Hi, Kristian!
Sure, I think being compatible with other systems in the branch is
important too. In order to do this, we should probably support two
compressing methods:
1) Compress both headers and body and add it in the SIP body - this will
offer better compression ratio, but is not compatible with any equipment
2) Add only the compressed body in the SIP body, and the headers in a
different SIP header - this will be compatible
Moreover, we are planning to be able to use different compression types
besides gzip (i.e. lzma, bzip, etc.).
Considering these adaptions, the functions we are going to use should
looks something like:
a) compress_msg("gzip, "bs", "Header1|Header2"); the first
parameter is the compressing method, then a set of flags ("b" indicates
that the body should be compressed, "s" that it has to be separated from
the headers), and a list of headers to be compressed
b)decompress_msg("bh"); the parameter is a set of flags that
indicates what exactly should be decompressed
What do you think about this approach?
Best regards,
Răzvan Crainea
OpenSIPS Solutions
www.opensips-solutions.com
On 09/03/2014 01:22 AM, Kristian Kielhofner wrote:
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 <[email protected]> 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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