3Com 4007, Руководство по внедрению, Страница: 570 / 684

570 C
HAPTER
22: Q
O
S
AND
RSVP
■
Nonflow classifiers — Apply to both switched and routed traffic.
You define this type of classifier to handle specific link-level
protocols
(IP, TCP/IP , IPX, or AppleTalk) , a cast type (broadcast,
unicast, or multicast) , and one or more IEEE 802.1p priority tag
values . Nonflow classifiers are numbered in a range of from 400
through 499. The Multilayer Switching Module automatically
defines a number of nonflow classifiers for you. The predefined
nonflow classifiers
(401 through 407) employ IEEE 802.1p tagging
by default for received frames.
You can configure QoS nonflow classifiers to prioritize or filter
based on IP, IPX, and AppleTalk protocols; Ethertype values; or
DSAP/SSAP values.
You can also specify starting and ending ranges for source and
destination ports when you define classifiers using TCP and UDP
protocols. Specifying a small port range lets you limit the amount
of classified traffic on the system. These port range choices are
shown in the
qos detail
display.
■
Controls
—
Define the following parameters to assign rate limits and
priorities to the packets that are associated with one or more
classifiers:
■
Rate limit — Limits the amount of input bandwidth used by
incoming classified traffic (optionally, on a per-port basis). When
you define a control, you can specify one of three rate limits:
none
(no rate limit),
receivePort
(a separate limit on each specified
receive port), or
aggregate
(limits on groups of receive ports).
■
Service levels — Specify a transmit priority and map to a specific
transmit queue. If you specify
receivePort
or
aggregate
for a
rate limit, you can assign a service level of
high
,
best
, or
low
both
to conforming packets (packets that are below the rate-limit
parameters) and to nonconforming excess packets (excess packets
that exceed the rate-limit parameters). If you set the rate limit to
none
, you can specify a service level of
high
,
best
,
low
, or
drop
for
conforming classified packets.
■
Time of day controls — A QoS timer option enables you to
configure a QoS control session. You set a start time and an end
time for the specific control. After it is set, the control that is
associated with this time setting becomes active if the current time
is within the range of start and end time. You can preset a time
period to activate the control.