IronPort Systems ES-1528 - Manual (Page 75)

Chapter 11 QoS
ES-1528 User’s Guide
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11.4.2 DSCP Based QoS
The switch allows you to create a mapping table between Differentiated Services Code Points
(DSCPs) tags and IEEE 802.1p priority tags.
11.4.3 Differentiated Services Code Point (DSCP) Overview
Differentiated Services (DiffServ) is a class of service (CoS) model that marks packets so that
they receive specific per-hop treatment at DiffServ-compliant network devices along the route
based on the application types and traffic flow. Packets are marked with DiffServ Code Points
(DSCPs) indicating the level of service desired. This allows the intermediary DiffServ-
compliant network devices to handle the packets differently depending on the code points
without the need to negotiate paths or remember state information for every flow. In addition,
applications do not have to request a particular service or give advanced notice of where the
traffic is going.
DiffServ defines a new DS (Differentiated Services) field to replace the Type of Service (ToS)
field in the IP header. The DS field contains a 2-bit unused field and a 6-bit DSCP field which
can define up to 64 service levels.
You can configure the DSCP to IEEE 802.1p mapping to allow the switch to prioritize all
traffic based on the incoming DSCP value according to the DiffServ to IEEE 802.1p mapping
table.
11.4.4 DSCP Based QoS Screen
You can configure the switch to assign a IEEE 802.1p priority to packets coming into the
switch with DSCPs assigned to them. Select DSCP Based QoS in the QoS Enhancement
Setting screen to view the following screen.
Port,
Priority
This is a summary table of your port to IEEE 802.1p priority mappings. The Port column
indicates the port number of the incoming packets and the Priority column indicates
what IEEE 802.1p priority gets assigned to those packets.
Apply
Change
Settings
Click this when you have reviewed the changes you want to make and you want to save
them to the switch’s memory.
Table 18 Port Based QoS (continued)
LABEL DESCRIPTION