[SR-Users] Redirect server for load balancing and HA

[Markus]

Hi list,

I'm new here, also to Kamailio. My goal is to achieve the "standard 
solution": Kamailio for load balancing and high availability of several 
Asterisk servers.

For starters, I've set it up with Kamailio+dispatcher+permissions acting 
as a proxy and it was working fine, but I'd like to try to keep it much 
more simple. For these reasons:

1) I'd like to maintain different peer settings in Asterisk (DTMF, codecs).

2) I don't want/need a database for Kamailio. I think it is mandatory 
for permissions module + IP auth. So, let's do Asterisk the 
authentication, it's already there.

3) Accounting. I'm using a software where it's really useful for 
accounting purposes if every peer/user has its own entry in Asterisk's 
sip.conf / in realtime table.

Long story short, my config now looks like this and it seems to be 
working fine for me:

request_route {
         route(DISPATCHER);
}

route[DISPATCHER] {

if ( method=="REGISTER") {
   ds_select_domain("1","4");
   sl_send_reply("300","Redirect");
   exit;
}

if ( method=="INVITE" ) {
   ds_select_domain("1","4");
   sl_send_reply("300","Redirect");
   exit;
}

if ( method=="SUBSCRIBE" ) {
   ds_select_domain("1","4");
   sl_send_reply("300","Redirect");
   exit;
}

}

My questions:

1) There are other approaches to the DTMF+codecs issue. Like this thread 
from 2013: 
http://lists.kamailio.org/pipermail/sr-users/2013-January/076379.html - 
but I have dozens of changing PSTN peers, so authentication/accounting 
based on port would be cumbersome. Are there new/alternative ways?

2) I searched the archive and the Web but did not find many questions 
about a "I-don't-want-Kamailio-to-show-as-the-only-peer-to-Asterisk" 
solution. Therefore I'm wondering: Is everyone a) running such 
homogeneous setups that they can survive with the same codec + DTMF 
settings in Asterisk for all their peers + users? Or b) doing some 
rewriting magic within Kamailio to deal with it? Or c) I'm overlooking a 
simple solution. Which one is it? :)

3) And the biggest question: Everywhere I read basically "Redirect 
server for LB + HA is not recommended, better use proxy". Is this still 
true, and if so, what are the reasons? Because I should be worried that 
not all clients/gateways out there respect a SIP 300 Redirect? Other 
reasons?

Thanks so much! :)
Markus