Queue Scheduling - HP 1920 Gigabit Ethernet Switch Series User Manual

Figure 457 802.1Q tag header
Byte 1
TPID (Tag protocol identifier)
1 0 0 0 0 0 0 1 0 0 0 0 0 0 0
7 6 5 4 3 2 1 0 7
Table 147 Description on 802.1p priority
802.1p priority (decimal)
0
1
2
3
4
5
6
7

Queue scheduling

In general, congestion management uses queuing technology. The system uses a certain queuing
algorithm for traffic classification, and then uses a certain precedence algorithm to send the traffic. Each
queuing algorithm handles a particular network traffic problem and has significant impacts on
bandwidth resource assignment, delay, and jitter.
In this section, two common hardware queue scheduling algorithms Strict Priority (SP) queuing and
Weighted Round Robin (WRR) queuing are introduced.
SP queuing
SP queuing is designed for mission-critical applications, which require preferential service to reduce
response delay when congestion occurs.
Byte 2
0 Priority
6 5 4 3 2 1 0 7 6
802.1p priority (binary)
000
001
010
011
100
101
110
111
471
Byte 3
TCI (Tag control information)
CFI
VLAN ID
5 4 3 2 1 0 7 6 5 4 3 2 1 0
Description
best-effort
background
spare
excellent-effort
controlled-load
video
voice
network-management
Byte 4