slow bandwidth issue on switch fixed by qos command

[carl_townshend]

Hi all

some colleagues had an issue with copying a file from pc to pc on the same switch, they said it took al long time to copy through the 100 meg port. The port had mls qos trust dscp enabled. they changed the command to autoqos voip trust cisco-phone, They said this then solved the file copy issue.

why would this be? would it be that the pc was tagging the packets ?

cheers

[cadet alain]

Hi,

If the pc was marking traffic it would have marked to get better treatment not worse.

The auto qos command is a macro which will put multiple commands, just do a show run to see the stuff added by this command.

Regards.

[johnlloyd_13]

i disagree. the pc doesn't have the capability to mark its own packets. the trust boundary was extended from the switch up to the IP phone. the IP phone does the marking/tagging for voice and data packets (from pc) and when it reached the switch, it knows what to do with those traffic resulting to an efficient file copy transfers.

[Lei Tian]

Hi,

With trust cisco-phone configured under the inteface, the port will become conditional trust. It will be in trust state when cisco phone is detected via cdp, otherwise, it will be in un-trust state. So, the port connecting to server will be un-trust and reset all packet to cos 0. It will be interesting to know what DSCP the server is marking and which queue is used for that DSCP. Sounds like the queue for cos 0 works better.

Regards,

Lei Tian

[cadet alain]

John,

i disagree. the pc doesn't have the capability to mark its own packets. 
the trust boundary was extended from the switch up to the IP phone. the 
IP phone does the marking/tagging for voice and data packets (from pc) 
and when it reached the switch, it knows what to do with those traffic 
resulting to an efficient file copy transfers.

I disagree also because first when the transfer was not good it had mls qos trust dscp which meant that it trusted dscp whether from data vlan or from voice vlan.

Now when the trust boundary is extended to switch then it only trust marking from phone and remarks data with port cos which by default is 0 and so whith normal cos-dscp map is also dscp 0 which is less better than what the phone is marking(cos5-dscp EF for voice traffic and cos 3-AF31 for call control).But AutoQoS also configures queues for congestion management and tht is surely what made the situation better.

Regards.

Alain.