Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Utility Patent
1998-01-08
2001-01-02
Pham, Chi H. (Department: 2731)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S400000
Utility Patent
active
06169739
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention relates to a multi-protocol client-server system for ATM (asynchronous transfer mode) virtual LANs (local area networks).
2. Description of the Related Art
With the expansion of the Internet and the increasing complexity of local area networks, businesses are focusing their attention on virtual local area networks (or VLANs), or subnets which can be created within an existing ATM network without restrictions which would otherwise be imposed by the physical topology of the network. The use of LAN emulation protocol is one way of implementing a virtual LAN in an ATM network. The IPOA (Internet Protocol over ATM) is one of such LAN emulation protocols. However, routers are still required for transporting packets between subnets because the IPOA emulation is based on the physical structure of the ATM network. Since the functions of a router are to reassemble arriving ATM cells into IP packets and then invoke a routing procedure, the amount of time taken by cell assemblage and packet routing is substantial. Another approach is the use of NHRP (next hop resolution protocol) which allows connections to be directly established over several subnets without using routers. Instead of routers, next hop servers are installed to exchange request and reply messages to resolve an ATM address and communicate the address to the requesting source. However, the address resolution time represents a substantial overhead for single packet transmissions, or datagrams.
Multi-protocol over ATM is proposed by the ATM forum. According to the Multi-Protocol Over ATM (MPOA), Version 1.0, February 1997 (ATM Forum/BTD-MPOA-MPOA-01.13), a traffic counter is used for measuring traffic of packets by looking up their source/destination address field. If the amount of traffic exceeds a predefined threshold, the traffic is recognized as a continuous stream of packets and the network changes the mode of transmission from hop-by-hop, connectionless mode to connection-oriented mode by establishing a connection.
However, the shortcoming, of the proposed multi-protocol for ATM networks is that, since initial packets of a data stream are still routed on a hop-by-hop basis, network routers must be capable of handling such packets as well as datagrams. There is still a need to decrease the connectionless traffic offered to routers.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a simple and yet effective solution to the problem by looking up the layer-
3
header address of packets to discriminate between connectionless and connection-oriented traffic.
The present invention provides an ATM network comprising a plurality of logical subnetworks, each of the logical subnetworks comprising a server and at least one client, the server having means for resolving ATM addresses of destination clients from a layer-
3
address of an ATM address resolution request message from a source client and means for routing a packet through the network by using a layer-
3
address of the packet. The source client examines a layer-
3
header of a packet to determine whether the packet has a connection-oriented traffic or a connectionless traffic. If the packet has a connectionless traffic, the source client transmits, the packet to the server for causing it to route the packet through the network, and transmits, if the packet has a connection-oriented traffic, an ATM address resolution request message to the server. The source client receives a reply message from the server containing a resolved ATM address, and transmits a signaling message containing the resolved ATM address to the network to establish a connection. Over the established connection, the source client transmits data packets.
REFERENCES:
patent: 5600644 (1997-02-01), Chang et al.
patent: 5617540 (1997-04-01), Civanlar et al.
patent: 5812552 (1998-09-01), Arora et al.
patent: 5822320 (1998-10-01), Horikawa
patent: 5825772 (1998-10-01), Dobbins et al.
patent: 5828844 (1998-10-01), Civanlar
patent: 5878212 (1999-03-01), Civanlar et al.
patent: 6016319 (2000-01-01), Kshirsagar
“The ATM Forum Technical Committee”, Multi-Protocol Over ATM Version 1.0, ATM Forum/BTD-MPOA-MPOA-MPOA-01.13, Feb. 1997, pp. 3-4 and 9-10.
NEC Corporation
Nguyen Steven
Pham Chi H.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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