Interlogix GE-DS-242-PoE, User Manual

Page: 110 / 218

Chapter 4: Web-Based Management
106 GE-DS-242-PoE Managed Ethernet Switch User Manual
DiffServ Code Point (DSCP) - is the traffic prioritization bits within an IP header
that are encoded by certain applications and/or devices to indicate the level of
service required by the packet across a network. DSCP are defined in RFC2597
for classifying traffic into different service classes. The Managed Switch extracts
the codepoint value of the DS field from IPv4 packets and identifies the priority of
the incoming IP packets based on the configured priority.
4 bit 4 bit 6 bit 2 bit
VER=0100
Header
Size
DiffServ
RES
Preamble
Destination
Address
Source
Address
VLAN
TAG
(Optional)
Ethernet
Type
(0800)
Data FCS
6 bytes 6 bytes 4 bytes 2 bytes 2 bytes 46-1517 bytes 4 bytes
The DSCP is six bits wide, allowing coding for up to 64 different forwarding
behaviors. The DSCP retains backward compatibility with the three precedence
bits so that non-DSCP compliant, TOS-enabled devices, will not conflict with the
DSCP mapping. Based on network policies, different kinds of traffic can be
marked for different kinds of forwarding.
TOS/DSCP Configuration
The TOS/DSCP page provides fields for defining output queue to specific DSCP
fields. When TCP/IP's TOS/DSCP mode is applied, the Managed Switch
recognizes TCP/IP Differentiated Service Codepoint (DSCP) priority information
from the DS-field defined in RFC2474.
Enable TOS/DSCP for traffic classification and then the DSCP to priority
mapping column is configurable, as Figure 4-8 shows: