Network system and communication node

Details Network system and communication node Network system and communication node

1998-10-01

2003-09-09

Vanderpuye, Ken (Department: 2661)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S412000

Reexamination Certificate

active

06618381

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ATM network system, and in particular to an ATM network system which connects a source (transmitting) terminal equipment to a destination (receiving) terminal equipment through a plurality of ATM communication nodes by the SVC (Switched Virtual Connection) method for establishing or releasing the connection between both of the terminal equipments by a signaling process.
In accordance with a recent development of an ATM network, there have been put into practice not only a network configuration by the PVC (Permanent Virtual Connection) method for establishing a fixed connection between ATM communication nodes prior to the communication but also a network configuration by the SVC method for establishing a connection only for a communication period.
For such an ATM network, a source terminal equipment requires a Quality of Service (QoS) upon establishing a connection, and the network performs a traffic control for assigning resources to guarantee the required QoS. This traffic control is important to efficiently use the network.
2. Description of the Related Art
FIG. 12
illustrates an arrangement of a general ATM network system, in which a source terminal
1
and a destination terminal
2
are mutually connected through ATM communication nodes
3
a
-
3
c
(hereinafter generally designated by reference numeral
3
).
FIG. 13
illustrates an arrangement of a prior art ATM communication node
3
, which is composed of a physical interface unit
4
connected to external ATM communication nodes and a SW (switch) control unit
5
connected to the physical interface unit
4
.
If the network shown in
FIG. 12
is set up by the PVC method, a PVC is set up which preliminarily designates as a parameter a priority level depending on a command input in advance of the communication.
Then, the source terminal
1
transmits a user s information cell, a frame, a datagram or the like to the ATM communication node
3
a.
In the ATM communication node
3
a
, the user's information cell is inputted from the physical interface unit
4
to the SW-control unit
5
(see FIG.
13
), in which the user's information cell is subject to a traffic control according to the designated priority level and is transferred from the physical interface unit
4
to the next ATM communication node
3
b
. Likewise, the user's information cell is subject to a traffic control according to the designated priority level in the ATM communication nodes
3
b
,
3
c
and is transferred to the destination terminal
2
.
The service categories set in the ATM network are as follows:
{circle around (
1
)} CBR service: Constant Bit Rate service
{circle around (
2
)} VBR service: Variable Bit Rate service
{circle around (
3
)} ABR service: Available Bit Rate service
It is to be noted that the VBR service includes rt-VBR service (real time-Variable Bit Rate service) and nrt-VBR (non real time-Variable Bit Rate service). It is also to be noted that the UBR service has a connection priority level lower than the other service categories because of soft requirements with regard to the traffic characteristics.
Upon establishing, i.e. setting up a PVC, each of the ATM communication nodes determines whether or not it is possible to accept the connection of the required service category depending on its buffer size, the link capacity, and how the resource of connection is used. If possible, a connection which is assigned a resource such as a buffer or a link band is set up.
FIG. 14
illustrates an arrangement of the SW control unit
5
, in which a buffer
51
is composed of a CBR/rt-VBR buffer
51
a
, an irt-VBR buffer
51
b
, and a UBR buffer
51
c
per a service category, the buffers
51
a
-
51
c
being connected to a readout controller
52
.
To the interface unit of the ATM communication node, is given the connections of the aforementioned service categories as multiplexed. The user's information cell of each of the connections is inputted to the CBR/rt-VBR buffer
51
a
, the nrt-VBR buffer
51
b
, or the UBR buffer
51
c
corresponding to the service category.
The readout controller
52
is provided with an available band on the interface to perform a readout control for the user's information cell. As a result, the quality of service of the user's information cell as read out can meet the requirement of the traffic characteristic.
On the other hand, if the network is set up by the PVC method, it is possible to layer the priority levels of the connection by receiving the priority levels as a parameter upon setting up the connection in advance of the communication. For example, by designating the priority levels of the connection with a command input upon setting up a PVC, it is possible to layer the priority levels also for the UBR communication connection.
Including an LAN emulation service integrating the existing LAN into the ATM network, a number of services or applications which enable an LAN system communication through the ATM network are based on the SVC method. For the ATM service category, the UBR service is generally used.
However, if the ATM network is set up by the SVC method, since it is not easy for the user to set the priority levels per each connection, a prior art ATM network system by the SVC method does not layer the priority levels in the UBR communication connection.
SUMMARY OF THE INVENTION
It is accordingly an object to provide an ATM network system connecting a source terminal equipment to a destination terminal equipment through a plurality of ATM communication nodes by the SVC method wherein the priority levels for the UBR communication connection can be easily layered.
[1] For the achievement of the above object, in an ATM network system according to the present invention, an ATM communication node adjacent to a source terminal equipment comprises a priority level definition table in which priority levels for an SVC whose service category is the UBR are preset per a physical port, a control unit which transmits a SETUP message including the priority levels when the SVC is set up, and a switch controller for controlling a readout level of a user's information cell based on the priority levels; each of ATM communication nodes having received the SETUP message comprising a switch controller which controls a readout level of the user's information cell of the SVC based on the priority levels included in the SETUP message.
Namely, in
FIG. 1A
, a priority level definition table
8
provided in an ATM communication node
3
a
(hereinafter occasionally referred to as a source ATM communication node) adjacent to a source terminal equipment is preset with priority levels per a physical port. A control unit (not shown) of the ATM communication node
3
a
having received a user's information cell of the UBR service retrieves the definition table
8
to recognize the priority levels from the physical port (accommodation position) which has received the user's information cell, so that a SETUP message
7
b
including the priority levels as an information element is transmitted for a communication request.
In
FIG. 1A
, a repeating ATM communication node
3
b
determines the priority levels of the UBR service from the information element in the received SETUP message
7
b
. Then the ATM communication node
3
b
transfers the received SETUP message
7
b
as a SETUP message
7
c
. The same operations will be repeated until an ATM communication node
3
c
adjacent to a destination terminal equipment receives the SETUP message.
In
FIG. 1C
, is illustrated an operation example in which a user's information cell
9
is transferred through the SVC of the UBR service set up between the source terminal
1
and the destination terminal
2
.
Switch controllers
52
in the ATM communication nodes
3
a
-
3
c
control reading out the user's information cell
9
from cell buffers (not shown) according to the priority levels.
As a result, the priority levels of the SVC with the service

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