Browse Prior Art Database

Router Automatic Link Re-Establishment Process

IP.com Disclosure Number: IPCOM000105270D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 148K

Publishing Venue

IBM

Related People

Alward, WA: AUTHOR [+6]

Abstract

A method to detect and automatically re-establish a communications link between two nodes in a network with automatic recovery.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 33% of the total text.

Router Automatic Link Re-Establishment Process

      A method to detect and automatically re-establish a
communications link between two nodes in a network with automatic
recovery.

      Any application is given the ability to automatically
re-establish a link whenever a link failure occurs and recover all in
progress data transmissions.  It includes an Application Program

Interface (API), which can be used to specify the degree and finesse
of the recovery attempt.

      The API for internal link establishment process will allow any
user application to control link recovery, or request that our
communications program, the router automatically re-establish a link
which has been interrupted.  The details are included below.

This concept works by both changing the internal link establishment
process inside the router and exposing new API calls or verbs that
the LU 6.2 applications that call the router can use to control the
link re-establishment process.

First, a change was made to the router to allow the specification of
two new parameters on a link specification entry used by the STARTRTR
program to establish initial links.   An example follows:

          TRLI LUNAME,LANADDR,ActiveRetryCount,RetryDelayTimer

          TRLI  Token-Ring Link Information Identifier

          LUNAME  AS/400* logical unit name for this connection

          LANADDR Token-Ring MAC (Media Access Control) adapter
address

          ActiveRetryCount  Link re-establishment specification.
Range (0-FFH)
          This value sets up the number of times the PCS/400 router
will attempt
          to re-establish a link.  The Link Establishment Procedures
will be
          different based on the Connection Type (SDLC vs.  LAN vs.
TWINAX vs.
          ASYNC).  The basic steps are:

1.  Establish the connection(physical Link) into the system(s) to be
    used by the PC Support Applications.  In the case of LAN
    connections, this could be to multiple AS/400s at a time.

2.  Perform the necessary BIND negotiation to each system that the
    Router was communicating with prior to the Link going down.

      This link re-establishment may be through the same network path
or an alternate network path since the router will attempt to locate
the AS/400 just as if the connection was for the first time.  The
advantage of this approach is the the router may find a new path to
the AS/400 by-passing a broken link from the old path that may be
down due to a hardware, or bridge failure.  On true Remote Switched
Connections, the Router could try using another Telephone number to
get into the network (it is possible that one port on the system is
down, or some intermediate switch in the network overloaded with
calls).

      The value used on this parameter will determine the number of
times that router will attempt to automatically re-establish the
link.  A value of 0...