User guide

180 CHAPTER 8: PRIORITIZING NETWORK TRAFFIC
Useful Information
and References
The following section provides useful information and references when
using the Prioritizing Network Traffic feature of 3Com Network
Administrator.
User Priority Field The user priority field (and the tagged header that it is present in) allows
information about the priority level of a packet to be carried with the
packet as it traverses the network. The field is defined with the IEEE
(Institute of Electrical and Electronics Engineers) 802.1D standard, which
is available from the IEEE website:
http://www.ieee.org/
This standard defines the use of the eight values that the field may take.
These definitions are shown in Tab le 17
.
Table 17 User Priority
As the table shows, the default value is 0. This allows some traffic to be
marked as less important than normal traffic.
The tagged header that the user priority field relies upon can be used in
any packet in place of the normal 802.1D header. However, the tagged
header is only normally used for packets if VLANs are being used within
the network. This means that if VLANs are not being used then the
information about the importance of traffic cannot be conveyed from a
complex classification device to a simple classification device using this
marking mechanism.
User Priority Use
1 Background
2 Spare
0 (Default) Best Effort
3 Excellent Effort
4 Controlled Load
5 “Video,” < 100 ms latency and jitter
6 “Voice,” < 10 ms latency and jitter
7 Network Control
3Com Network Administrator for HP OpenView.book Page 180 Wednesday, November 12, 2003 2:33 PM