Controlling congestion in a packet switched data network
View Patent ↗A method of controlling congestion in a packet switched network includes transmitting a pause message to a node upstream of a congested node to instruct it to cease sending for a period of time. The congested node also sends information to the upstream node informing it of the buffer size required to relieve congestion. If the buffer capacity of the upstream node is greater than or equal to the signalled amount required, no further action is taken. If the buffer capacity of the upstream node is less that the required amount, it in turn sends a pause message to a node upstream of it, together with an indication of the required buffer size to reduce congestion, taking into account the amount available from the sending nodes.
1. A method of controlling congestion in a packet switched data network, comprising the steps of:
detecting congestion at a first node of the packet switched data network via one or more techniques, and one of the techniques is based on a rate of receipt of incoming packets;
when the congestion is detected, sending a pause message to a second node, upstream from the first node, to stop a transmission of data to the first node for a period of time, and sending information to the second node that indicates an amount of buffer space required to relieve the congestion;
and, when a buffer capacity of the second node is less than that required, acting to reduce the congestion.
2. The method of claim 1 , further comprising the step of dropping, via the second node, packets to reduce congestion.
3. The method of claim 1 , further comprising the step of, when the buffer capacity of the second node is less than that required, sending a pause message to a third node, upstream from the second node, to reduce the congestion.
4. The method of claim 3 , further comprising the step of, when the buffer capacity of the second node is less than that required, sending information to the third node to indicate the amount of buffer space required that takes into account the buffer capacity of the second node.
5. The method of claim 1 , wherein the pause messages are PAUSE messages in accordance with Ethernet protocols.
6. The method of claim 1 , wherein the pause messages include information that indicates the amount of buffer space required.
7. The method of claim 6 , wherein the pause messages are PAUSE messages in accordance with Ethernet protocols, and a PAUSE message frame in accordance with IEEE 802.3x includes additional bits used to indicate an existence of congestion and the amount of buffer capacity required.
8. The method of claim 1 , further comprising the step of sending information that indicates the amount of buffer space required in a different type of message than a pause message.
9. The method of claim 1 , further comprising the step of sending information that indicates an existence of congestion from the first node to a traffic management system;
wherein the traffic management system is operable to inform the first node of at least one of the amount of buffer space required to relieve the congestion and the packet switched data network path required to relieve the congestion.
10. The method of claim 9 , wherein, when the first node is informed of said packet switched data network path, the pause messages are directed only along said packet switched data network path.
11. The method of claim 1 , wherein the amount of buffer space required to relieve the congestion is dependent on a type of the congestion.
12. A packet switched data network comprising:
a first node;
a second node upstream of the first node;
a detector to detect congestion at the first node;
a pause message generator; and
a congestion control mechanism, wherein when the detector detects congestion at the first node based on a rate of receipt of incoming packets, the pause message generator sends a pause message to the second node to stop transmission of data to the first node for a period of time, and an indication is sent to the second node about an amount of buffer space required to relieve congestion; and, when the buffer capacity of the second node is less than that required, the congestion control mechanism is operable to reduce the congestion.
13. The method of claim 1 , further comprising the step of comparing the amount of buffer space required to resolve the congestion to a buffer capacity of the first node prior to the step of sending a pause message to a second node.
14. The method of claim 1 , wherein another technique to detect the congestion is when the first node is unable to receive another data packet because the buffer has insufficient space to accommodate even one additional packet.
15. The method of claim 1 , wherein another technique to detect the congestion is to measure an average queue occupancy and determine whether the average queue occupancy exceeds a certain pre-specified threshold.