IronPort Systems ES-1528 User Manual

 Chapter 11 QoS

ES-1528 User’s Guide

The switch allows you to create a mapping table between Differentiated Services Code Points 
(DSCPs) tags and IEEE 802.1p priority tags.

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.  

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)