A originating terminal sends an ATM address interrogation request to a server if the ATM address of another party's terminal is unknown at the time of communication. Upon receiving the ATM address interrogation request from the terminal, the server refers to an ATM address table, searches the table for an ATM address corresponding to a protocol address contained in the interrogation request and notifies the originating terminal of this ATM address. If an ATM address corresponding to the protocol address has not been registered in the ATM address table, the server transfers (broadcasts) the ATM address interrogation request to all terminals. The server notifies the originating terminal of an ATM address obtained by an answer in response to this interrogation request and registers the ATM address in the ATM address table.
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12. A server in a communication system equipped with a plurality of terminals, the server for managing a corresponding relationship between a protocol address and terminal address of each terminal, and an exchange which accommodates each terminal and the server, said the server comprising:
an address table for storing the corresponding relationship between a protocol address and terminal address of each of the plurality of terminals;
search means for referring to said address table and searching for a terminal address corresponding to a protocol address contained in a terminal address interrogation request from a terminal; and
interrogation means which, if a terminal address corresponding to the protocol address has not been registered in the address table, is for interrogating all receiving, from an originating terminal, an address interrogation request including a first value indicative of a request and a first address, and for transferring the address interrogation request to a plurality of terminals, via an exchange, or the terminal address corresponding to this protocol address; wherein in response to receipt of a terminal address interrogation request from an originating terminal, said search means refers to said address table to obtain the terminal address conforming to the protocol address contained in this terminal address interrogation request and, if this terminal address has not been registered, said interrogation means interrogates the terminals for terminal address ;
means for receiving, form one of the plurality of terminals having it's own second address which is not registered in the server, an answer including a second value indicative of an answer and a second address which corresponds to the first address, in response to the address interrogation request which has been transferred from the server; and
registration means for registering, in a memory, a corresponding relationship between the first address and the second address which is included in the answer.
0. 26. In a network system having a server, the method comprising the steps of:
receiving, from an originating terminal by the server, an address interrogation request including a first address and a first value indicative of a request;
transferring, by the server, the address interrogation request to a plurality of terminals;
receiving, from an originating terminal by the server, an answer including a second value indicative of an answer and second address which corresponds to a first address;
deleting, from the server, an entry which has a corresponding relationship between a first address and a second address from the server to form a vacancy when the server cannot register a corresponding relationship between the first address and the second address which is included in the answer; and
registering in a vacancy of the server a corresponding relationship between the first address and the second address which is included in the answer.
0. 16. In a network system having a server, the method of registering in the server a corresponding relationship between a first identifier and a second identifier for a communication party, comprising the steps of:
receiving an interrogation request including a first value indicative of a request and a first identifier;
determining a corresponding second identifier is not registered in the server;
transferring the interrogation request to a plurality of terminals which can accommodate the communication party;
receiving, from a terminal having it's own second identifier which is not registered in the server, an answer including a second value indicative of an answer and a second identifier which corresponds to the communication party identified by the first identifier, in response to the interrogation request; and
registering a corresponding relationship between the first identifier and the second identifier which is included in the answer.
0. 32. A sever comprising:
means for receiving, from an originating terminal, an address interrogation request including a first address and a first value indicative of a request;
means for transferring the address information request to a plurality of terminals;
means for receiving an answer including a second value indicative of an answer and a second address which corresponds to the first address from one of the plurality of terminals in response to the address interrogation request which has been transferred; and
means for registering, in a memory of the server, a corresponding relationship between the first and the second address in a place designated by an index value which is calculated based on a value of the first address or the second address,
wherein when the server receives the answer including the second address corresponding to the first address from the one of the plurality of terminals, the registration means deletes a corresponding relationship, referred to least recently, when the server can not accommodate a corresponding relationship between the first address and the second address, and registers the corresponding relationship between the first address and the second address which is included in the answer.
8. A communication system equipped with a plurality of terminals, and a server having an address table for storing registering a corresponding relationship between a protocol first address and terminal second address of each terminal, and an exchange which accommodates each terminal and the server, wherein each of the said the terminals comprises:
means for sending a terminal , to the server, an address interrogation request to the server if the terminal address of another party's terminal is unknown at the time of communication which includes a first value indicative of a request and a first address; and
communication means for communicating with the other party's terminal via the exchange using a terminal address of which it has been notified by the server in response to the interrogation request; and
terminal address answering means for answering the server with an answer including its own terminal address if which is not registered in the server and a second value indicative of an answer when a protocol first address contained , included in an a terminal address interrogation request transferred which has been received from the server agrees with its own protocol first address; and
said the server comprises:
means for referring to the address table and searching for a terminal address corresponding to a protocol address contained in a terminal address interrogation request from a terminal;
means which, if a terminal address corresponding to said protocol address has not been registered in the address table, is for transferring the terminal address interrogation request containing said protocol which includes the first value and the first address to all a plurality of terminals via the exchange ; and
means for notifying the terminal which has issued the interrogation request of a terminal address found from the address table or of a terminal address obtained by an answer from a terminal
registration means for registering, in the server, a corresponding relationship between the first address and the second address which is included in the answer which has been received from one of the plurality of terminals in response to the address interrogation request which has been transferred from the server.
0. 28. An address resolution system equipped with a plurality of terminals, a switch or exchange which accommodates each terminal of a plurality of terminals and a server, wherein
each terminal of the plurality of terminals comprises:
means for sending a terminal address interrogation request which includes a first value indicative of a request and a first address to the server if a second address of another party's terminal is unknown at the time of communication; and
means for answering the server with an answer including a terminal own second address and a second value indicative of an answer when a first address included in a terminal address interrogation request received from the server agrees with a terminal own first address; and
the server comprises:
means for transferring the terminal address interrogation request including the first value indicative of the request and the first address to the plurality of terminals; and
receiving means for receiving, in response to the terminal address interrogation request which has been transferred by the server, an answer including a second address corresponding to the first address from one of the plurality of terminals;
means for registering in the server a corresponding relationship between the first address and the second address which has been included in the answer.
0. 34. In a network system including communication parties accommodated by terminals, a method of registering a corresponding relationship between a first identifier and a second identifier for a communicating party, comprising the steps of:
when a communication request is issued, determining, in a terminal accommodating an originating party, whether a second identifier for another communicating party is registered;
sending to a server an interrogation request including a first value indicative of a request and a first identifier of the other communicating party when the second identifier is not registered in the terminal;
transferring, by the server, the interrogation request to a plurality of terminals which can accommodate the other communicating party when the second identifier corresponding to the first identifier is not registered in the server;
receiving, at the server, an answer including a second value indicative of an answer and the second identifier which corresponds to the other communicating party identified by the first identifier in response to the interrogation request, said answer from a terminal having it's own second identifier which is not registered in the server;
sending the answer to the terminal accommodating the originating party; and
registering, in the terminal accommodating the originating party, a corresponding relationship between the first identifier and the second identifier which is included in the answer.
1. An address management method in a communication system equipped with a plurality of terminals, and a server having an address table for storing registering a corresponding relationship between a protocol first address and terminal a second address of each terminal, and an exchange which accommodates each terminal and the server, said the method comprising the steps of:
a first step in which an originating terminal sends a terminal address interrogation request to the server if the terminal address of another party's terminal is unknown at the time of communication;
a second step in which the server, upon receiving the terminal address interrogation request from the terminal, refers to the address table and searches for a terminal address corresponding to a protocol address contained in said interrogation request;
a third step in which, if a terminal address corresponding to said protocol address is obtained from the address table, the server notifies the terminal of this terminal address;
a fourth step in which, if the terminal address is not obtained from the address table, the server transfers the terminal address interrogation request containing said protocol address to all terminals via the exchange;
sending, to the server by an originating terminal, an address interrogation request which includes a fist value indicative of a request and a first address;
transferring, to a plurality of terminals by the server, the address interrogation request which includes the first value and the first address;
the fifth step in which, when receiving, by each terminal receives the terminal address interrogation request transferred from the server, the terminal determines ;
determining by each terminal whether the protocol first address contained included in the address interrogation request received from the server agrees with its a terminal's own protocol first address and notifies the server of its own terminal address if agreement is achieved; and, ;
a sixth step in which the server notifies the originating terminal of the terminal address of which it has been notified
notifying, by each terminal, in response to the address interrogation request, the server of an answer which includes a terminal's own second address which is not registered in the server and a second value indicative of an answer when agreement is achieved;
receiving, from one of the plurality of terminals by the server, the answer which includes the second value and the second address which corresponds to the first address; and
registering, in the server, a corresponding relationship between the first address and the second address which is included in the answer.
0. 40. A network identifier resolution system equipped with a plurality of terminals, a switch or exchange which accommodates each terminal of a plurality of terminals and a server, wherein:
each terminal of the plurality of terminals comprising:
a processor that receives a communication request message, determines a first identifier from the communication request message, checks a local storage area for a corresponding second identifier, and when a second identifier is not registered, creates an interrogation request message which includes a first value indicative of a request and the first identifier; and
a network interface unit that sends to the server the interrogation request message and receives answers and interrogation request messages from the server;
the server comprising:
a processor that receives the interrogation request message, checks a storage area for a corresponding second identifier, and when a second identifier is not registered, forwards the interrogation request;
network interface unit for transferring the interrogation request message including the first value indicative of the request and the first identifier to a plurality of terminals, and receiving, in response to the interrogation request message, an answer including a second identifier corresponding to the first identifier from one of the plurality of terminals having it's own second identifier which is not registered in the server; and
the storage area for registering a corresponding relationship between the first identifier and the second identifier which has been included in the answer.
2. The method according to
a step in which the exchange or switch connects the server with all a plurality of terminals by PVCs (permanent virtual channels) having identical values ; and
a step in which, when a terminal an address interrogation request having said identical a predetermined value for a PVC has entered from the server, the exchange or switch performs cell copying, whereby said the address interrogation request cell is transferred to all the plurality of terminals.
3. The method according to
a step in which the exchange or switch connects the server with all a plurality of terminals by PVCs (permanent virtual channels) having identical values and divides all the plurality of terminals into a plurality of groups;
a step in which, when a terminal an address interrogation request having said identical a predetermined value for a PVC has entered from the server, the exchange or switch performs cell copying, wherein said the address interrogation request cell is transferred to all terminals in first group;
a step in which the server performs monitoring to determine whether a prescribed terminal has answered with a terminal second address within a set period of time;
a step in which the server sends the address interrogation request cell to all the plurality of terminals of the next group if no terminal answers with a terminal second address within the set period of time; and
a step in which the server transfers the address interrogation request cell while successively changing the group until a prescribed terminal answers with a terminal second address.
0. 4. The method according to
0. 5. The method according to
6. The method according to
a seventh step in which, when the server receives the answer of the terminal address from the terminal, the server deletes a corresponding relationship, referred to least recently, between a protocol address and terminal address if the address memory is full An address management method in a communication system equipped with a plurality of terminals, and a server for registering a corresponding relationship between a first address and a second address of each terminal, the method comprising the steps of:
sending, to the server by an originating terminal, an address interrogation request which includes a first value indicative of a request and a first address;
transferring, to a plurality of terminals by the server, the address interrogation request which includes the first value and first address;
receiving, by each terminal, the address interrogation request transferred from the server;
determining by each terminal whether the first address included in the address interrogation request from the server agrees with a terminal's own first address;
notifying, by the terminal, in response to the address interrogation request, the server of an answer which includes a terminal's own second address which is not registered in the server and a second value indicative of an answer when agreement is achieved;
receiving, from one of the plurality of terminals by the server, the answer which includes the second value and the second address which corresponds to the first address;
deleting a corresponding relationship, referred to least recently, between a first address and a second address if the server cannot accommodate a corresponding relationship between the first address and second address included in the answer received form a prescribed terminal; and
an eight step registering, in which a memory by the server newly stores the , a corresponding relationship between said protocol the first address and the terminal second address, of which is has been notified, is included in the address table answer.
0. 7. The method according to
0. 9. The communication system according to
means for connecting the server with all terminals by PVSs (permanent virtual channels) having identical values; and
means which, when a terminal address interrogation request having said identical value for PVC has entered from the server, is for performing cell copying and transferring said interrogation request cell to all terminals.
0. 10. The communication system according to
11. The communication system according to claim 10 8, wherein when the server receives the answer of the terminal address cannot register a corresponding relationship between the first address, and second address included in the answer which is received from the prescribed terminal, said the registration means deletes a corresponding relationship, referred to least recently, between a protocol first address and terminal second address if the address memory is full .
0. 13. The server according to
means for receiving notification of an answer from a prescribed terminal in response to the terminal address interrogation request; and
registration means for newly registering the corresponding relationship between the protocol address and the terminal address, of which it has been notified, in said address table.
14. The server according to claim 13 12, wherein when the server receives the an answer of the terminal including a second value indicative of an answer and a second address from the prescribed terminal one of the plurality of terminals, said the registration means deletes a corresponding relationship, referred to least recently, if said address memory is full the server can not accommodate a corresponding relationship between the first address and second address, and registers, in a memory of the server, the corresponding relationship between the protocol first address and the terminal second address, of which it has been notified, in said address table which is included in the answer.
15. The server according to
0. 17. The method according to
0. 18. The method according to
0. 19. The method according to
a step in which the switch or exchange connects the server with a plurality of terminals by PVCs (permanent virtual channels);
a step in which, when the interrogation request, in the form of a cell having a predetermined virtual channel identifier, is entered from the server, the switch or exchange appends tag information indicating a terminal group to the cell, performs cell copying based on the tag information indicating the terminal group, and transfers the cell to terminals of the terminal group.
0. 20. The method according to
a step in which the switch or exchange connects the server with a plurality of terminals by PVCs (permanent virtual channels) and divides the plurality of terminals into a plurality of groups;
a step in which, when the interrogation request in the form of a cell is entered from the server, the switch or exchange performs cell copying, whereby the interrogation request cell is transferred in a first group;
a step in which the server performs monitoring to determine whether a prescribed terminal has answered with its own identifier within a set period of time;
a step in which the server sends the interrogation request cell to all terminals of the next group when no terminal answers with its own identifier within the set period of time; and
a step in which the server transfers the interrogation request while successively changing the group until a prescribed terminal answers with its own identifier.
0. 21. The method according to
0. 22. The method according to
0. 23. The method of
0. 24. The method of
0. 25. The method of
0. 27. The method according to
0. 29. The address resolution system according to
means for connecting the server with a plurality of terminals by PVCs (permanent virtual channels); and
means which, when a terminal address interrogation request cell having a predetermined value for a PVC is entered from the server, is for performing cell copying and transferring of the interrogation request cell to the plurality of terminals.
0. 30. The address resolution system according to
0. 31. The address resolution system according to
0. 33. The server according to
0. 35. The method of
registering, in the server, the corresponding relationship between the first identifier and the second identifier which is included in the answer.
0. 36. The method of
0. 37. The method of
0. 38. The method of
0. 39. The method of
0. 41. The method of
0. 42. The method of
0. 43. The method of
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This invention relates to a communication system such as an ATM-LAN, a server and an address management method. More particularly, the invention relates to a communication system equipped with a plurality of terminals, a server having an ATM address table for storing the corresponding relationship between the protocol address and ATM address of each terminal, and an ATM exchange which accommodates each terminal and the server.
Improvements in the performance of personal computers and work stations have been accompanied by the rapid proliferation of applications for dealing with high-speed data and multimedia. In addition, such techniques as remote file access and decentralized computing have been established though use of LANS. For these reasons, there is expected to be greater demand for higher speed LANs for multimedia purposes.
In order to satisfy these expectations, there has been increased activity in the research and development of LANs (ATM-LANs) using ATM communication. An ATM-LAN is a switching LAN in which terminals are connected in a star-like configuration to an apparatus (an ATM exchange, for example) having an ATM switching function. Each terminal establishes a virtual channel (VC) directed toward a destination terminal and performs a data transmission by means of a fixed-length packet, referred to as an ATM cell, comprising a five-byte header and 48-byte data. As a result, it is possible to set a number of VCs on a terminal interface (where the number is capable of being expressed by the VPI/VCI) so that the terminal is capable of communicating with a plurality of other terminals simultaneously via the set VCs.
When communication is performed on a LAN, it is generally required that the originating terminal know the physical address of the terminal of the other party. In a conventional LAN, the physical address is a MAC address. Data in a LAN is transmitted in frame units, with each frame containing the addresses of the originating and terminating terminals.
Communication with another terminal is not possible if the MAC address of the terminal is not known. If the MAC address of a party's terminal is unknown (but the protocol address is known), therefore, the original terminal determines the MAC address of the higher-order protocol address (IP address) by an address resolution protocol (ARP) and performs communication upon disassembling the higher-order packet (IP packet) into frames using the MAC address.
Upon receiving this ARP frame, each terminal determines whether the frame has its own address or is a broadcast frame. In this case, the frame is a broadcast frame and therefore the frame is accepted (step S11). Next, after verification of the fact that the frame is an ARP frame, each terminal determines whether the protocol address of the destination agrees with its own protocol address (step S12). Processing is terminated if the two addresses disagree. If the two addresses do agree, however, an answer frame which contains the terminals own MAC address is created at sent back to the originating terminal (step S13). Upon receiving the answer frame (YES at step S3), the originating terminal registers the correspondence between the MAC address of the other party's terminal contained in this answer frame and the protocol address in an internal IP-MAC address table (step S4) and then creates a frame (see
The foregoing is for the case of connection-less communication. In an ATM-LAN based upon connection-type communication, a VC is established between terminals and communication is performed while forming a higher-order packet into cells. In such an ATM-LAN, a physical address corresponds to the address (VPI/VCI) of the ATM layer, and this ATM layer address (VPI/VCI) is decided by a set-up sequence using the ATM address of the terminal. A set-up sequence is a call set-up processing sequence executed at the time of an outgoing call.
Thus, when the ATM address of the other party's terminal is unknown in an ATM-LAN, communication cannot be performed. This necessitates a method of analyzing the ATM address based upon the higher-order protocol address.
Conventional methods of acquiring the ATM address of another party's terminal include ARM
{circle around (3)} In order to broadcast the ATM address interrogation cell to all terminals, the VPI/VCI of the cell is made FF−FFFF on the server side. This is in addition to {circle around (2)} above.
When cells (ATM address interrogation cells) for which VPI/VCI=FF−FFFF holds enter from the terminals 11˜14, the terminal accommodating sections 33a˜33d replace the VPI/VCIs with 00-0001˜00-0004, add the tag information TAG (C=0, S=1), onto the cells and then transfer the cells to the ATM switch 32.
On the basis of the tag information TAG (C=0, S=1), the ATM switch 32 transfers the input cells (ATM address interrogation cells) to the server 21.
If an ATM address interrogation cell is received, the server 21 obtains the ATM address and notifies the terminal that issued the interrogation cell. It should be noted that the server 21 can identify from which terminal a cell has arrived depending upon the VPI/VCI (=00-0001, ˜00-0004) updated by the terminal accommodation sections 33a˜33d.
The answer cells of the ATM addresses from the server 21 to the terminals 11˜14 have VPI/VCIs (=00-0001˜00-0004) conforming to the terminals which are the destination of transmission. When the answer cell enters, the server accommodation section 34 updates the value of the VPI/VCI from 00-0001˜00-0004 to FF−FFFF, adds on the tag information TAG (S=0, C=0, a1, a2=destination terminals) and transfers the cell to the ATM switch 32. On the basis of the tag information TAG, the ATM switch 32 switches the input cell, sends the cell to the line to which the prescribed terminal is connected and enters the cell into this terminal.
In the case of a broadcast, on the other hand, the interrogation request cell sent from the server 21 has FF−FFFF as the VPI/VCI. When the interrogation cell for which VPI/VCI=FF−FFFF holds enters, the server accommodating section 34 adds on the tag information TAG (C=1, S=0) specifying all paths and then transfers the cell to the ATM switch 32. In this case, the value of the VPI/VCI is not changed. On the basis of the tag information TAG (C=1, S=0), the ATM switch 32 switches to all paths and enters the cell into all terminals.
A broadcast method of broadcasting an interrogation request to all terminal:
If the ATM address of another party's terminal is unknown at the moment a communication request is issued in the broadcast method, a broadcast is made within the network and the terminal is interrogated directly. Unlike the server method, implementation is easy because it is unnecessary to create a data base in advance. However, in cases where frequent communication is made with an unspecified terminal whose ATM address is unknown, broadcast of the interrogation request is made whenever a communication request is issued. A problem which arises as a consequence is an increase in control traffic. This problem becomes particularly pronounced with an increase in the number of terminals or depending upon the scale of the network.
{circle around (1)} The originating terminal 11 refers to its own cache memory and determines whether the ATM address of the other party has been registered. It should be noted that information regarding a party to be communicated with will not have been registered in the cache memory when power is introduced to the system. If the information has been registered, set-up is executed to set a path using this ATM address and communication is carried out. If the information has not been registered, however, the originating terminal 11 puts an ATM-ARP request (an ATM address interrogation request) message into the form of a cell and sends the cell to the server 21 in order to inquire as to the ASTM address of the communicating party 14.
The message includes protocol type 100, which indicates the type (IP, etc.) of host protocol; ATM address length 101, which indicates address length of the ATM address used in an ATM network; protocol address length 102, which indicates address length (four bytes in case of protocol type IP) of the host protocol; an operation code (“1”: request, “2”: answer) 103; ATM address (source address) 104 of the requesting terminal; a protocol address (source address) 105 of the requesting terminal; ATM address 106 of the target terminal, which is all “1's” or all “0's” in case of a request message; with the ATM address being inserted in case of the answer message; and protocol address 107 of the target terminal.
{circle around (2)} Upon receiving the ATM-ARP request from the terminal 11, the server 21 determines whether the ATM address corresponding to the protocol address of the target terminal contained in the request has been registered in the ATM address table 21a. If the ATM address has been registered, an ATM-ARP answer message containing this information (ATM address) is formed into a cell and sent back to the terminal 11.
If the ATM address has not bene registered, the server 21 transfers the ATM-ARP request to all terminals using the broadcast function of the ATM switch 32.
{circle around (3)} Upon receiving the ATM-ARP request transferred (broadcast) from the server 21, each of the terminals 11˜14 determines whether the protocol address of the target terminal contained in this request agrees with its own protocol address. If agreement is achieved, the terminal forms the ATM-ARP answer message indicating its own ATM address into a cell and sends the message back to the server 21.
{circle around (4)} Upon receiving the ATM-ARP message from the terminal 14, the server 21 obtains the ATM address of the target terminal 14. The search/registration means 21b correlates the ATM address d and the reference time with the protocol address D of the target terminal 14 and registers the correlation in the ATM address table 21a, as shown in FIG. 3. If the ATM address table 21a is saturated (full), the entry having the oldest reference time is deleted and the a new entry is registered. It should be noted that an arrangement can be adopted in which, rather than storing the reference time, correlation are stored in order starting from the oldest correlations by the LRU (least recently used) method.
{circle around (5)} Further, when the ATM-ARP answer message is received from the terminal 14, the server 21 transfers the ATM address contained in the answer message to the requesting terminal 11 that transmitted the ATM-ARP request message.
{circle around (6)} Upon receiving the ATM-ARP answer message at {circle around (2)} or {circle around (5)}, the terminal 11 that issued the ATM-ARP request message at {circle around (1)} above recognizes the ATM address of the communicating party 14, correlates this ATM address with the protocol address and saves the correlation in its own cache memory.
{circle around (7)} Further, the terminal 11 executes set-up using the ATM address of the communicating party, establishes a path and communicates with the terminal 14.
Thus, in a case where the ATM address has been registered in the ATM address table 21a, the server 21 operates in the same manner as in the conventional server method. If the ATM address has not been registered in the ATM address table 21a, however, the server 21 can obtain the target ATM address by broadcast of the ATM-ARP request message. Accordingly, the server need not register the information of all terminals in the ATM address table 21a in advance, and the stored content of the ATM address table can be perfected by a learning function. This is effective in terms of implementing the ATM address table by small-scale circuitry.
{circle around (1)} The terminal 12 that has issued the communication request refers to its own cache memory and determines whether the ATM address of the communicating party has been registered. If the ATM address has not been registered, set-up is executed to set a path using this ATM address and communication is carried out. If the information has not been registered, however, the terminal 12 puts the ATM-ARP request message into the form of a cell and sends the message to the server 21 in order to inquire as to the ATM address corresponding to the protocol address of the communicating party 14.
{circle around (2)} Upon receiving the ATM-ARP request from the terminal 12, the server 21 determines whether the ATM address corresponding to the protocol address of the terminal 14 contained in the request has been registered in the ATM address table 21a. If the ATM address has been registered, an ATM-ARP answer message containing this information (ATM address) is formed into a cell and is sent back to the terminal 12.
{circle around (3)} Upon receiving the ATM-ARP request from the server 21, the terminal 12 recognizes the ATM address of the communicating party 14, correlates this ATM address with the protocol address and saves the correlation in its own cache memory.
{circle around (4)} Next, the terminal 12 executes set-up using the ATM address of the communicating party, establishes a path and communicates with the terminal 14.
Thus, in a case where the ATM address has been registered in the ATM address table 21a, the server 21 operates in the same manner as in the conventional server method.
When a communication request is issued (step 201), the terminal refers to its own cache memory and determines whether the ATM address of the communicating terminal is en entry in the memory (step 202). If ATM address is an entry, the terminal executes set-up using the ATM address, establishes a path and performs communication (step 203),
If the ATM address is not an entry in the cache memory, however, the terminal puts the ATM-ARP request message into the form of a cell and send the message to the server 21 in order to inquire as to the ATM address corresponding to the protocol address of the communicating party (step 204).
The terminal then waits for transmission of the ATM-ARP answer message from the server 21 (step 205). If the ATM-ARP answer message is received, then the terminal registers the ATM address of the other party's terminal contained in the message in the cache memory (step 206) and subsequently executes set-up using this ATM address, establishes a path and performs communication step (step 203).
Upon receiving the ATM-ARP request message (an ATM address interrogation request message) from the server 21 (step 301), each terminal determines whether the protocol address of the target terminal contained in this request agrees with its own protocol address (step 302). If agreement with its own protocol address is not achieved, the terminal ends processing. If agreement is achieved, the terminal creates an ATM-ARP response message in order to give notice of its own ATM address and sends the message back to the server 21 in the form of a cell (step 303).
Upon receiving an ATM-ARP request from a prescribed terminal (step 400), the server 21 registers the corresponding relationship between the protocol address and ATM address of the original terminal contained in the request, as well as the time, in the ATM address table 21a (step 401).
Next, the server 21 determines whether the ATM address corresponding to the protocol address of the target terminal has been registered in the ATM address table 21a (step 402). If the ATM address has been registered, the reference time in the ATM address table 21a is updated (step 403). The server 21 thenceforth creates an ATM-ARP response message in order to give notice of the above-mentioned ATM address and'sends the message back to the requesting terminal in the form of a cell (step 400).
On the other hand, if it is found at step 402 that the desired ATM address has not bee registered, the server 21 transfers the ATM-ARP request to all terminals using the broadcast function of the ATM switch 42 (step 405). Next, the server waits for reception of the ATM-ARP answer message in response to the above-mentioned ATM-ARP request (step 406).
If the ATM-ARP answer message is received from a prescribed terminal, the server 21 newly registers the ATM address contained in this message as well as the reference time in the ATM address table 21a (step 407).
Processing for registering the ATM address anew is as follows: The server 21 checks to see whether the ATM address table 21a is full (step 407a). If the table is not full, the server 21 refers to the ATM address using the protocol address as index, and newly registers the ATM address and reference time in the ATM address table 21a in correspondence with the protocol address of the terminal (step 407b). In a case where the ATM address table 21a is full, the server deletes the entry having the oldest reference time to form a vacancy (step 407c) and registers the new entry (the ATM address and reference time) in this vacancy (step 407b).
After making the new registration, the server 21 creates an ATM-ARP answer message to notify of the ATM address and sends the message back to the requesting terminal in the form of a cell (step 404).
The foregoing is for a case in which the ATM-ARP request is broadcast to all terminals en masse at step 405. However, all of the terminals 11˜14 can be divided up into a plurality of groups and the request can be broadcast group by group.
If it is found at step 402 in
If the ATM-ARP answer message is not received even upon elapse of the set time, the group is incremented by the operation i+1→i (step 405e) and processing from step 405b onward is executed with regard to the next step.
If the ATM-ARP answer message is received from the prescribed terminal within the set time, then the program jumps to step 407 of FIG. 16 and executes the processing from this step onward.
It should be noted that the ATM address table 21a holds N-number of corresponding relationships between protocol addresses and ATM addresses referred to most recently. Accordingly, by arranging is so that a terminal periodically sends an ATM address interrogation request for its own terminal to the server 21, the corresponding relationship between the terminal's own protocol address and the ATM address can be kept in the ATM address table at all times.
The operation of each unit in response to an ATM-ARP request will now be described.
Upon receiving a cell form the ATM exchange 31, the cell receiver 51 assemblies a cell for every VPI/VCI and transfers the cell to the message receiver 52. The latter transfers the message received from the cell receiver 51 to the reception buffer 53 and notifies the CPU 54, by means of an interrupt, of the fact that an ATM address interrogation request message or answer message has been received.
When the interrupt to notify of reception is generated, the CPU 54 reads in the message from the reception buffer 53, analyzes the operation code (see
When received message is interrogation request message
If the received message is the interrogation request message, the CPU 54 registers, in the table 21a, the corresponding relationship between the protocol address and ATM address of the originating terminal contained in the message. Next, the CPU 54 executes processing to search the ATM address table 21a using the protocol address of the target as an index. If the target ATM address has been registered in the ATM address table 21a, the CPU 54 creates an answer message for giving notice of the ATM address, writes the message in the transmission buffer 57 and requests the message transmitter 58 to transfer the answer message to the originating terminal based upon the prescribed VPI/VCI.
If the target ATM address has not been registered in the ATM address table 21a, however, the CPU 54 transfers the interrogation request message stored in the reception buffer 53 to the transmission buffer 57 and requests the message transmitter 58 to carry out a transfer based upon the VPI/VCI for the purpose of broadcast.
When received message is answer message
If the received message is the answer message, on the other hand, the CPU 54 correlates the target ATM address contained in the answer message with the target protocol address, registers the correlation in the ATM address 21a and transfers the answer message in the reception buffer 53 to the transmission buffer 57 as is. Thereafter, the CPU 54 requests the message transmitter 58 to transfer the above-mentioned answer message to the originating terminal based upon the prescribed VPI/VCI.
Upon receiving the transmission request from the CPU 54, the message transmitter 58 transfers the data in the transmission buffer 57 to the cell transmitter 59 and gives notice of the value of the VPI/VCI. The cell transmitter 59 transfers the message, which has been received from the message transmitter 58, to the ATM exchange 31 upon forming the message into a cell based upon the VPI/VCI of which it has been notified.
The operation of each component of the ATM interface card will now be described.
The ATM interface card 61 mounts the local processor 63 and the local memory 64, which stores various programs, and is connected with the WS or PC 60 by loose coupling implemented by communication between memories. Examples of the programs are a program for managing the overall ATM interface card, a control program for the ATM address notification request and for giving notice of an answer, a communication control program, etc.
The system-bus interface circuit 62 has a control mechanism for communicating with the WS or PC 60. The circuit 62 provides an interface dependent upon the WS or PC. A communication request message generated by an application in the WS is transferred to the local memory 64 via the system-bus interface circuit 62.
Upon receiving the communication request message, the local processor 63 obtains the ATM address of the other party's terminal based upon the destination protocol address contained in the message. That is, since the correspondence between the protocol address and the ATM address has been stored in, say, a storage area (address cache memory) in the local memory 64, the processor 63 searches the address cache memory.
If the ATM address corresponding to the destination protocol address has not been registered in the cache memory, the local processor 63 creates the ATM address interrogation request message, stores the message in the buffer memory 65 and starts up the CLAD circuit 66. As a result, the CLAD circuit 66 forms the ATM address interrogation request message into a cell (VPI/VCI=FF−FFFF) and transfer the cell to the ATM exchange 31 via the physical interface circuit 67.
When notice of the ATM address in response to the interrogation request is received from the ATM exchange 31, the local processor 63 registers the ATM address in the address cache memory. Thereafter, the local processor 63 starts up the communication control program, creates a set-up message using the received ATM address under the control of the communication program and stores the message in the buffer memory 65. The CLAD circuit 66 forms the set-up message into a cell and transfers the cell to the ATM exchange 31 via the physical interface circuit 67. It should be noted that if the ATM address has been registered in the address cache memory, the local processor 63 creates the set-up message immediately without making an inquiry and transfers the message to the ATM exchange 31.
The ATM exchange 31 executes call processing in response to the set-up message and sends back a connect message. Upon receiving the connect message via the physical interface circuit 67, the CLAD circuit 66 forms the message into a cell, stores the cell in the buffer memory 65 and notifies the local processor 63 of receipt of the message. As a result, the local processor 63 accepts the connect message from the buffer memory 65, verifies establishment of the communication path based upon the message and terminates the communication control program.
Thereafter, the local processor 63 starts message transfer using the identifier (VPI/VCI) of the communication path of which it has been notified by the connect message. More specifically, in response to establishment of the communication path, the local processor 63 stores the message received from the WS or PC in the buffer memory 65 and notifies the CLAD circuit 66 of the identifier (VPI/VCI) of the set communication path. As a result, the CLAD circuit 66 forms the message in the buffer memory 65 into a cell using the value of the VPI/VCI and transfers the cell to the ATM exchange 31 via the physical interface circuit 67.
In a case where a cell stream is received from the ATM exchange 31 via the physical interface circuit 67, the CLAD circuit 66 disassembles the cell and assembles a message, stores the message in the buffer memory 65 and then notifies the local processor 63 of the fact that the message has been received. In response to notification of receipt from the CLAD circuit 66, the local processor 63 accepts the message from the buffer memory 65 and transfers the message to the WS via the system-bus interface circuit 62.
In accordance with the present invention, the arrangement is such that if an ATM address has been registered in the ATM address table of a server when an interrogation request has been issued for this ATM address, the target ATM address can be obtained through an operation similar to that performed in the conventional server method. If the ATM address has not been registered in the ATM address table, however, the target ATM address can be obtained by broadcasting the interrogation request for the ATM address. In other words, according to the invention, ATM addresses are managed by making joint use of the server method and broadcast method. This makes it possible to hold down at increase in control traffic. Moreover, ATM addresses can be perfected by successively registering corresponding relationships, which have been found using the broadcast method, in the ATM address table. In addition, it is possible to dispense with a task for initially setting the ATM address table and a task for updating the table when terminals are added on or moved.
Further, in accordance with the present invention, all terminals are divided up into a plurality of groups. When a broadcast is made, the server transfers the ATM address interrogation request cell to all terminals of the first group. If there is no notice of answer of the ATM address within a set time, the server transfers the interrogation request cell to all terminals of the next group. Thenceforth, and in similar fashion, the server transfers the interrogation request cell while successively changing groups until the prescribed terminal answers with the ATM address. As a result, there is a good possibility that the desired ATM address will be obtained without broadcasting the interrogation request cell to all terminals. Consequently, an increase in traffic can be suppressed.
Furthermore, in accordance with the invention, (1) upon receiving notification of the ATM address from the prescribed terminal, the server newly registers the correspondence between the protocol address of this terminal and the ATM address, of which it has been notified, in the ATM address table. Further, (2) the server registers, in the ATM address table, the corresponding relationship between the protocol address of the originating terminal, which address is contained in the ATM address interrogation request received from the originating terminal, and the ATM address. Accordingly, if an inquiry for the above-mentioned ATM address is issued after registration, it is unnecessary to broadcast this interrogation request; the ATM address can be obtained in simple fashion from the ATM address table.
Further, in accordance with the present invention, if the ATM address table is full when the prescribed terminal has answered with the ATM address, the server erases the oldest corresponding relationship referred to and newly registers the ATM address of which it has been notified in the ATM address table. As a result, a large-capacity ATM address table is unnecessary and the scale of the server hardware can be minimized.
Furthermore, in accordance with the invention, a terminal periodically sends an ATM address interrogation request for its own terminal to the server, whereby the corresponding relationship between the terminal's own protocol address and the ATM address can be kept in the ATM address table at all times.
As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.
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