[asterisk-users] High Availability with PRI failover

[Vicente Aguilar]

Hi

After a month or so using Asterisk we've had or first downtime period
due to a faulty RAM chip on the server, so we're starting to think about
the possible high-availability solutions.

We still haven't gone completely VoIP: we're using Asterisk in
conjunction with our old PBX and analog handsets, placing calls via a
PRI. No outgoing SIP calls yet and just a copule of VoIP local terminals
for testing, Asterisk is currently handling the advanced services like
call center queues, conference rooms, voicemail, time-based call
forwardings and the like.

Our current setup looks like this, using a TE210P (2xPRI) card on the
server:

Telco <--PRI--> Asterisk <--PRI--> Legacy PBX

In the event of another server failure, we don't see the real problem as
having several servers and doing failover between them (been there, done
that), but physically (and automatically!) plugging both PRIs to the
active server.

As far as I can tell, we've got two options:

1) Use some kind of physical layer switch on the E1 lines, like the
Jughanns ISDNguard or any of the other products referenced on the
voip-wiki, like this:

                 +--> Asterisk 1 <--+
Telco <-PRI-> SWITCH              SWITCH <-PRI-> PBX
                 +--> Asterisk 2 <--+

We would need to boy the switch(es?), and one TE210P per Asterisk
server. And this option would only handle an active/passive server
scenario, if we needed to scale up in capacity these switches wouldn't
fit on a load-balancing setup, am I wrong?

2) Use a Redfone's foneBRIDGE and heartbeat/ultramonkey/whatever to
manage the automatic failover between the different Asterisk servers,
like in:

     Telco <--PRI-+                    +-> Asterisk 1
                 foneBRIDGE <-- TCP/IP --> Asterisk 2
Legacy PBX <--PRI-+                    +-> Asterisk n

I prefer this option, conceptually it looks simpler and the total price
wouldn't increase if we need more servers. Besides, the price of one
foneBRIDGE is similar to that of one ISDNguard plus two TE210P, so the
cost of the simplest case (2 Asterisk servers) is almost the same for
both options.

Anybody has first-hand experience with any (or both) of these options?
Are there any other possibilites that I'm missing? Some other
foneBRIDGE-like product I still haven't heard of?

Thanks in advance

-- 
 Vicente Aguilar <vjaguilar at renr.es>
 Departamento de Sistemas
 Tlf.: 965 98 71 92

 Recursos en la Red, S.L.U.
 http://www.renr.es