[cisco-voip] MGCP Audio Cut Through Delay

[Jonathan Charles]

So, is this a phone firmware issue? The PSTN caller (and the IP Phone)
do NOT hear anything for about 4-5 seconds once the IP phone call is
answered.

This is also inbound only.

CCM is 4.1(3)sr5b and Gateway is a 2811 running 12.4(3g)




Jonathan

On Wed, Jul 9, 2008 at 4:24 PM, Wes Sisk <wsisk at cisco.com> wrote:
> at the end the router reports call statistics:
> P: PS=978, OS=156480, PR=980, OR=156800, PL=0, JI=0, LA=0
> PS = packets sent
> PR = packets received
> 978 is close enough to 980. this means all RTP packets made it through the
> network between the endpoints.
> 980 packets * 20msec/packet = 19,600msec of audio.
>
> Time from sendrecv to recvonly = 03:51:40.645 - 03:52:00.227 = 19.6 seconds
> (approximately).
> 19.6 seconds connected and 19.6 seconds of RTP traffic.  Thus audio was
> successfully established and packets were sent and received successfully for
> the duration of the connection.
>
> Router responded correctly and offered its ip address to receive RTP
> stream.  the mgcp call agent (cm?) sent instruction to establish
> bidirectional audio full 15 seconds later.  Need to see what took the call
> agent(cm?) so long to obtain the media ip/port from the other endpoint.
>
> debugs with comments:
> //create connection to setup new call
> Jul 10 03:51:25.534 CST: MGCP Packet received from 10.1.1.10:2427--->
> CRCX 89768
>
> //router provides ip & port for RTP stream:
> Jul 10 03:51:25.550 CST: MGCP Packet sent to 10.1.1.10:2427--->
> 200 89768 OK
> I: 6
>
> // router receives instruction to change audio mode to sendrecv. this is
> usually 2 way audio
> Jul 10 03:51:40.645 CST: MGCP Packet received from 10.1.1.10:2427--->
> MDCX 89773 AALN/S0/SU1/3 at MC003776.mcenery.local MGCP 0.1
> C: A00000000200d51c000000F5
> I: 6
> X: 0
> L: p:20, a:PCMU, s:off, t:b8
> M: sendrecv
> R: L/hu, D/[0-9ABCD*#]
> S:
> Q: process,loop
>
> v=0
> o=- 6 0 IN EPN AALN/S0/SU1/3 at MC003776.mcenery.local
> s=Cisco SDP 0
> t=0 0
> m=audio 18840 RTP/AVP 0
> c=IN IP4 172.20.113.10
> <---
>
> //router receives instruction to stop transmitting audio
> Jul 10 03:52:00.227 CST: MGCP Packet received from 10.1.1.10:2427--->
> MDCX 89775 AALN/S0/SU1/3 at MC003776.mcenery.local MGCP 0.1
> C: A00000000200d51c000000F5
> I: 6
> X: 0
> M: recvonly
>
> // router reports call statistics:
> Jul 10 03:52:00.287 CST: MGCP Packet sent to 10.1.1.10:2427--->
> 250 89776 OK
> P: PS=978, OS=156480, PR=980, OR=156800, PL=0, JI=0, LA=0
>
>
>
>
>
>
> v=0
> c=IN IP4 172.20.115.254
> m=audio 17344 RTP/AVP 0 100
>
>
>
> /Wes
>
>
> Jonathan Charles wrote:
>
> Here you go... no obvious errors...
>
>
>
> Jonathan
>
> On Wed, Jul 9, 2008 at 2:42 PM, Wes Sisk <wsisk at cisco.com> wrote:
>
>
> yep
>
> Jonathan Charles wrote:
>
>
> The MGCP packet debug?
>
>
> J
>
> On Wed, Jul 9, 2008 at 1:02 PM, Wes Sisk <wsisk at cisco.com> wrote:
>
>
>
> can you share the debug (blank out the actual phone numbers) with debug
> datetime msec?
>
> /wes
>
> Jonathan Charles wrote:
>
>
>
> We have a remote site via a VPN tunnel (over MPLS), and we are seeing
> significant audio cut through delays.
>
> We did a debug mgcp packet and saw no retries.
>
> We can also see the problem when PSTN callers are placed on hold and
> retrieved.
>
> Delay lasts between 3 to 4 seconds...
>
> Any ideas?
>
> MGCP config is the default (no special packages enabled/disabled)...
>
>
>
> Jonathan
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