tomkb
Premium
join:2000-11-15
Avon, OH
clubs:
 ·RoadRunner Cable
| Unexpected side effect of turning QOS on
We turned qos on our 4510 switch in order to support a voip deployment.
We used cisco's auto qos. One thing though, it seems we are unable to use our T3 at it's full capacity for a single user. IE - multiple users could max out the T3 collectively, but a single person is somehow limited to no more than 33KB download speed, or roughly 1/5 T1 speed.
Any tips would be appreciated. |
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Euphrates
join:2007-04-30
Bellingham, WA
| Not being familiar with this feature (haven't had the chance to play around with it yet) but from what you are saying, it seems that auto qos may have implemented some sort of bandwidth cap that a single user cannot go past. Hopefully, someone else will be able to provide more information. I would suggest posting the configs of your switch as well as your router (if your using a Cisco router for your T-3) for the other users to look at. In the mean time, your best bet would be to search Cisco's documentation about auto qos on your device. |
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SkellBasher
Yes Sorto, I'll take my Prozac
join:2000-10-22
North Tonawanda, NY
| reply to tomkb
If you could pop up the QoS commands that were created from auto-qos, that would be a good start. I looked at a couple of examples, some of them showed some harder bandwidth policies than others. It's very conceivable that the auto-qos dropped some of these harder policies in place, and that's what the trouble is.
Tough to say for sure , since it seems that the auto-qos feature is extremely varied on different platforms and images. |
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jwhitecs
Premium
join:2006-10-11
 ·Verizon FIOS
| reply to tomkb
For starters refer to the link below which is the Enterprise QoS SRND.
»www.cisco.com/univercd/cc/td/doc···srnd.pdf
pg 2-62 Catalyst 4500 Supervisor II+/III/IV/V— QoS Considerations and Design
pg 2-64 Catalyst 4500—Auto QoS VoIP Model |
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jwhitecs
Premium
join:2006-10-11 | There must be a service policy applied on the T3 interface as well outside of the 4500 auto-qos being enabled. Please paste the entire config's. |
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tomkb
Premium
join:2000-11-15
Avon, OH
clubs:
·RoadRunner Cable
| reply to tomkb
Thanks for replying.
Here are the relevant parts of the config of the switch where the phone and pc's reside.
qos dbl
qos map dscp 24 25 26 27 28 29 30 31 to tx-queue 4
qos map dscp 32 33 34 35 36 37 38 39 to tx-queue 4
qos map cos 3 to dscp 26
qos map cos 5 to dscp 46
qos
policy-map autoqos-voip-policy
class class-default
dbl
and now a typical trunk port
interface GigabitEthernet1/1
switchport trunk encapsulation dot1q
switchport mode trunk
service-policy output autoqos-voip-policy
qos trust cos
udld port
flowcontrol receive on
flowcontrol send on
auto qos voip trust
tx-queue 3
bandwidth percent 33
priority high
shape percent 33
and finally a typical port that a phone plugs into and daisy chains to the pc
switchport voice vlan 13
service-policy output autoqos-voip-policy
qos trust device cisco-phone
qos trust cos
auto qos voip cisco-phone
tx-queue 3
bandwidth percent 33
priority high
shape percent 33
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SkellBasher
Yes Sorto, I'll take my Prozac
join:2000-10-22
North Tonawanda, NY
| reply to tomkb
I think this may have something to do with the queuing setup.
qos map dscp 24 25 26 27 28 29 30 31 to tx-queue 4
qos map dscp 32 33 34 35 36 37 38 39 to tx-queue 4
qos map cos 3 to dscp 26
qos map cos 5 to dscp 46
Now, on the interfaces, this is defining tx-queue 3 as the high priority queue.
tx-queue 3
bandwidth percent 33
priority high
shape percent 33
Cisco IP phones send the voice payload with a COS of 5, VoIP control traffic with a COS of 3, and the generic data traffic from the workstation connected to it as COS 0. So, we expect to see COS 5 / DSCP 46 traffic to be assigned to the priority egress queue, COS 3 / DSCP 26 as the the next lowest priority egress queue, and everything else as the 'best effort' queue.
The only queue that seems to have been adjusted from default is tx-queue 3, however nothing seems to be associated with that queue. VoIP control traffic is assigned to tx-queue 4, and VoIP payloads are associated with nothing.
This could be because some settings in play here aren't show by what you're copied, I'm not 100% sure.
If you do a 'show qos interface [interface]' on some of these, it should show the queue settings for each interface. If you could also do a 'show qos maps dscp tx-queue' , it should show what DSCP values go to what queues.
We can start there. :) |
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seanc123
| reply to tomkb
Could a single user max your t3 before? If so with what protocols/programs?
If you aren't sure, the easy thing to do is just shut off QoS( conf t, no qos) on the 4500's and see if performance improves.
Aside from that, we need 'sho service-policy int' to see whats happening on the device with the t3 interface. |
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tomkb
Premium
join:2000-11-15
Avon, OH
clubs:
·RoadRunner Cable
| reply to tomkb
turns out that qos was applied to a router interface where it was not needed. IE- one router interface was dedicated to voip routing, the other to our normal lan via router on a stick.
Basically, I removed the qos from the non voip interface and all returned to normal. Essentially, you have to apply any qos to the physical interfaces and not the virtuals so it make sense to carve up your ethernet interfaces on your router this way if you have them available. |
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SkellBasher
Yes Sorto, I'll take my Prozac
join:2000-10-22
North Tonawanda, NY | Glad you ended up figuring it out.  |
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