Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-02-24
2002-03-19
Rao, Seema S. (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S409000, C370S419000, C370S468000
Reexamination Certificate
active
06359889
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital switching system, and more particularly to a technique for controlling a fixed rate connection such as a CBR (Constant Bit Rate) connection, etc. within a cell switching system such as an ATM (Asynchronous Transfer Mode) system, etc.
2. Description of the Related Art
A data transfer based on an ATM method has been made practical as a way of realizing a B-ISDN (Broadband-Integrated Service Digital Network). The B-ISDN handles data used by computers and services such as telephony speech signals, facsimile signals, VOD (Video On Demand) signals, etc. within a single network.
To support these various services, a CBR service for securing a fixed bandwidth and services such as rt-VBR, nrt-VBR, ABR, UBR, etc. whose bandwidths in use (simply referred to as bandwidths hereinafter) change depending on the use state of the network, are provided. These services are provided in order to be adaptable to different upper applications depending on use purposes.
Among the above described services, a CBR service is intended to handle an upper application service such as telephony speech, VOD, etc., which requires a strict delay condition.
An ATM exchange occupies a physical bandwidth corresponding to a requested bandwidth when establishing a CBR service connection.
FIG. 1
shows the configuration of a conventional ATM switching system.
When a subscriber telephone
2
, terminal
3
, or television (TV)
4
, which is to receive a VOD (Video On Demand) service, originates a call, a CAC (Connection Admission Control) unit
9
within a node
1
, which is an ATM exchange that receives the signal via a subscriber line
5
,
6
, or
7
, checks whether or not there is an empty band of a CBR connection to a destination by referencing a bandwidth table
10
. If there is an empty band, the CAC unit
9
establishes a connection.
For the services (such as rt-VBR, nrt-VBR, ABR, and UBR) whose bandwidths change depending on cell traffic, the node
1
controls their cell traffic and performs statistical multiplexing control. Therefore, a line efficiency is high and subscribers are not troubled so much.
However, because the CBR service occupies a bandwidth based on a PCR (Peak Cell Rate), the subscriber TV
4
which receives a CBR service occupies a particular bandwidth resource possessed by the node
1
. Accordingly, the subscriber telephone
2
or terminal
3
, which handles another application, can perform statistical multiplexing only with the remaining bandwidth resource except for the bandwidth occupied by the CBR service.
Conventionally, the CBR service could not accept a subscriber who requests a physical bandwidth exceeding a total bandwidth allocated to the CBR service.
With the above described conventional technique, no special restriction is imposed when an ATM exchange establishes a CBR connection. Namely, if the physical bandwidth used by the CBR connection permits, any large number of CBR connections can be set up. Therefore, the CBR service which handles an application service with a strict delay condition such as a VOD service, a speech service, etc. occupies the bandwidth of a switch within an ATM exchange, which leads to the connection disability of a subscriber using a different application service (such as an Internet service).
As a result, the number of CBR service subscribers must be restricted so as to overcome the above described problems. In this case, however, cost per subscriber cannot be reduced.
SUMMARY OF THE INVENTION
The present invention was developed in the above described background, and aims at effectively using the bandwidth of a switch within an exchange, and at preventing each service subscriber from being troubled, when a cell exchange such as an ATM exchange, etc. establishes a fixed rate connection.
The present invention assumes an ATM switching device (an ATM exchange) for switching fixed-length cells (ATM cells), and for controlling a fixed rate connection (CBR connection).
A fixed rate bandwidth setting unit (bandwidth table
20
) sets fixed rate bandwidth (CBR bandwidth) information being the information about the bandwidth that a fixed rate connection can occupy.
A use state setting unit (use state
22
) sets fixed rate used bandwidth information (bandwidth used by a CBR service) being the information about the bandwidth that a fixed rate connection currently uses.
A call controlling unit (CAC unit
19
) controls whether or not to permit the establishment of a fixed rate connection while performing an overbooking bandwidth control which permits the bandwidth indicated by fixed rate used bandwidth information to exceed the bandwidth indicated by fixed rate bandwidth information, based on the fixed rate bandwidth information set in the fixed rate bandwidth setting unit and on the fixed rate used bandwidth information set in the use state setting unit, when establishing the fixed rate connection, and updates the fixed rate used bandwidth information set in the use state setting unit.
The above described configuration according to the present invention can be implemented so that the fixed rate bandwidth setting unit and the use state setting unit are arranged for a corresponding capability part such as a line device (line unit
30
) for switching or concentration-multiplexing cells, a shelf device (shelf unit
31
) for concentrating the line device, a switching device (switching unit
32
) for switching cells input/output to/from the shelf device, etc., and the call controlling unit controls the overbooking bandwidth control for the corresponding capability part while referencing the fixed rate bandwidth setting unit and the use state setting unit, which are arranged for the corresponding capability part.
The configuration according to the present invention described so far can be implemented so that the call controlling unit attempts to broaden the bandwidth that a fixed rate connection can occupy, if the bandwidth that the fixed rate connection currently uses covers the bandwidth that the fixed rate connection can occupy, when performing the overbooking bandwidth control; changes the fixed rate bandwidth information set in the fixed rate bandwidth setting unit according to the broadened bandwidth; and controls whether or not to permit the establishment of the fixed rate connection.
In this case, the call controlling unit can be configured to attempt to broaden the bandwidth that the fixed rate connection can occupy based on the bandwidth information of the fixed rate connection, which is notified from an adjacent cell switching device, if the bandwidth that the fixed rate connection currently uses covers the bandwidth that the fixed rate connection can occupy, when performing the overbooking bandwidth control; and notifies the adjacent cell switching device of the new bandwidth information about the fixed rate connection according to the control result. In this case, the communication of the above described bandwidth information is made between the cell switching devices, for example, by using a resource management cell or a signaling message.
Or, the call controlling unit can be configured to attempt to broaden the bandwidth that a fixed rate connection can occupy based on the state of the bandwidth of the fixed rate connection controlled in other capability units within the cell switching device, if the bandwidth that the fixed rate connection currently uses covers the bandwidth that the fixed rate connection can occupy, when performing the overbooking bandwidth control.
The configuration according to the present invention described so far can be implemented so that the fixed rate bandwidth information set in the fixed rate bandwidth setting unit is changed according to a use rate change of the fixed rate connection, which depends on a time zone, or an increase/decrease in a requested number of fixed rate connections.
The configuration according to the present invention described so far can be implemented so that each of cell switching devices for exchanging a signaling
Kamo Toshiyuki
Kumagai Masatoshi
Tazaki Yuji
Fujitsu Limited
Rao Seema S.
Rosenman & Colin LLP
LandOfFree
Cell switching device for controlling a fixed rate connection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cell switching device for controlling a fixed rate connection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cell switching device for controlling a fixed rate connection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2877549