Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1997-08-12
2001-04-17
Nguyen, Chau (Department: 2663)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S236000
Reexamination Certificate
active
06219337
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a reconstructible network and, in particular, to an ATM network allowing logical reconstruction by modifying the capacity of a virtual connection.
A conventional reconstructible network of the type is described, for example, in an article entitled “Implementation Performance Evaluation for Self-sizing Network Operation” written by Yuka KATO and three others and contributed to Technical Report of IEICE (Institute of Electronics, Information and Communication Engineers), SSE-95-122 (December, 1995), pp. 37-42. As described in the KATO et al. article, the reconstructible network is aimed at reassigning physical network resources to meet variation in traffic load upon virtual paths in an ATM network in order to assure network performance.
In an asynchronous transfer mode (abbreviated ATM), a fixed-length block called a cell is used as a unit in multiplexing and exchange for a physical link. The cell contains an identifier indicative of virtual connection through which information is to be transferred. The virtual connection includes a virtual path (VP) and a virtual channel (VC). Within the cell, the identifier for the virtual connection is partly assigned to the virtual path and partly assigned to the virtual channel. As a result, a particular virtual path accommodates a plurality of virtual channels. A particular physical link accommodates a plurality of virtual paths.
Referring to
FIG. 1
, a conventional reconstructible network comprises a plurality of virtual channels (VC's)
1
, a plurality of virtual channel handlers (VCH's)
2
(
2
-
1
through
2
-
6
in the figure), a plurality of virtual paths (VP's)
3
(
3
-
1
through
3
-
3
in the figure), a plurality of virtual path handlers (VPH's)
4
(
4
-
1
through
4
-
4
in the figure), a plurality of physical links
5
(
5
-
1
through
5
-
3
in the figure) accommodating the virtual paths
3
, and a network managing system (NMS)
6
.
The virtual channel handlers
2
terminate the virtual paths
3
and make the virtual paths
3
accommodate the virtual channels
1
in response to accommodation requests. Such accommodation requests (for example, telephone calls) are randomly produced so that the accommodation of the virtual channels
1
into the virtual paths
3
may not completely be successful. The probability of unsuccessfulness is used as a measure for the performance of the virtual paths
3
. A product of the frequency of production of the accommodation requests and the required accommodation time is called a traffic.
The virtual path handlers
4
terminate the virtual paths
3
and make the physical links
5
accommodate the virtual paths
3
. The virtual paths
3
are handled as channel groups comprising a plurality of channels such as telephone channels. The accommodation of the virtual paths
3
into the physical links
5
are definitely carried out.
The virtual channels
1
and the virtual paths
3
are collectively called the virtual connection while the virtual channel handlers
2
and the virtual path handlers
4
are collectively called communication nodes.
Supplied with a capacity setting request message from the network managing system
6
, each of the virtual channel handlers
2
and the virtual path handlers
4
modifies a capacity managing table. In addition, each of the virtual channel handlers
2
terminating the virtual paths
3
modifies a traffic shaper to adjust a cell flow in each virtual path
3
and, after completion of the modification, returns a capacity setting response message. Supplied with a traffic/performance information request message, the virtual channel handler
2
returns a traffic/performance response message to the network managing system
6
. Thus, the network managing system
6
controls and manages the virtual channel handlers
2
and the virtual path handlers
4
by the use of the messages transmitted and received in a polling fashion.
The virtual channel handlers
2
and the virtual path handlers
4
as the communication nodes are respectively assigned with node numbers which can be uniquely identified within the network. The physical links
5
connected to one of the communication nodes are assigned with port numbers which can be uniquely identified within the communication node in consideration. Therefore, a particular one of the physical links
5
downward from a particular one of the communication nodes can be uniquely identified within the network with reference to a combination of a specific node number and a specific port number. Such combination of the specific node number and the specific port number will hereafter be called a physical link number.
In order to reassign network resources from those virtual paths having spare capacity to those virtual paths requiring additional capacity, the network managing system
6
periodically collects traffic/performance information from the virtual channel handlers
2
to evaluate the performance, calculates VP capacity required for each VP path, and sets the capacity in each of the virtual path handlers
4
and the virtual channel handlers
2
. To this end, the network managing system
6
is connected to all of the virtual channel handlers
2
and the virtual path handlers
4
within the network through managing virtual channels.
Referring to
FIG. 2
, the network managing system
6
comprises a database (DB) section
10
, a control section
11
, and a message transmit/receive section
12
.
The database section
10
comprises a traffic database
101
, a topology database
102
, and a routing list database
103
.
As illustrated in
FIG. 3A
, the traffic database
101
holds a traffic information table storing traffic and performance information related to the traffic and the performance of each virtual path
3
within the network and collected from each virtual channel handler
2
. Specifically, the traffic information table comprises first through fourth entries indicative of a VP number, traffic information, performance information, and a VP capacity, respectively. The VP number comprises a set of a node number, a port number, and a VP identifier uniquely identified by the port number. Thus, the VP number is uniquely identified within the network.
As illustrated in
FIG. 3B
, the topology database
102
holds a topology information table indicative of the state of connection of the virtual channel handlers
2
and the virtual path handlers
4
as well as idle capacity of the physical links
5
connecting the virtual channel handlers
2
and the virtual path handlers
4
. Specifically, the topology information table comprises first through third entries indicative of the physical link number of an adjacent node, the node number, and the idle capacity.
As illustrated in
FIG. 3C
, the routing list database
103
holds a routing list table indicative of a routing list comprising a sequence of the physical link numbers of those physical links through which each virtual path
3
within the network passes. Specifically, the routing list table comprises first and second entries indicative of the VP number and the physical link number.
The control section
11
comprises a capacity managing unit
111
, a performance managing unit
112
, a capacity calculating unit
113
, a capacity setting unit
114
, and a reduction candidate selecting unit
115
.
The performance managing unit
112
periodically collects in a polling fashion the traffic and the performance information of a virtual channel
1
accommodated in a virtual path
3
terminated by a particular virtual channel handler
2
in consideration, and renews the traffic database
101
. In response to a request from the capacity managing unit
111
, the performance managing unit
112
acquires from the traffic database
101
the performance information of the virtual path
3
and evaluates whether or not the performance is satisfactory.
The capacity calculating unit
113
acquires from the traffic database
101
the traffic information and the performance information of the virtual path
3
specified by the capa
Kwoh Jasper
NEC Corporation
Nguyen Chau
Ostrolenk Faber Gerb & Soffen, LLP
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