
o NT=TBD1: The NAI is an IPv6 node ID with Algorithm.
This document defines the following NAIs:
'IPv4 Node ID with Algorithm' is specified as an IPv4 address and
Algorithm identifier. In this case, the NT value is TBD1 and the
NAI field length is 8 octets.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: NAI for IPv4 Node SID with Algorithm
Tokar, et al. Expires January 1, 2020 [Page 3]
Internet-Draft SID Algorithm in PCEP June 2019
'IPv6 Node ID with Algorithm' is specified as an IPv6 address and
Algorithm identifier. In this case, the NT value is TBD2 and the
NAI field length is 20 octets.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Node IPv6 address (16 octets) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: NAI for IPv6 Node SID with Algorithm
4. Operation
IPv4 prefix SIDs used by SR-TE paths with an associated Algorithm
SHOULD be encoded with 'IPv4 Node ID with Algorithm' NAI.
IPv6 prefix SIDs used by SR-TE paths with an associated Algorithm
SHOULD be encoded with 'IPv6 Node ID with Algorithm' NAI.
5. Security Considerations
No additional security measure is required.
6. IANA Considerations
6.1. PCEP SR-ERO NAI Types
IANA is requested to allocate new SR-ERO NAI types for the new NAI
types specified in this document.
Value Description Reference
TBD1 IPv4 Node ID with This document
Algorithm
TBD2 IPv6 Node ID with This document
Algorithm
7. Normative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., and B. Decraene, "IS-IS Extensions for
Segment Routing", draft-ietf-isis-segment-routing-
extensions-25 (work in progress), May 2019.
Tokar, et al. Expires January 1, 2020 [Page 4]
Internet-Draft SID Algorithm in PCEP June 2019
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-27 (work in progress), December 2018.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-16 (work in progress),
March 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Authors' Addresses
Alex Tokar
Cisco Systems, Inc.
Eurovea Central 3.
Pribinova 10
Bratislava 811 09
Slovakia
Email: atokar@cisco.com
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: msiva@cisco.com
Mahendra Singh Negi
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: mahendrasingh@huawei.com
Tokar, et al. Expires January 1, 2020 [Page 5]