Why TLS for SIP

Question

Why is TLS the chosen link encryption for SIP?

From a paper, it seems that TLS can't handle UDP, whereas SIP doesn't require anyone to use TCP alone! So how is the interoperability ensured by TLS!

What would have been the issues if IPSec would have been used instead?

Answer 1

From a paper, it seems that TLS can't handle UDP, whereas SIP doesn't require anyone to use TCP alone! So how is the interoperability ensured by TLS!

That used to be true. DTLS provides TLS for datagram based protocols like UDP

Answer 2

From a paper, it seems that TLS can't handle UDP, whereas SIP doesn't require anyone to use TCP alone!

TLS is working on TCP level, so TLS requires to use SIP over TCP.

SIP is created under influence of HTTP. TLS is optimized for HTTP (and for SIP too).

One main disadvantage of IPSec is the extra size added to the original packet. TLS needs less overhead than IPSec.

Some comparison between TLS and IPsec

What would have been the issues if IPSec would have been used instead?

According to RFC 2119, RECOMMENDED has the same strength as SHOULD.

"3. SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course."

Discussion

Answer 3

You have other methods for UDP like header encryption.

23.4.3 Tunneling Encryption in rfc 3261