Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Utility Patent
1997-10-30
2001-01-02
Pham, Chi H. (Department: 2731)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S231000, C370S395430
Utility Patent
active
06169740
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to traffic management in a communications network. In particular, it is directed to traffic management by the use of one or more virtual links.
BACKGROUND OF THE INVENTION
Some form of traffic management is always present in any communications networks and the invention can be applied to various traffic management schemes. The description which follows below refers particularly to traffic management in an asynchronous transfer mode (ATM) network. The exact form and features of traffic management in a switch within the network is heavily influenced by how traffic is assigned to queues at any queuing point within the switch.
There are various methods of queue assignment known in the art. Traffic management features are usually arranged around the queuing structure but it affects more than just queuing. For example, scheduling, buffer management, discard thresholds, flow control mechanisms, and billing information may all be affected. It is logical, therefore, to describe how a switch generically organizes its traffic, without restricting the description to queuing.
Two common such organizations known in the art are based on class-based queuing, and per-connection queuing. Class-based queuing consists of the traffic of connections having similar requirements sharing a queue. Assuming an implementation is based on shared memory, admittance into a queue may consider the level of occupancy of the shared memory as well as of the specific queue. This permits preventing a single queue from consuming all of the shared memory resource. The act of determining which queue is to provide the next cell to dequeue is referred to as scheduling. With class-based queuing, scheduling is done by considering the state of each class queue, and the performance requirements of each class.
Per-connection queuing assigns a separate queue to each connection, rather than to a class, and thus makes the features available to all connections. Sometimes, but not necessarily, the concept of the class is retained. This impacts the scheduling and buffer management algorithms by creating an additional level of hierarchy within them. For example, a class-level scheduler can still be employed to determine which class to serve, but it must hand off to a connection-level scheduler that will choose a connection, and hence a queue, from within the indicated class. Admittance into a queue may now consider the occupancy of the shared memory, the class, and the connection queue.
Let us consider a network shown in
FIG. 1
in which a switch
10
connects via a high bandwidth link
12
to an access mux/demux
14
(hereinafter called mux for short) that drives lower bandwidth links
16
. The mux is a potential congestion point in the downstream direction (from high to low bandwidth links) simply because traffic can arrive at a greater rate over the high bandwidth link than it can exit through the lower bandwidth link. Note that it is assumed that the high bandwidth link is not channelized according to the lower bandwidth links. It is further assumed that there are no other sources of traffic to the lower bandwidth link other than the high bandwidth link (i.e. there is no internal switching from other low bandwidth link upstream traffic, and there is no other high bandwidth link), which is generally the case with simple low-cost muxes. The fact that the mux is a congestion point requires it to provide traffic management features and sufficient buffering that will assure good performance for the diverse requirements of the variety of connections competing for the links. Further, if the mux is terminating a customer link, since cells may be dropped at this point, accounting of delivered traffic must also be done for billing purposes.
Now, referring back to
FIG. 1
, if the switch driving the high bandwidth link to the mux supports virtual links, then according to one aspect of the invention, all of the traffic destined for a particular low bandwidth link can be organized into a unique virtual link. This virtual link can be scheduled at a maximum rate not exceeding the bandwidth of the low bandwidth link, thus preventing the mux from ever becoming a congestion point. Therefore, the amount of mux buffering can be reduced to a very small amount (for jitter absorption). The advantage of the invention in this example is potentially large cost reductions in the high volume access mux at the lesser expense of a more complex low volume switch. Other benefits can become apparent in the description that follows below.
Recognizing that as described above, there are different organizational views of the total link traffic, the invention defines a virtual link to be an organizational view similar to a typical link view, and allows virtual links to replace connections in the link view, thereby creating one or more additional levels of hierarchy to how traffic is managed.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide a method of and apparatus for managing communications traffic which results in simplified equipment downstream.
It is another object of the invention to provide a method of and apparatus for scheduling the traffic on a link so that congestion downstream can be better controlled.
It is yet a further object of the invention to provide a method of and apparatus for traffic management which can be implemented with little modification to functionalities and features which are already present in the network.
SUMMARY OF THE INVENTION
Briefly stated, in accordance with one aspect the invention resides in a communications network in which a link connects node A and one or more downstream destination nodes, having one or more output ports. The invention is directed to a method of managing traffic at node A in which the traffic flows from node A through the link. The method comprises steps of obtaining resource capacity requirements of one or more groups of one or more connections outputted from said one or more output ports of the one or more downstream destination nodes and forming said one or more groups of the connections into one or more virtual links. The method further includes steps of identifying the groups of the connections by virtual link identifiers and managing the traffic in the one or more virtual links by performing thereto at node A, one or more of the following algorithms, connection admission control algorithm, buffer management algorithm, flow control algorithm and scheduling algorithm so that said resource capacity requirements are satisfied.
In accordance with a further aspect, the invention is directed to an apparatus for managing traffic in a link of a communications network in which the link connects node A and one or more downstream destination nodes, said one or more downstream destination node having one or more output ports. The apparatus comprises a control signal receiver for obtaining resource capacity requirements of one or more groups of one or more connections outputted from said one or more output ports of the one or more downstream destination node. The apparatus further includes a traffic handler for forming the groups of the connections into one or more virtual links, and for identifying the groups of the connections by virtual link identifiers and a traffic controller having one or more of the following algorithms, connection admission control algorithm, buffer management algorithm, flow control algorithm and scheduling algorithm and for performing to said one or more virtual links said one or more algorithm concurrently or separately so that said resource capacity requirements are satisfied.
REFERENCES:
patent: 5581544 (1996-12-01), Hamada et al.
patent: 5748614 (1998-05-01), Wallmeier
patent: 5953338 (1999-09-01), Ma et al.
patent: 0596159A1 (1994-11-01), None
patent: 0798942A2 (1997-01-01), None
Fisher David Anthony
Graves Alan Frank
Lyon Norman Allan
Morris Todd Douglas
Duong Frank
Gowling Lafleur Henderson LLP
Nortel Networks Limited
Pham Chi H.
Toyooka Yoshi Haru
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