[cisco-voip] Weird Conference Voice Quality (FOLLOW UP)
Vandy Hamidi
vandy.hamidi at markettools.com
Wed Jan 12 10:47:39 EST 2005
I'm sending this as a follow-up to this thread I started months back.
Problem of voice quality was a few things.
1) The 6608 dejitter buffer is horrible and very sensitive to Jitter and
varying jitter.
2) The Sprint MPLS network I was using was configure correctly on my
side (with QOS), but Sprint was not prioritizing traffic when handing
off to me. Which meant that data traffic was getting the same priority
as voice on the remote end of my WAN. Sprint applied QOS and we haven't
had many voice quality issues (knock on wood) with the conference calls
on the 6608.
-=Vandy=-
-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Vandy Hamidi
Sent: Thursday, July 22, 2004 11:17 PM
To: Wes Sisk; cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] Weird Conference Voice Quality
Thanks Wes,
In answer to your 75% question. It's a 3.0MB link (2 Bonded T1's using
MLPPP).
For over 6 hours, I've been over and over the config of the router with
Cisco and they are adamant it should work fine and is configured right.
We changed a ton of configs just in case anyways.
Show Policy-map shows no voip voice or control drops and only default
traffic dropping.
Yet I continue to get sound degradation and the phone (when you double
tap the "?") shows up to 500ms of jitter and dropped packets.
Cisco wants to sniff both ends which is good, but grasping at straws.
They are using words like WAN sniffer.
Tested by limiting the default traffic to 500Kbps (out of the full
3.0Mbps) and still the voice traffic suffers when I generate traffic
over the link.
They suspect the voice carrier.
They also suspect the 2 port MFT may have a problem. They won't give me
a straight answer when I ask about it, but they say it may be a
performance issue with the VWIC they've seen stuff on. Uh huh...Share
the internal tech info you have.
The only site that doesn't have CRAPPY voice quality when I generate
traffic is using a trusty old WIC-1T-DSU.
Anyways, I'm building a lab with an extra 2651xm and hooking it up to my
hubsite using a T1 cross-over. We'll see how that goes.
Thanks all for your help. IF you have any suggestions, share with the
group. I'll update with my findings.
-=Vandy=-
-----Original Message-----
From: Wes Sisk [mailto:wsisk at cisco.com]
Sent: Thursday, July 22, 2004 2:52 PM
To: Vandy Hamidi; cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] Weird Conference Voice Quality
Vandy,
This looks mostly correct - just a cpl questions-
Can we see the rest of the config for the route-map on the FastE
"ip policy route-map SET-IP-QOS" This may be re-marking your VOIP
traffic
so it does not match your outbound QOS policy, which identifies VOIP
bearer
traffic based on:
ip access-list extended VOIP-Classify-Voice
permit ip any any precedence critical
permit ip any any dscp ef
Also, your QOS-POLICY appears to allocate 650kbps, this ususally should
only
be 75% of available bw, so do your links offer 650/0.75= 866kbps at
least?
This is discussed in the QOS srnd at http://www.cisco.com/go/srnd if
you'd
like to read more.
/Wes
> -----Original Message-----
> From: Vandy Hamidi [mailto:vandy.hamidi at markettools.com]
> Sent: Thursday, July 22, 2004 5:27 PM
> To: Wes Sisk; cisco-voip at puck.nether.net
> Subject: RE: [cisco-voip] Weird Conference Voice Quality
>
>
> Thanks Wes, that explains a lot and confirms a hunch I had. It looks
> like the 6608 waiting for a jittery stream will cause choppiness for
all
> participants. That's a real great design...
>
> Because conference voice quality is always GOOD when data isn't
> competing, the QOS classifying and policing must not be setup right.
We
> had outside consultants install our base system and I've been using
> their QOS to stamp out other remote sites.
> Something must be misconfigured.
>
> Can anyone just give it a once over. I cut and paste just the
pertinent
> parts of my 2651XM config below.
>
> If anyone could email me their QOS setup, I would be extremely
grateful.
> This problem is high priority and high visibility and I've be very
> thankful.
> Thank you in advanced,
>
> -=Vandy-=
>
> class-map match-all VOIP-VOICE_CONTROL
> match access-group name VOIP-Classify-Control
> class-map match-all VOIP-VOICE
> match access-group name VOIP-Classify-Voice
> !
> !
> policy-map QOS-POLICY
> class VOIP-VOICE
> priority 600
> class VOIP-VOICE_CONTROL
> bandwidth 50
> class class-default
> fair-queue
> !
> interface Multilink1
> description Market Tools PL431562
> ip address 172.16.16.70 255.255.255.252
> service-policy output QOS-POLICY
> load-interval 30
> no peer neighbor-route
> no cdp enable
> ppp multilink
> ppp multilink fragment delay 20
> ppp multilink interleave
> ppp multilink group 1
> !
> interface FastEthernet0/0
> description User/Server VLAN
> encapsulation dot1Q 1 native
> ip address 10.21.0.1 255.255.255.0
> ip policy route-map SET-IP-QOS
> !
> interface FastEthernet0/1
> description VOIP Phone VLAN
> encapsulation dot1Q 4
> ip address 10.21.4.1 255.255.252.0
> ip policy route-map SET-IP-QOS
> !
> ip access-list extended VOIP-Classify-Control
> permit ip any any precedence flash
> permit ip any any dscp af31
> ip access-list extended VOIP-Classify-Voice
> permit ip any any precedence critical
> permit ip any any dscp ef
> ip access-list extended VOIP-Control
> permit tcp any any range 2000 2002
> permit tcp any any eq 1720
> permit tcp any any range 11000 11999
> permit udp any any eq 2427
> ip access-list extended VOIP-Routine
> permit ip any any
> ip access-list extended VOIP-Voice
> permit udp any any range 16384 32767
>
>
> -----Original Message-----
> From: Wes Sisk [mailto:wsisk at cisco.com]
> Sent: Thursday, July 22, 2004 6:07 AM
> To: Vandy Hamidi; cisco-voip at puck.nether.net
> Subject: RE: [cisco-voip] Weird Conference Voice Quality
>
> Vandy,
>
> If audio coming from the source device to the conference device has
> large,
> irregular jitter, then everyone listening to the conference will be
> affected.
>
> Simple way to test this out:
> setup conference with remote users and 1 central user.
> have all remote users go on "mute" (no RTP stream generated on mute)
> have central user speak.
> How is voice quality?
>
> Now, have everyone except 1 remote user go on mute.
> How is voice quality?
>
> We need to make sure those streams coming from the remote sites are
> "good"
> with very low jitter as the 6608 uses a static dejitter buffer in
> contrast
> with most ipphones and gateways which use dynamic jitter buffers.
This
> makes fragmentation critical on the WAN links.
>
> CSCdx78486 6608 configured as CFB has a static jitter buffer, needs
> adaptive
> Problem Description: Voice quality suffers with choppiness when
> conference
> particants are located across low speed links and the device providing
> for
> conferencing is the 6608.
>
> Workaround: None
>
> /Wes
>
> > -----Original Message-----
> > From: cisco-voip-bounces at puck.nether.net
> > [mailto:cisco-voip-bounces at puck.nether.net]On Behalf Of Vandy Hamidi
> > Sent: Wednesday, July 21, 2004 11:30 PM
> > To: cisco-voip at puck.nether.net
> > Subject: [cisco-voip] Weird Conference Voice Quality
> >
> >
> > Hey guys,
> > I'm having a weird problem that isn't making sense
> >
> > I have a 6608-T1 blade in my main office performing conferencing for
> > most of the remote offices in the company. I know, not recommended,
> but
> > read on.
> >
> > All the offices are connected Hub/Spoke to the main office and I
have
> > QOS setup (supposedly correctly) on my wan links and call quality is
> > great. I've tested the QOS by maxing out the line during voice
calls.
> >
> > We've been receiving user complaints of voice quality problems.
> Cutting
> > out, delays, overall chopping communication. All these complaints
are
> > when they are on conference calls.
> >
> > We've performed testing and during high wan usage the conference
call
> > quality becomes horrible to/from the remote sites and sometimes for
> all
> > users for example I'll have a hard time understanding a conference
> > attendee in my own office.
> > We're able to reproduce with windows copies during conference calls.
> >
> > 1) Why is the voice quality ok with phone to phone calls, but become
> > horrible during a conference call.
> > 2) Does the 6608-T1 blade change/alter the QOS/TOS bits on the
> packets?
> > 3) Why would this issue affect local attendee conference quality
when
> > everyone is connected to the same switch where the 6608 blade is.
> >
> > TIA,
> >
> > -=Vandy=-
> >
> >
> > _______________________________________________
> > cisco-voip mailing list
> > cisco-voip at puck.nether.net
> > https://puck.nether.net/mailman/listinfo/cisco-voip
>
>
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