Internet DRAFT - draft-chunduri-lsr-isis-prefix-multi-algo
draft-chunduri-lsr-isis-prefix-multi-algo
LSR Working Group U. Chunduri
Internet-Draft Y. Qu
Intended status: Standards Track Huawei USA
Expires: April 25, 2019 October 22, 2018
Multiple Algorithm support for IS-IS Prefixes
draft-chunduri-lsr-isis-prefix-multi-algo-01
Abstract
This document specifies an extension to Intermediate System to
Intermediate System (IS-IS) protocol by adding an Algorithm support
for prefixes advertised. This allows multiple independent algorithm
usage for computing the reachability of nodes and prefixes as opposed
to only one algorithm.
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 [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 April 25, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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
Chunduri & Qu Expires April 25, 2019 [Page 1]
Internet-DraftMultiple Algorithm support for IS-IS Prefixes October 2018
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
1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2. IS-IS Route Computation Algorithm sub-TLV in prefixes . . . . 3
3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 4
3.1. Single Topology or Multi-Topology Mode . . . . . . . . . 4
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Reachability of various nodes or prefixes attached to these nodes is
done through Shortest Path First (SPF) algorithm as defined in
[ISO10589]. This is done today with in a single topology [RFC5305]
[RFC5308] or in multi-topology (MT) routing [RFC5120] and with out
any explicit advertisement of computation algorithm that is being
used.
IS-IS Segment Routing (SR) extensions
[I-D.ietf-isis-segment-routing-extensions], extended the support for
reachability computation for other algorithms other than SPF. This
is done by advertising the computation algorithms supported at node
level and also by advertising the algorithm being supported by Prefix
Segment Identifier (SID) sub-TLV advertised in reachability prefixes.
While the above would give the flexibility to use different
reachability computation algorithm than the SPF, it is restricted to
one particular data plane as opposed to the prefix itself. This
document removes that restriction and advertises the algorithm to be
used for reachability computation in the prefix itself, thus applying
the same to any underlying data plane (E.g. SR-MPLS, SRH, IPv6,
IPv4).
Section 2 details the details of the sub-TLV and Section 3 talks
about how to use te same and restrictions around it.
Chunduri & Qu Expires April 25, 2019 [Page 2]
Internet-DraftMultiple Algorithm support for IS-IS Prefixes October 2018
1.1. Acronyms
IGP - Interior Gateway Protocols
IS-IS - Intermediate System to Intermediate System
LSR - Link State Routing
MT - Multi Topology
OSPF - Open Shortest Path First
SID - Segment Identifier
SR - Segment Routing
2. IS-IS Route Computation Algorithm sub-TLV in prefixes
This section defines the encoding of Route Computation Algorithm
(RCA) value that MUST be used while calculating the reachability to
other nodes or to the prefixes attached to the other nodes. The RCA
sub-TLV has the following format:
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 | Flags | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// sub-sub-TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Route Computation Algorithm - sub-TLV Format
Type - TBD (IANA) from Sub-TLVs for TLVs 135, 235, 236, and 237
(Extended IP reachability, MT IP. Reach, IPv6 IP. Reach, and MT
IPv6 IP. Reach TLVs) registry.
Length - Total length of the value field in bytes (variable).
Flags - TBD
Algorithm - Route Computation Algorithm value as defined in "IGP
Algorithm Types" registry defined under "Interior Gateway Protocol
(IGP) Parameters" IANA registries.
sub-sub-TLVs - Optional and can be used to specify any information
w.r.t to the algorithm being advertised with this prefix (TBD).
Chunduri & Qu Expires April 25, 2019 [Page 3]
Internet-DraftMultiple Algorithm support for IS-IS Prefixes October 2018
If multiple algorithms have to be adevrtised for the prefix, multiple
instances of this sub-TLV with different algorithms can be used. If
Algorithm value is '0' is the only algorithm on the prefix, it is
optional to advertise it in this sub-TLV. Thus, not including such a
sub-TLV in the prefix implies Algorithm value '0' capability only.
3. Elements of Procedure
When provisioned an IS-IS node MUST compute reachability for more
than one algorithm as indicated in the reachability prefix through
this sub-TLV.
Default metrics used for computation of any algorithm MUST be as
defined in [RFC5120]. However, a particular algorithm can define
other than default metrics and can be used while doing the
computation. If non-default metrics are being used, those MUST be
configured on the links and MUST be advertised through IS-IS Area/
domain.
If a prefix is provisioned with multiple algorithms and after the
reachability computation, nexthop is different for each algorithm it
MUST use the lowest algorithm number to resolve the conflict.
Once computation is done with the specified algorithm, this is
applicable to all the data planes that are being supported for the
prefix. If a particular data plane specific 'algorithms' as defined
is in [I-D.ietf-isis-segment-routing-extensions] conflict (for e.g.
preference) with data plane independent prefix algorithm (as defined
in this draft); preference defined in a particular data plane MUST be
used.
3.1. Single Topology or Multi-Topology Mode
An SPF trigger can be common to multiple IS-IS Levels or for multiple
address families with multi-topologies. Currently there is no
specified order for reachability computation today and it is
implementation dependent. This document specifies the order of
reachability computation MUST be IS-IS area/level, topology [RFC5120]
and algorithm specified in the reachability prefix. Doing
computation in a particular order is also important for avoiding
micro-loops as described in [I-D.ietf-rtgwg-spf-uloop-pb-statement].
If network uses single topology mode with only IPv4 adress family
[RFC 5305] or in Single topology mode with IPv6 address family [RFC
5308] - a node configured with multiple algorithms MUST do route
computation with all the algorithms as advertised in the prefixes.
If network uses MT [RFC 5120], for each MT ID, per algorithm route
computation MUST be done.
Chunduri & Qu Expires April 25, 2019 [Page 4]
Internet-DraftMultiple Algorithm support for IS-IS Prefixes October 2018
4. Acknowledgements
TBD.
5. IANA Considerations
This document requests IANA to assign a sub-TLV code point from the
"Sub-TLVs for TLVs 135, 235, 236, and 237 (Extended IP reachability,
MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs)"
registry as follows: Route Computation Algorithm - Route Computation
Algorithm sub-TLV as described in Section 2.
TLV # Name
----- --------------------------------------------------------
TBD Route Computation Algorithm sub-TLV in IS-IS Prefix TLVs
6. Security Considerations
Security concerns for IS-IS are addressed in [RFC5304] and [RFC5310].
Further security analysis for IS-IS protocol is done in [RFC7645]
including analysis of both the above documents. Advertisement of the
additional information defined in this document introduces no new
security concerns in IS-IS protocol.
7. References
7.1. Normative References
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <https://www.rfc-editor.org/info/rfc1195>.
[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>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
Chunduri & Qu Expires April 25, 2019 [Page 5]
Internet-DraftMultiple Algorithm support for IS-IS Prefixes October 2018
7.2. Informative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
"IS-IS Extensions for Segment Routing", draft-ietf-isis-
segment-routing-extensions-19 (work in progress), July
2018.
[I-D.ietf-rtgwg-spf-uloop-pb-statement]
Litkowski, S., Decraene, B., and M. Horneffer, "Link State
protocols SPF trigger and delay algorithm impact on IGP
micro-loops", draft-ietf-rtgwg-spf-uloop-pb-statement-07
(work in progress), May 2018.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
DOI 10.17487/RFC5308, October 2008,
<https://www.rfc-editor.org/info/rfc5308>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>.
[RFC7645] Chunduri, U., Tian, A., and W. Lu, "The Keying and
Authentication for Routing Protocol (KARP) IS-IS Security
Analysis", RFC 7645, DOI 10.17487/RFC7645, September 2015,
<https://www.rfc-editor.org/info/rfc7645>.
Authors' Addresses
Uma Chunduri
Huawei USA
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: uma.chunduri@huawei.com
Chunduri & Qu Expires April 25, 2019 [Page 6]
Internet-DraftMultiple Algorithm support for IS-IS Prefixes October 2018
Yingzhen Qu
Huawei USA
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: yingzhen.qu@huawei.com
Chunduri & Qu Expires April 25, 2019 [Page 7]
