Browse Prior Art Database

Scoping Multicasts in WAN Interconnected Local Networks

IP.com Disclosure Number: IPCOM000106912D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 191K

Publishing Venue

IBM

Related People

Derby, J: AUTHOR [+9]

Abstract

Disclosed is an improvement in the interconnection of local area networks (LANs) over a wide area network (WAN) that solves the problem of so-called "broadcast storms" arising when broadcast protocols used on LANs, such as TCP/IPs "address resolution protocol" or Source Routing's "all-routes broadcast", occur in a bridged LAN having many LAN segments. This invention improves performance over simple LAN bridging by limiting LAN broadcasts to a predetermined group of LANs. For purposes of this invention, LANs are grouped on the basis of two characteristics. One characteristic is the protocol used by some subset of the end stations on the LAN, above the data link layer (layer 2 of the Open Systems Interconnection reference model).

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

Scoping Multicasts in WAN Interconnected Local Networks

       Disclosed is an improvement in the interconnection of
local area networks (LANs) over a wide area network (WAN) that solves
the problem of so-called "broadcast storms" arising when broadcast
protocols used on LANs, such as TCP/IPs "address resolution protocol"
or Source Routing's "all-routes broadcast", occur in a bridged LAN
having many LAN segments.  This invention improves performance over
simple LAN bridging by limiting LAN broadcasts to a predetermined
group of LANs.  For purposes of this invention, LANs are grouped on
the basis of two characteristics.  One characteristic is the protocol
used by some subset of the end stations on the LAN, above the data
link layer (layer 2 of the Open Systems Interconnection reference
model).  The other characteristic is a network identifier (or virtual
network identifier, in the case of LAN protocols that do not use
network identifiers).

      The idea of extending spanning tree algorithms, such as those
used by link-layer bridges or routers, across a WAN for the purpose
of routing the datagram packets of a particular transmission layer
protocol such as TCP/IP is not new (1).  However, this invention goes
well beyond the prior art in addressing broadcast problems in the
context of a utility transport network that carries all types of
traffic generated as a result of interconnecting many different types
of local networks supporting a variety of transmission layer
protocols.  It also takes advantage of fast packet switching
capabilities such as those described in (2).

      The following terminology applies throughout this article.
Resources are sources and sinks of data that use the transport
services provided by the utility transport network.  A network
identifier (NETID) refers to a collection of resources grouped into a
logical network; a NETID maps a logical network onto one or more
physical networks.  Directory service refers to a collection of
functions that uses a distributed database to support the mapping of
resource (type, name) tuples to WAN transport addresses.  Queries to
the directory database use a client-server distributed computing
paradigm such as that in Advanced Peer-to-Peer Networking.  Client
refers to the sender of a query.  Server refers to the receiver of a
query; depending on the protocol, the server may send a reply to the
client.  If the client's query is a multicast (i.e., a transmission
by one sender to multiple receivers), then more than one server can
receive the query and, possibly, respond.  Access agents provide
standard interfaces or points of attachment where protocol-specific
local network traffic enters the WAN backbone.  Access agents have
one or more protocol agents (which know a particular LAN protocol,
e.g., IEEE standard 802.2 or 802.5). Access agents assume the role of
client or server to send or receive directory queries.  Access agents
associated with a local networ...