LAN-to-LAN communication method, and LAN-to-LAN connecting unit

• US 5,548,578 A
• Filed: 09/02/1994
• Issued: 08/20/1996
• Est. Priority Date: 11/05/1993
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Matsune, Hideaki, Yamato, Koji
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): VU, HUY DUY
• Application Number:
  US08/300,793
• Time in Patent Office: 718 Days
• Field of Search: 370/85.13, 370/16, 370/16.1, 370/13, 370/14, 370/17, 370/85.14, 370/85.1, 370/85.6, 370/85.7, 370/110.1, 370/54, 370/77, 370/79, 370/85.8, 340/825.06, 340/825.07, 340/825.08, 395/200.02, 395/200.15, 395/200.16, 395/200.17, 395/200.18, 395/200.2
• US Class Current: 370/248
• CPC Class Codes: H04L 12/46 Interconnection of networks
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

Abstract

A LAN-to-LAN connecting unit sends a node-status confirmation packet PKTC to LAN terminals under its command to confirm the status of each terminal. Upon receiving the confirmation packet, a normal terminal sends a response packet PKTR back to the LAN-to-LAN connecting unit. However, a LAN terminal incapable of receiving data because of a pulled cable or some other problem cannot send back the response packet. The LAN-to-LAN connecting unit identifies and stores information indicating whether a LAN terminal is capable or incapable of reception depending upon whether the response packet is received. In a case where an incoming call has been terminated at a prescribed LAN terminal and this terminal is capable of reception, the LAN-to-LAN connecting unit receives the data sent from the other party'"'"'s LAN terminal and transmits this data to the LAN. In a case where the prescribed LAN terminal is incapable of reception, the connecting unit disconnects the line immediately. If a transfer destination has been registered to correspond to a terminal that is incapable of reception, received data is transferred to the transfer destination.

Claims

1. A LAN-to-LAN communication method in which LA-to-LAN connecting units are provided between LANs and a WAN and LAN-to-LAN communication is performed by the LAN-to-LAN connecting unit via the WAN, the method comprising the steps of:

sending confirmation data from a LAN-to-LAN connecting unit to LAN terminals, which are under the command of said LAN-to-LAN connecting unit, in order to confirm the status of each LAN terminal;

identifying and storing information indicating whether a LAN terminal is in a reception possible/impossible state depending upon whether or not said LAN terminal responds to the confirmation data;

in a case where an incoming call from another party has been terminated at a prescribed LAN terminal, determining whether said prescribed LAN terminal is in the reception-possible state by referring to the stored information;

receiving data sent from said another party and sending said data to said prescribed LAN terminal in a case where said prescribed LAN terminal is in the reception-possible state;

disconnecting a line between said another party and said LAN-to-LAN connecting unit in a case where said prescribed LAN terminal is in the reception-impossible state;

in a case where an incoming call has been terminated at the prescribed LAN terminal, obtaining a LAN terminal which is a transfer destination by referring to the table when said prescribed LAN terminal is in the reception-impossible state; and

rewriting a MAC address contained in the received data to a MAC address of the transfer destination and then sending said MAC address to a LAN terminal at said transfer destination.

2. A LAN-to-LAN communication method in which LAN-to-LAN connecting units are provided between LANs and an electronic exchange and LAN-to-LAN communication is performed by the LAN-to-LAN connecting units via the electronic exchange, the method comprising the steps of:

previously registering a corresponding relationship between a LAN-to-LAN connecting unit and a destination LAN-to-LAN connecting unit in a memory of said electronic exchange in 1;

1 correspondence;

when a connection request is received from a prescribed LAN-to-LAN connecting unit, causing the electronic exchange to obtain a destination LAN-to-LAN connecting unit which corresponds to said prescribed LAN-to-LAN connecting unit;

causing the electronic exchange to connect said prescribed LAN-to-LAN connecting unit that issued the connection request to the destination LAN-to-LAN connecting unit obtained and perform LAN-to-LAN communication;

when an external device issues a change request for changing the destination LAN-to-LAN connecting unit in said corresponding relationship registered in said memory to another destination LAN-to-LAN connecting unit, causing the electronic exchange to update the corresponding relationship in response to the change request; and

when a subsequent connection request is received from said prescribed LAN-to-LAN connecting unit, causing the electronic exchange to connect said prescribed LAN-to-LAN connecting unit to said another destination LAN-to-LAN connecting unit and perform LAN-to-LAN communication.

3. The method according to claim 2, further comprising the steps of:

previously registering, by an external device, a transfer-destination LAN-to-LAN connecting unit in the memory of the electronic exchange in correspondence to said destination LAN-to-LAN connecting unit; and

when a connection request is received from a prescribed LAN-to-LAN connecting unit, causing the electronic exchange to connect said prescribed LAN-to-LAN connecting unit to the transfer-destination LAN-to-LAN connecting unit and perform LAN-to-LAN communication.

4. The method according to claim 2, further comprising the steps of:

previously registering, by an external device, a transfer-destination LAN-to-LAN connecting unit and a transfer time period in the memory of the electronic exchange in correspondence to said destination LAN-to-LAN connecting unit;

when a connection request is received from a prescribed LAN-to-LAN connecting unit, causing the electronic exchange to determine whether a time at which the connection request was issued falls within said transfer time period; and

causing the electronic exchange to connect said prescribed LAN-to-LAN connecting unit that issued the connection request to the transfer-destination LAN-to-LAN connecting unit and perform LAN-to-LAN communication if the time at which the connection request was issued falls within said transfer time period.

5. The method according to claim 2, wherein said external device is a telephone connected to the electronic exchange or another LAN-to-LAN connecting unit connected to the electronic exchange.

6. A LAN-to-LAN connecting unit for interconnecting LANs and performing LAN-to-LAN communication via a WAN, comprising:

confirmation-data sending means for sending confirmation data to LAN terminals, which are under command, in order to confirm the status of each LAN terminal;

means for identifying and storing, in a memory, information indicating whether a LAN terminal is in a reception possible/impossible state depending upon whether or not said LAN terminal responds to the confirmation data;

means for determining whether a prescribed LAN terminal is in the reception-possible state by referring to the stored information in a case where an incoming call from another party has been terminated at said prescribed LAN terminal;

means for receiving data sent from said another party and sending said data to said prescribed LAN in a case where said prescribed LAN terminal is in the reception-possible state;

a routing table in which LAN terminals which are transfer-destinations of received data have been registered;

means for obtaining a LAN terminal which is a transfer destination by referring to said routing table if, when an incoming call has been terminated at a prescribed LAN terminal, said prescribed LAN terminal is in the reception-impossible state; and

means for rewriting a MAC address contained in the received data to a MAC address of the LAN terminal of the transfer destination and then sending said MAC address to a LAN terminal at said transfer destination.