Elastic traffic marking for multi-priority packet streams in a communications network
View Patent ↗Routers in a communications network mark packets of a multi-priority stream to establish a drop precedence of the packets during network congestion. For each packet received, a router employs one of two types of packet-marking mechanisms to associate low drop precedence with a high-priority, out-of-profile packet. One type, called “token bucket with loan bucket,” uses a token bucket to determine whether a packet is in conformance, i.e., in-profile, with a traffic profile and at least one loan bucket to determine whether a high priority, out-of-profile packet may borrow bandwidth. Another mechanism type, called “token bucket with color-exchange queue,” uses a color-exchange queue to delay packet forwarding for a fixed period. During this delay, a high-drop-precedence marking of an out-of-profile, high-priority packet may be exchanged with a low-drop-precedence marking of an in-profile, low-priority packet. The packet-marking mechanisms are useful in improving the quality of video viewing.
1. In a communications network, a system for marking packets of a multi-priority stream to establish a drop precedence for each packet, the system comprising:
means for receiving a first packet and a second packet of the multi-priority stream, the first packet having a higher priority than the second packet;
a token bucket for determining whether each received packet is conforming to a traffic profile, the token bucket determining that the first packet is non-conforming with respect to the traffic profile and that the second packet is conforming with respect to the traffic profile; and
a loan bucket for use in determining whether the non-conforming first packet can be associated with low drop precedence and whether the conforming second packet is to be associated with high drop precedence in order to compensate for associating the non-conforming first packet with low drop precedence.
2. The system of claim 1 , wherein the loan bucket has a threshold associated therewith, and further comprising a packet marker for marking the non-conforming first packet with low drop precedence if a number of tokens in the loan bucket is less than the threshold, otherwise marking the non-conforming first packet with high drop precedence.
3. The system of claim 1 , further comprising a packet marker for marking the conforming second packet with high drop precedence if the loan bucket has at least one token.
4. The system of claim 1 , further comprising means for adding at least one token to the loan bucket in response to associating the non-conforming first packet with low drop precedence.
5. The system of claim 1 , further comprising means for removing at least one token from the loan bucket in response to associating the conforming second packet with high drop precedence.
6. The system of claim 1 , wherein the multi-priority stream is a video stream.