Ack for each RTP packet?

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Jun 18th, 2009
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Hi,


we are experiencing call drops, but only from particular numbers (provider). This happens intermittently and only on incoming calls from outside over a SIP trunk.

When collecting traffic we can see that Cisco 2811 is sending "200 OK SDP" events towards provider for each RDP packet.The call gets connected and is OK, until ASA firewall drops the call after 20 seconds.


Has anyone seen such intermittent behaviour (SDP packet for each RTP)?


This is the trace:


25 |2020,869 | RTP (g711A) |RTP Num packets:976 Duration:19.494s SSRC:0x5F1F33EA

| |(23368) <------------------ (17518) |

25 |2020,882 | 200 OK SDP ( g711A telephone-event) |SIP Status

| |(5060) <------------------ (5060) |

25 |2020,985 | RTP (g711A) |RTP Num packets:20 Duration:0.376s SSRC:0x5A407753

| |(23368) ------------------> (17518) |

25 |2021,380 | 200 OK SDP ( g711A telephone-event) |SIP Status

| |(5060) <------------------ (5060) |

25 |2021,382 | RTP (g711A) |RTP Num packets:50 Duration:0.979s SSRC:0x5A407753

| |(23368) ------------------> (17518) |

25 |2022,381 | 200 OK SDP ( g711A telephone-event) |SIP Status

| |(5060) <------------------ (5060) |

25 |2022,382 | RTP (g711A) |RTP Num packets:100 Duration:1.979s SSRC:0x5A407753

| |(23368) ------------------> (17518) |

25 |2024,380 | 200 OK SDP ( g711A telephone-event) |SIP Status

| |(5060) <------------------ (5060) |

25 |2024,381 | RTP (g711A) |RTP Num packets:200 Duration:3.978s SSRC:0x5A407753

| |(23368) ------------------> (17518) |

25 |2028,379 | 200 OK SDP ( g711A telephone-event) |SIP Status

| |(5060) <------------------ (5060) |

25 |2028,380 | RTP (g711A) |RTP Num packets:200 Duration:3.979s SSRC:0x5A407753

| |(23368) ------------------> (17518) |

25 |2032,378 | 200 OK SDP ( g711A telephone-event) |SIP Status

| |(5060) <------------------ (5060) |

25 |2032,379 | RTP (g711A) |RTP Num packets:200 Duration:3.978s SSRC:0x5A407753

| |(23368) ------------------> (17518) |

25 |2036,377 | 200 OK SDP ( g711A telephone-event) |SIP Status

| |(5060) <------------------ (5060) |

25 |2036,378 | RTP (g711A) |RTP Num packets:201 Duration:3.998s SSRC:0x5A407753


BR,


Marko

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Nicholas Matthews Thu, 06/18/2009 - 15:54
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Hi Marko,


I have never heard of such a thing. What a mess. What does 'debug ccsip messages' look like? What version / platform are you on?


-nick

markotisler Tue, 06/30/2009 - 00:07
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It seems that the provider sometimes is not sending the final ACK message upon establishing the call, and thats the reason why these messages are being sent and the call being dropped after no ACK is recieved.

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