The assured forwarding classes are Assured (af) and Low 1 (l1). Assured forwarding classes provide services with a committed rate and a peak rate, much like Frame Relay. Packets transmitted through the queue at or below the committed transmission rate are marked in-profile. If the core service network has sufficient bandwidth along the path for the assured traffic, all aggregate in-profile service packets reach the service destination.
Packets transmitted from the service queue that are above the committed rate are marked out-of-profile. When an assured out-of-profile service packet is received at a congestion point in the network, it is discarded before in-profile assured service packets.
Multiple assured classes are supported with relative weighting between them. In DiffServ, the code points for the various Assured classes are AF4, AF3, AF2, and AF1. Typically, AF4 has the highest weight of the four and AF1 the lowest. The Assured and Low-1 classes are differentiated based on the default DSCP mappings. All DSCP and EXP mappings can be modified by the user.