Question

QOS for voice traffic

Asked by: stamperb

OK I had a question posted similar to this before and I thought I had what I needed but maybe not.  So here is what I have:
Site1
1 -  3560
1 - 4507R
1 - 3845
 
Site2
1 -  3560
1 - 2811

At Site 1 the 3560 port Gi 0/1 plugs into the 4507R on Gi 7/46.  The 3845 router Gi 0/0 plugs into the 4507R on port Gi 3/1.  Site two is basically the same the 3560 port Fa 0/48 plugs into the 2811 on port Gi 0/1.
Now at both sites I'll have IP phones plugged into the 3560's.  On the ports where I will have the IP phones plugged in I've done the following:
auto qos voip trust
mls qos trust device cisco-phone (these phones are nortel but I was told this would probably work fine)

Now at site 1 on port Gi 0/1 of the 3560, ports Gi 7/46 and Gi 3/1 of the 4507R i've done the following.
auto qos voip trust

Now on the routers at each side I have the following:
class-map match-all control
 match access-group 151
class-map match-all voice
 match access-group 150
!
!
policy-map voip
 class voice
  priority 1024
 class control
  bandwidth 50
 class class-default
  fair-queue
  random-detect dscp-based
And then on the serial interface I have:
service policy output voip

Now as i troubleshoot:
Show policy-map voice - looks fine
show policy-map interface serial 1/0 - I see that everything appears to be falling into the class default.  Nothing is showing under the voip.  

Is there a way to troubleshoot on each device to make sure things are getting marked properly and or what am i missing here.

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Asked On
2007-09-20 at 04:37:13ID22840997
Tags

dscp

Topics

Network Routers

,

Voice Over IP

Participating Experts
1
Points
500
Comments
12

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Answers

 

by: tvman_odPosted on 2007-09-20 at 06:38:50ID: 19928163

And what's in access list 151 and 150
it should be something like

ip access-list extended 151
  permit ip any any dscp AF4
ip access-list extended 150
  permit ip any any dscp EF

 

by: stamperbPosted on 2007-09-20 at 07:39:21ID: 19928673

Extended IP access list 150
    10 permit ip any any dscp ef
Extended IP access list 151
    10 permit ip any any dscp cs5

 

by: stamperbPosted on 2007-09-20 at 07:39:31ID: 19928675

That is what is there.  

 

by: tvman_odPosted on 2007-09-20 at 10:44:02ID: 19930086

Does your equipment mark voice traffic with EF?

try to ping remote one of the remote hosts

ping -v 184 <IP>

-v is TOS field
tos = 184 = 10111000
dscp = 101110 = 46 = ef

Do you see hits on access list 150

 

by: stamperbPosted on 2007-09-20 at 18:10:42ID: 19932812

OK an update on this.  So i have everything working properly.  The issue oddly enough was that the simulation program that the nortel tech was using was not setting the dscp.  Once we got the system up and running between the sites we started seeing matches.  Now the last issue is with the routers.  Site 1 has a 3845 and site 2 has a 2811.
On the serial interfaces on both of the routers I have the service-policy output voip applied
Also on the Ethernet interfaces I set the same service-policy output voip.
At site 1 and 2 when I do a:
show policy-map interface serial #/# (this is the ds3  to the mpls at site 1 and the t-1 to the mpls at site 2) i am seeing matches and packets in the class voice and class signaling that I setup as my class maps.
At site 2 when I do a
show policy-map interface fastehternet 0/0 (this plugs into my lan at site 2) I am also seeing matches
At site 1 when I do a
Show policy-map interface gigabitethernet 0/0 (this plugs into my lan at site 2) I am NOT seeing any matches?

So if i understand I am seeing the traffic marked as it leaves both sites.  However, when the traffic comes in at site 1 i'm not seeing it marked as it leaves the Gigeth0/0 to the lan?  I called my mpls company and they see the matches all the way thru and are providing the qos.  Any ideas on this?  Also using the command below can i test this issue somehow?


AWESOME I was looking for a command that would let me do this!!  But my question is how does the dscp = 101110 = 46 = ef work?  I'm not quite understanding that.  I mean 184 = 1011000 is a pretty easy calculation.  As i see it you've dropped the last two bits? to make it 46?

 

by: tvman_odPosted on 2007-09-20 at 18:44:05ID: 19932903

Correct, dscp takes just 6 bits. You should see matches. Look for typos in the config. Check policy stats and access list stats. Actually I would not worry about QoS while traffic coming out from a slow interface to fast.

 

by: stamperbPosted on 2007-09-20 at 20:07:40ID: 19933129

Yea i'm not so worried about it.  I just wanted to make sure it was there.  Simply because thats coming out of the mpls I wanted to make sure the priority wasn't getting lost in the MPLS cloud somewhere.  So this is odd.  My phone generates hits on the access lists when I call the other site.   Also my phone is plugged into a 3560 switch on port FastEthernet 0/41 and if i simply pick up the phone and call anyone and on the 3560 switch  i issue a:
show mls qos interface FastEthernet 0/41 statistics
I see matches on dscp 40 (Signaling) and 46 (voice)
So i know this is right
However I have a PC plugged into port FastEthernet 0/47
on that pc if i ping -v 184 anywhere I don't see any matches on dscp 40 or 46?

Here is the config on both of those ports:
interface FastEthernet0/41
 switchport trunk encapsulation dot1q
 switchport mode trunk
 srr-queue bandwidth share 10 10 60 20
 srr-queue bandwidth shape  10  0  0  0
 mls qos trust dscp
 auto qos voip trust

interface FastEthernet0/47
 switchport access vlan 150
 srr-queue bandwidth share 10 10 60 20
 srr-queue bandwidth shape  10  0  0  0
 mls qos trust dscp
 auto qos voip trust

 

by: stamperbPosted on 2007-09-21 at 04:36:30ID: 19934663

Also the ping command above doesn't seem to do it for me.

But if I use ping from the cisco cli and set it there to 0xb8 i see increments.  So if I can generate that from the serial interface of the RTR back into the network I might be able to get some test results. It allows me to specify a source interface or address but i've yet to figure out that.

 

by: tvman_odPosted on 2007-09-21 at 07:11:34ID: 19935708

According to documentation the CoS bits exist inside Ehernet frames only when 802.1Q trunking used.
dscp doesn't make sense for L2 networks and exist only in L3 headers.

 

by: stamperbPosted on 2007-09-21 at 08:56:20ID: 19936668

But my acl on the GI 0/0 was set to tag for that dscp bit.  I've figure out the problem (by accident). I called cisco yesterday for some help with this.  The engineer had changed the acl.  Applied the policy to the interface.  I then went in and changed the ACL back to match ef from whatever he had.  This morning I mirrored the port on my 4507R that that router was plugged into and sure enough when i sent the ping from the router with the 0xb8 tos set I saw the field in the packets marked in my capture.  The show policy-map interface Gi0/0 still wasn't showing anything.  So i removed the policy and re-added it and now i'm getting matches.  However, your point on the trunk ports is valid and I bet thats why his voip call simulation software is not working!!  I'll get this fixed and we'll test again.

 

by: tvman_odPosted on 2007-09-21 at 10:58:32ID: 19937687

How many switches and trunks your voice traffic will cross mixed with data? How heavy is your data traffic in the ethernet segment. In most cases you can just leave L2 ethernet without QoS. Most of my sites have a separate physical interface in access mode to a router but mixed with data in the switch. We don't use ethernet port at the back of the phone for computers. As we discovered that 2600,2600 and 3800 routers have performance issues with ethernet trunk ports. CPU load jups up to the sky. 4500 prbably can handle it but still there was some negative experience.

 

by: stamperbPosted on 2007-09-21 at 15:26:54ID: 19939639

Thanks again for all of your help

20120131-EE-VQP-002

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