Re: [tsvwg] The List (of application-layer desired features)

[Michael Tuexen <[e-mail]>]

On Aug 28, 2013, at 3:34 PM, William Chan (陈智昌) <[e-mail]> wrote:

> On Wed, Aug 28, 2013 at 7:53 PM, Michael Welzl <[e-mail]> wrote:
> 
> On 28. aug. 2013, at 11:53, William Chan (陈智昌) wrote:
> 
>> On Aug 28, 2013 4:01 PM, "Michael Welzl" <[e-mail]> wrote:
>> >
>> > Hi,
>> >
>> > I agree 100% with Michael Tuexen here... just one thing, in line:
>> >
>> >
>> >>> You're right, SCTP is non-deployable, which makes it a non-starter.  SCTP also does not address handshake issues or TLS issues.
>> >>
>> >> I agree that SCTP over IP can't be deployed now due to missing NAT support.
>> >
>> >
>> > Indeed that's not an argument against SCTP/UDP/IP, but I also wonder why, instead of saying "can't be deployed", people don't just go ahead and use it whenever it's there and works, with a fall-back to TCP? This could be done with (this version of) Happy Eyeballs:
>> > http://tools.ietf.org/html/draft-wing-tsvwg-happy-eyeballs-sctp-02
>> >
>> > Good reasons against doing this are... what? Anyone?
>> 
>> Implementation usefulness. Why bother adding code that barely gets used (and that is unlikely to improve in the near future), adds complexity, code bloat, etc...?
>> 
> Fair point. That's why I think the OS should in fact do Happy Eyeballs for you!
> 
> 
> I'm not sure if you're trolling me. In case you aren't, you may want to look at the graph at: http://gs.statcounter.com/#os-ww-monthly-201207-201307. Windows XP (released in 2001) is still around 20% of browser usage. If you have the ability to get Microsoft to backport SCTP/IP onto their XP stack, I'd love to know. We're not going to ignore large segments of our user base when we could use UDP and deploy for all relevant OSes. That may be acceptable for some applications, but not for the browser I work on.
You can build SCTP in your browser and run it on top of UDP. This is what is done
in RTCWeb. They use SCTP over DTLS over UDP with SCTP and DTLS running in the
application layer. This is available in recent versions of Firefox and running
on Windows XP...

Best regards
Michael
> 
> This is why Roberto said:
> """
> Wide, "safe" deployment
> """
>> SCTP/UDP has a much higher likelihood of usefulness. But as Roberto has mentioned, it still has deficiencies, mostly around RTTs (connection + DTLS setup). If they can be fixed, great. Let's do it.
>> 
> Why shouldn't it be possible to fix SCTP to do whatever you want? Anyway it sounds to me like a simpler approach than building a whole new protocol. Of course, SCTP++ isn't the nicest acronym...  then again, RTMFP isn't either, if you ask me, sounds almost like RTFM...  QUIC is great though!
> 
> I have no attachments to the protocol name or frame format or whatever. Look at what we're doing in HTTP/2 which was inspired by SPDY but now has undergone substantial changes. We're serious about this. As long as the transport provides all the features we need, we'll use it. This conversation got started because tsvwg asked httpbis what the application layer wants from the transport. We're telling you. I think the constructive next step is for tsvwg folks to ask for clarification on any requirement they don't understand, discuss whether or not the requirements are reasonable, and discuss what may need to be done to address them.
>  
> 
> Cheers,
> Michael
> 
>