Quality of Service
ExtremeWare XOS 11.3 Concepts Guide
300
Configuring DiffServ
Contained in the header of every IP packet is a field for IP Type of Service (TOS), now also called the
Differentiated Services (DiffServ) field. The DiffServ field is used by the switch to determine the type of
service provided to the packet.
Figure 15 shows the encapsulation of an IP packet header.
Figure 15: IP packet header encapsulation
Observing DiffServ code points as a traffic grouping mechanism for defining QoS policies and
overwriting the Diffserv code point fields are supported.
This section covers the following sections:
â—Ź DiffServ information on the BlackDiamond 10K only
â—Ź Observing DiffServ information
â—Ź Changing DiffServ code point (DSCP) mapping
â—Ź Replacing DSCP information
DiffServ information on the BlackDiamond 10K only. The default VLAN DiffServ examination mappings
apply on ports in more than one VR. If you attempt to configure examining or replacing DiffServ
information on a port that is in more than one virtual router, the system returns the following message:
Warning: Port belongs to more than one VR. Port properties related to diff serv and
code replacement will not take effect.
EW_023
Type-of-service
DiffServ code point
IHL
Data (variable)
0 bits 31
Options (+ padding)
Destination address
Source address
07654321
Total lengthVersion
ProtocolTime-to-live
Header checksum
FlagsIdentification Fragment offset
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