Hello, sctp is the best by design protocol for sip, however, the implementations (libs/kernel/etc) are young comparing with the other transports, so you need to to some testing on performances and be sure you keep using the latest kernel. tcp is quite scalable, but the state maching the read the sip messages from the streams is more complex than the udp (where is just a read). On the other hand, you get rid of retranmissions. udp should still be the most flexible and fast in routing, even in some cases there might be retransmissions. In your network, when the connection is more or less guaranteed with good speed, that is very unlikely to happen. Also, you can control the nodes and be sure UDP fragmentation is properly handled (all recent linuxes/bsdes do it). As a conclusion, I would go for UDP if the nodes are in same network or network that has QoS guaranteed, with not very long distance between the nodes. If I would have time to play, perhaps I would look a bit at sctp. I haven't seen a good reason to go for tcp inside the internal network. Cheers, Daniel On 24/03/15 08:21, Mickael Marrache wrote: -- Daniel-Constantin Mierla http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda Kamailio World Conference, May 27-29, 2015 Berlin, Germany - http://www.kamailioworld.com