Flow specification consists of the following parameters:

• Service type: The service type parameter indicates the level of service for this flow. A value of 0 indicates that no traffic will be transmitted on this channel. A value of 1 indicates a best effort service; the device will transmit data as quickly as possible but with no guarantees about performance. A value of 2 indicates a guaranteed service the sender will transmit data that conform to the remaining QoS parameters.

• Token rate And Token bucket size: The token rate and token bucket size parameters define a token bucket scheme that is often used in QoS specifications. The advantage of this scheme is that it provides a concise description of the peak and average traffic load the recipient can expect and it also provides a convenient mechanism by which the sender can implement the traffic flow policy.

• Peak bandwidth: The peak bandwidth, expressed in bytes per second, limits how fast packets may be sent back-to-back from applications. Some intermediate systems can take advantage of this information, resulting in more efficient resource allocation. Consider that if the token bucket is full, it is possible for the flow to send a series of back-to-back packets equal to the size of the token bucket. If the token bucket size is large, this back-to-back run may be long enough to exceed the recipient's capacity. To limit this effect, the maximum transmission rate bounds how fast successive packets may be placed on the network.

• Latency: The latency is the maximum acceptable delay between transmission of a bit by the sender and its initial transmission over the air, expressed in microseconds.

• Delay variation: The delay variation is the difference, in microseconds, between the maximum and minimum possible delay that a packet will experience. This value is used by applications to determine the amount of buffer space needed at the receiving side in order to restore the original data transmission pattern. If a receiving application requires data to be delivered in the same pattern that the data were transmitted, it may be necessary for the receiving host briefly to buffer data as they are received so that the receiver can restore the old transmission pattern. An example of this is a case where an application wishes to send and transmit data such as voice samples, which are generated and played at regular intervals. The amount of buffer space that the receiving host is willing to provide determines the amount of variation in delay permitted for individual packets within a given flow.