Method and apparatus for supporting multiple class of service connections in a communications network

A communications network comprising:

• (a) a connection for transmitting traffic over the communications network;
• (b) a network interface associated with the connection for receiving incoming traffic having a particular priority, for transmitting over the connection a priority indicator comprising information identifying the priority of the incoming traffic, and for transmitting the incoming traffic over the connection as network traffic;
• (c) a downstream node connected to the network interface by way of the connection, the downstream node comprising a queue for queuing the network traffic received on the connection at the downstream node, the queue being associated with a congestion measure indicative of congestion in the queue and having an adjustable discard range corresponding to the traffic carried over the connection;
• and
• wherein when the priority indicator is received at the downstream node the discard range is adjusted to correspond to the priority identified in the priority indicator, and wherein the network traffic thereafter received at the downstream node is placed in the queue if the congestion measure is outside the discard range and not placed in the queue if the congestion measure is within the discard range.

A method for transmitting traffic associated with one of a plurality of different levels of priority over a single connection in an ATM network using ATM cells, each ATM cell having a cell header with a first and a second priority-indicating bit, the method comprising the steps of:

• a. in an ATM cell carrying the traffic, setting the first and second priority-indicating bits to values corresponding to the level of priority of the traffic;
• b. transmitting the ATM cell over the connection to a downstream node having a queue associated with a congestion measure and having a plurality of discard ranges corresponding to the different levels of priority;
• c. at the downstream node, receiving the ATM cell transmitted over the connection and checking the first and second priority-indicating bits thereof to determine the level of priority of the received ATM cell;
• d. selecting one of said plurality of discard ranges to correspond to the level of priority identified by said first and second priority indicating bits;
• and
• e. queuing the received ATM cell in the queue if the congestion measure is outside the selected discard range corresponding to the level of priority of the ATM cell and discarding the ATM cell if the congestion measure is within the discard range corresponding to the level of priority of the ATM cell.