Multiplex communications – Fault recovery
Reexamination Certificate
1998-03-09
2001-06-05
Olms, Douglas (Department: 2661)
Multiplex communications
Fault recovery
C370S395430
Reexamination Certificate
active
06243357
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a technology effective in an application to a-LAN emulation technology in an ATM communication network.
A system for actualizing a LAN emulation in an ATM network involves a data transmission between LAN emulation terminals connected to an ATM switch via the ATM network. Connected to the ATM switch are a group of servers for actualizing a LAN emulation function such as, e.g., a LAN emulation server (LES), a Broadcast and Unknown Server (BUS) and a LAN emulation configuration server (LECS).
If a fault occurs in the server group for the LAN emulation, it follows that a trouble is caused in communications between LAN emulation clients. In the great majority of cases, there exists only one system of the LAN emulation configuration server (LECS) in the network, and, if the fault occurs in this LECS, there must be a high possibility in which the whole network might fall into a system-down.
There can be considered the following contrivances for avoiding the above system-down.
(1) An implementation system, i.e., the server group for providing the LAN emulation service function is constructed as a dual structure.
(2) The implementation system for providing the LAN emulation service function incorporates a line dual function.
(3) The ATM switch itself incorporates the line dual function.
In the above contrivances (2) and (3), it is required that the dual function based on the same procedures be incorporated into the implementation system (the server group) connected to an opposite equipment, i.e., the ATM switch existing on the opposite side and therefore be incorporated at a plurality of places. This conduces to a problem in which the incorporation of the function itself becomes heavy.
Accordingly, it is considered optimal to adopt the contrivance (1), however, there has been made no examination about a concrete method of actualizing it.
It is a primary object of the present invention, which was contrived in view of the point described above, to provide a LAN emulation system capable of avoiding a fault without making the line dual by a local dual structure on the premise that a LAN emulation server is made dual.
SUMMARY OF THE INVENTION
To accomplish the above object, according to a first aspect of the present invention, an ATM switch, to which a LAN emulation terminal is connected, includes a line fault detecting unit, a routing table in which to define a correspondence between a specified address and a line, and a line status table rewritten based on a result of detection by the fault detecting unit. Further, a LAN emulation configuration server (LECS) connected to the ATM switch is constructed to have a dual structure.
A line status is monitored, and, if a fault occurs in a connection to the LAN emulation configuration server, it is feasible to easily make a connection to the dual LAN emulation configuration server. Besides, the line is not required to be made dual, and hence a fault avoiding system can be easily constructed.
According to a second aspect of the present invention, in the LAN emulation system according to the first aspect of the invention, one or two or more LAN emulation execution servers and address set servers for the LAN emulation are connected to the LAN emulation configuration server, and the LAN emulation configuration server includes a server registration table in which to set a combination of a LAN emulation executing server connected to the LAN emulation configuration server and an address set server for the LAN emulation.
According to a third aspect of the present invention, in the LAN emulation system according to the second aspect of the invention, the LAN emulation configuration server is provided with a plurality of server registration tables, and the server registration table alternatively different is registered in each of the dual LAN emulation configuration servers.
According to the second aspect of the invention, the LAN emulation execution server is defined as a LES (LAN emulation Server) prescribed in an ATM Forum UNI Version 1.0, and the address set server for the LAN emulation is defined as a BUS (Broadcast and Unknown Server).
According to the first and second aspects of the invention, a content of the server registration table is changed per dual LAN emulation configuration server, whereby a load can be decentralized when a fault occurs due to an overload of the line.
According to a fourth aspect of the present invention, a well-known address for the LAN emulation configuration server is set as a specified address of the routing table.
The well-known address is a well-known LECS address prescribed in the ATM Forum UNI Version 1.0.
Thus, the well-known LECS address is used as the specified address of the routing table, thereby making it possible to set routing while steering clear of a line with an occurrence of fault by use of a SETUP signal transmitted from the LAN emulation terminal (LEC).
According to a fifth aspect of the present invention, an ATM switch connected to a LAN emulation configuration server comprises a control unit provided corresponding to two or more lines, a switch unit for switching the line, a cell inserting/extracting unit for inserting and extracting cells transferred via the line, a signaling processing unit for detecting a fault in the line, and a line correspondence data unit including a routing table in which to define a correspondence of the well-known address to the line and a line status table rewritten based on a result of detection by the fault detecting unit. Then, the routing table is set so as to lead a connection to the well-known address from an external terminal to the LAN emulation configuration server selectively from the two or more lines on the basis of a change in the line status table.
With such a construction of the ATM switch, a fault avoiding system can be constructed simply by making the LAN emulation configuration server dual without making the line dual.
REFERENCES:
patent: 5258977 (1993-11-01), Walker et al.
patent: 5398236 (1995-03-01), Hemmady et al.
patent: 5812552 (1998-09-01), Arora et al.
patent: 5828665 (1998-10-01), Hasakl
patent: 5835481 (1998-11-01), Akyol et al.
patent: 5982773 (1999-11-01), Nishimura et al.
Fujitsu Limited
Helfgott & Karas P.C.
Olms Douglas
Vanderpuye Ken
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