[SR-Users] Few newbie questions

Alex Balashov abalashov at evaristesys.com
Thu Sep 17 08:40:18 CEST 2020


See inline:

On 2020-09-16 18:35, Adam Rutkowski wrote:

> 1 Does this topology seem right ?

"Right" isn't very addressable. It is a possible topology.

> 2 If Kamailio is used as registar and load balancer, does that mean all 
> domains, extensions must be present on all the FS boxes ?

No; the endpoints can be reached through Kamailio over a trunk/bridge, e.g.

    <action application="bridge" data="sofia/$PROFILE/$NUMBER at kamailio"/>

> 3 How will auto provisioning work in this case ?

I don't know much about Freeswitch autoprovisioning, but as I understand 
it, it works over HTTP and the URL is pushed over DHCP option 66 (i.e. 
the TFTP server option). Centralising the registrar won't change that.

> 4 Is there any reason to keep the FS farm ? or Kamailio poxying calls
> to VOIP providers is enough ?
Kamailio proxying the calls to VoIP providers is enough.

... on a technical level, anyway. Practically, this question hits upon a 
complex controversy that draws a broad array of disciplinary knowledge 
in VoIP. Whether a proxy is suitable as a carrier interface depends on, 
among other things:

1. Interoperability - whether the UAs on both sides can talk to each 
other through the very "thin" interoperability layer of a proxy, and 
also whether the carrier and customer gateways properly handle proxies 
(as the core SIP standard, RFC 3261, requires). Mishandling of 
Record-Route and things like that is fairly common;

2. Network topology hiding needs - proxies don't hide topology, and the 
addressing on both sides is readily exposed in SIP headers (though 
Kamailio does have 'topoh' and 'topos' modules as possible solutions to 
this problem);

3. Policy.

These are the waters in which the Session Border Controller (SBC) 
industry swims. At the risk of self-dealing, here's one of my articles 
on the subject:


And an admittedly opinionated conference talk:


> 5 What roles Kamailio could be used for in this case ?

That's a bit vague.

> 6 Is deploying on prem PBX for a customer a popular solution ?

Not at all (anymore), with the possible exception of large organisations 
and enterprises.

> 7 Anyone deployed above on Docker/ Kubernetes ? How's the performance 
> and the bad bits if any ?

Kamailio will run in Docker containers. "Docker/Kubernetes" is hard to 
parse; Docker and Kubernetes aren't remotely the same thing, do not 
belong in the same taxonomic category, aren't interchangeable bits of 
vocabulary, etc.

Otherwise, it's a really complicated and unwieldy question to address 
due to its breadth. Kubernetes is a complete universe unto itself and 
then some. As always, architectural choices of various kinds confer many 
costs, benefits and trade-offs. A little Googling will drum up some 
talks on Kamailio and Kubernetes, and the various shims and adaptation 
layers required to do Kamailio things the Kubernetes way.

But ultimately, it comes down to more fundamental issues around the 
merits of containerisation and various models of container deployment.

-- Alex

Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

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