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New Member

One Way Speech problem

Hi all,

We have been doing some testing between a H323 Stack and Netmeeting. In between is a Cisco 3620 router with two fastethernet interfaces and one FR serial interface. From the H323 host we are setting up a direct routed call (no Gatekeeper involved) to the Netmeeting host and are only getting one way speech.

The network scenario is as follows:

analogue phone-----PSTN switch-----PRI-----H323 Stack-----3620Rtr-----Internet-----Netmeeting.

In this call scenario the analogue phone can hear the Nemeeting audio stream, but the Netmeeting user cannot hear the analogue phone stream. In researching Cisco website and their forum, one possibility they refer to is basic routing connectivity issues. I wonder if this is the case but we have a packet sniffer running for the duration of the call - the sniffer is on the same collission and broadcast domain as the H323 stack and I can't see the audio stream coming from the H323 EP, while I can see it coming from Netmeeting.

This tells me that the H323 stack (running on Dialogic hardware) is failing to send its media stream. The H.245 OpenLogicalChannelAck from Dialogic advises of the port and IP address that Netmeeting should send its mediastream to. The OpenLogicalChannelAck from Netmeeting advises of the port and IP address that Dialogic should send its mediastream to. Upon connection, the voice data is sent from Netmeeting to the Dialogic card, but the Dialogic card is not sending its media stream to Netmeeting. In between the Dialogic (H323 stack) and

3620Rtr we have a hub and a host connected with Etherpeek running - we would expect to see the mediastream coming out of the Dialogic card on Etherpeek, but nothing is appearing. We can however see the mediastream coming from Netmeeting towards the Dialogic IP address. We suspect that something is wrong with the Dialogic card and we are not sure if it is an actual bug, or if we are sending something wrong in the H.225.0 and/or H.245 setup messages, that the Dialogic card does not like.

I am happy to supply the decoded messages, and the Dialogic config if that helps. However from a router perspective I have a few mysteries I am not sure about. Traffic Shaping is running on all interfaces, and this is the following configuration for one interface (I have excluded stuff to make the info clearer):

NEC_ASP_WLG-0#sh traffic-shape statistics fa0/0

Access Packets Bytes

I/F List

Fa0/0 103 64713295 1836542520

Fa0/0 104 0 0

Fa0/0 105 0 0

Fa0/0 106 0 0

Fa0/0 112 0 0

Fa0/0 113 0 0

Fa0/0 114 0 0

Fa0/0 115 0 0

Fa0/0 116 0 0

NEC_ASP_WLG-0#sh access-list 103


I am quite mystified as if there is no access list then shouldn't implicit 'deny all' prevent any traffic going through. Oddly enough, I have access-list configurations for 112 - 116 and the following traffic-shaping applying:

interface FastEthernet0/0

ip address x1.x2.x3.x4 y1.y2.y3.y4 secondary

ip address

ip access-group 102 in

ip nat inside

duplex auto

speed auto

traffic-shape group 103 8500000 1000000 500000 1000

traffic-shape group 104 1000000 100000 0 1000

traffic-shape group 105 500000 50000 0 1000

traffic-shape group 106 100000 10000 0 1000

traffic-shape group 112 9109920 1000000 0 1

traffic-shape group 113 64950 18563 17225 1

traffic-shape group 114 250000 25000 0 1

traffic-shape group 115 50000 5000 0 1

traffic-shape group 116 100000 10000 0 1

Why would it use ACL103 only?

Finally, if in my access-list I accidentally exclude an IP address that should be subject to traffic-shaping, then under 'what bucket' will that IP address be included in when leaving the interface - is it true to say that all IP addresses not included in access lists for traffic shaping get assigned lowest priority and go out anyway; or are they barred ?

Any help here most appreciated. I have checked the Cisco site troubleshooting for one way speech path problems, and have IP routing enabled.



New Member

Re: One Way Speech problem

Are you able to sniff the H.245 handshaking? Most one-way audio problems I have seen have been caused by the H.323 gateway grabbing the wrong source address to advertise the near end of the RTP stream, an addess that the far end device can't route to, like an inside address or an unadvertised loopback. On Cisco H.323 gateways, there is a command to specify the advertised source address for RTP stream. This might not be the issue you're running into, but it's at least something to check.

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