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Beginner

SPA112 Ringer Delay

Hi,

I have a Cisco SPA112, connected to a Draytek 2820 router, a fiber connection and using the SIPGATE VOIP service. Everything is working fine except my phone does not ring until the caller hears it ring 2-3 times; often causing me to miss calls. I have tried software phones on other devices such as my computer and Android phone, and these work fine. Can anyone offer any advice?

Many thanks,

George

1 ACCEPTED SOLUTION

Accepted Solutions
Advocate

Re: SPA112 Ringer Delay

Despite your are environmental engineer ;-), I will try to explain what captured data mean. But before it, I downloaded your file, removed irrelevant packets  (packets belonging to other device) and attached resulting file here.

Green numbers in paragraphs bellow are reference to packet number in the attached file. In the following text, the term ATA will be used for your SPA112, term phone will mean the analog phone device connected to it.

OK, lets start.

Packets [2] is INVITE packet, announcing the incomming connection to you. Packets [5] and [90] are "100 Trying" and "183 Ringing" responses to the INVITE. The first one mean nothing for us, the second inform the caller your side is ringing (caller should got the ringback tone from it's phone).

So, what happened on your side in real ?

Your ATA has started to send ringing signal to your phone ([41])  0.1 second before it responded '183 ringing' [90] to caller.

So there has been no noticeable delay between caller's view about your ringing state and ATA ringing signal. Once more - you phone received ringing signal here [41], caller has been informed and should listen ring-back tone here [90].

If you phone remained silent, then it decided not to ring despite ringing signal.

It's not bug but feature.

Caller ID data are transferred ([97] - [106]) between first and second ring. Some phones supress first ring waiting for caller-id data. It's true  especially for advanced phones like FSMS capable phones, phones with  custom selection of distinct rings, phones with black lists and so on. Such kind of phone need to know  the caller info for decision "to ring or not to ring" and for selection of ring type (if decided to ring).

So, the first ring seems to be stolen by phone. The second ring start [107] 5.9s past first ring.

I assume you heared this second ring as your's phone entered [113] off hook state.

Phone becomed off-hook at 9.3 second past first ring = 3.4 second past second ring. The caller has been informed within 0.05 sec [126] about it. Ringback tones had been turned off at caller side, call entered 'established' phase.

Conclusion ? Phone seems to mute first ring, causing 6 second of minimal delay (you are not aware about incoming call untill second ring started). Such delay doesn't hurt in most cases. If you want to avoid it, you need configure your phone not to mute first ring. Most of phones allow such kind of configuration. Problem can't be solved by ATA configuration. Search phone's documentation how disable first ring skip.

Hope it help.

Message was edited by: Dan Lukes - I attached filtered version of capture file and modified accordingly the packet numbers in text.

View solution in original post

5 REPLIES 5
Advocate

SPA112 Ringer Delay

Capture SIP packets and syslog/debug messages related to incomming call

Then we can analyze the problem.

Beginner

SPA112 Ringer Delay

Hi Dan,

This all looks a bit technical for my degree in Environmental Engineering! I have done my best to record the debug information during a 30sec period around an incoming call. The SPA112 is on IP 192.168.1.5 and my computer 192.168.1.13.

I can not see how to attach a file to this post, so have uploaded it to my dropbox: https://dl.dropbox.com/u/19578624/Logfile.pcapng

I hope you find this information useful in diagnosing my issues.

Many thanks!

George

Advocate

Re: SPA112 Ringer Delay

Despite your are environmental engineer ;-), I will try to explain what captured data mean. But before it, I downloaded your file, removed irrelevant packets  (packets belonging to other device) and attached resulting file here.

Green numbers in paragraphs bellow are reference to packet number in the attached file. In the following text, the term ATA will be used for your SPA112, term phone will mean the analog phone device connected to it.

OK, lets start.

Packets [2] is INVITE packet, announcing the incomming connection to you. Packets [5] and [90] are "100 Trying" and "183 Ringing" responses to the INVITE. The first one mean nothing for us, the second inform the caller your side is ringing (caller should got the ringback tone from it's phone).

So, what happened on your side in real ?

Your ATA has started to send ringing signal to your phone ([41])  0.1 second before it responded '183 ringing' [90] to caller.

So there has been no noticeable delay between caller's view about your ringing state and ATA ringing signal. Once more - you phone received ringing signal here [41], caller has been informed and should listen ring-back tone here [90].

If you phone remained silent, then it decided not to ring despite ringing signal.

It's not bug but feature.

Caller ID data are transferred ([97] - [106]) between first and second ring. Some phones supress first ring waiting for caller-id data. It's true  especially for advanced phones like FSMS capable phones, phones with  custom selection of distinct rings, phones with black lists and so on. Such kind of phone need to know  the caller info for decision "to ring or not to ring" and for selection of ring type (if decided to ring).

So, the first ring seems to be stolen by phone. The second ring start [107] 5.9s past first ring.

I assume you heared this second ring as your's phone entered [113] off hook state.

Phone becomed off-hook at 9.3 second past first ring = 3.4 second past second ring. The caller has been informed within 0.05 sec [126] about it. Ringback tones had been turned off at caller side, call entered 'established' phase.

Conclusion ? Phone seems to mute first ring, causing 6 second of minimal delay (you are not aware about incoming call untill second ring started). Such delay doesn't hurt in most cases. If you want to avoid it, you need configure your phone not to mute first ring. Most of phones allow such kind of configuration. Problem can't be solved by ATA configuration. Search phone's documentation how disable first ring skip.

Hope it help.

Message was edited by: Dan Lukes - I attached filtered version of capture file and modified accordingly the packet numbers in text.

View solution in original post

Highlighted
Advocate

Re: SPA112 Ringer Delay

Just side note - acordign the INVITE your provider prefer a-law codec over u-law codec. It's not surprising as we are in Europe. But configuration of your's ATA seems to prefer u-Law over a-law. It's suboptimal here. Unnecesarry transcoding take ATA's computing power and have negative impact on voice quality.

Consider change of Voice/Line[1|2]/Audio Configuration/Preferred Codec.

By the way, we are in wrong forum with such thread. Please move it (see 'Action', top of right column) to 'ATAs, Gateways and Accessories in Small Business Voice and Conferencing'

Beginner

SPA112 Ringer Delay

Dan,

That all seems to make pretty good sense. I borrowed an old corded phone and it rings immediately. Thanks for providing such a full and informative explanation. Thanks also for the codec tip.

George