Browse Prior Art Database

Link and Control Point Failure

IP.com Disclosure Number: IPCOM000108818D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 93K

Publishing Venue

IBM

Related People

Drake, JE: AUTHOR [+3]

Abstract

This article describes a protocol that permits a node's control point to fail incrementally while allowing traffic to continue to transit the node.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Link and Control Point Failure

       This article describes a protocol that permits a node's
control point to fail incrementally while allowing traffic to
continue to transit the node.

      Control-point functions may be distributed within a node such
that the functions are relatively independent.  In particular, there
is a function that allows a node to activate and maintain the links
to its adjacent nodes, and there is a function that allows a node to
participate in the network control algorithms that distribute
information about the current state of the nodes and links in the
network. The later function maintains a tree connecting all of the
nodes in the network (the CP spanning tree) by dynamically marking
certain of the links in the network.

      As mentioned earlier, these functions are independent, and the
failure of the network control function does not impact the ability
of the node with the failure to properly switch traffic through it.

      A node establishes separate connections with each of its
adjacent nodes to monitor the status of these two functions in these
adjacent nodes.  Effectively, a connection exists between the peer
functions, and a node uses the failure of a connection to infer the
failure of the peer function in the adjacent node.

      The connection used to monitor the link activation/maintenance
function is termed the 'link liveness' connection, and the connection
used to monitor the network control function is termed the 'CP
maintenance' connection.  The link liveness connection is maintained
across all active lines, while the CP maintenance connection is
maintained only across links that have been marked as being on the CP
spanning tree.

      TEST messages are sent periodically by the link
activation/maintenance function across a link, when it is not
receiving packets from the adjacent node, to determine if the link is
still active.  These messages are sent on the link liveness
connection.  This connection is activated by the node with the
higher-valued node name at the time the link is activated, and it
remains active unless the link or the link activation/maintenance
function in the adjacent node fails, after which the 'link liveness...