Why is SCTP not much used/known

Question

I recently checked out the book \"UNIX Network Programming, Vol. 1\" by Richards Stevens and I found that there is a third transport layer standard besides TCP and UDP:

Answer 1

In reference to all of the comments about commercial routers being broken or lacking SCTP support, the issue is that SCTP with NAT is still in draft form with the IETF. So there is no RFC specification for them to implement it.

https://tools.ietf.org/html/draft-ietf-behave-sctpnat-09

Answer 2

We have been deploying SCTP in several applications now, and encountered significant problem with SCTP support in various home routers. They simply don't handle SCTP correctly. I believe this is primarily a performance issue (the SCTP protocol specification require checksums for the whole packets to be recalculated and not just for headers).

Like many other promising protocols SCTP is sadly dead in the water until D-link and Netgear fixes their broken NAT boxes.

Answer 3

p1. SCTP mapped directly over IPv4 requires support in NAT gateways, which has never been widely deployed anywhere, and without it the typical NAT gateway will only permit one private host per public address to be using SCTP at a time.

p2. SCTP mapped over UDP/IPv4 allows more private hosts per public address, but UDP mappings in IPv4/NAT gateways are notoriously tricky to establish and keep maintained, due to the fact that UDP is a connectionless transport without any explicit state for a NAT to track.

p3. SCTP mapped directly over IPv6 requires... well... IPv6. Have you tried to deploy IPv6? If so, have you tried to buy an IPv6 firewall? Does it support SCTP? How about a load balancer? A SSL accelerator?

p4. Finally, a lot of the Internet is pretty much constrained to what can fit through TCP port 80 and port 443, so SCTP of any flavor tends to lose there. Hence, you see efforts like the MPTCP working group in IETF.

Answer 4

Sctp is born too late, and for many situation TCP is enough.

Also, as I know most of its usage is on telecommunication area.

Answer 5

Many of us will be using SCTP soon, since it's used by WebRTC datachannels to create a TCP-like reliable layer on top of UDP -- SCTP over DTLS over UDP: https://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-13#section-6