Port Traffic Controls

Guaranteed Minimum Bandwidth (GMB)

Notes: Configuring 0% for a queue can result in that queue being starved if any higher queue becomes over­ subscribed and is then given all unused bandwidth. The switch applies the bandwidth calculation to the link speed the port is currently using. For example, if a 10/100 Mbs port negotiates to 10 Mbps on the link, then it bases its GMB calculations on 10 Mbps; not 100 Mbps.

Use show bandwidth output < port-list> to display the current GMB configuration. (The show config and show running commands do not include GMB configuration data.)

For example, suppose you wanted to configure the following outbound mini­ mum bandwidth availability for ports A1 and A2:

Priority of

Minimum

Effect on Outbound Bandwidth Allocation

Outbound

Bandwidth

 

Port Queue

%

 

8

20

Queue 8 has the first priority use of all outbound bandwidth not

 

 

specifically allocated to queues 1 - 7. If, for example, bandwidth

 

 

allocated to queue 5 is not being used and queues 7 and 8 become

 

 

oversubscribed, queue 8 has first-priority use of the unused

 

 

bandwidth allocated to queue 5.

7

15

Queue 7 has a guaranteed minimum bandwidth of15% available

 

 

for outbound traffic. If queue 7 becomes oversubscribed and

 

 

queue 8 is not already using all of the unallocated bandwidth, then

 

 

queue 7 can use the unallocated bandwidth. Also, any unused

 

 

bandwidth allocated to queues 6 to queue 1 is available to queue

 

 

7 if queue 8 has not already claimed it.

6

10

Queue 6 has a guaranteed minimum bandwidth of 10% and, if

 

 

oversubscribed, is subordinate to queues 8 and 7 in priority for

 

 

any unused outbound bandwidth available on the port.

5

10

Queue 5 has a guaranteed minimum bandwidth of 10% and, if

 

 

oversubscribed, is subordinate to queues 8, 7, and 6 for any

 

 

unused outbound bandwidth available on the port.

410% Queue 4 has a guaranteed minimum bandwidth of 10% and, if oversubscribed, is subordinate to queues, 8, 7, 6, and 5 for any unused outbound bandwidth available on the port.

330% Queue 3 has a guaranteed minimum bandwidth of 30% and, if oversubscribed, is subordinate to queues, 8, 7, 6, 5, and 4 for any unused outbound bandwidth available on the port.

23% Queue 2 has a guaranteed minimum bandwidth of 3% and, if oversubscribed, is subordinate to queues, 8, 7, 6, 5, 4, and 3 for any unused outbound bandwidth available on the port.

12% Queue 1 has a guaranteed minimum bandwidth of 2% and, if oversubscribed, is subordinate to all the other queues for any unused outbound bandwidth available on the port.

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