[Asterisk-Users] Date Time Stamp with Caller ID

[John Todd]

At 4:13 PM +0100 on 6/20/04, Kevin Walsh wrote:
>Kubat, Philip [pkubat at kubat.com] wrote:
>>  (Article auto-converted from unnecessary HTML to nice plain text.)
>>
>>  Where does the date/time stamp from Caller ID come from?  On my
>>  extensions ATA188 and IAX2 soft phone the caller id date / time is 12/30
>>  12:00AM.  The Linux time is correct.  SayUnixTime return the correct
>>  time. 
>>
>My phones have a built-in clock.  The Cisco 7960s are configured to
>take their time from a NTP server.  I have a couple of portable DECT
>phones connected to a Sipura SPA-2000.  The phones allow the time to
>be set from within the setup menu, and the Sipura uses our local NTP
>server.
>
>Check whether your phones have a clock.  All of mine do in one way or
>another, so I always get the correct time associated with the
>Caller*ID notices.
>
>It's possible that the time/date is also encoded into the Caller*ID
>signal.  I haven't had cause to look into that.  It's possible that
>the DECT phones ignore the local time and use the time provided by the
>Sipura (if the Caller*ID signal does indeed supply this information).
>Again, I haven't had cause to look into that.
>
>Check whether your ATA device can be configured to use a NTP server.
>Also check whether your soft phone, and the phone connected to your
>ATA, has a clock you can set.
>
>--
>    _/   _/  _/_/_/_/  _/    _/  _/_/_/  _/    _/
>   _/_/_/   _/_/      _/    _/    _/    _/_/  _/   K e v i n   W a l s h
>  _/ _/    _/          _/ _/     _/    _/  _/_/    kevin at cursor.biz
>_/   _/  _/_/_/_/      _/    _/_/_/  _/    _/


While many media adapters (SIP deskphones, analog-to-SIP converters, 
etc.) use NTP as their time-setting protocol, several (SNOM and 
others) use the Date: stamp in the SIP header to set their clocks 
upon an INVITE.

This implies that the time is correctly set (via ntp) on your 
Asterisk server/SIP proxy.  Asterisk currently sends a Date: stamp as 
part of the INVITE, so NTP is not always necessary.  SER recently had 
an update to support this header - see the mailing list.

I actually prefer having both methods on a device (selectable), since 
having to open up firewalls/etc. for NTP from the phones breaks some 
ease-of-implementation models.  (Minor point, but valid in some 
environments.)  SIP should contain everything you need when talking 
to a User-Agent.  Personally, I don't like devices which _require_ 
(other than for provisioning) protocols other than SIP to be 
functional (web, telnet, syslog, snmp, ntp, etc.)

It sounds neat to have things in different protocols, but that leads 
to customer service nightmares in the future.  NTP is pretty 
innocuous, but it's still another "tech note" that you have to give 
to the customer's network team (which, not surprisingly, might not be 
the people installing the phones.)

JT