DragonWave Inc. 34
Horizon Compact Release 1.01.00 Wireless Ethernet Product User Manual – Volume 2
level, then no delay should occur. This technique prevents out of order packets over the Horizon Compact
system.
For example: QUEUE 3 has 25% CIR or 25 Mbps on a 100 Mbps link. The CoS Queue CBS is set to
25% or 25 Mbits. If Queue 3 receives a burst of traffic in excess of 25 Mbps then QUEUE 3 would
continue to transmit at 25 Mbps until the 25 Mbit “burst buffer” is empty, regardless of whether or not the
the traffic source is sending packets. If the traffic source continues to send packets then the original 25
Mbps is transmitted, followed by the “burst buffer” traffic, followed by new incoming packets.
3.3.4 Expedite Queuing
Expedite Queuing is a mechanism that allows one or more of the 4 Queues to transmit its data as priority
traffic, at the expense of the remaining Queues. When Expedite Queue feature is enabled, then as long
as there is data in the Expedite Queue, or Queues, that data will be transmitted first. This allows time
critical, or error-sensitive, traffic to have priority data delivery.
The Horizon Compact system allows the user to configure one or more Queues as “expedite” Queues.
Any or all of the 4 Queues can be made into Expedite Queues. This allows custom configurations such
as QUEUE 4 = Voice, QUEUE 3 = Video over IP, QUEUE 2 = database transfers, QUEUE 1 = Internet
email, Web, etc. The Scheduler continues to service QUEUE 4 through QUEUE 1 in order, however
when a Queue is set as an Expedite Queue it will service the Expedite Queue first and continue to service
it until it is empty. After the Expedite Queue has been flushed of data, the Scheduler will continue to
service the other Queues according to its main algorithm.
To configure a Queue to be an Expedite Queue (once the “set Expedite Queue on” command has been
issued”) assign the CIR for that Queue to 100%. Each of the 4 Queues can be assigned a CIR of 100%.
The total CIR can now be greater than 100%, up to a maximum of 400% (4 Queues). A total CIR of
400% means ALL 4 Queues are Expedite Queues and each one can use 100% of the bandwidth. It
does not mean the Horizon Compact system can achieve 400% of the Horizon Compact maximum
bandwidth, simply that if any bandwidth is available after a previous Queue has been serviced, the
next Queue in line will be given full access to the remaining bandwidth until fully serviced. IF
Expedite Queuing is turned OFF, then the total CIR cannot exceed 100%.
As network services increase, the need for multiple Expedite Queues becomes evident. A network
administrator may require 3 Expedite Queues and decide to send all network routing protocols through
the highest Expedite Queue, send IP Voice through the next highest Expedite Queue, send Video over IP
through the next highest Expedite Queue. Send all other traffic to the remaining Queue, which is not
configured as an Expedite Queue. To do this, the administrator would configure Queues 4,3 and 2 as
Expedite Queues and configure Queue 1 as a standard Queue with a particular CIR.
3.3.5 Operation of QoS using multiple Expedite Queues
When multiple Expedite Queues are enabled, the Scheduler will continue to follow in the same
sequence/rules as the previous release.
The sequence is:
• Service QUEUE 4
• Recheck QUEUE 4 and if empty, service QUEUE 3
• Recheck QUEUE 4 and if empty, check QUEUE 3 and if empty, service QUEUE 2
• Recheck QUEUE 4 and if empty, check QUEUE 3 and if empty, check QUEUE 2 and if
empty, service QUEUE 1
Each Queue having 100% CIR (priority) will be serviced until empty, then the Scheduler moves on to the
next priority Queue. The effect of setting a Queue as an Expedite Queue is to override the Scheduler’s
sequence and force it to service the Expedite Queue first and continue to service it until empty. Any
Queue can be configured as an Expedite Queue and therefore override the Scheduler’s sequence. For
example: if Queue 1 is set as the only Expedite Queue then QUEUE 1 will be serviced first, followed by
Queue 4 then Queue 3 then Queue 2. At any time, should data arrive in Queue 1, then the Scheduler will
“jump” to Queue 1 in order to service it.
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