Transition Networks
S4224 Web User Guide
33558 Rev. C
Page 332 of 669
DSCP-Based QoS
The S4224 DSCP-based QoS Ingress Classification page is available from the
Configuration
>
QoS
>
DSCP-Based QoS
menu path. DSCP (Differentiated Services Code Point) is a field in the header of IP
packets for packet classification purposes.
DSCP Traffic class (IP priority)
: If the ingress frame is an IP packet, then the priority is decided by the
IP DSCP bits. This priority is used for all frames processing inside the device. Each of the 64 traffic
classes can be marked as trusted or untrusted and the QoS Class and Drop priority level can be
assigned.
This page lets you configure all of the S4224 QoS DSCP-based QoS Ingress Classification settings.
The displayed settings are explained below.
DSCP
The DiffServ standards define 64 DSCP values. Some of them are recommended for marking
particular classes of QoS services (e.g. a value of 46 is usually recommended for real-time traffic with
the strictest latency requirements).
Per the MEF, DiffServ defines several per-hop behaviors (PHBs) that provide robust QoS capabilities
compared to other methods. DiffServ provides 64 different values called DiffServ Code Points, or
DSCPs, that are used to determine the Class of Service (CoS). EF (Expedited Forwarding) for low
delay / low loss service, AF Assured Forwarding) in four classes for bursty real time and non-real time
services, CS (Class Selector) for partial backward compatibility with IP TOS, and DF (Default
Forwarding) for best effort services.
The maximum number of supported DSCP values is 64. In the DSCP column, the DSCP Name can
be
BE
,
CSx
,
EFx
, or
AFx
where:
AF
refers to Assured Forwarding is provided in four classes for bursty real time and non-real time
services.
BE
: refers to Standard (Best Effort) forwarding.
CS
refers to the Class Selector (per
).
EF
refers to the Expedited Forwarding (
). The EF PHB has the characteristics of low
delay, low loss and low jitter. These characteristics are suitable for voice, video and other real-
time services.