3Com 4007, Руководство по внедрению, Страница: 569 / 684

Key Concepts 569
The IEEE 802.1p standard addresses separate queuing of time-critical
frames to reduce the jitter that is caused by multicast flooding. This
standard also defines the Generic Attribute Registration Protocol (GARP),
a Layer 2 transport mechanism that allows switches and end systems to
propagate information across the switching domain.
Resource Reservation Protocol (RSVP)
This connection-oriented IP protocol handles bandwidth reservation. The
request for comments document, RFC 2205, describes the details of
RSVP.
RSVP aims to meet the demands of real-time voice and video applications
with its QoS flow specification, which mandates parameters such as the
maximum frame transmission rate, long-term average frame transmission
rate, maximum frame jitter, and maximum end-to-end delay. RSVP
supports the QoS flow specifications by managing
resource reservations
across the network.
With RSVP, all devices in the path from the source to the destination must
agree to observe the RSVP call request parameters before traffic can flow.
Terminology The following terms apply to QoS:
■
Classifiers — Two types of classifiers define how your Multilayer
Switching Module groups packets in order to schedule them with the
appropriate service level:
■
Flow classifiers — Apply to routed IP unicast and IP multicast
traffic only, not bridged traffic. (When the Multilayer Switching
Module is bridging, you cannot classify to the IP address or socket
level.) These classifiers are numbered in a range of from
1 through 399. To define filtering parameters for a flow classifier,
set the source IP address, source IP address mask, the destination IP
address, destination IP address mask, and the TCP or UDP source
and destination port range. Because these classifiers have lower
class numbers, they take precedence over nonflow classifiers.
When a packet falls into more than one controlled classifier, the
Multilayer Switching Module uses the lower-numbered classifier to
classify the packet. A Multilayer Switching Module predefines two
flow classifiers for you: Telnet and FTP.