RFC 1046 (rfc1046) - Page 2 of 11
Queuing algorithm to provide type-of-service for IP links
Alternative Format: Original Text Document
RFC 1046 Type-of-Service Queuing February 1988 satellite link introduces is less than the MGD, that link should be considered in the route. If however, the MGD is less than the satellite link can provide, it should not be used. For this discussion it is assumed that delay for individual links are low enough that a sending node can provide the MGD service. Low delay class of service is not the same as low Round Trip Time (RTT). Class of service is unidirectional. The datagrams responding to low delay traffic (i.e., Acking the data) might be sent with a high reliability class of service, but not low delay. The performance of TCP might be significantly improved with an accurate estimate of the round trip time and the retransmission timeout. The TCP retransmission timeout could be set to the maximum delay for the current route (if the current route could be determined). The timeout value would have to be redetermined when the number of hops in the route changes. High throughput class of service should get a large volume of data through the Internet. Requesters of this class are less concerned with the delay the datagrams have crossing the Internet and the reliability of their delivery. This type of traffic might be served well by a satellite link, especially if the bandwidth is high. Another attribute this class might have is consistent one way traversal time for a given burst of datagrams. This class of service will have its traversal times affected by the amount of Internet load. As the Internet load goes up, the throughput for each source will go down. High reliability class of service should see most of its datagrams delivered if the Internet is not too heavily loaded. Source Quenches (SQ) should not be sent only when datagrams are discarded. SQs should be sent well before the queues become full, to advise the sender of the rate that can be currently supported. Priority service should allow data that has a higher priority to be queued ahead of other lower priority data. It is important to limit the amount of priority data. The amount of preemption a lower priority datagram suffers must also be limited. It is assumed that a queuing algorithm provides these classes of service. For one facility to be used over another, that is, making different routing decisions based upon the TOS, requires a more sophisticated routing algorithm and larger routing database. These issues are not discussed in this document. Prue & Postel
