Douglas Mortensen
2011-Nov-14 21:51 UTC
[asterisk-users] How do extensions "stay registered"
I know this is probably a very basic question for many on this list. But in troubleshooting an issue, I wanted to take a step back & ask the question. In Asterisk (or maybe all SIP), how do extensions stay registered with the SIP server? Do the extensions simply register repeatedly as a means of telling asterisk "I'm still here", or are there actual keepalive packets that are transmitted to actually keep a TCP session alive? My guess is the former. But am I oversimplifying it? Is there more to the process? Thanks, - Doug Mortensen Network Consultant Impala Networks Inc CCNA, MCSA, Security+, A+ Linux+, Network+, Server+ . www.impalanetworks.com<http://www.impalanetworks.com> P: (505) 327-7300 F: (505) 327-7545 . -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.digium.com/pipermail/asterisk-users/attachments/20111114/098bd661/attachment.htm>
SIP normally doesn't use TCP, it uses UDP, and is sessionless in that context. The exact mechanics of a registration can get deeply involved, so I'm going to give a very cursory overview. The endpoint tells the server (Asterisk, or whatever) that it would like to register, with a username and password, and what its IP address and port are. The server puts this in a list, and when it has a call for that endpoint, sends UDP packets to the known IP and port. There it typically encounters a NAT rounter, which had opened the port during the original registration and hopefully still has it open. You can enable a feature called NAT keep-alive on most endpoints to overcome bad NAT in some routers. On Mon, Nov 14, 2011 at 2:51 PM, Douglas Mortensen <doug at impalanetworks.com>wrote:> I know this is probably a very basic question for many on this list. But > in troubleshooting an issue, I wanted to take a step back & ask the > question. In Asterisk (or maybe all SIP), how do extensions stay registered > with the SIP server?**** > > ** ** > > Do the extensions simply register repeatedly as a means of telling > asterisk ?I?m still here?, or are there actual keepalive packets that are > transmitted to actually keep a TCP session alive? My guess is the former.* > *** > > ** ** > > But am I oversimplifying it? Is there more to the process?**** > > ** ** > > Thanks,**** > > -**** > > Doug Mortensen**** > > Network Consultant**** > > *Impala Networks Inc* > > CCNA, MCSA, Security+, A+**** > > Linux+, Network+, Server+**** > > .**** > > www.impalanetworks.com**** > > P: (505) 327-7300**** > > F: (505) 327-7545**** > > .**** > > ** ** > > -- > _____________________________________________________________________ > -- Bandwidth and Colocation Provided by http://www.api-digital.com -- > New to Asterisk? Join us for a live introductory webinar every Thurs: > http://www.asterisk.org/hello > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users >-- Carlos Alvarez TelEvolve 602-889-3003 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.digium.com/pipermail/asterisk-users/attachments/20111114/cd795e4d/attachment.htm>
"Extensions" do not register - peers do. A peer can register itself or be registered by Asterisk. In most cases the "extension" is equivalent to the "peer" (301 = 301) but it can be quite different (301 = sipuser1) or (301 doug at impalanetworks.com). From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Douglas Mortensen Sent: Monday, November 14, 2011 3:52 PM To: 'asterisk-users at lists.digium.com' Subject: [asterisk-users] How do extensions "stay registered" I know this is probably a very basic question for many on this list. But in troubleshooting an issue, I wanted to take a step back & ask the question. In Asterisk (or maybe all SIP), how do extensions stay registered with the SIP server? Do the extensions simply register repeatedly as a means of telling asterisk "I'm still here", or are there actual keepalive packets that are transmitted to actually keep a TCP session alive? My guess is the former. But am I oversimplifying it? Is there more to the process? Thanks, - Doug Mortensen Network Consultant Impala Networks Inc CCNA, MCSA, Security+, A+ Linux+, Network+, Server+ . www.impalanetworks.com P: (505) 327-7300 F: (505) 327-7545 . -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.digium.com/pipermail/asterisk-users/attachments/20111114/87b57dc6/attachment.htm>