[cisco-voip] Weird Conference Voice Quality

[Vandy Hamidi]

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=-
>
>
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