[SIPForum-discussion] Does anybody familar with what empty Accept-Language means?

ZHANG Joey yongz at alcatel-lucent.com
Mon May 11 10:03:39 UTC 2009



Thanks for your reply. We can follow RFC2616, so RFC3261 needs to be
updated to reflect this? Since many SIP devices follow RFC3261 and maybe
catch such issue. 






From: Tomasz Zieleniewski [mailto:tzieleniewski at gmail.com] 
Sent: Monday, May 11, 2009 5:22 PM
To: ZHANG Joey
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Does anybody familar with what empty
Accept-Language means?



In HTTP if an Accept-Language header is present, then all languages
which are assigned a quality factor greater than 0 are acceptable.
>From specification it is one non-empty list of "language-range"'s. There
is a special range "*" which represent everything which wasn't matched
by ranges.
SIP defines Accept-Language as: "Accept-Language:" + optional sequence.
This is not consistent with HTTP specification.

Accept-Language  =  "Accept-Language" HCOLON

                     [ language *(COMMA language) ]

language         =  language-range *(SEMI accept-param)

language-range   =  ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) / "*" )

So trying to applie rules from RFC 2616 with SIP definition I would say
if the header value is empty and there is no special range "*" present
(everything which wasn't matched by ranges)
then this means that no language is acceptable.

Kind regards,
- Tomasz Zieleniewski

2009/5/8 ZHANG Joey <yongz at alcatel-lucent.com>



I encounter one issue about the syntax of Accept-Language, seems that
RFC3261 is inconsistent with RFC2616.  From revision of HTTP spec (see
), Accept-Language can't be empty. But from RFC 3261 ABNF,
Accept-Language can be empty since the field value is optional.


Can anybody tell me should the Accept-Language be empty?  And what does
empty Accept-Language means? 





Joey Zhang


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