[asterisk-users] sip register peer (the quest for near 100% availability)

[Dave Platt]

> Is there any way to force this? I have several user agents and I want to achieve 
> near 100% availability for all peers. I realise that the peer will be 'woken' up 
> at my qualify intervals, but can I actually force registration from the CLI?

For those peers which are at known, fixed, predictable IP addresses
(e.g. in-house phones which have statically-configured IP addresses or
which get non-dynamic addresses from a DHCP server you control) you do
not need to use registration at all.  You can simply hard-code the
peer's address into sip.conf (or, I presume, an equivalent realtime
table).

When you Dial() such a peer, Asterisk will start sending out the INVITE
packets, regardless of whether it has heard anything at all from that
peer in the last hour or fifty.  No need for "qualify" although you
can use this to keep track of whether the peers are actually alive
or not.

If you take this approach, you'll save yourself a great deal of
heartburn if you can figure out an automated way of keeping the
IP addresses synchronized, between Asterisk and whatever
"hand out the addresses" mechanism the phones use (DHCP,
TFTP-based provisioning files, etc.).  Keep a "master list" of peers
and addresses in a simple table or file somewhere, and use this to
populate the other pieces of software which need to know.

For peers which can move around to arbitrary IP addresses, and where
your server system won't know what those addresses may be in
advance, using REGISTER from the device is really the only
good approach.  If you've got a setup where devices change their
IP address frequently and need to be on-line constantly, I'd say
you have a fundamental problem with no easy solution.  Using a
short registration time limit (e.g. 30 seconds) is probably the
least awful way to handle this, and if you're talking about a very
large number of phones you may want to set up a dedicated SIP
proxy to handle this registration burden and keep Asterisk from
having to deal with it.