ACCEPTS:
<iq to="asterisk.host.com" from="user@host.com" type="get" xmlns="jabber:client">
	<query xmlns="http://jabber.org/protocol/disco#items" node="http://nureality.ca/protocol/iax#extension">
		<item jid="user2@host.com" />
	</query>
</iq>

RESPONSE:
<iq to="user@host.com" from="asterisk.host.com" type="result" xmlns="jabber:client">
	<query xmlns="http://jabber.org/protocol/disco#items" node="http://nureality.ca/protocol/iax#extension">
		<item jid="user2@host.com" extension="1111" />
	</query>
</iq>