LSR Working Group L. Ginsberg
Internet-Draft P. Psenak
Intended status: Standards Track Cisco Systems
Expires: 15 April 2025 Z. Zhang
ZTE Corporation
12 October 2024
IGP Flex Soft Dataplane
draft-ginsberg-lsr-flex-soft-dataplane-00
Abstract
Advertisement of IGP Flex-Algo participation requires a dataplane
context. This document defines a "soft dataplane" usable in cases
where existing defined dataplanes are not suitable.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Use Case Discussion . . . . . . . . . . . . . . . . . . . . . 2
4. IS-IS Soft Dataplane Algorithm Sub-TLV . . . . . . . . . . . 3
5. OSPF Soft Dataplane Algorithm TLV . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6.1. OSPF Router Information TLV Registry . . . . . . . . . . 5
6.2. IS-IS Router Capability sub-TLV Registry . . . . . . . . 6
6.3. Security Considerations . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Advertisement of IGP Flex-Algo[RFC9350] participation requires a
dataplane context. Existing data planes which have been defined
include:
Segment Routing Dataplane [RFC8667] [RFC8665]
IP Flex Dataplane [RFC9502]
The need to use an IGP Flexible Algorithm may occur in deployments
where none of the existing dataplanes are supported or suitable.
In such cases a "soft dataplane" MAY be used to provide the necessary
context for advertisement of Flex-Algo support. This document
defines the mechanisms to advertise such a dataplane.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Use Case Discussion
A deployment may require the use of flex-algo to achieve traffic
flows that meet certain constraints. In some cases, flex-algo paths
may be used by an application that does not require the use of any of
the currently defined dataplanes supported by flex-algo. The use of
these dataplanes may not be desired and/or is not supported in the
network. IP Flex-algo extends flex-algo so that it can be used
directly with IPv4 and IPv6 forwarding, but the use of IPv4/IPv6
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Algorithm specific prefix adverisements may not always be possible,
especially if the existing deployment does not allow for the lack of
reachability using the base IGP SPF (AKA algorithm 0) for these
prefixes. The use of a soft dataplane provides context which still
allows flex-algo to be deployed in such cases.
The new dataplane is referred to as "soft" because the flex-algo
paths computed for this dataplane are not expected to be used by
forwarding directly - e.g., they will not be installed in the data
path. They may be used by an application to create a forwarding
state that is maintained by the application itself. One such use
case might be to support multicast distribution over a constrained
topology in an IP only network.
Note that multiple flex algorithms - each defined for a different use
case - can be advertised in the context of a single soft dataplane.
Therefore, it is expected that a single soft dataplane will suffice
for all possible use cases.
The following sections define how to advertise flex-algorithm support
in the context of the soft dataplane.
4. IS-IS Soft Dataplane Algorithm Sub-TLV
The IS-IS [ISO10589] Soft Dataplane Algorithm Sub-TLV is a sub-TLV of
the IS-IS Router Capability TLV [RFC7981] and 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IS-IS Soft Dataplane Algorithm Sub-TLV
Type (1 octet): Soft Dataplane Algorithm Sub-TLV (Value TBD)
Length (1 octet): Variable
Algorithm (1 octet): Value from 128 to 255
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The IS-IS Soft Dataplane Algorithm Sub-TLV MUST be propagated
throughout the level and MUST NOT be advertised across level
boundaries. Therefore, the S bit in the Router Capability TLV, in
which the IS-IS Soft Dataplane Algorithm Sub-TLV is advertised, MUST
NOT be set.
The IS-IS Soft Dataplane Algorithm Sub-TLV is optional. It MUST NOT
be advertised more than once at a given level. A router receiving
multiple IS-IS Soft Dataplane Algorithm sub-TLVs from the same
originator MUST select the first advertisement in the lowest-numbered
Link State PDU (LSP), and subsequent instances of the IS-IS Soft
Dataplane Algorithm Sub-TLV MUST be ignored.
Algorithms outside the Flex-Algorithm range (128-255) MUST be ignored
by the receiver. This situation SHOULD be logged as an error.
The Flex-Algorithm participation advertised in the IS-IS Soft
Dataplane Algorithm Sub-TLV is topology independent. When a router
advertises participation in the IS-IS Soft Dataplane Algorithm Sub-
TLV, the participation applies to all topologies in which the
advertising node participates.
5. OSPF Soft Dataplane Algorithm TLV
The OSPF [RFC2328] Soft Dataplane Algorithm TLV is a top-level TLV of
the Router Information Opaque Link State Advertisement (LSA)
[RFC7770] and 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm... | Algorithm n | |
+- -+
| |
+ +
Figure 2: OSPF Soft Dataplane Algorithm TLV
Type (2 octets): Soft Dataplane Algorithm TLV (TBD)
Length( 2 octets): Variable
Algorithm (1 octet): Value from 128 to 255
The OSPF Soft Dataplane Algorithm TLV is optional. It MUST only be
advertised once in the Router Information LSA.
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Algorithms outside the Flex-Algorithm range (128-255) MUST be ignored
by the receiver. This situation SHOULD be logged as an error.
When multiple OSPF Soft Dataplane Algorithm TLVs are received from a
given router, the receiver MUST use the first occurrence of the TLV
in the Router Information LSA. If the OSPF Soft Dataplane Algorithm
TLV appears in multiple Router Information LSAs that have different
flooding scopes, the OSPF Soft Dataplane Algorithm TLV in the Router
Information LSA with the area-scoped flooding scope MUST be used. If
the OSPF Soft Dataplane Algorithm TLV appears in multiple Router
Information LSAs that have the same flooding scope, the OSPF Soft
Dataplane Algorithm TLV in the Router Information LSA with the
numerically smallest Instance ID (Opaque ID for OSPFv2 or Link State
ID for OSPFv3) MUST be used, and subsequent instances of the OSPF
Soft Dataplane Algorithm TLV MUST be ignored.
The Router Information LSA can be advertised at any of the defined
flooding scopes (link, area, or Autonomous System (AS)). For the
purpose of OSPF Soft Dataplane Algorithm TLV advertisement, area or
AS-scoped flooding is REQUIRED. The AS flooding scope SHOULD NOT be
used unless local configuration policy on the originating router
indicates domain-wide flooding.
The Flexible Algorithm participation advertised in the OSPF Soft
Dataplane Algorithm TLV is topology independent. When a router
advertises participation in an OSPF Soft Dataplane Algorithm TLV, the
participation applies to all topologies in which the advertising node
participates.
6. IANA Considerations
6.1. OSPF Router Information TLV Registry
This document updates the "OSPF Router Information (RI) TLVs"
registry as follows:
+=======+================+===================================+
| Value | TLV Name | Reference |
+=======+================+===================================+
| TBD | Soft Dataplane | draft-ginsberg-lsr-soft-dataplane |
| | Algorithm | |
+-------+----------------+-----------------------------------+
Table 1
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6.2. IS-IS Router Capability sub-TLV Registry
This document updates the "IS-IS Sub-TLVs for IS-IS Router CAPABILITY
TLV" registry as follows:
+=======+================+===================================+
| Value | TLV Name | Reference |
+=======+================+===================================+
| TBD | Soft Dataplane | draft-ginsberg-lsr-soft-dataplane |
| | Algorithm | |
+-------+----------------+-----------------------------------+
Table 2
6.3. Security Considerations
This document creates no new security issues for the IGPs.
7. Normative References
[ISO10589] ISO, "Intermediate system to Intermediate system routing
information exchange protocol for use in conjunction with
the Protocol for providing the Connectionless-mode Network
Service (ISO 8473)", August 1987, <ISO/IEC 10589:2002>.
[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>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>.
[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<https://www.rfc-editor.org/info/rfc7981>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", RFC 8665,
DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.
[RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
Extensions for Segment Routing", RFC 8667,
DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.
[RFC9350] Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,
and A. Gulko, "IGP Flexible Algorithm", RFC 9350,
DOI 10.17487/RFC9350, February 2023,
<https://www.rfc-editor.org/info/rfc9350>.
[RFC9502] Britto, W., Hegde, S., Kaneriya, P., Shetty, R., Bonica,
R., and P. Psenak, "IGP Flexible Algorithm in IP
Networks", RFC 9502, DOI 10.17487/RFC9502, November 2023,
<https://www.rfc-editor.org/info/rfc9502>.
Authors' Addresses
Les Ginsberg
Cisco Systems
Email: ginsberg@cisco.com
Peter Psenak
Cisco Systems
Apollo Business Center
Mlynske nivy 43
82109 Bratislava
Slovakia
Email: ppsenak@cisco.com
Zheng Zhang
ZTE Corporation
China
Email: zhang.zheng@zte.com.cn
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