Interesting, I definitely hand port filter. Now it makes sense. Thanks Kaufman.
On Thu, 13 Mar 2025 at 10:19 PM, Ben Kaufman <bkauf...@bcmone.com> wrote: > Note that it's not just the -A option you have going. I will guess that > you've got a capture filter like port 5060. The fragmented UDP packets > don't have port numbers, so they will get dropped by the capture. > > Regards, > Kaufman > > ------------------------------ > *From:* Pavan Kumar via sr-users <sr-users@lists.kamailio.org> > *Sent:* Thursday, March 13, 2025 11:16 AM > *To:* James Browne <ja...@frideo.com> > *Cc:* Kamailio (SER) - Users Mailing List <sr-users@lists.kamailio.org>; > Fred Posner <f...@pgpx.io>; Pavan Kumar <pavanput...@gmail.com> > *Subject:* [SR-Users] Re: SDP Truncation When Relaying from WebSocket to > UDP – Expected Behavior? > > > *CAUTION:* This email originated from outside the organization. *Do not > click links or open attachments* unless you recognize the sender and know > the content is safe. > > Thanks, Fred and James, for pointing me to the UDP fragmentation mechanism. > > As James mentioned, using tcpdump with the -A option didn’t display the > fragmented part, that's where all confusion arised. > > Best regards, > Pavan Kumar > > On Wed, Mar 12, 2025 at 3:42 PM James Browne <ja...@frideo.com> wrote: > > Hi > > Technically, the SDP does not get truncated. At the SIP/SDP level, > there's no truncation. Fragmentation happens at the IP layer. > If kamailio sends a large SIP/SDP message and the other side receives > only one fragment, then it the receiving SIP application will never > see it. There's no danger of the SIP application getting only a > partial SIP/SDP message due to fragmentation. > > > is FreeSWITCH handling the partial SDP > No. It cannot receive only a partial SDP. It's all or nothing. > > > Should I be concerned about ... missing codec negotiation > No. It can't happen. > > Maybe you captured traffic and didn't see all of the fragments. Check > it again and see that the whole SDP was definitely sent and received. > If the traffic is working, then (as Fred says) you may just be fine to > let it go as is. You're possibly simply thinking you have a problem > when it may not even exist. On the other hand, if you start getting > packet loss, then you may have a problem. > > James > > On Wed, 12 Mar 2025 at 03:27, Fred Posner via sr-users > <sr-users@lists.kamailio.org> wrote: > > > > On Mar 11, 2025, at 10:24 PM, Pavan Kumar via sr-users < > sr-users@lists.kamailio.org> wrote: > > > > > > Hello Kamailio Community, > > > • Is this expected behavior? Should Kamailio automatically > truncate SDP when relaying from WebSocket to UDP? > > > > Yes. Often referred to as UDP fragmentation. > > > > > • Could this be working accidentally? For example, is FreeSWITCH > handling the partial SDP gracefully by default? > > > > It could be working non-accidentally. ;) As long as the packets are > received well, there may not be a problem. > > > > > • Should I be concerned about potential failures in different > scenarios? (e.g., ICE candidate loss, missing codec negotiation) > > > > Alex Balashov wrote up a nice piece many years ago… > > > https://blog.evaristesys.com/2016/02/04/sip-udp-fragmentation-and-kamailio-the-sip-header-diet/ > > > > There’s generally 2 ways of approaching it… > > > > A) Switch to TCP for that connection > > B) Keep as is > > > > Depending on the amount of traffic you are pushing through, TCP is > generally a safe method of handling. If you’re running a considerable load > (especially considering the system is also running websockets), you may > need to tune your system appropriately. > > > > If these two systems were (let’s say) on the same LAN and even lucky > enough to be on dedicated VLAN, then if there wasn’t any problem in the > fragmentation, you may just be fine to let it go as is. > > > > > > Regards, > > > > Fred Posner > > > > > > __________________________________________________________ > > Kamailio - Users Mailing List - Non Commercial Discussions -- > sr-users@lists.kamailio.org > > To unsubscribe send an email to sr-users-le...@lists.kamailio.org > > Important: keep the mailing list in the recipients, do not reply only to > the sender! > >
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