QoS for VLAN on 2960 - how to.

[Nathan Farrar]

I am being asked to implement a QoS configuration across a network with many 2960s. The telephony vendor is asking that we have all voice data be set to an IP precedence of 6. Currently he is seeing 5, which is what I assume the phones are tagging the packets with. The phones are connected to the switch and trunked to allow the data port on the phone to be used as well. I understand how to mark all packets on an interface with IPP of 6 but I only need the Voice VLAN which is VLAN 10. I've found configurations with L3 switches but of course this switch cannot use the mls qos vlan-based command as they can.

What can I do to mark all packets in this VLAN with IPP 6 ?

Thanks!!

[Joseph W. Doherty]

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Posting

The telephony vendor is asking that we have all voice data be set to an IP precedence of 6.

That's inadvisable!  (BTW, many telephony vendor service folk know little about supporting their VoIP products on a data network.  This request, alone, would make be wonder about your vendor's competence.)

If there's VoIP quality issue now, with an IPP of 5, likely you don't have QoS treatment either enabled or correctly configured.  Remarking voice packet to a different marking, alone, doesn't guarantee better service.

What can I do to mark all packets in this VLAN with IPP 6 ?

An ingress policy should allow you to remark.

PS:

On the question of competence with VoIP, there's a reason network vendors, such as Cisco, now have certifications related to voice.

[Nathan Farrar]

I completely agree with you! They are using a Mitel PBX and I asked him that very question "Marking the packets is all good but what are you doing with those markings?" I've setup QoS before but I'm not certian what it is that this guy wants to do. Maybe he doesn't know and is just forwarding a reqest on to me. There are currently NO policies policing or shaping the traffic anywhere in the network, so setting this value is pretty much pointless. His note was:

"For QOS the voice VLAN is 10 with a priority of 6."

Called him and asked if all he wanted was to mark the voice packets with IPP of 6, he said yes and that they are currently coming across with an IPP of 5. I am relatively new to VoIP so I just said I'd do it thinking he must have some reason for it. Aren't 6 and 7 reserved anyway?

I am in the process of learning a lot about Voice and have setup a few UC540s. I have my CCNA and CCNA-Security, just to reference that I know some stuff but not much experience with voice.

To start with, isn't it true that the phones themselves will mark the packets wtith the correct CoS and DSCP values automatically? Typically I thought that CS3 was signaling and EF was for the voice packets (haven't worked with CoS, only DSCP).

This is what I did on the switch:

mls qos

policy-map VLAN10

class class-default

  set precedence 6

interface vlan 10

no ip address

service-policy input VLAN10

Not sure if the mls qos command is required. Will this do what I am wanting it to do?

I am also going to call the guy back now and dig a bit more into it.

Thanks!

[Joseph W. Doherty · Accepted solution]

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

As to setting any CoS(L2)/ToS(L3) marking, yes, it is rather pointless unless it's used for some purpose.  Many Cisco switches and routers, by default, don't do anything "special" with marked frames/packets.  Many Cisco switches, though, if QoS is enabled, will have default QoS treatment, so you might see different results against frames/packets with different CoS/ToS.

Yes, CoS/IPP 6 and 7 are usually set aside for network control.  5 is normally the "highest" setting for any kind of host traffic.

Also yes, most VoIP phones can mark CoS/ToS.  Often they are configurable.  EF (ToS) is normally used for VoIP bearer.  CS3 (ToS) is one of the common markings used for signally (Cisco recommends CS3 [earlier they used AF31] and RFC 4594 recommends CS5).

I think what you might still need to do, for policy to work on a 2960, would be to enable QoS (edit - oh, just noticed you did that) and on any port with VLAN 10, set it to VLAN based trust.

[Nathan Farrar]

Thanks for your input! I haven't heard back from the vendor yet but I am curious as to what he thinks or expects this adjustment to do.

As for your last comment about VLAN based trust, is this the command?

interface g1/0/1

mls qos trust

?

Doesn't that just tell the switch to trust and keep the CoS as it is from the device?

Thanks again.

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

As for your last comment about VLAN based trust, is this the command?
interface g1/0/1
 mls qos trust

No, it's something like "mls qos vlan-based".  On you switch, use question mark to see other options.

[Nathan Farrar]

The mls qos vlan-based command doesn't seem to exist on this model. I was looking for it previously. Seems this is a feature in L3 switching platforms only. I saw config examples for 3550s. Documentation suggests that sit available either.

Ideas on testing? I wish I had wish I had wiresshark on that switch!!

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

The mls qos vlan-based command doesn't seem to exist on this model. I was looking for it previously. Seems this is a feature in L3 switching platforms only. I saw config examples for 3550s. Documentation suggests that sit available either.

Yes, do have a couple of ideas.

If your VoIP VLAN is the only VLAN on the port, you might just be able to mark all ingress traffic to your desired marking.

Or, if the 2960 takes an ingress service policy, you can "look" at the ingress traffic and select traffic you want to remark.  If the phone is already marking, you could match against that and then just remark that traffic.

[greyiago85]

Personally I'm a fan of "auto qos voip trust"