TEG1210P 10-Port Gigabit Intelligent PoE Switch User Guide
The figure below displays the detailed content of a 802.1Q tag header. The priority field in
TCI indicates 802.1p priority, namely, CoS priority which consists of 3 bits and has a
value range of 0
～
7.
802.1Q Tag Header
3. DSCP Priority
DSCP priority resides in an IP packet header where TOS field includes 8 bits:
The first 3 bits indicate IP priority with a value range of 0
～
7
；
The middle 4 bits ( bit-3 to bit-6) indicate TOS priority with a value range of 0
～
15
；
RFC2474 redefines the TOS field in IP packet header as DS field. The DSCP
（
Differentiated Services Codepoint
）
priority is thus denoted by the first 6 bits
（
0
～
5bits
）
in this field with a value range of 0
～
63 and the last 2 bits
（
bit 6 and bit 7
）
are reserved.
DS Field and TOS Byte
¾
SNMP
1. Overview of SNMP
SNMP
（
Simple Network Management Protocol
）
is used to guarantee that management
information is transmitted between any two nodes in a network so as to make it more
convenient for network administrators to retrieve/ modify information, locate and
diagnosticate malfunction, plan out capacity as well as generate reports in any nodes on
a network.
It adopts poll scheme and provides basic functions, thus specially adapting to the
application in small-sized, fast and low-cost network environment. It is implemented
based on unconnected transport layer protocol UDP,thus enabling access to multiple
devices without difficulties.
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