Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1998-01-27
2001-12-11
Kizou, Hassan (Department: 2662)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S233000, C370S234000
Reexamination Certificate
active
06330226
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to traffic congestion management of a data network. In particular, it is directed to a technique by which congestion in the data network is controlled by limiting new TCP connection setups based on packet loss characteristics of the data network.
BACKGROUND OF THE INVENTION
The current data networks are handling not only enormous volume of traffic but more and more diversified multi media traffic, causing the data network to become congested more often. When congestion causes an excessive number of packets to be dropped, it can easily impact many traffic flows, and cause many timeouts. By guaranteeing a certain number of traffic flows a minimum bandwidth and treating the remainder as best effort, it is possible to avoid spreading high packet loss over so many flows and to reduce the number of aborted flows. Pending U.S. patent application Ser. No. 08/772,256 filed on Dec. 23, 1996 and Ser. No. 08/818,612 filed on Mar. 14, 1997 by the present inventors describe dynamic traffic conditioning techniques which make use of this concept. The dynamic traffic conditioning techniques described therein allow the network to discover the nature of the service for each traffic flow, classify it dynamically, and exercise traffic conditioning by means of such techniques as admission control and scheduling when delivering the traffic downstream to support the service appropriately.
Congestion at a network node can be aggravated by having too many TCP connections. TCP will adjust to try to share bandwidth among all connections but when the available buffer space is insufficient, time-outs will occur and as the congestion increases there will be an exponentially growing number of packets resent. The effect of having too many connections is that much of the bandwidth in the upstream network is wasted carrying packets that will be discarded at the congested node because there is not enough buffer there.
A simple method of avoiding the bad effects of too many TCP connections is to limit the number of connections or to discard one or more packets from one or more existing connections. Limiting the number of connections is achieved by an admission control which delays or even discards the connection set-up packets. In the case of discarding packets, which packets and from which connection to discard packets are decided by preset algorithms or policies. By invoking this control to limit the number of connections, each packet is inspected to see if it is a connection set-up packet, e.g., TCP SYN packet. This control packet is used to initiate a TCP connection and no traffic can flow until it is acknowledged by the other end of the proposed connection.
In one example, a decision to invoke the admission control, i.e. deciding when to limit the TCP traffic, can be made as follows:
Keep track of all TCP connections and thus keep count of the total number. Apply a calculation to see how many connections the available buffer can support and limit new connections. This is not a good way for a general implementation because it requires keeping state information on all TCP flows and being provided with information on the configured buffer size.
A better solution is when buffers get full and packet loss gets above some configured threshold, an admission control algorithm will apply some policy to reduce connections or the amount of traffic to keep the loss below the threshold. The reduction can be by discarding traffic from existing connections or, preferably, by preventing new connections from being set up.
The invention performs the admission control algorithm to achieve this effect.
OBJECTS OF INVENTION
It is therefore an object of the invention to provide a method of managing a data network for congestion.
It is a further object of the invention to provide a method of continuously monitoring the TCP traffic flows for congestion in a data network.
It is another object of the invention to provide a method of managing the data network by performing admission control for TCP traffic.
It is yet an object of the invention to provide a method of managing the data network by exercising the connection admission control for a new TCP connection request based on the packet loss characteristic.
SUMMARY OF THE INVENTION
Briefly stated, the invention resides in a packet data network for multimedia traffic having one or more nodes in which network one or more packets are discarded to control congestion. According to one aspect, a method of performing admission control to connection oriented traffic flows comprises steps of monitoring packets of all the traffic flows, deriving a packet loss characteristic of the traffic flows and disabling the serving of a new connection request when the packet loss characteristic matches a predefined pattern.
In another aspect, a method of performing admission control to TCP traffic flows comprises steps of storing all TCP connection setup packets in a connection request queue, monitoring packets of all active TCP traffic flows according to their port numbers and sequence numbers, and recording the count of either resent or discarded packets for any TCP traffic flows. The method further includes steps of building a history table containing the history of the sequence numbers, port numbers, and the count of either resent or discarded packets, computing a packet loss characteristic using the contents of the history table, and deciding enabling or disabling the connection request queue based on the packet loss characteristic with respect to a predefined pattern.
In a further aspect, the invention is directed to a TCP admission control apparatus for controlling congestion of a data network. The apparatus comprises a TCP output buffer for buffering and inspecting all the TCP packets of an incoming traffic flow, and a connection request queue for storing new connection requests. The apparatus further includes a history table for storing traffic information with respect to the TCP packets inspected above to derive a packet loss characteristic, and a queue controller for enabling or disabling the connection request queue upon detecting the matching of the packet loss characteristic with a predefined pattern.
REFERENCES:
patent: 5349578 (1994-09-01), Tatsuki et al.
patent: 5361372 (1994-11-01), Rege et al.
patent: 5410536 (1995-04-01), Shah et al.
patent: 5444706 (1995-08-01), Osaki
patent: 5553057 (1996-09-01), Nakayama
patent: 5729530 (1998-03-01), Kawaguchi et al.
patent: 5812525 (1998-09-01), Teraslinna
patent: 6041038 (2000-03-01), Aimoto
patent: 0 473 188 (1992-03-01), None
patent: 99/66676 (1999-12-01), None
Chapman Alan Stanley John
Kung Hsiang-Tsung
Kizou Hassan
Millard Allan P.
Nortel Networks Limited
Tran Thien
LandOfFree
TCP admission control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with TCP admission control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and TCP admission control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2559082