[OpenSIPS-Users] Message compression in OpenSIPS 1.12

[Kristian Kielhofner]

Hello,

  SIP body compression using gzip has already been implemented in a few places:

http://blog.krisk.org/2013/09/learning-stupid-nat-tricks-from-apple.html
https://jira.freeswitch.org/browse/FS-5814

  Compliance with this "standard" in OpenSIPS would be a good thing :).

On Tue, Sep 2, 2014 at 12:25 PM, Răzvan Crainea <razvan at opensips.org> wrote:
> Hi all,
>
> The first topic presented in the last public meeting[1] was related to
> Message compression - the idea is to reduce the size of the SIP messages to
> avoid UDP fragmentationor to save bandwidth and processing power.
>
> This topic was split in two parts:
>
> 1) SIP-wise changes over the messages (RFC3261 compliant -> supported by all
> user agents)
>     a) function that converts all header names to the short form (i.e. From
> -> f, Call-ID -> i, etc.). A single function will be exported in the script
> that will be called for the requests that should use the short form.
>     b) function that joins together headers that support multiple bodies
> (i.e. Record-Route, Via, Contact, etc.). There will be a function that
> indicates whether the outgoing request should merge these headers in a
> single one. An example of usage is when having two Via headers such as the
> following example:
>
> Via: SIP/2.0/UDP bigbox3.site3.atlanta.com;branch=z9hG4bK77ef4c2312983.1
> Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bKnashds8
>
> These headers will be merged in a single header:
>
>     Via: SIP/2.0/UDP
> bigbox3.site3.atlanta.com;branch=z9hG4bK77ef4c2312983.1, SIP/2.0/UDP
> pc33.atlanta.com;branch=z9hG4bKnashds8
>
>     c)delete irrelevant headers: create a new function that is used to
> delete certain headers that are not mandatory in the SIP protocol. By
> default, all headers but the mandatory ones are deleted. However, the
> function should receive a headers whitelist as a parameter: a list of
> headers that should not be deleted because they might be useful for the
> platform or end-users.
>
>     comp_delete_headers("X-Source-IP|User-Agent|Date");
>
>     d) remove redefined SDP attributes: provide a function that removes
> attributes that are redefined for some of the static codecs. For example,
> consider the following SDP:
>
>     m=audio 49230 RTP/AVP 0 98
>     a=rtpmap:0 PCMU/8000
>     a=rtpmap:98 L16/11025/2
>
> The SDP above can be suppressed to the following form:
>
>     m=audio 49230 RTP/AVP 0 98
>     a=rtpmap:98 L16/11025/2
>
>
> 2)Compressing the SIP message (using gzip). The idea is to take the SDP body
> and several headers that are not used in the routing logic, compress them,
> apply a base64 transformation and add to the message's body. A use case for
> this is a platform that has several edge servers (SBCs) and a few core
> instances - when entering the platform the message compression should be
> applied and then sent to the core servers. Inside the core networks, the
> messages should be carried in the compressed format to reduce the bandwidth.
> When leaving the network, the message has to be decompressed and forwarded
> to the next gateway without any compression, since the other equipments
> might not understand them.
> There will be several functions exported in the script:
>
>     a) compress_msg("1","Header1|Header2"); compresses the body of the
> message and listed headers
>     b) decompress_msg(); decompress both headers and body
>
> What do you think about this approach? Is this something you find useful?
> Since we don't have a final decision for this topic, we are looking for more
> input from you guys.Anybody is welcome to throw any kind of useful feedback
> on this matter, so don't be shy!
>
> [1] http://www.opensips.org/Community/IRCmeeting20140827
>
> Best regards,
>
> --
> Răzvan Crainea
> OpenSIPS Solutions
> www.opensips-solutions.com
>
>
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-- 
Kristian Kielhofner