On Tue, Oct 12, 2010 at 4:06 PM, Alex Balashov <abalas...@evaristesys.com> wrote: > On 10/12/2010 12:15 PM, Iñaki Baz Castillo wrote: > >> Second paragraph of Section 18.1.1 of RFC 3261: >> >> ------------------------- >> If a request is within 200 bytes of the path MTU, or if it is larger >> than 1300 bytes and the path MTU is unknown, the request MUST be sent >> using an RFC 2914 [43] congestion controlled transport protocol, such >> as TCP. >> ------------------------- >> >> IMHO this is an exotic specification. What about if the >> proxy/registart has to route a long request to a user registered in a >> UDP location? should the proxy try TCP? to which port? what about NAT? >> So this is a so exotic "feature" that I strongly understand everybody >> ignores it [*]. > > Strongly agreed. > > This is one of the most batshit inane, idiotic requirements I have > ever seen, and it should be rightly ignored by everyone in light of > the realities of today's Internet.
MTU discovery using ICMP can give you the maximum size of UDP packet. Usually it is simpler to implement the following strategy: - If the message is below 64K, send the message using UDP. - If the UDP transaction times out, try TCP transport. The SIP protocol requires that both UDP and TCP be supported for the port where the stack is listening. > > UDP is designed to be able to transport up to 65535 bytes of payload, On a LAN that is generally true. On a WAN that is not necessarily true. > and that is what a protocol using UDP as a transport should allow. > All SIP UDP endpoints and ALGs should support IP/UDP reassembly, > without question. Mandating use of TCP in this situation is simply > not realistic, especially when so many otherwise mainstream and > well-heeled, stable SIP stacks don't support it (for example, > Asterisk, many softphones, etc.). They *should* support TCP. Mandating IP/UDP reassembly is less realistic than requiring that endpoints support UDP and TCP. > > -- > Alex Balashov - Principal > Evariste Systems LLC > 1170 Peachtree Street > 12th Floor, Suite 1200 > Atlanta, GA 30309 > Tel: +1-678-954-0670 > Fax: +1-404-961-1892 > Web: http://www.evaristesys.com/ > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors -- M. Ranganathan _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
