Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-12-31
2003-08-12
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395310, C370S401000, C370S390000
Reexamination Certificate
active
06606323
ABSTRACT:
TECHNICAL FIELD
This invention relates Asynchronous Transfer Mode (ATM) protocols, and more particularly, to a protocol that enables mobility services for hosts interconnected to an ATM network via Local Area Networks (LANs).
BACKGROUND OF THE INVENTION
Notebook and palmtop computers are becoming very commonplace, and their computing capabilities are continually expanding. It is not surprising, therefore, to find such computers connected to local area networks, and serving as network hosts or as information repositories. Because these computers are easily moveable, the problems associated with mobility of hosts in a LAN are becoming important to solve. This mobility problem is heightened by the fact that, in recent years, the ATM network has emerged as the network of choice for interconnecting a collection of LANs and for providing high throughput and guaranteed quality-of-service (QOS). A standard has been created by the ATM Forum (an industry group), known as “LAN emulation” (LANE), to support existing LAN applications with no modification to inter-LAN communications. Unfortunately, ATM Forum's LANE inter-network protocol does not easily accommodate mobile hosts that are connected to LANs.
More specifically, when a host moves from one place to another, the host looses its identity with respect to its original location and, consequently, complications arise when a host that has the old address of a mobile host attempts to communicate to the mobile host's old address. To overcome this problem, some systems regularly flush all address-caches and, after flushing, resolve the addresses for all hosts anew. The LANE protocol does not provide mechanisms for performing address cache flushing selectively, such as only for the mobile hosts.
The situation becomes more burdensome when communication needs to be established among the LAN-based mobile hosts when these hosts change their locations frequently.
SUMMARY OF THE INVENTION
We realized that it would be advantageous to create a mechanism that, while conforms to the LANE standard, efficiently follows mobile hosts and is transparent to end user applications. This is accomplished by allowing devices to move at will from LAN to LAN, with no action being taken in response to a move. Rather, notice is taken of the LANE Emulation Client (LEC) address at which a device can be reached when the device that moved chooses to communicate with some other device. In such a case, a table is updated in a LAN Emulation Server (LES), which is an entity maintained by the WAN that interconnects a number of LECs. A similar table is maintained in each LEC, and the table of each LEC is updated whenever a connection is made between one of its devices and some other device. At times, of course, a LEC would have an incorrect address of a sought destination device. In such a case, the LEC sends a query to the LES, and the LES provides what the LES believes to be the correct LEC address. When the LES-provided address proves to be incorrect (or the LES does not have an address), a message is broadcast to the LES entities of other “emulated LANs,” or ELANs, which contains their own LES entities, and those LES entities have an opportunity to provide the correct address.
In one embodiment, the concept of each device having a “home LEC” is included, which would allow the network to provide enhanced levels of service to devices in their home LECs, as compared to the levels of service outside the home LECs.
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Ramamurthy Ram S.
Roy Radhika R.
Stuntebeck Peter H.
AT&T Corp.
Elallam Ahmed
Kizou Hassan
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