Configuring Diffserv - Extreme Networks Summit 200-24 Installation And User Manual

Quality of Service (QoS)

Configuring DiffServ

Contained in the header of every IP packet is a field for IP Type of Service (TOS), now also called the
DiffServ field. The TOS field is used by the switch to determine the type of service provided to the
packet.
Observing DiffServ code points as a traffic grouping mechanism for defining QoS policies and
overwriting the Diffserv code point fields are supported in the Summit 200 series switch.
Figure 29 shows the encapsulation of an IP packet header.
Figure 29: IP packet header encapsulation
0 bits
Version IHL
Identification
Time-to-live
Table 41 lists the commands used to configure DiffServ. Some of the commands are described in more
detail in the following paragraphs.
Table 41: DiffServ Configuration Commands
Command
disable diffserv examination ports [<portlist> |
all]
enable diffserv examination ports [<portlist> |
all]
Observing DiffServ Information
When a packet arrives at the switch on an ingress port, the switch examines the first six of eight TOS
bits, called the code point. The switch can assign the QoS profile used to subsequently transmit the
packet based on the code point. The QoS profile controls a hardware queue used when transmitting the
packet out of the switch, and determines the forwarding characteristics of a particular code point.
150
0 1 2 3
DiffServ code point
Type-of-service
Flags
Protocol Header checksum
Source address
Destination address
Options (+ padding)
Data (variable)
Description
Disables the examination of the diffserv field in
an IP packet.
Enables the diffserv field of an ingress IP packet
to be examined by the switch in order to select a
QoS profile. The default setting is disabled.
4 5 6 7
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Total length
Fragment offset
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Summit 200 Series Switch Installation and User Guide