Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1998-12-15
2003-12-02
Pham, Chi (Department: 2667)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S444000, C370S468000, C379S211020
Reexamination Certificate
active
06657965
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to communications networks and more particularly to a system and a method for routing data through multiple network nodes.
DESCRIPTION OF THE RELATED ART
Various communications systems require routing of voice and data packets, blocks, frames or cells (collectively referred to herein as “packets”) through two or more network nodes via communication links to provide connectivity between sites that are located at different networks. In a sophisticated communications system, the nodes that provide the connectivity between the networks operate using a routing algorithm that allows prioritization of packets that are relayed through the nodes. For example, voice packets are typically placed ahead of data packets because the voice packets carry real-time information.
In addition to prioritization of packets, the nodes may be configured to monitor the topology of the system, including the status of the communication links. The link status information may include the operational state and the remaining available bandwidth for each communication link in the system. Using the link status information, the nodes compute routing paths to establish new connections. A reservation protocol may be utilized by the nodes to reserve bandwidth on one or more communication links that define the computed routing paths. Such reservation protocol may be necessary to guarantee space on each communication link along the routing paths. The computed routing paths may vary depending on routing parameters that are being utilized by a particular node. The routing parameters may include the number of hops, the amount of toll charge associated with the path, and the distance between the two connecting nodes.
In a normal packet traffic condition, the path chosen by a source node (i.e., the network node associated with a connection-originating network) may be the optimal path in accordance with the prescribed routing parameters. However, when a communication link in the optimal path is over-crowded with reservations of established connections, the source node may be forced to route the new connection through a less preferred path. A concern is that bandwidth of the over-crowded communication link may be depleted due to a number of low priority connections that have been previously routed through the now over-crowded communication link. The problem arises when the pending connection to be made is a high priority connection, such as a connection for voice data transmission. The connectivity resources of the system are not being utilized efficiently when the high priority connection must be routed through a less preferred path, because the optimal path is being utilized by the lower priority connections.
The problem will be further described with reference to FIG.
1
. In
FIG. 1
, a prior art communications system
10
having networks
12
,
14
,
16
and
18
is shown. The networks
12
-
18
are illustrated as local area networks (LANs). However, the networks
12
-
18
can be other types of network, such as wide area networks (WANs) or metropolitan area networks (MANs). Each LAN
12
-
18
can support a number of sites that may be physically located in a confined area, such as an office building, a building complex or a campus. For simplification, only the LANs
12
and
18
are shown with a number of associated sites. The LAN
12
includes sites
20
,
22
and
24
. The LAN
18
includes sites
26
,
28
and
30
. At each site
20
-
30
, a computer
32
and/or a telephone
34
may be connected to their respective network.
The LANs
12
-
18
are interconnected by communication links
36
,
38
,
40
and
42
. The communication links
36
,
38
,
40
and
42
may be in a form of physical communication links, such as fiber optic cables, or in a form of wireless communication links. The communication links
36
-
42
provide connectivity between nodes
44
,
46
,
48
and
50
. The communication link
36
connects the node
44
to the node
46
. The communication link
38
connects the node
44
to the node
50
. The communication link
40
connects the node
46
to the node
50
. The communication link
42
connects the node
48
to the node
50
. The nodes
44
-
50
may be gateways, switches or routers having prioritizing and routing capabilities. However, the nodes
44
-
50
are identified in
FIG. 1
as routers. Each router
44
-
50
is associated with one of the LANs
12
,
14
,
16
and
18
. The router
44
is associated with the LAN
12
, while the router
46
is associated with the LAN
14
. The router
48
is associated with the LAN
16
, whereas the router
50
is associated with the LAN
18
.
The above-described problem may arise in the following manner. Initially, the packet traffic on the communication links
36
-
42
is light and much of the bandwidth on each of the links is available. One of the sites at LAN
12
, for example the site
20
, may request a data connection to another site at LAN
18
, for example the site
26
. Assuming that the optimal path for the data connection from LAN
12
to LAN
18
is through the communication link
38
, the router
44
responds to the request by reserving the required bandwidth on the communication link
38
. As additional data connections are made through the communication link
38
, the available bandwidth on the communication link
38
may be down to 5% of its capacity. The established connections through the communication link
38
may include many data connections that have a lower priority than voice connections. At such time, a site at LAN
12
, for example the site
24
, requests a voice connection to a site at LAN
18
, for example the site
28
. This voice connection requires 10% of the total bandwidth of the communication link
38
. When this request is received by the router
44
, the router
44
has no choice except to route the voice connection through the communication links
36
and
40
via the router
46
due to lack of sufficient bandwidth remaining on the communication link
38
, even though the optimal path is through the communication link
38
.
The compulsory routing of the voice connection through the router
46
can have a negative effect on the packet traffic at the router
46
. Since the voice connection has a high priority, the router
46
must relay the packets of the voice connection ahead of lower priority packets that are being transmitted through the established connections via the router
46
. The newly introduced voice connection may cause congestion and may increase the probability of dropped packets at the router
46
. In addition, the conventional routing technique inefficiently utilizes the connectivity resources of the system
10
, since the high priority connection is routed through the less preferred path, while the optimal path for the high priority connection is occupied by the lower priority connections.
What is needed is a communications system and a method that can efficiently utilize the connectivity resources of the system to provide the best possible paths for connections according to the priority status of the connections, regardless of the order that the connections were established.
SUMMARY OF THE INVENTION
In accordance with the present invention, a network node and a method of dynamically reconfiguring routes of established connections in a communications system operate to provide the optimal path for a new connection based on a priority status of the new connection. The optimal path is provided even when a communication link along the optimal path does not have a sufficient amount of available bandwidth to accommodate the new connection. The network node operates in conjunction with other network nodes in the system to reroute one or more established connections that have reserved bandwidth on a communication link on the optimal route and have a lower priority status than the new connection, thereby increasing the available bandwidth on the communication link to accommodate the new connection. The network node also performs conventional functions of a router.
Beyda William J.
Shaffer Shmuel
Boakye Alexander O.
Pham Chi
Siemens Information & Communication Networks, Inc.
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