[VoiceOps] "Timeout" on VoIP call traversing Verizon data

[Mark Wiles]

Yes, I think the softphone client does use TCP.

-----Original Message-----
From: Peter Beckman <beckman at angryox.com> 
Sent: Thursday, June 10, 2021 4:07 PM
To: Mark Wiles <mwiles at akabis.com>
Cc: Dovid Bender <dovid at telecurve.com>; voiceops at voiceops.org
Subject: Re: [VoiceOps] "Timeout" on VoIP call traversing Verizon data

uhhhh.... SIP here is UDP, no?

There's no connection to close for UDP.

The source port for UDP doesn't matter. It's not part of the whole conversation, unless your switch cares that all communications continue to come from the source port. It's connectionless.

TCP 5060 isn't even listening on our switches.

So, maybe you're doing SIP over TCP?

On Thu, 10 Jun 2021, Mark Wiles wrote:

> Hi Dovid,
>
> So just thinking about this… granted, there wasn’t SIP traffic for “X” amount of time… but there would have been RTP… so wouldn’t that have been seen as traffic?
> Hmmm… but as soon as I typed that, SIP traffic’s on one port… RTP 
> traffic’s on another port… so even with the RTP flowing along and 
> happy… the SIP’s another matter… right?  Duh!  (I’ve not had my coffee 
> yet)
>
> Are you saying that you’re using Metaswitch MaX UC and you’re doing a SIP OPTIONS message every 49 seconds?
> I totally agree it does sound like a NAT pinhole is closing.  It would seem that if that’s the case, Meta would have run into this before and had “recommendations” to address this.
> I’ll bounce your thoughts off of them.
>
> Thanks!
>
> Mark
>
>
>
>
>
> From: Dovid Bender <dovid at telecurve.com>
> Sent: Thursday, June 10, 2021 8:47 AM
> To: Mark Wiles <mwiles at akabis.com>
> Cc: voiceops at voiceops.org
> Subject: Re: [VoiceOps] "Timeout" on VoIP call traversing Verizon data
>
> If I had to guess Verizon is using CGNAT and since there is no traffic for X amount of time the NAT hole for the SIP traffic is closed. When you send a re-invite at the 30 minute mark that session as far as Verizon's CGNAT devices are concerned have been closed a long time ago. You would need to send a packet to the phone or have the phone send to your switch some sort of traffic (we send SIP OPTIONS every 49 seconds) to ensure that the session stays alive.
>
>
>
> On Wed, Jun 9, 2021 at 3:27 PM Mark Wiles <mwiles at akabis.com<mailto:mwiles at akabis.com>> wrote:
> If there’s a Verizon cellular data guru monitoring here, I’d love to get your insight!
>
> Otherwise, let me toss this out to the group for thoughts and opinions 
> please…
>
> We’re a Metaswitch shop, and use their MaX UC mobile softphone client (iPhone/Android).
>
> We had a customer using the MaX UC client on a long call… they were using Verizon cellular data (confirmed by IP address).
> At thirty (30) minutes into the call, the call “dropped”.  The call was re-established, and again, after thirty minutes, the call dropped.
> We’re pretty sure the user was in a static position (non-mobile)… and logically assume they were on the same cell tower for both calls that dropped (the Verizon IP was the same).
>
> Looking at Metaswitch SAS (their diagnostics tool), at the thirty minute mark, we send out a re-INVITE message to the softphone client… and we receive no reply… so after ten seconds, we breakdown the call assuming they’re gone.  Then about eight seconds later, we see an INVITE message from the softphone’s same IP address (with the same Call ID)… however, it’s coming from a different port.  So to be clear, the original call setup and connection was using 1.2.3.4:6789… then eight seconds after we ended the call with a BYE (assuming they were gone due to lack of reply), we get an INVITE (with the same Call ID) from 1.2.3.4:9876<http://1.2.3.4:9876>.
>
> Metaswitch looked at the diags from the softphone (we downloaded them), and they’re confirming that the softphone never received our re-INVITE at the 30 minute mark.
>
> Metaswitch also looked at the bug/crash logs on the softphone, and confirmed neither was the case.
>
> It almost sounds like a NAT thing going on… but I’m pretty ignorant 
> when it comes to cellular data.  It looks to me as if the Verizon side 
> simply changed port numbers, and assumed we’d know maybe via mental 
> telepathy?  😊
>
> Has anyone had experience with such an occurrence… or any thoughts?
>
> Thank you!
>
> Mark
>
>
>
>
>
>
>
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Peter Beckman                                                  Internet Guy
beckman at angryox.com                                 https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.angryox.com%2f&c=E,1,J6mY4TPlvkxXFJlo4jt1Dj9QhcS3KQtRG8KcfXg8TXaxp7H4XZ3K1Gw3lisyYqyDucpfqlw7sVGfMRAJ-SlXawjEtAhfocHELyvhLeDmgfJr&typo=1
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