Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-11-14
2002-06-25
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S392000, C370S395100, C370S397000, C370S432000, C370S471000, C370S474000
Reexamination Certificate
active
06411620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ATM-network-based connectionless communication system which accommodates local connectionless information, such as data in a local area network (LAN), i.e., information sent by a system arranged to immediately transfer data with the address of a receiving terminal placed in the header of a message without establishing a path to the receiving terminal, in an asynchronous transfer mode (ATM) network that uses a connection-oriented communication system, i.e., a system which, before data transfer is made, verifies that a path to a receiving terminal has been established, and interconnects LANs.
2. Description of the Related Art
Local area networks (LANs) installed in companies, which are progressing in a direction that increases speed and capacity, have been made increasingly large in scale and area. The need for connection among LANs scattered through companies is increasing. In general, LANs are adapted for connectionless communication. In contrast with the connectionless communication system, there is a connection-oriented communication system that is used in a broadband ISDN (integrated services digital network).
The connection-oriented communication system is a system which verifies that a path has been established between sending and receiving terminals before data transfer is made. In contrast, the connectionless (CL) communication system, which is used with LANs, is a system in which data transfer is made immediately with a destination address placed in the header without establishing a path to a receiving terminal.
For connection between networks, for example, local area networks, the so-called N−1 connection is generally established between entities, which is realized through the function of a low layer.
In the case where a large quantity of information is to be transmitted as in file transfer, the time required to establish connection can be disregarded. In the case of transmission of a slight quantity of data, such as addresses, however, if connection were established as in the case of transmission of a large quantity of data, the time therefore could not be disregarded. In the recent LAN/distributed processing systems, such short messages are continually transferred. To meet such a requirement, an idea of dividing connection services into conventional connection-oriented services and connectionless services has been introduced.
The need for accommodating local connectionless information, such as LAN data, by a global connection-oriented type ATM network to establish the connection between LANs is increasing. As a network for establishing the connection between LANs, the MAN (Metropolitan Area Network) is investigated at present, but it is not yet put to practice use. The ATM network is globally recognized as a next generation of broadband ISDN. Thus, building the ATM network in such a configuration as involves the functions of the MAN is very significant.
In general, connectionless information is variable in length and starts with a destination address. In order to accommodate such connectionless information in an ATM network which exchanges information as fixed-length cells, it is necessary to perform cell assembly/disassembly of variable-length data, and destination analysis and routing control on a cell-by-cell basis. In the case of communication of such connectionless information, the upper protocol is provided with a timer having a time-out period of several tens of milliseconds to several hundreds of milliseconds to verify the arrival of information. Although connectionless information was transmitted, if no acknowledgment signal is received from a receiving station until timer runout occurs, then the information will be retransmitted over and over again. Therefore, the cell-by-cell routing analysis must be performed fast, within tens of milliseconds. With the present-day techniques, it is required to perform the routing by means of hardware.
Heretofore, when messages are transferred between pieces of user equipment (UE) such as geographically scattered local area networks (LANs), host computers, etc., a connection unit to which one or more pieces of user equipment are connected terminates geographical or logical interface with the user equipment. Within a relay network, messages are relayed through private lines and packet networks.
FIG. 1
illustrates a prior art message transferring system in a wide-area relay network. In this figure, two or more pieces of user equipment (UE)
2
are connected to a relay network (NW)
1
, which comprises UE accommodators
3
for accommodating the respective individual user equipment
2
and packet exchange switches or line exchange switches (SW)
4
for exchanging data within the relay network. Each of the UE accommodators
3
serves as a connection unit.
In
FIG. 1
, the relay network
1
is a packet switched network or line switched network. On this communication network, permanently or semipermanently fixed communication paths are established for message transfers.
With the prior art system of
FIG. 1
, even if messages are transferred between LANS, the connection between the LANs is not made in such a form as involves the functions of the LANs themselves. Thus, a problem with the prior art is that no ATM network is provided in a form that includes the LAN's functions.
FIG. 2
is a schematic illustration of a communication system in a local area network. In this figure, a sending terminal
7
places a machine (MAC) address in data to be transmitted and then transmits that data onto a network
8
, while a receiving terminal
9
verifies the MAC address, i.e. 133.160.41.99, and then accepts that data from the network
8
.
FIG. 3
is a diagram for use in explanation of a prior art inter-LAN communication system using call setting as a communication system which sends LAN communication data as described in connection with
FIG. 2
to another LAN over an ATM (asynchronous transfer mode) network. In this figure, data from a sending terminal
11
is sent to a sending-area terminal adapter (TA)
13
via a sending-area LAN
12
. In the TA
13
, a MAC address is translated into the telephone number of a receiving terminal. A request to call the telephone number is sent to a receiving-area TA
16
via a sending-area ATM switching unit
14
and a receiving-area ATM switching unit
15
.
On the other hand, the receiving-area TA
16
alerts the sending-area TA
13
to the completion of the call setting via the ATM switching units
15
and
14
. Subsequently, the sending-area TA
13
sends data to be actually transmitted to the receiving-area TA
16
. That data is transferred to the receiving terminal
18
via a receiving-area LAN
17
. A problem with the prior art communication system utilizing call setting is that data to be transmitted cannot be transferred until call setting is completed between the sending-area TA
13
and the receiving-area TA
16
.
In practice, data are transferred as accommodated in fixed-length ATM cells in communicating variable-length connectionless information, such as LAN data, between LANs via an ATM network. In such a case, it will be required to install between the receiving-area ATM switching unit
15
and the TA
16
of
FIG. 3
a cell error processing system for detecting errors of received cell.
FIG. 4
is a conceptual diagram of a conventional ATM cell error processing system. A number of n of error processing units
20
are connected in series, where n is the number of types of cell errors. The error processing units
20
exist independently of one another and perform the processes of detecting cell errors, rejecting erroneous cells, and alerting of error information, etc. A failure monitor
19
is alerted by the error processing units
20
of their respective results of error processing.
FIG. 5
is a block diagram illustrating a specific arrangement of the error processing units
20
. This circuit arrangement operates as follows.
{circle around (1)} An error checker
21
checks cell data inputs for
Hagihara Teruaki
Hajikano Kazuo
Kakuma Satoshi
Kamoi Jyoei
Kawasaki Takeshi
Fujitsu Limited
Hsu Alpus H.
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