Browse Prior Art Database

Providing Backup and Non-Disruptive Recovery of Local Area Network Traffic Across a Connection Oriented Wide Area Network

IP.com Disclosure Number: IPCOM000118770D
Original Publication Date: 1997-Jun-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 3 page(s) / 153K

Publishing Venue

IBM

Related People

Ogle, DM: AUTHOR [+3]

Abstract

Disclosed is an algorithm for providing backup and non-disruptive recovery between multiple gateways connecting Local Area Networks (LAN) via a Wide Area Network (WAN).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 39% of the total text.

Providing Backup and Non-Disruptive Recovery of Local Area Network
Traffic Across a Connection Oriented Wide Area Network

      Disclosed is an algorithm for providing backup and
non-disruptive recovery between multiple gateways connecting Local
Area Networks (LAN) via a Wide Area Network (WAN).

      This disclosure addresses an effective way to allow customers
to install multiple gateways to connect LANs via a connection
oriented WAN, while minimizing the amount of administration required.
The algorithm provides for backup and non-disruptive recovery.  The
algorithm is predicated on the fact that the WAN is connection
oriented and that  once a connection is established between two
points, it is easier, faster, and more cost effective to use the same
path for all traffic between those two points.

The problems addressed by this disclosure are:
  o  Backup - How to ensure that when there are multiple gateways
      serving a site and one of those gateways goes down, that the
      other gateway(s) picks up the duties of the down gateway.
  o  Non-Disruptive Recovery - How to ensure that when a gateway
      comes back online, it can start picking up its load without
      disrupting any existing connections.

      The Figure defines some terms.  X, Y, and Z are "parallel"
gateways since they all connect the same LAN to the WAN.  A parallel
gateway 'set' is a set containing all the parallel gateways
connecting a particular LAN to a particular WAN.  For instance, X, Y,
and Z make up  a parallel gateway set.  Gateways A and B are
non-parallel gateways. A  parallel gateway "serves" a set of
destinations across the WAN. Which  set of destinations a particular
parallel gateway serves is not important  for the backup and recovery
discussion.  When a parallel gateway, say X, serves a particular
destination, say M1, it means that all traffic coming from LAN 'W'
that is destined for M1, will come through X. All  traffic coming
from M1, destined to any address on LAN 'W', will come through X.  It
is important to note that the definition of 'destination  address' is
intentionally vague since it could be the machine's address,  the
network address, the port number of the application, etc.

      The first problem addressed by this disclosure is backup.  A
method is necessary for one parallel gateway to determine that
another parallel gateway is down and to dynamically determine which
gateway should take over for the down gateway.  The algorithm used to
do this is  explained below.

      It is worth noting now that the parallel gateways may or may
not be exchanging routing information both with each other and with
the other machines on the LAN using a native routing protocol (like
Routing Information Protocol (RIP)).  Use of a native routing
protocol makes it easier for machines on the LAN to determine which
gateway they should send packets to, and it helps the machines on the
LAN determine...