Network access mechanism and method
View Patent ↗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, by a network adapter, a collision on the network during transmission of a first frame containing data according to a first type;
waiting, by the network adapter, a time delay before retransmitting the first frame;
selecting, by the network adapter, the time delay using a first algorithm that generates a random time delay based on a predetermined mean delay, wherein generating the random time delay based on the predetermined mean delay comprises using the predetermined mean delay, by a random number generator, to generate the random time delay, wherein the first algorithm is applied to frames containing data according to the first type;
detecting a collision on the network during transmission of a second frame containing a second type of data; and
waiting a second time delay before retransmitting the second frame, wherein waiting the second time delay before retransmitting the second frame uses an exponential backoff algorithm that selects the second time delay from a group of delay periods that increases exponentially with a number of collisions.
2. The method of claim 1 , wherein detecting the collisions on the network comprises detecting the collisions on an Ethernet network.
3. The method of claim 1 , further comprising transmitting the first frame containing data associated with a real-time interactive communication over the network.
4. The method of claim 1 , further comprising transmitting the first frame containing manufacturing process control signaling.
5. The method of claim 1 , further comprising transmitting the first frame containing speech data over the network.
6. The method of claim 1 , further comprising:
determining whether to apply the first algorithm or the exponential backoff algorithm based on a priority level associated with the first frame or the second frame.
7. The method of claim 6 , wherein determining whether to apply the first algorithm or the exponential backoff algorithm is based on differentiated services (DiffServ) classification.
8. A network adapter, comprising:
a controller to transmit data onto a communications channel, the controller to detect a collision on the communications channel and to select a backoff time delay in response to the detected collision,
the controller including a random number generator configured to use a predetermined mean backoff time delay to generate the backoff time delay by randomly generating a random number K based on the predetermined mean backoff time delay, the backoff time delay equal to the random number K multiplied by a time period, wherein the random number generator to generate the backoff time delay is used for data according to a first type,
the controller configured to further select an exponential backoff delay algorithm in response to a detected collision when transmitting data according to a second type, wherein the exponential backoff delay algorithm selects a backoff time delay for the data according to the second type from a group of delay periods, the group of delay periods having members that grow exponentially with a number of collisions.
9. The network adapter of claim 8 , wherein selection of a backoff delay using the random number generator is part of a first algorithm, and wherein the controller is configured to select one of the first algorithm and the exponential backoff delay algorithm based on a priority level associated with the data according to the first type or the data according to the second type.
10. The network adapter of claim 9 , wherein the priority level is associated with differentiated services (DiffServ) classification.
11. The method of claim 1 , wherein the random number generator is to generate a random number based on the predetermined mean delay, and wherein the random time delay is calculated by multiplying the generated random number with a slot time.
12. The network adapter of claim 8 , wherein the time period is a length of a time slot.