Re: [Stox] Comments on draft-ietf-stox-im-11

[Ben Campbell <[e-mail]>]

> On Feb 11, 2015, at 8:47 PM, Peter Saint-Andre - &yet <[e-mail]> wrote:
> 
> On 2/11/15 7:16 PM, Peter Saint-Andre - &yet wrote:
>> On 2/9/15 4:27 PM, Ben Campbell wrote:
>>> (No hats)
>>> 
>>> Hi,
>>> 
>>> (I apologize that these comments are late in the process. Please feel
>>> free to defer them to last call.)
>>> 
>>> This version mostly looks good, but there are a few minor issues:
>>> 
>>> -- Message Size
>>> 
>>> It might be worth a discussion on message size limits (e.g. the SIP
>>> MESSAGE method limits the size to 1300 octets except under some
>>> pretty narrow circumstances.)
>> 
>> Thank you for pointing this out. I had glossed over it in my reading of
>> RFC 3428. I think it deserves a section of its own in the -im document.
> 
> I propose the following text:
> 
>   [RFC3428] specifies that (outside of a media session) the size of a
>   MESSAGE request is not allowed to exceed 1300 bytes.  Although in
>   practice XMPP instant messages do not often exceed that size, neither
>   [RFC6120] nor [RFC6121] sets an upper limit on the size of XMPP
>   stanzas.  However, XMPP server deployments usually do limit the size
>   of stanzas in order to help prevent denial of service attacks, and
>   [RFC6120] states that if a server sets a maximum stanza size then the
>   limit is not allowed to be less than 10,000 bytes.  Because of this
>   mismatch, an XMPP-to-SIP gateway MUST return a <policy-violation/>
>   stanza error if an XMPP user attempts to send an XMPP message stanza
>   that would result in a SIP MESSAGE greater than 1300 bytes.
> 

That just stepped in a bit of discomfort on my part, in that I'm not sure how a gateway that happened to support both stox-im and stox-chat decides which to invoke. I'm mostly willing to ignore that particular elephant, but would it be reasonable for an implementation to decide that larger messages would get promoted to MSRP (assuming support at the other end)? If so, the MUST return a <policy-violation/> seems to forbid it.

(While I'm still standing in it--what happens in stox-chat if the MSRP side sends a message larger than the largest allowed? Apologies if the draft talks about that--I don't have it in front of me.)


> Peter
> 
> --
> Peter Saint-Andre
> https://andyet.com/