3Com 4007, Implementation Manual, Page: 571 / 684

Key Concepts 571
Drop causes the Multilayer Switching Module to drop all packets on all
ports that are associated with the control and its classifier. To drop
conforming packets for only a subset of ports, specify the receivePort or
aggregate rate limit, set the rate limit to 0, and specify the group of
ports.
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Loss-eligible status — Loss-eligible packets are conforming
packets that are discarded instead of queued when transmit
queues back up beyond a threshold. You can specify whether
conforming packets (as well as nonconforming excess packets) are
loss eligible when you define a control. Marking packets as loss
eligible helps create an intelligent discard of traffic in a congestion
situation. When the Multilayer Switching Module is congested, you
can decide which traffic can be discarded and mark that traffic as
loss eligible.
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Burst size — The maximum amount of data that you can transmit
at the line rate before the transmission is policed. This value
accommodates variations in speeds and allows you to occasionally
exceed the configured rate.
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TCP drop control — TCP drop control allows you to create QoS
Flow Classifiers that allow traffic going from source IP addresses to
destination IP addresses to be dropped or otherwise controlled
using one-way TCP flow filtering. This control can only be used for
flow classifiers that use the TCP/IP protocol.
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Timer option — The QoS Timer option allows you to configure a
QoS session to take effect during a predefined time period by
setting the start and end times for the specific control.
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IEEE 802.1Q priority tag — When you define a control for a
classifier, you can select an IEEE 802.1p priority tag value to insert
into forwarded frames. Verify that this priority tag is applied to
ports that are configured for IEEE 802.1Q tagging.
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QoS bandwidth — Specifies the weighting of the high-priority and
best-effort transmit queues. The bandwidth for the control queue is
set by means of RSVP. By default, 75 percent of the bandwidth is used
for high-priority traffic and 25 percent is used for best-effort packets.
(That is, three high-priority packets are sent for each best effort
packet). Low-priority packets have no bandwidth allocated.