Internet DRAFT - draft-wang-lsr-redistribution-credibility-id
draft-wang-lsr-redistribution-credibility-id
Network Working Group Q. Wang
Internet-Draft Huawei Technologies
Intended status: Standards Track 16 August 2023
Expires: 17 February 2024
Route Redistribution Credibility ID for Avoiding Routing Loop
draft-wang-lsr-redistribution-credibility-id-01
Abstract
The route redistribution is often deployed in current network between
two different protocols domain or instance/process, such as the ISIS
domain redistribute to OSPF domain, the OSPF domain redistribute to
BGP domain, IS-IS redistribute to another IS-IS instance/process and
so on. The existing network have more complex multiple IGP domains
architecture. Therefore, bidirectional route redistribution
deployment is more complex for different protocols or instances/
processes to learn routes from each other. In recent years, these
route redistributions have had many routing loops cases that cause
network incident.
This document proposes a simplified method to positively avoid
routing loop, and introduces new sub-TLVs to support advertisement
IPv4 and IPv6 prefix extended attribute as Redistribution Credibility
ID, while redistributing route from one protocol domain or instance/
process to another.
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 RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 17 February 2024.
Copyright Notice
Copyright (c) 2023 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
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Route Redistribution Credibility ID . . . . . . . . . . . . . 3
3.1. IS-IS Redistribution Credibility ID Sub-TLV . . . . . . . 3
3.2. OSPF Redistribution Credibility ID Sub-TLV . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Due to network scope, architecture or network management requirement,
many existing network have multiple different IGP protocol domains,
including multiple routing protocol and multiple routing instance/
process with same protocol. These IGP domains boundary routers need
to deploy bidirectional route redistribution to learn routing prefix
information for each other. Because of reliability design
consideration, these route redistribution configuration have been
deployed at least two routers, or even more boundary routers between
these adjacent IGP domain.
However, there is no routing loop prevention mechanism in multiple
routing protocol domain or instance/process scenario. As traditional
method, these redistribution routers must be configured complex route
control policies, using IP prefix, cost and preference/
administrative distance (AD) and etc., to avoid routing loops and
nonoptimal routing problems.
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As the network scale grows and irregular distribution, these multiple
Route Redistribution node configuration become more and more
difficult to control. Maybe any network change have to adjust these
route redistribution configuration. The manually configured routing
policy adjustment mode have more complex and high risky that cannot
meet the requirements of the current network. As a result, many
serious network loop accidents occur and service traffic had been
affected. A simple and low-cost Layer 3 routing loop prevention
solution is urgently needed.
2. Terminology
IS-IS: Intermediate System to Intermediate System
OSPF: Open Shortest Path First
TTR: Times-to-Redistribution
Cred route-type: Credibility route-type
3. Route Redistribution Credibility ID
This document defines a new Route Redistribution Credibility ID sub-
TLV to solve the Layer 3 routing loop problem. The Route
Redistribution Credibility ID indicates the Route Credit Rating when
this routing prefix has been propagated across multiple routing
protocol domain or instance/process. The Route Redistribution
Credibility ID is automatically attenuated when the routing prefix
cross redistribution node. If a route is redistributed more times,
this route’s risk probability of routing loop is higher and its
Credibility is lower.
3.1. IS-IS Redistribution Credibility ID Sub-TLV
This section describes the Route Redistribution Credibility ID Sub-
TLV for IS-IS.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Redistribution Credibility ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IS-IS Route Redistribution Credibility ID Sub-TLV
where:
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Type: 33(is suggested)
Length: (1 octet), the length value is 4 octets
Redistribution Credibility ID: (4 octets), includes:
1. Times-to-Redistribution (called TTR, 1 octet)
2. Credibility route-type (called Cred route-type, 1 octet)
3. Reserved (2 octet)
The format of Redistribution Credibility ID sub-TLV in ISIS is as the
following:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TTR |Cred route-type| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Route Redistribution Credibility ID Field
where:
TTR: Times-to-Redistribution (called TTR, 1 octet), it indicates the
number of redistribution times, the value from 0 to 255 is used as
quantity of routing domain (means different routing protocol domain
or instance/process) to be traveled across from the routing prefix
original node to this route redistribution node. For example, each
time the route is redistributed, the Times-to-Redistribution (called
TTR) value decreases by 1, the route with greater Times-to-
Redistribution (called TTR) value can be preferred. This indicate
that the route is more closed to the route original node. When the
Times-to-Redistribution (called TTR) value is 0, it indicate the
route is not trusted.
Cred route-type: Credibility route-type (called Cred route-type, 1
octet), it indicate that the route is internal or external Cred route
type according to network administration scope. For the routing
prefix with same Times-to-Redistribution(called TTR) value scenario,
the internal Cred route-type that network administration scope
identification is the same as local, can be preferred rather than
external Cred route-type with different identification. The network
administration scope is specified according to the network layer of
logical architecture. The different routing domains (means different
routing protocol domain or instance/process) may have a same network
administration scope identification, or may have different network
administration scope identification.
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3.2. OSPF Redistribution Credibility ID Sub-TLV
TBD
4. IANA Considerations
This document requests that IANA allocates new IS-IS Route
Redistribution Credibility ID sub-TLV types from the "IS-IS Sub-TLVs
for TLVs Advertising Prefix Reachability" registry as specified.
+============+================+==+===+=====+=====+=====+===========+
| Type | Description |27|135| 235 | 236 | 237 | Reference |
+============+================+==+===+=====+=====+=====+===========+
| 33 (is | Redistribution |y |y | y | y | y | This |
| suggested) | Credibility ID | | | | | | document |
+------------+----------------+--+---+-----+-----+-----+-----------+
Table 1: IS-IS Sub-TLVs for TLVs Advertising Prefix Reachability
Registry
5. Security Considerations
This document introduces the Route Redistribution Credibility ID, The
feature introduces the advertisement of avoiding routing Loop
capability information to all routers in routing domain. This
information can be confirmed for discovery and verification that all
routers in the routing domain support the capability before the
feature is turned on. Advertisement of the information defined in
this document introduces no new security concerns.
6. Acknowledgements
The author would like to thank people for their comments on this
work.
7. Normative References
[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>.
Author's Address
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Qiang Wang
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing,
100095
China
Email: wangqiang88@huawei.com
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