Extreme Networks Summit Summit24, Инструкция по установке и эксплуатации

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140 Summit24e3 Switch Installation and User Guide
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 Summit24e3 switch.
Figure 25 shows the encapsulation of an IP packet header.
Figure 25: IP packet header encapsulation
Table 36 lists the commands used to configure DiffServ. Some of the commands are described in more
detail in the following paragraphs.
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.
Viewing DiffServ information can be enabled or disabled; by default it is disabled. To view DiffServ
information, use the following command:
Table 36: DiffServ Configuration Commands
Command Description
disable diffserv examination ports [<portlist> |
all] Disables the examination of the diffserv field in
an IP packet.
enable diffserv examination ports [<portlist> |
all] 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.
EW_023
Type-of-service
DiffServ code point
IHL
Data (variable)
0 bits 31
Options (+ padding)
Destination address
Source address
0 7 6 5 4 3 2 1
Total length Version
Protocol Time-to-live Header checksum
Flags Identification Fragment offset