On Fri, Apr 19, 2019 at 5:29 AM Mohit Dhiman <mohitdhiman...@gmail.com> wrote: > > As per the RFC 4347 section-4.1.1 > > Each DTLS record MUST fit within a single datagram. In order to > avoid IP fragmentation [MOGUL], DTLS implementations SHOULD determine > the MTU and send records smaller than the MTU. DTLS implementations > SHOULD provide a way for applications to determine the value of the > PMTU (or, alternately, the maximum application datagram size, which > is the PMTU minus the DTLS per-record overhead). If the application > attempts to send a record larger than the MTU, the DTLS > implementation SHOULD generate an error, thus avoiding sending a > packet which will be fragmented. > > But i think that res_rtp_asterisk's implementation of DTLS does not ensures > the DTLS record size to be less than MTU > and because of this i am getting IP fragmentation of DTLS packets which is > causing problems with certain ISPs while using WebRTC. > > can someone please confirm this, and if it is true that asterisk's RTP engine > does not ensure application layer fragmentation of DTLS > then is there some specific reason behind this implementation?
We looked into this a while ago, and as I recall, the SSL library didn't have a good way of doing fragmentation internally so that would require us at an application layer to fragment DTLS packets properly. It seemed like it was going to be quite a bit of work at the time and the current implementation works for a lot of people. More importantly though, nobody else has taken on the task to improve it, so thus, it does not exist yet :-) The path MTU detection was another dimension to this that needed to be worked on as well. -- Matthew Fredrickson Digium - A Sangoma Company | Asterisk Project Lead 445 Jan Davis Drive NW - Huntsville, AL 35806 - USA -- _____________________________________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-dev mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
