| Description | string | This class represents a specialization to the general concept of forwarding network traffic by adding specific semantics that characterize the operation of the Assured Forwarding (AF) Service (RFC2597). This RFC defines four different AF classes to represent four different treatments of traffic (e.g., a different amount of forwarding resources, such as buffer space and bandwidth, are allocated. Within each AF class, IP packets are marked with one of three possible drop precedence values. The drop precedence of a packet determines the relative importance of that packet compared to other packets within the same AF class if congestion occurs. A congested interface will try to avoid dropping packets with a lower drop precedence value by instead discarding packets with a higher drop precedence value.
Note that this RFC defines 12 DSCPs that together implement the AF Per-Hop Behavior (PHB) group. Implementations are free to extend this (e.g., add more classes and/or drop precedences) and indeed do not have to implement the AF PHB to be considered compliant to DiffServ. However, implementations should use this set of DSCPs if they implement the AF PHB.
The AFService class is modeled as a specialization of DiffServService, which is in turn a specialization of QoSService. This enables it to be related to a higher-level QoS services as well as to lower-level sub-services (e.g., classification, metering, dropping, queuing, and others). | None | TRANSLATABLE= true |