[Serusers] About a SIP load balancing document involving SER

[Victor Pascual Ávila]

Hi Iñaki,
thanks for your comments.

On Wed, Oct 8, 2008 at 10:52 PM, Iñaki Baz Castillo <ibc at aliax.net> wrote:
> This is completely true, but next page (8) says:
> --------------------
> Transparency for responses
>  Prevent Load Balancer from inserting a VIA header
>     E.g. in SER utilizing the SEND core command
>  Modify the SIP's Proxy core to ignore the VIA-header
>  added by the Load Balancer
> -------------------
>
>
> There is an important error that unfortunatelly I've realized it's very
> common. Section 18.2.2 of RFC 3261 says clearly that the responses are
> *always* sent through the same nodes the request came from. So the response
> should always traverse the load balancer.
>
> 1) Load balancer --- (SIP UDP) ---> UAS
> In this case the UAS would always reply to the *real* source IP (if this is
> different of the Via "sent-by" then UAS adds "received" parameter and replies
> there).
>
> 2) Load balancer --- (SIP TCP/SCTP) ---> UAS
> By definition a UAS must reply using the incoming TCP connection.

I agree this should be the proper behavior as per RFC3261.

> So it's extrange for me that a document about SIP load balancing tries to
> offer solutions that are not SIP compliant and also unfeasible (UAS will
> always reply to the real source IP regardless of the Via content).
>
> Since the document proposes SER based solutions (using "SEND" command) I'd
> just like to confirm if I'm completely right, or maybe it's common those not
> SIP compliant methods by some vendors in order to provide a load balancing
> solution.

Actually I understand this document to be part of a research project.
I don't believe that ignoring a VIA header or preventing a SIP entity
from inserting a VIA header is a common praxis in the industry. But as
you might imagine, research is research and prototypes are prototypes
:-)

Thanks,
-- 
Victor Pascual Ávila