3Com CoreBuilder 3500, Implementation Manual, Page: 513 / 592

Transmit Queues and QoS Bandwidth 513
The accompanying control definition:
Transmit Queues
and QoS Bandwidth
QoS uses four transmit queues:
■
Control queue
— The transmit queue for reserved network control
traffic, such as RIP or OSPF updates, as well as RSVP data flows. This
queue is always serviced first. Bandwidth for this queue is set via RSVP.
■
High priority queue — The transmit queue with the second highest
priority. You can map classifiers directly to this queue.
■
Best effort queue — The transmit queue used by default for all
traffic except reserved traffic.
■
Low priority queue — The transmit queue with the lowest priority.
All traffic assigned to this queue is forwarded only if there is
bandwidth still available after the other queues are serviced. Low
priority packets do not have bandwidth allocated.
You can configure the weighting of the high priority and best effort
transmit queues by using the option to modify QoS bandwidth. By
default, the weighting of the queues is 75 percent high priority traffic and
25 percent best effort traffic. Keep in mind that the weighting does not
represent guaranteed output bandwidth for these queues, since they are
serviced in relative percentages after the control queue is serviced.
Control Field Definition
Control Number 5
Control Name VideoServer1
Rate Limit Type receivePort
Service Level high
Loss Eligible Status no
Excess Service Level low
Excess Loss Eligible Status yes
Representation of Rate Limit Kbytes/sec
Rate Limit Value 1024
Burst Size 128
Bridge Ports all (1 to 19)
802.1p tag for forwarded frames 4
Classifiers controlled 25