[Asterisk-Users] IAX2 and asterisk servers linking to each other

[Rich Adamson]

> > Guys. I have a few IAX2 connectivity questions that maybe somebody can
> > clarify to me:
> > 
> > I have my * server and another one with a friend. We are both inside nat and
> > doing port forwarding:
> > 
> > * -> nat -> internet -> nat -> *
> > 
> > Now, what I dont understand is this, why FWD needs to be configured in
> > iax.conf with a register and a peer and user entries:
> > 
> > register => user:pw at iax2.fwdnet.net
> > 
> > [iaxfwd]
> > type=user
> > context=fwd-incoming
> > auth=rsa
> > inkeys=freeworlddialup
> > 
> > [fwd-gw]
> > type=peer
> > host=iax2.fwdnet.net
> > user=user
> > secret=pw
> > qualify=2000
> > disallow=all
> > allow=ulaw
> > callerid=Anton Krall
> > 
> > But for connecting 2 * servers you need just this:
> > 
> > register => user:pw at asteriskhost.com
> > 
> > [remoteasterisk]
> > type=friend
> > language=sp
> > host=dynamic
> > secret=pw
> > context=mty-incoming
> > disallow=all
> > allow=ilbc
> > auth=md5
> > trunk=no
> > qualify=3000
> > accountcode=mike
> > 
> > Why not use a peer and user entries also? And when do you need to use
> > trunking? In this example, trunk=no.. Why?
> > 
> > Any enlightment on this will be greatly appreciated.
> 
> The register statement is primarily intended to let the other end
> know your system is available. Options with the statement include
> the ability to inform the other end how you want to be contacted
> (eg, an extension number they should use when sending a call to you).
> 
> The User and Peer context types are primarily used to specify
> specific parameters for incoming and outgoing calls. Maybe a bad
> example, but you could specify ulaw for outgoing calls and gsm
> for incoming calls, or whatever.
> 
> You might have an extensions.conf entry that looks something like:
>  exten => _6X.,1,Dial(IAX2/rsa-laptop/${EXTEN:1})
> where the call is directed to context=rsa-laptop, or,
>  exten => _6X.,1,Dial(IAX2/1.2.3.4/${EXTEN:1})
> where the call is directed to a specific IP address and does not
> reference a context.
> 
> In the first case, the parameters from the context are used. The
> second case does not reference a context, therefore default parameter
> values will be used (whatever they happen to be).
> 
> So, for you and your friend, if both asterisk systems are always
> on and available, there really is no value to register. Just use
> the User and Peer contexts, and set passwords and security parameters
> to your needs.

Ops, in the above I missed that you're using nat. The use of register
(and qualify) will help keep the nat tables active in the nat boxes.
Not all nat boxes are created equal; some timeout udp nat table entries
in a couple of minutes while other boxes will hold the table entries
for much longer periods of time. (Long periods of time consum large
amounts of memory under heavy traffic loads.)

The trunk=yes statement essentially allows multiple simultanous calls
to share the same IP packet, thus conserving IP packet overhead. In
other words two calls with trunk=no will have each call transmitted
with its own IP header, etc. While trunk=yes puts the voice packets
for both calls in the same packet with a single IP header. Unless
you truly have two or more simultanous calls going on, trunk=yes has
no value.

If I recall correctly, trunk=yes also needs to have a timing source
with the asterisk box (eg, digium card, ztdummy, etc). Think there
are some issues with trunk=yes and echo cancellation, therefore you
should probably use trunk=no for now.

FWD wants you to register with them so their system can easily
determine that your system is running (and available for call
completion).