Re: [rtcweb] SRTP not mandatory-to-use

[Bernard Aboba <[e-mail]>]

Ted Hardie said: 

> I'm a little lost.  In a gateway implemented in a back-to-back user
> agent, won't you end up with the same illusion?
> 
> The case I think you're talking about is this:
> 
> UA--1<-Connection1->B2BUA/Gateway<-Connection-2->UA-2
> 
> Do you expect that the gateway would be refuse to use SRTP on one side
> if it intended not to use it on the other? 



[BA] If the SBC needed to enable communication with a legacy endpoint, then it
might want to negotiate security compatible with that endpoint. 


Today there are PSTN gateways that support SRTP with SDES, but interop is 
frequently an issue (I've had to debug interop issues countless times), so 
I've often had to advise customers to turn SRTP off until an issue was resolved. 

Few PSTN gateways support any flavor of end-to-end security today (e.g. ZRTP, DTLS/SRTP, etc.), 
so a failover option is even more likely in that case. 

> If the requirement is SRTP always for WEBRTC, then a b2bUA would have
> to run SRTP on boths ides if both UA-1 and UA-2 were WEBRTC
> applications, but that seems to be what we want.

[BA] What you're missing is what legacy systems actually implement (see the SIPIt reports).