Multiplex communications – Fault recovery
Reexamination Certificate
1998-03-26
2001-02-27
Jung, Min (Department: 2739)
Multiplex communications
Fault recovery
C370S392000, C370S466000
Reexamination Certificate
active
06195329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a trouble releasing system for an ATM (Asynchronous Transfer Mode) logic IP (Internet Protocol) network, and more particularly to a trouble releasing system for an ATM logic IP network which is constructed in an ATM network wherein a plurality of ATM switches and ATM terminals are connected arbitrarily and which uses an NHRP (Next Hop Address Resolution Protocol) as an address solution system between the ATM switches and the ATM terminals.
2. Description of the Related Art
In order to perform communication, in a logic IP subnetwork constructed in an ATM network, between an arbitrary ATM switch and ATM terminal, IP addresses of the ATM switch and the ATM terminal must be known.
One of such address solution methods employs an NHRP. The NHRP is an Internet draft proposed by the IETF (Internet Engineering Task Force) and is designated as <draft-ietf-rolc-nhrp-10.txt>.
The NHRP stores, for each logic IP subnetwork, ATM addresses and IP addresses of all of ATM switches and ATM terminals included in the logic IP subnetwork in a paired relationship with each other, and installs a server (NHS: NHRP server) for managing the ATM addresses and the IP addresses. Thereafter, the NHRP installs, for the ATM switches and the ATM terminals included in the logic IP subnetwork, clients (NHC: NHRP clients) which communicate with the NHS. Then, when any of the ATM switches and the ATM terminals tries to communicate with another ATM switch or ATM terminal, the NHC of the NHRP inquires the NHS to acquire address information to allow such communication.
Here, if the NHS which manages the addresses of the logic IP subnetwork suffers from a trouble or the like and cannot communicate any more, then the address information cannot be solved any more. This sometimes results in failure in communication with all of the ATM switches and the ATM terminals included in the logic IP subnetwork.
An example of a technique which solves a trouble of a network which arises from such failure in operation of an address server is a “Network Connection Apparatus” disclosed in Japanese Patent Laid-Open Application No. 120,950/94.
In the network connection apparatus mentioned, a router which interconnects different LANs (Local Area Networks) additionally has a function of backing up information of a server into an alternative server, another function of supervising the state of the server and a further function of holding address information of the alternative server. The network connection apparatus uses, if the server fails, alternative addresses registered in the router in advance and serving as the backup information of the server to maintain communication and avoid the trouble.
However, the prior art described above has the following problems.
First, in order to realize an end-to-end seamless connection aimed by an original ATM network and avoid a bottleneck of a drop of the transfer rate by a router, recent ATM networks which employ a system wherein a plurality of LANs are connected directly to each other without the intervention of a router are gradually increasing.
Therefore, the concept of a logic IP network has become required. Consequently, the prior art network connection apparatus disclosed in Japanese Patent Laid-Open Application NO. 120,950/94 which requires a router has a problem in that it cannot be applied to such recent ATM networks.
Second, the network connection apparatus disclosed in the document mentioned above is directed to application only to a LAN of the broadcast type which commonly has communication media such as, for example, the Ethernet.
However, with an ATM network which is an NBMA (Non-Broadcast Multi-Access) network, since it is so constructed that a connection is established when communication is to be performed, even if another address is given, communication is not performed immediately. For this communication, address solution on the logic IP subnetwork is required. However, in order to realize this, taking such a construction of a server and a client as described above into consideration, releasing means of both of them must be controlled.
In this manner, the technique of the prior art is disadvantageous in that it cannot take a countermeasure against a trouble of a server of the address solution system of a logic IP subnetwork.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a trouble releasing system and method for an ATM logic IP subnetwork wherein, when a server suffers from a trouble, address solution of the logic IP subnetwork can be performed on the client side by maintaining a communication function with another server which can perform address solution.
According to an aspect of the present invention, there is provided a trouble releasing system for an ATM logic IP subnetwork, comprising a logic IP subnetwork composed of at least one ATM switch and a plurality of ATM terminals, an NHRP server for managing a pair of an ATM address and an IP address of the ATM switch or the ATM terminals which are present in the logic IP network, an NHRP client for communicating with the NHRP server, and a standby NHRP server for performing server operation in place of the currently used NHRP server when the currently used NHRP server has a trouble, and wherein, when the currently used NHRP server which performs address solution in the logic IP subnetwork stops the server operation because of a trouble thereof and the standby NHRP server issues an instruction for change to a server operation, the NHRP client retrieves an address of the standby NHRP server registered in advance and causes communication of a request for address solution to be switchably performed by the standby NHRP server.
The trouble releasing system for an ATM logic IP subnetwork may be constructed such that the NHRP server includes a first communication unit for communicating with the NHRP client, and a first address table for holding an address of an ATM node of the logic IP subnetwork managed by the NHRP server itself, that the NHRP client includes a server address data base for registering an address of the NHRP server and an address of the standby NHRP server, a second communication unit for communicating with the NHRP server, and an NHC control unit for controlling switching from the NHRP server to the standby NHRP server, that the standby NHRP server includes a third communication unit for communicating with the NHRP client and the NHRP server, a second address table for periodically acquiring and holding the addresses of the NHRP server and the ATM node of the logic IP subnetwork managed by the NHRP server, and a standby NHS control unit for performing switching of the NHRP server, and that, when communication between the ATM switch and the ATM terminal is to be performed based on an address solution function by the NHRP server, at a point of time when communication of the NHRP client with the NHRP server in accordance with an NHR protocol is disabled for a fixed period of time and the communication is not secured, it is discriminated that the NHRP server is in a stopping state, and the NHC control unit resumes communication using the address of the standby NHRP server acquired as an object of address solution from the server address database, whereupon the standby NHRP server accepts a protocol of a request for address registration from the NHRP client and the standby NHS control unit discriminates that switching from the NHRP server to the standby NHRP server is performed and updates the information based on the address of the logic IP subnetwork acquired from the NHRP server in advance and then performs address management of the belonging logic IP subnetwork so that the standby NHRP server operates as a main NHRP server to release the trouble.
According to another aspect of the present invention, there is provided a trouble releasing method for an ATM logic IP subnetwork described above, wherein the standby NHS server executes a first step wherein the standby NHS server issues a request for registration
Jung Min
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
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