H3C S3610-28P, Руководство по эксплуатации, Страница: 1072 / 1547

Operation Manual – QoS
H3C S3610&S5510 Series Ethernet Switches Chapter 2 Traffic Classification, TP, and TS
Configuration
2-4
2) 802.1p priority
802.1p priority lies in Layer 2 packet headers and is applicable to occasions where the
Layer 3 packet header does not need analysis but QoS must be assured at Layer 2.
Figure 2-2 An Ethernet frame with an 802.1Q tag header
As shown in the figure above, the 4-byte 802.1Q tag header contains a 2-byte Tag
Protocol Identifier (TPID) whose value is 8100 and a 2-byte Tag Control Information
(TCI). TPID is a new class defined by IEEE to indicate a packet with an 802.1Q tag.
Figure 2-3 describes the detailed contents of an 802.1Q tag header.
Figure 2-3 802.1Q tag headers
In the figure above, the 3-bit priority field in TCI is 802.1p priority in the range of 0 to 7.
In the figure above, the priority field (three bits in length) in TCI is 802.1p priority (also
known as CoS precedence), which ranges from 0 to 7.
Table 2-3 Description on 802.1p priority
802.1p priority (decimal) 802.1p priority (binary) Description
0 000 best-effort
1 001 background
2 010 spare
3 011 excellent-effort
4 100 controlled-load
5 101 video
6 110 voice