[Standards] Council on Stanza Repeaters without Multicast

Dave Cridland dave at cridland.net
Thu Apr 3 08:47:42 UTC 2008


On Thu Apr  3 00:56:51 2008, Tobias Markmann wrote:
> That's nice to hear for OpenSSL but there is GnuTLS, NSS(Mozilla),  
> Windows'
> SSAPI(SChannel) and YASSL.

I can't speak for any of them, but my understanding is that  
compression is pretty commonplace on "desktop" TLS stacks, now, hence  
a very long and protracted argument about why it's not prevelant on  
mobile devices.

Certainly GnuTLS does DEFLATE according to RFC 3749. YASSL notes  
"zlib compression support" on its front page. On a quick skim,  
neither NSS nor SChannel docs were very forthcoming, and I don't have  
the data off-hand, but it'd surprise me if they don't as well.

>  I doubt compression can be used between any two
> different implementations which is a pretty bad situation one might  
> not want
> to base on.

No, that's tosh, sorry. RFC 3749 dictates how DEFLATE is used as a  
standard TLS compression codec, and it's known to be interoperable.  
(DEFLATE itself isn't known to be interoperable, oddly, but everyone  
uses zlib anyway, and its usage within TLS is known to work.)

>  Though it is nice if servers can use TLS' capabilities of
> compression it seems better to me also or only implement usage of  
> XEP-0138
> before TLS.

Both is fine. OpenSSL, at least, allows applications to check whether  
compression is in effect, allowing (in this case) servers to decide  
whether to advertize, or attempt, XEP-0138. But lack of compression  
support in TLS should be considered a bug at this point, and I see no  
reason at all to avoid using it. (I'm not sure how to, without simply  
using SSL instead of TLS.)

Dave.
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