User manual

66D-Link DSL-500B User Manual
Web Conguration
QoS-DSCP Setting
In order to understand what is differentiated services code point (DSCP), you should be familiar with the differen-
tiated services model (Diffserv).
Diffserv is a class of service (CoS) model that enhances best-effort Internet services via differentiating trafc by
users, service requirements and other criteria. Packets are specically marked, allowing network nodes to provide
different levels of service via priority queuing or bandwidth allocation, or by choosing dedicated routes for specic
trafc ows.
As displayed in following diagram, the IPV4 packet has a TOS led. Diffserv denes TOS eld in IP packet headers
referred to as DSCP. Hosts or routes that pass trafc to a Diffserv-enabled network typically mark each trans-
mitted packet with an appropriate DSCP. The DSCP markings are used by Diffserv network routers to appropriately
classify packets and to apply particular queue handing or scheduling behavior.
Layer 3 IPV4 Packet
Version/
Length
TOS
(1 Word)
Length ID Offset/
Mark
TTL Protocol Checksum IP-SA IP-DA Data
TOS Filed-IP priority (TOS front 3 bit) or DSCP (front 6 bit)
7 6 5 4 3 2 1 0
IP Priority Undened
DSCP Flow Control