77
802.1p priority
802.1p priority lies in the Layer 2 header. It applies to occasions where Layer 3 header analysis is not
needed and QoS must be assured at Layer 2.
Figure 24 An Ethernet frame with an 802.1Q tag header
As shown in
, the 4-byte 802.1Q tag header contains the 2-byte tag protocol identifier (TPID)
and the 2-byte tag control information (TCI). The value of the TPID is 0x8100.
shows the
format of the 802.1Q tag header. The Priority field in the 802.1Q tag header is called 802.1p priority,
because its use is defined in IEEE 802.1p.
shows the values for 802.1p priority.
Figure 25 802.1Q tag header
Table 8 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
7 111
network-management
EXP values
The EXP field is in MPLS labels for MPLS QoS purposes. As shown in
, the EXP field is
3-bit long and is in the range of 0 to 7.
Summary of Contents for FlexFabric 5940 Series
Page 23: ...17 Figure 3 QoS processing flow ...
Page 84: ...78 Figure 26 MPLS label structure ...
Page 91: ...85 Switch burst mode enable ...