IS-IS Working Group N. Shen
Internet-Draft T. Li
Intended status: Informational Cisco Systems, Inc.
Expires: August 18, 2013 S. Amante
Level 3 Communications
M. Abrahamsson
Tele2
February 14, 2013
IS-IS Operational Enhancements for Network Maintenance Events
draft-ietf-isis-oper-enhance-03
Abstract
This document describes an improved IS-IS neighbor management scheme
which can be used to enhance operational experience in terms of
convergence speed and finer control of neighbor cost over a LAN.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Interface Shutdown Black Hole . . . . . . . . . . . . . . 2
1.2. LAN of Last Resort . . . . . . . . . . . . . . . . . . . 2
1.3. Specification of Requirements . . . . . . . . . . . . . . 3
2. Sending Hellos with Fast Exit Notification . . . . . . . . . 3
3. Pseudonodes with Non-zero Metrics . . . . . . . . . . . . . . 3
3.1. Alternative Approaches . . . . . . . . . . . . . . . . . 4
4. Operational Considerations . . . . . . . . . . . . . . . . . 4
4.1. Operational Considerations: Fast Exit Notification . . . 4
4.2. Operational Considerations: Pseudonodes with Non-zero
Metrics . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The IS-IS [ISO10589] routing protocol has been widely used in
Internet Service Provider IP/MPLS networks. Operational experience
with the protocol, combined with ever increasing requirements for
lossless operations have demonstrated some operational issues. This
document describes those issues and some mechanisms for dealing with
those issues. These mechanisms do involve implementation support,
but do not require protocol changes.
1.1. Interface Shutdown Black Hole
One of these operationally problematic issues occurs when IS-IS is
disabled on only one side of a link. This can result in a
significant delay before neighbor(s) on the other end of the same
link notice this change. In turn, this can result in several seconds
during which traffic is blackholed, until the IS-IS neighbor(s) time
out the adjacency and IS-IS reconverges.
1.2. LAN of Last Resort
Another issue stems from a situation when operators want to
temporarily make an interface a "last resort" link for transit
traffic. This is a straightforward, though cumbersome, operation to
perform on a point-to-point link. Each device on the link is
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