[asterisk-users] Confused by concepts behind pjsip: endpoint, aor, contact

George Joseph george.joseph at fairview5.com
Sun Jan 4 16:45:28 CST 2015

On Sun, Jan 4, 2015 at 3:29 PM, Antonio Gómez Soto <
antonio.gomez.soto at gmail.com> wrote:

> Hello,
> I am slightly confused by the difference between chan_sip and pjsip.
> Especially the new (to me) objects aor and contact.
> I am having trouble mapping them to the typical SIP configuration settings
> on a phone.

There's some info on the wiki here...

> Suppose I have a phone with two line buttons, for two extension numbers.
> Now,
> I think that means two 'endpoints' in pjsip right?

Generally correct, if you set up 1 extension to 1 endpoint.

> But what exactly is the difference
> between aor and contact?

AORs contain contacts.  They can be permanent or dynamic.   You'd define
permanent contacts for trunks or devices where the peer ip address is knon
using the 'contact' parameter.   If you don't define any contacts, then
dynamic is assumed and the aor/endpoint will accept inbound registrations.
  You'd use dynamic for most phones.

> So why does aor have a max_contacts value?

If you're accepting registrations, max contacts defines how many peers will
be allowed to register.  For most scenarios it's 1 but you COULD have 2
devices register to the same endpoint.  When a call is sent to that
endpoint, the first available contact will be dialed.

> And where do phone registrations fit in, where are those kept anyway?

See above.

> I hope someone can shed some light for me here.
> Thanks,
> Antonio
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