Delay After Answer

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I am having an issue with a couple of phones where they ring, but there is a long delay after the phone is picked up before the audio starts.

My setup:

* Server running Asterisk 13.9.1, Dahdi 2.11.1 w/ OSLEC
* Server is CentOS 7
* Quad core CPU with 16GB Ram
* 2 Snom 300 phones.
* NO NAT. Server and phone are on the same subnet with only a gigabit
switch between them.
* Digium TDM400 analog card with 2 incoming analog PSTN lines

When a call comes in, the system answers, IVR plays, caller dials an extension, Snom 300 rings, handset picked up. Caller continues to hear ringing for another 7 to 10 seconds. Answerer hears a click, a quick burst of audio, then silence, then another click and audio is engaged.

I have tried both SIP and RTP debugging and there are absolutely no messages indicating any timeout or retransmit. I am at a total loss.
In the past I’ve always been able to find an answer to issues like this on my own, but this time I just don’t know. I was even beginning to suspect the network switch might be bad, but pinging between the server and the phones shows no packet loss and 0.969ms average response time.

What am I missing*?*

Thanks, Brent Davidson*

6 thoughts on - Delay After Answer

  • I’ve seen this sort of thing where a DNS server is programmed in resolv.conf but is not accessible over the network. Threads get blocked, and you have to wait for the DNS query to timeout.

  • I’ve faced the same issue. The issue was related to DNS, the reverse lookup query failure caused the delay around(7-9 seconds). The purpose of reverse lookup is to block IP Spoofing attacks.

    Regards, Faheem

  • Well, I thought I had the problem solved. Ported everything over to PJSip and build RDNS records for the phones and the server, but I am still experiencing the problem on incoming calls.


  • Are you sure *nslookup *command is returning as expected?
    Also check the output of the below command.

    On Tue, Jun 7, 2016 at 11:54 PM, Brent Davidson

  • Are you using stun? I have seen that when using stun
    בתאריך 8 ביוני 2016 09:54,‏ “Faheem Muhammad” כתב:

  • Another thing i would check is encryption is disabled on the snom
    בתאריך 8 ביוני 2016 10:07,‏ “Israel Gottlieb” כתב: