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Queuing on serial interfaces

I have been working on tracking down high utilization on my factional T1s that interconnect my facilities. I have noticed that some locations are using fair-queue and some are using fifo. Advantages of one over the other? Would things such as Exchange attachments be interfearing with my telnet sessions if locations are utilizing fifo?


Re: Queuing on serial interfaces

Even though fifo is simple and fast, it can causes starvation, delay and jitter.

Where as fair-queue allocated bandwidth among all flows and ensures that queues do not starve for bandwidth,Low-volume traffic streams, which make up most of the traffic, receive preferential service. High-volume traffic streams proportionally share the remaining capacity.

Yes there is a chance for interfering with telnet seesions when using fifo.

Re: Queuing on serial interfaces


The basic difference between WFQ and FIFO is WFQ does the classification based on the flows.

Flows basically can be defined as the packets having same source/destination address as well as adderssed to same ports on both the ends.

With FIFO its just the first come first serve basis whatever packet arrives on the first instance it will be forwarded.

By default its WFQ(fair-queue) which is enabled on the interfaces you can disable and enable FIFO using no fair-queue.

I would suggest to have some kinda uniformity here in configuring either FIFO or WFQ in you network.

Also would suggest to check something inline with CBWFQ in which you can configure different class of services and bandwidth guranteed configured to it.

So that as you said your telnet packets may not get backlogged or else if you are concerned only with your telnet session then you can deploy out a priority list prioritizing the telnet packets.


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