IS-IS Minimum Remaining Lifetime
RFC 7987
Internet Engineering Task Force (IETF) L. Ginsberg
Request for Comments: 7987 P. Wells
Category: Standards Track Cisco Systems
ISSN: 2070-1721 B. Decraene
Orange
T. Przygienda
Juniper
H. Gredler
RtBrick Inc.
October 2016
IS-IS Minimum Remaining Lifetime
Abstract
Corruption of the Remaining Lifetime field in a Link State Protocol
Data Unit (LSP) can go undetected. In certain scenarios, this may
cause or exacerbate flooding storms. It is also a possible denial-
of-service attack vector. This document defines a backwards-
compatible solution to this problem.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7987.
Ginsberg, et al. Standards Track [Page 1]
RFC 7987 IS-IS Remaining Lifetime October 2016
Copyright Notice
Copyright (c) 2016 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
(http://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. Problem Statement ...............................................3
1.1. Requirements Language ......................................4
2. Solution ........................................................4
3. Deployment Considerations .......................................5
3.1. Inconsistent Values for MaxAge .............................5
3.2. Reporting Corrupted Lifetime ...............................6
3.3. Impact of Delayed LSP Purging ..............................7
4. Security Considerations .........................................7
5. References ......................................................7
5.1. Normative References .......................................7
5.2. Informative References .....................................8
Acknowledgements ...................................................8
Contributors .......................................................8
Authors' Addresses .................................................9
Ginsberg, et al. Standards Track [Page 2]
RFC 7987 IS-IS Remaining Lifetime October 2016
1. Problem Statement
[ISO10589] defines the format of a Link State PDU (LSP) that includes
a Remaining Lifetime field. This field is set by the originator
based on local configuration and then decremented by all systems once
the entry is stored in their LSP Database (LSPDB) consistent with the
passing of time. This allows all Intermediate Systems (ISs) to age
out the LSP at approximately the same time.
Each LSP also has a checksum field to allow receiving systems to
detect errors that may have occurred during transmission. [ISO10589]
mandates that the checksum is calculated by the originator of the LSP
and cannot be modified by other routers. Therefore, the Remaining
Lifetime is deliberately excluded from the checksum calculation. In
cases where cryptographic authentication is included in an LSP
([RFC5304] or [RFC5310]), the Remaining Lifetime field is also
excluded from the hash calculation. If the Remaining Lifetime field
gets corrupted during flooding, this corruption is therefore
undetectable. The consequences of such corruption depend upon how
the Remaining Lifetime is altered.
In cases where the Remaining Lifetime becomes larger than the
Show full document text