74
QoS/DSCP (the DiffServ model)
DSCP-ECN defines QoS at Layer 3 (Network Layer). The Differentiated Services (DiffServ) model is
based on packet marking and router queuing disciplines. The marking is done by adding a field to the
IP header, called the DSCP (Differentiated Services Codepoint). This is a 6-bit field that provides 64
different class IDs. It gives an indication of how a given packet is to be forwarded, known as the Per Hop
Behavior (PHB). The PHB describes a particular service level in terms of bandwidth, queueing theory,
and dropping (discarding the packet) decisions. Routers at each network node classify packets according
to their DSCP value and give them a particular forwarding treatment; for example, how much bandwidth
to reserve for it.
Below are the setting options of DSCP (DiffServ Codepoint). Specify the DSCP value for each application
(0~63).
