3Com 4007, Руководство по внедрению, Страница: 568 / 684

568 C
HAPTER
22: Q
O
S
AND
RSVP
If you use QoS with RSVP, you are opting for a more complex type of
end-to-end QoS that aims for a
guaranteed quality of service. To use
RSVP, you must be routing. In addition, RSVP is required at the desktop,
which may present issues of desktop control and upgrade issues
concerning the resident operating-system and applications.
Key Concepts
Before you configure QoS, review the following standards and terms.
Related Standards
and Protocols
The Switch 4007 Multilayer Switching Modules support IEEE 802.1Q, IEEE
802.1p, and the RSVP protocol.
IEEE 802.1p
This finalized standard, part of IEEE 802.1D, covers traffic class and
dynamic multicast filtering services in bridged LANs. It uses the same tag
format as the proposed IEEE 802.1Q standard, but it uses three additional
bits of the tag control information to set a user priority level (for
policy-based services such as QoS). You can classify traffic using a specific
IEEE 802.1p priority tag value (or several tag values). You can also define a
control that inserts a priority tag value in forwarded frames.
The IEEE 802.1p priority tag values are 0 through 7. Table 92 shows the
IEEE 802.1p (user-priority) values and the corresponding traffic types. The
value 7 (Network Control) is the highest priority and 1 (Background
Traffic) is the lowest priority. The value 0 (the default, Best Effort) has a
higher priority than value 2 (Standard).
Table 92 IEEE 802.1p User Priority Tag Values
Tag Value Traffic Type
1 Background
2 Standard (spare)
0 (the default) Best Effort
3 Excellent Effort (Business Critical)
4 Controlled Load (Streaming Multimedia)
5 Video (Interactive Media), less than 100 milliseconds latency and
jitter
6 Voice (Interactive Voice), less than 10 milliseconds latency and jitter
7 Network Control (Reserved Traffic)