Elastic traffic marking for multi-priority packet streams in a communications network

Abstract

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.

What is claimed is: 
     
         1 . A router of a core network receiving a multi-priority stream of packets from a provider network, the router comprising:
 a packet marking mechanism including   a token bucket for determining whether each received packet is conforming to a traffic profile, and   a loan bucket for determining whether bandwidth can be borrowed for a non-conforming packet,   wherein the loan bucket associates the non-conforming packet with a lower drop precedence when bandwidth can be borrowed for the non-conforming packet, and the loan bucket associates the non-conforming packet with a higher drop precedence when bandwidth cannot be borrowed for the non-conforming packet.   
     
     
         2 . A router of a core network receiving a multi-priority stream of packets from a provider network, the router comprising:
 a packet marking mechanism including   a token bucket for determining whether each received packet is conforming to a traffic profile, wherein a first received packet is determined to be non-conforming and to have a higher priority than a second received packet determined to be conforming, and   a loan bucket for borrowing bandwidth for the first received packet from the second received packet and thereafter associating the first received packet with lower drop precedence and associating the second received packet with higher drop precedence.