Joseph W. Doherty Tue, 01/22/2008 - 16:00
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Usually serial ports faster than T1/E1 default to FIFO. Hold queue out will set the FIFO queue size. In theory, queue depth should be large enough to accommodate the bandwidth delay product to allow TCP to fully ramp up.


You can also adjust the size of the ingress queue with the hold queue in. It's unusual to need to adjust the inbound queue size.

Tshi M Tue, 01/22/2008 - 16:41
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So it is default to FIFO, why have it in the config? Is configuring it disable the default FIFO? Is there any gain configuring it? First time I see it being used. The serial interface show some errors and I was wondering if that settings could have been the problem? Also users complain about slow performance over the DS3? I basically want to remove those lines.

Joseph W. Doherty Tue, 01/22/2008 - 19:30
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Why in the config? One guess would be someone saw taildrops and was trying to preclude them.


Does changing it disable the default FIFO? The default queue size, yes.


Any gain configuring it? Could be, can also work against you. Much depends on what your goal is, the kind of traffic flowing across the link, distance based latency, etc.


re: showing some errors - if you're referring to hardware errors, not likely.


re: slow performance - could be, transactional traffic performance often suffers within FIFO queues, especially large ones. Not only could you try reverting to the defaults, but in your hardware and software support CBWFQ, suggest trying it with FQ in default class.


e.g.


policy-map CBWFQ

class class-default

fair-queue


serial #

service-policy CBWFQ output

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