Differentiated Services Code Point (Dscp)-Based Qos - NETGEAR GS748TNA Software User Manual

2. From each 802.1p priority value pull-down menu, select one of the four hardware priority
queues.
3. Click Apply.

Differentiated Services Code Point (DSCP)-based QoS

The 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. DSCPs 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.
The DSCP to Priority Mapping table contains fields for mapping DSCP values to the eight 802.1p
priority values. For the DSCP QoS to work properly, make sure that the priority values are
correctly mapped to the appropriate hardware queues.
To map DSCP values to 802.1p priorities:
1. Select QoS > Advanced > DSCP Priority Mapping from the main menu. The DSCP to Priority
Mapping screen will display.
2. Select one of the eight priority values for each DSCP value.
• 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.
3. Click Apply.
Configuring the Switch
Smart Switch Software User Manual GS748T
v1.0, October 2007
4-19