NETGEAR GS748TNA, GS748TS-100NAS user manual Differentiated Services Code Point DSCP-based QoS

GS748T Software User Manual

Differentiated Services Code Point (DSCP)-based QoS

The Differentiated Services Code Point (DSCP) 6-bit field in an IP packet header enables levels of service to be assigned to network traffic according to the field’s binary value. This 6-bit field comprises three IP Precedence MSBs with a least-significant 3-bit expansion field as defined in RFC 2474. The IP Precedence bits in the DSCP field are compatible with routers that only support IP Precedence. DCSPs specifically tailored to be backward compatible with routers that only support IP precedence lack the 3-bit expansion field and are called Class-selector DSCPs. See the following diagram for the setting page for DCCP priorities.

Figure 4-10

Match these DHCP values to set “Per Hop Behavior” (PHB) priorities by selecting a QoS service- class value of between 0 and 7. Packets within these service classes are treated with equal priority.

RFC 2597 defines the assured forwarding (AF) PHB. It guarantees a certain amount of bandwidth to an AF class.

The Expedited Forwarding (EF) PHB is defined in RFC 2598 and uses Codepoint 101110. The EF PHB is used to build a low loss, low latency, low jitter, assured bandwidth service. This premium service can appear to the user be a point to point connection.

4-6 Configuring the Switch

v2.0, April 2007