Hello community,

We currently have some issues with Kamailio SCSCF forwarding a large SIP UDP INVITE packet(size around 3000bytes), it got dropped somewhere in the ethernet. I tried increase the MTU size on both sides’ interface and even define it on the switch port, but still no luck.

So I am thinking to force SCSCF to send this INVITE over TCP, I followed this link: https://andersbrownworth.com/cms/264/, enabled naptr in SCSCF config and configured NAPTR and SRV DNS record, but the SCSCF still stop even forward it out. I think I did the DNS part right cause when I switch the NAPTR record to point to UDP it worked.

Anyone have some experience with configure SCSCF forwarding SIP through TCP?

BR,

Weiqi