Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-12-01
2003-12-30
Olms, Douglas (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395530
Reexamination Certificate
active
06671281
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ATM LAN emulation network employing the ATM (asynchronous transfer mode) as the communication method, in particular, to an automatic accessing technique.
This application is based on patent application Ser. No. Hei 10-344637 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
As generally known, the ATM LAN emulation network is realized by interconnecting an existing LAN (local area network) and an ATM LAN which employs the ATM so as to execute an application (software) on the ATM LAN as well as on the existing LAN. In such an ATM LAN emulation network, a plurality of ELANs (i.e., emulated LANs) are connected to each other via routers.
In the above ATM LAN emulation network, if a terminal which was connected to an ELAN then accesses this ELAN via another ELAN so as to execute an operation, the terminal must designate (i) the ATM address of the LES (LAN emulation server) which manages the ELAN to be accessed and (ii) the name of the ELAN to be accessed.
As an existing LAN emulation function, the ELAN accessing method using a “Well-known” address is known. However, in this function, the terminal can only access an LECS (LAN emulation configuration server) designated by the Well-known address, and cannot access the target ELAN unless the ELAN name is designated.
As described above, in order that a terminal accesses a target ELAN (to which this terminal was previously connected) via another ELAN in the conventional ATM LAN emulation network, it is necessary to designate (i) the ATM address of the LES which manages the target ELAN and (ii) the ELAN name of the target ELAN. However, at the terminal side, the management of the ATM addresses are scarcely performed; thus, it is difficult for the terminal to designate the above ATM address of the LES. Therefore, the terminal has to execute a very complicated operation so as to access a target ELAN (physically separated from the terminal) other than the ELAN to 10 which the terminal is connected.
SUMMARY OF THE INVENTION
In consideration of the above circumstances, an objective of the present invention is to provide an ATM LAN emulation network in which a terminal can easily access a target ELAN (to which the terminal was previously connected) via another ELAN so as to execute an operation in the target ELAN.
Therefore, the present invention provides an ATM LAN emulation network comprising emulated LANs (ELANs) in which a plurality of terminals are connected to each other via ATM switches and communication between the terminals is managed by a LAN emulation server (LES) mounted at the ATM switch, where the ELANs are interconnected by interconnecting the ATM switches via LAN emulation clients (LECs) mounted at routers, the ATM LAN emulation network comprising:
a LAN emulation configuration server (LECS), mounted at each router, for managing communication with the LES, where the ATM address of the LECS is stored in advance in the LES of the ATM switch connected to the relevant router; and
a broadcast unknown server (BUS) mounted at the ATM switch which is connected to the router, and
wherein when a specified terminal accesses the first ELAN and communicates with the relevant LECS by using a Well-known address, and sends a request, including its own IP address, for obtaining the ATM address of the LES which manages the second ELAN to which the specified terminal was previously connected and thus the IP address is related, the LECS which receives the request then determines whether the specified terminal is registered in the first ELAN connected to the router at which this LECS is mounted, based on the IP address of the specified terminal and IP routing information of this router,
if the specified terminal is not registered in the first ELAN, then the LECS obtains the MAC address of the LEC mounted at the router as the next hop indicated by the IP routing information, via the BUS mounted at the ATM switch of a candidate ELAN other than the first ELAN, and the LECS sends the candidate LES which manages the candidate ELAN a request for obtaining the ATM address of the LEC mounted at the next-hop router, based on the obtained MAC address,
the candidate LES which receives the above request then sends its own ATM address together with the ATM address of the LECS of the next-hop router, which is stored in advance,
the LECS communicating with the specified terminal receives the ATM address of the LECS of the next-hop router, and transfers the request received from the specified terminal to this LECS according to the obtained ATM address,
if the candidate ELAN is the second ELAN, the LECS which receives the transferred request then returns the ATM address of the LES which manages the second ELAN, and
the specified terminal X obtains this returned ATM address of the LES via the LECS communicating with the specified terminal, and accesses the second ELAN according to the obtained ATM address of the LES so as to operate on the second ELAN.
The present invention also provides an ATM LAN emulation network having similar ELANs, comprising:
a LAN emulation configuration server (LECS), mounted at each router, for managing communication with the LES, the LECS having a table storing the ATM addresses of the LECSs mounted at the other routers together with the corresponding IP addresses; and
a broadcast unknown server (BUS) mounted at the ATM switch which is connected to the router, and
wherein when a specified terminal accesses the first ELAN and communicates with the relevant LECS by using a Well-known address, and sends a request, including its own IP address, for obtaining the ATM address of the LES which manages the second ELAN to which the specified terminal was previously connected and thus the IP address is related, the LECS which receives the request then searches the table and detects the ATM address of the LECS of the second ELAN corresponding to the IP address of the specified terminal, and transfers the request to the LECS of the second ELAN,
the LECS of the second ELAN, which receives the transferred request, then returns the ATM address of the LES which manages the second ELAN, and
the specified terminal X obtains this returned ATM address of the LES via the LECS communicating with the specified terminal, and accesses the second ELAN according to the obtained ATM address of the LES so as to operate on the second ELAN.
According to the present invention, the specified terminal can automatically obtain the ATM address of the LES of the target ELAN to be accessed so as to access and operate on the target ELAN. Therefore, the specified ELAN can access the target ELAN via any ELAN (at any location) other than the target ELAN, thereby improving the convenience of the ATM LAN emulation network. For example, if the specified terminal which is a portable type and was previously operated on the second ELAN is moved and connected to the first ELAN in a distant area, no specific setting change is necessary for the specified terminal, and the specified terminal can easily access and operate on the second ELAN via the first ELAN.
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patent: 6104870 (2000-08-01), Frick et al.
patent: 6189041 (2001-02-01), Cox et al.
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patent: 8-223181 (1996-08-01), None
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“Definitive Explanations of ATM Protocols,” translated by Harumi Ase et al, Nikkei BP Publishing, Oct. 19th, 1998 pp. 121-144.
Nikkei Communication No. 173, pp. 47-55.
“ATM-LAN,” by Hiroshi Shimizu et al, Software Research Center, Jul. 5th, 1995, pp. 135-153.
NEC Corporation
Nguyen Brian
Olms Douglas
Sughrue & Mion, PLLC
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