Mechanism and method to select a time delay in response to a collision
A communications system includes a network that is coupled to a number of terminals, at least some of which are capable of audio or other forms of real-time interactive data communications over the network. Each of the terminals includes a network adapter that is capable of detecting a collision with another terminal on the network. If a collision is detected, transmission of a data frame is aborted, and a backoff time delay is selected. The backoff time delay is selected from a group of delay periods that vary at a rate different than exponentially with a number of collisions. The group of one or more delay periods can contain delay periods that increase linearly with the number of collisions, delay periods that increase according to some power of n, where n is the number of collisions, or a delay period that is selected at random based on a predetermined mean backoff delay. Alternatively, the selected backoff time delay is selected from a group of delay periods that increases exponentially with the number of collisions, but with a maximum value set that is less than the maximum set according to conventional backoff algorithms.
1. A method of providing access to a network, comprising:
detecting a collision on the network during transmission of a frame;
waiting a first time delay before retransmitting the frame; and
selecting the first time delay using a first algorithm that varies the first time delay at a rate less than an exponential rate based on a number of collisions,
wherein the acts of detecting, waiting, and selecting are performed by a first terminal, the method further comprising another terminal:
detecting the collision;
waiting a second time delay before retransmitting a frame from the other terminal; and
selecting the second time delay using a second algorithm that varies the second time delay exponentially with a number of collisions.
2. The method of claim 1 , wherein selecting the first time delay using the first algorithm comprises selecting a delay period from a group of delay periods that grows at a rate less than exponentially with the number of collisions.
3. The method of claim 1 , wherein selecting the first time delay using the first algorithm comprises selecting a delay period from a group of delay periods that grows at a rate less than exponentially with n collisions, where n is less than or equal to 10.
4. The method of claim 1 , wherein selecting the first time delay uses the first algorithm that varies the time delay linearly with the number of collisions.
5. The method of claim 4 , wherein selecting the first time delay comprises selecting a time delay, K×time, where K is selected from the group [0 through j×n], j being greater than or equal to one, where n indicates a number of detected collisions.
6. The method of claim 1 , wherein selecting the first time delay is performed using an algorithm that varies the time delay according to a polynomial of n, where n is the number of collisions.
7. The method of claim 1 , wherein selecting the first time delay comprises selecting the first time delay from a group of delay periods ranging from 0 to Dmax, where Dmax varies with N, where the detected collision is an Nth detected collision, and where Dmax varies less than exponentially with N for N less than or equal to 10.
8. A network system, comprising:
a network;
a first terminal having a first network adapter capable of communicating over the network;
a second terminal having a second network adapter capable of communicating over the network;
the first network adapter to employ a first backoff algorithm in response to a collision, and the second network adapter to employ a second, different backoff algorithm in response to the collision,
wherein the first backoff algorithm comprises an exponential backoff algorithm that selects a backoff delay from a group of delay periods that increases exponentially with a number of collisions,
wherein the second backoff algorithm comprises an algorithm that selects a backoff delay from a second group of one or more delay periods that varies at less than exponentially with a number of collisions.
9. The network system of claim 8 , wherein the second group contains a random delay period randomly selected based on a predetermined mean delay period.
10. The network system of claim 8 , wherein the second group of delay periods increases linearly with a number of collisions.
11. The network system of claim 8 , wherein the second group of delay periods increases according to a polynomial of n, where n is a number of collisions.