H3C S7500 Series Operation Manual page 691

Operation Manual – QoS
H3C S7500 Series Ethernet Switches
af23
af31
af32
af33
af41
af42
af43
cs1
cs2
cs3
cs4
cs5
cs6
cs7
default (be)
2) 802.1p priority
802.1p priority lies in a layer 2 frame headers and is applicable to occasions where
layer 3 packet headers do not need analysis but QoS must be assured at layer 2.
Destination
Address
6 bytes
Figure 1-2 An Ethernet frame with a 802.1Q tag heade
As shown in
header after the source address field of the former Ethernet frame header when
sending packets.
The 4-bit 802.1Q tag header contains a 2-bit tag protocol identifier (TPID) whose value
is 8100 and a 2-bit tag control information (TCI). TPID is a new class defined by IEEE to
identify a frame with an 802.1Q tag.
802.1Q tag header.
Keyword
22
26
28
30
34
36
38
8
16
24
32
40
48
56
0
802.1Q
header
Source
Address
TPID
6 bytes 4 bytes
Figure 1-2, each host supporting 802.1Q protocol adds a 4-bit 802.1Q tag
DSCP precedence
(decimal)
Length/Type
TCI
2 bytes
Figure 1-3 describes the detailed contents of an
1-4
Chapter 1 QoS Configuration
DSCP precedence
(binary)
010110
011010
011100
011110
100010
100100
100110
001000
010000
011000
100000
101000
110000
111000
000000
Data
(CRC - 32)
46~1500 bytes 4 bytes
r
FCS