Multiplex communications – Data flow congestion prevention or control
Reexamination Certificate
1998-04-30
2003-09-30
Chin, Wellington (Department: 2664)
Multiplex communications
Data flow congestion prevention or control
C370S235000, C370S413000
Reexamination Certificate
active
06628609
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of data communication networks.
BACKGROUND OF THE INVENTION
The following paragraphs give definitions of terms relevant to this document:
Physical Link: A single point-to-point serial transmission link between two nodes in a network (such as between two routers or between a router and a host machine).
Physical Output Port: The output port of a switch, such as a router that supports at least one physical link.
Logical Link: A point-to-point traffic path between two switches that is composed of multiple parallel physical links and appears from a routing point of view to be one link.
Logical Output Port: The collection of physical output ports that support the physical links of a logical link.
Logical Pathway: A pathway internal to a switch connecting an input port to an output port.
Internet Protocol (IP): A library of routines called on by various network communications applications. IP is responsible for transporting packets of data from node to node. It forwards each packet based on a four-byte destination address (IP number).
Switch: The term switch refers to a single router or packet switch within a communications network. Alternatively, it can refer to a contained network with a determined population of inputs and outputs.
A typical data communication network operates in a connectionless mode whereby there is no negotiation between the transmitter receiver and the network with regard to the type or quantity of traffic that is to be sent. The transmitter simply sends the traffic on the network, and relies on the network components to deliver that traffic to the receiver accurately. These network components consist typically of routing nodes (also known as routers or switches) joined by physical links. The main function of the routing nodes is to direct incoming packets to the appropriate outgoing links. In the event of too much traffic arriving for an outgoing link, the router applies specific policies to decide which traffic is forwarded and which is discarded. It is important that these policies are not subverted by having arbitrary loss of the forwarded traffic as it moves to the next point that implements the management policies. The term non-lossy, as applied to a router, implies that any traffic taken from an input port will be delivered without loss to the output port. As applied to a network, the term non-lossy implies that no traffic is lost between one routing node and the next routing node on the particular traffic path. Consequently, in the case of a non-lossy fabric the input port to a router or routing node has full control over which traffic gets discarded when congestion occurs.
Narrowing the focus to communication network applications that have adopted the Internet Protocol, it is important to note that traffic on the Internet is growing very fast. Not only is it expected that within a short time routes within the network will need multiple physical links to support higher transmission rates, but also that there will exist the necessity for bandwidth allocation to different classes of traffic, perhaps for a particular customer or a class of customer. Therefore, the general architecture for future IP-layer large switches will have the traffic buffered at many inputs while waiting for transfer to an output, where the outgoing link will most likely be a logical link consisting of multiple physical links. Indeed, future implementations of routing networks will have input ports connected to output ports that are geographically remote, and where those ports are connected by wide area non-lossy fabrics.
A particularly important objective to achieve within these future IP-layer networks will be the efficient management of bandwidth allocation. In other words, the network must ensure that the bandwidth available on an outgoing link be efficiently distributed between all traffic being routed through the switch fabric.
One solution to this problem is the protocol currently used to enforce a given bandwidth allocation for a traffic class, consisting of rate control exerted at the egress ports of the network. Output buffering is provided to allow for the mismatch between aggregate input rates and the assigned output rate. The output buffers take traffic from every input port and schedule the output of the various classes based on their allocation.
The problem with Egress based control of bandwidth is that ideally the output would like to take traffic from all ports as soon as it arrives. This requires that the output port receive traffic at a rate equal to the maximum sum of all the input rates. For large values of N (number of input ports) and input bandwidth rates, this is not economically sound and lower transfer rates are used. This in turn requires that the output port be selective in what traffic it transfers. In particular, the output port will give preference to traffic whose bandwidth allocation has not been satisfied and delay transferring traffic that can not currently be sent. This normally requires that some bandwidth be consumed in allowing output ports to discover the traffic status of input ports. The output buffered model is further complicated when multi-link trunks (logical links) are employed and the bandwidth allocation must be satisfied over the total bandwidth of the logical output port.
The background information herein clearly shows that there exists a need in the industry to provide a method for improving the management of IP-layer bandwidth allocation within a non-lossy data communication network arrangement.
OBJECTS AND STATEMENT OF THE INVENTION
An object of this invention is to provide a novel switch device capable of controlling the transport of data units, such as IP data packets, between the input ports and the output ports of the switch to limit the possibility of congestion that can arise at the output port level of the switch.
Another object of this invention is to provide a method for controlling the data units transport process in a switch to reduce the risk of internal congestion.
Another object of this invention is to provide a novel multi-node data transmission device, capable of transporting data units, such as IP data packets, capable of effecting inter-node negotiation for managing the transport of data units on a common data transmission pathway interconnecting the nodes.
Another object of this invention is to provide a method for transmitting data units over a multi-node data transmission device, by effecting inter-node negotiation.
As embodied and broadly described herein, the invention provides a switch for processing data units, said switch including:
a plurality of input ports, each input port capable of receiving data units;
a plurality of output ports, each output port capable of releasing data units from said switch;
a switch fabric capable of selectively establishing a plurality of logical pathways between said input ports and said output ports, each logical pathway connecting a certain input port to a certain output port, whereby a data unit received at the certain input port can be transported to the certain output port on the logical pathway;
a plurality of bandwidth control mechanisms for regulating the transport of data units in said switch, each bandwidth control mechanism being associated with a different logical pathway established through said switch fabric.
In a most preferred embodiment, the switch as defined in general terms above can be implemented as a router. Such a router forms a node in a network and it is used to receive data packets at input ports, analyze each packet to determine is destination and through a routing table select the output port through which the data packet is to be released so it can reach its intended destination. To reduce the likelihood of congestion, the router controls the release of data packets received at its input ports to the switch fabric independently for each logical pathway that can be established in the switch fabric. More specifically, when a logical pathway is established through the switch fabric
Chapman Alan Stanley John
Kung Hsiang-Tsung
Chin Wellington
Nortel Networks Limited
Tran Maikhanh
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