[VoIP] Naive question

[Steph Kerman]

Chad Perkins wrote:
> On 12 Dec 2006 at 16:29, Steph Kerman wrote:
>> Chad Perkins wrote:
>>> On 11 Dec 2006 at 21:03, Steph Kerman wrote:
>>>> Chad,
>>>> Thanks for exploring some of the ramifications of my question.
> [big snip]
>> Most people in the population at large, for sure. I was thinking in 
>> terms of the people who have commercial Voip and might be inclined to 
>> provide a second access to CNET.
> CNET is a "techie" bunch for the most part, some more than others, 
> some in different areas. In an effort to get more of our Telephone 
> Museum members involved I have been trying to perfect a configuration 
> using two-line ATAs (similar to what Greg has
> done) as many of these folks are "telephone people" and/or 
> "collectors" but not "computer" or "Internet" people.
What is it you are referring to that Greg has done?
>> That said, there are ways to combine the two separate lines into an 
>> RJ14 config. using OTS stuff from Radio Shack.
> I know, probably $10. Two extra line cords, a splitter and a coupler 
> hitched up back to front. I'm still tempted to warm up the solder 
> gun... [snip]
I've seen plenty of single line devices that were equipped with 
2-contact jacks and the remaining 4 hole locations were not even drilled 
to facilitate replacing the jack, if you could find one with an 
identical footprint.  I've seen devices where the holes were drilled for 
4 but not 6.  I've seen devices where the holes did not have solder 
pads, but for jumpering this would not matter much.

Another alternative is this:  Some retail purchased products come with 
2-conductor line cords that have a narrow cross section.  Others have 
full width but the bulk is plastic jacket where the outer 2 conductors 
would be.  I save the narrow cross section cords for special purposes 
such as jumper fields where they can serve well to reduce the bulk of 
the jumper bundle and making special hydra cables. 

Another possible use is this: two of these cords will fit side-by side 
in a single plug.  This makes it possible to crimp 2 of these cords into 
a single plug, one connected to the outer (2 & 5 or Line 2) and the 
other to the inner (3 & 4 or Line 1) contacts of the plug.  This 
requires crossing over conductors but that should not pose any problem.  
The other ends each go to contacts 3 & 4 of two separate plugs.  This 
special cord, together with a simple cord coupler, can be used to 
fabricate a dual RJ11 to RJ14 converter that would be less bulky and 
much less vulnerable to breakage than the 267C adapter back-to-back with 
a cord coupler.
>> So who is your "SIP provider" from whom they capture your IP address?
> Normally the commercial (SIP) provider is going to capture the IP 
> address when the SIP application (device) starts so that they know 
> where to send calls, status monitoring and "messages" (message waiting 
> indication for example), etc.
>
> Here's a question if anyone knows, if a Vonage customer calls another 
> Vonage customer, does it ever hit the PSTN? I think I can safely say 
> the other providers I use/am acquainted with do not.
>> Is that another party other than Stanaphone or FWD?
> No, one in the same.
>> I see. But a switching function, if I understand correctly, would 
>> double the delay so an ENUM would seem to be the best way.
> Yes and no. Even with a switching function in the middle many VoIP 
> implementations allow for the voice (and video) channels to be 
> redirected to the end points as soon as the connection comes to avoid 
> this very issue. The end points do however maintain a control 
> connection with the switch for things like the ability to transfer, 
> conference, etc., update Call Detail Records, and more.
>>> In our CNET we use Asterisk switches as tandems to front end the EM 
>>> machines and equipment. In addition to Cl.4-ish tandem functions 
>>> most of us also have Cl.5 services in our Asterisk tandems too; for 
>>> some that includes SIP extensions.
>> Please ID what "CI.4" and "CI.5" refer to . Are these abbreviations 
>> for something?
> Sorry, Class 4 and Class 5.
Thanks.  The lower-case "L" was indistinguishable from an upper case "i" 
here.
>>> As I eluded to in my previous post, if the SIP device is registered 
>>> to a commercial providers switch as the opposed to a CNET switch 
>>> (Asterisk tandem) it still may be possible to have both on one (port 
>>> of a) SIP device, but the configuration would become
>>> totally manual.
>> I assumed that if it were feasible at all, it would have to be 
>> manually installed. Is any of this configuration at the ATA itself or 
>> is it all done at the Asterisk that is sharing it?
> This is a theoretical answer and based on some assumptions not having 
> done this quite this way personally ...
>
> 1. SIP device: The ATA (or IP phone) would have to be (re)configured 
> to accept unsolicited connections (if you think that sounds kind of 
> risky you are right, read on).
>
> 2. Firewall: Based on #1 the SIP device had better be "behind" are 
> firewall (I have no experience with the combo units). Because the 
> device is only registered with the commercial provider, the firewall 
> isn't going to be expecting, or know what to do with incoming IP 
> packets from the Asterisk "tandem"; therefore the firewall will need 
> to have port forwarding enabled for the proper (SIP) ports ... and 
> because the device is
> now open to the Internet on those ports you would want to add an 
> access list restricting connections to just the Asterisk tandem (and 
> hope you don't kill the commercial connection in the process). This is 
> an area that varies widely from vendor to vendor.
>
> 3. Asterisk tandem: Because the device isn't registering the him he 
"the him he"?
> isn't going to automatically know where on the Internet the device is 
> in terms of IP address, so the 'sip.conf' file in the /etc/asterisk 
> directory will created/modified to specify the address to use in 
> connection with that device. This would probably be done one of two 
> ways, either by hardcoded IP address, or by a dynamic DNS (DDNS) name.
>
> 4. Internet Address: Because of #3 above, the end device is going to 
> have to either have/share a fixed ISP IP address; or you would need to 
> setup a DDNS entry. Unfortunately I don't think I've seen a device 
> with firmware that supports DDNS. One should be able to install a DDNS 
> client on a regular PC on the same network as the device to get around 
> this though.
>
> FWIW these four basic items are roughly the same steps one needs to 
> address in an ENUM setup, in fact I see no reason why under the right 
> circumstances such a device couldn't participate in an ENUM based 
> network (mind you while CNET is an ENUM network, it is also based 
> primarily on the IAX2 protocol as opposed to SIP which can be a pain 
> in the neck.
>
> Moral of the story, go with an unlocked two line unit, use the 
> standard registration process; it will be a lot easier with a lot less 
> problems.
Thanks for exploring this with us.

Steph