Internet Telephone

It looks as if many of the Grandstream VoIP phones support "direct IP calling" right out of the box.

formatting link

Reply to
Dave Platt
Loading thread data ...

OK, the problem is that most places where you can just plug in and get internet access via DHCP are behind a firewall with NAT, so these nodes can NOT be reached by knowing the IP address assigned to the device by the DHCP daemon. So, two of them would almost never be able to create a connection between them. You would either need the local IT authorities to set up a WAN address for you at least at one end, or use some 3rd party server somewhere to complete the connection.

You can do this with most anything that can access the net, using various apps. Basically, it works like Skype, there now appear to be dozens of similar systems/apps available. Since a LOT of institutional PCs, etc. are behind a firewall with NAT, they all have the same problem they can't be reached from the net without a 3rd party server.

There are apparently now thousands of companies offering VOIP service for insanely low fees. These all allow you to set up soft clients from anywhere in the world, they could be phones with TCP access, PCs, tablets, etc. All you need is a microphone and a speaker.

Jon

Reply to
Jon Elson

It is not an ATA, it is a complete phone. And yes, I can dial *192*168*100*2# and be connected to the phone at that address. But of course that only works when the other phone is on a directly reachable address, i.e. it will not work when the other phone is behind some consumer internet router.

With a server (e.g. a Raspberry Pi running Asterisk) it becomes much more usable. But I have also entered details of a VoIP provider on internet so I can make and receive regular calls on the POTS network.

This particular phone can handle 4 different accouns, has 7 programmable memory keys, has an LCD display indicating caller and presenting all kinds of menus and even weather and stock info, etc.

It is the Grandstream GXP2100. It has since been replaced by newer similar models.

Reply to
Rob

True, but it's easy to deternine the Internet IP and enter it into the device. Just Google proxy test for one of the sites I frequently use to find the Internet IP at any location. There are other ways to do it but a quick Google is often the quickest.

Do you mean forward a port? Once location A has a port forwarded from the WAN to the LAN then a device at location B can make an outboud TCP/IP connection to point B. Once the connection is established communication can begin in both directions.

It's true that most people couldn't forward a port if their life depended on it. I'll give you that.

Or did you mean that some locations don't allow direct access outside and have the browser connected to an internal proxy and the email connected to an exchange server or something similar? In that case yes you can't do it without local IT cooperation but the device I have in mind is not intended for that situation.

Well I can't claim to know a lot about apps. They were called application programs when I last had much to do with them.

In that case how do they manage to connect their browsers to web servers so that not only can the web server reach them (and thus send them the contents of the page) but they can also, for example, fill in a form on a website and thus send informaion out? And how do they manage to fill up with viruses and malware so quickly if they are behind a firewall? At least the ones I frequently have to deal with.

The same problem exists in, say, a hotel room. Call the front desk and ask for a port to be forwarded and you're likely to find a bottle of wine arrives at your room. But who cares? You did the port forwarding at home didn't you? So you don't have to do it at the hotel.

Ok here's an assignment for you, not for anyone else reading this. Early telephones used a carbon microphone. Without using Wikipedia, find out what that is and explain how it works.

Reply to
John Smith

Correction:

Reply to
John Smith

So did altavista.digital.com until they added additional features I just didn't want. So I switched to Google and never looked back. Yandex isn't bad but I keep finding my way back to Google.

Google is the standard telephone of search engines. It just works.

Quotes do make a difference but that may not be what you meant. ATA has other meanings as I'm sure you know.

Since Spehro seemed to be referring to a specific device, or a family of devices, I thought I'd ask for further details.

Reply to
John Smith

Grandstream looks very interesting. I wish their site was a little less cluttered but thanks for the pointer.

Reply to
John Smith

There's very little magic in IP to IP calling. This is my cheat sheet for Linksys (Sipura) devices. I forgot to record from where I stole the recipe, but my thanks to the unknown author. Please note that the SPA3000 has both FXO and FXS ports.

How to link a SPA to the FXO jack on a SPA-3000 to make and receive call directly.

Unit 1 (SPA any type) with phone attached. From default settings.

  1. Set static IP.
  2. In Advance Admin interface go to Line 1 or 2.
  3. For Proxy set IP of SPA-3000 colon and the sip port number for its FXO port IE 192.168.1.111:5061
  4. Set "Make call without reg" and "Ans call without reg" to yes.
  5. Set a User ID EX 100
  6. Save Settings.

Unit 2 (SPA-3000) attached to POTS line via line port. From default settings.

  1. Set static IP.
  2. In Advance Admin interface go to PSTN line.
  3. Set "Make call Without Reg" and "Answer call without Reg" to YES.
  4. Under Dial Plans for Dial Plan 1 put (S0) IE (S0)
  5. Under VOIP To PSTN Gateway setup set "Line 1 VoIP Caller DP:" and VoIP Caller Default DP to none.
  6. Under FXO Timer value put "PSTN Answer delay" to 0.
  7. Save settings.

Other instructions (which I haven't tested):

Incidentally, IP to IP calling is one reason you should buy a 4 line SIP phone (Linksys SPA942) instead of just a 1 line SIP phone (SPA941). The first line (port 5060) usually gets programmed for my service provider (Future-Nine.com). Lines 2 and 3 (ports 5061 and

5062) are extensions off a customers Asterisk switch. Line 4 (port 5063) is for direct IP to IP calling.
--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

For VoIP, this problem is handled by either a STUN or TURN server: and RFC5389 and RFC5766:

You don't need to operate your own STUN server as there are plenty of public STUN servers available on the internet. However, if you want to do your own:

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

My Grandstream can do direct IP calling on any "line", so does not require a line key to be reserved for that.

However, you normally don't want to leave your phone open for direct IP calling, especially on port 5060, because you will have false calls all day. The bad guys, you know. Like to portscan.

Reply to
Rob

Depending on your point of view, I could be considered one of the bad guys.

Yes, open ports are a problem. On systems that have decent routers, I usually build firewall rules that drop 5060 from unknown sources. That takes care of the bad guys looking for open Asterisk switches. However, for direct IP to IP, I never know the source IP so those are wide open, like my port 5063 example. So, all the port scans, attacks, and junk goes directly to my home and office phones. I sometimes notice that the phone is in some comatose state, probably from an attack using commonly available tools: My various phones are rather old (inherited from customer upgrades) so the firmware has not kept up to date. Common exploits will easily crash them. In the distant past, I would inspect the router logs trying to determine the exploit type and its country of origin. I gave up when I found that my office IP was being port scanned almost continuously, mostly from hijacked machines. My firewall rules soon became rather messy, unreliable, and unmaintainable. So, you're right, I shouldn't have an open port, but having an appliance timer reboot the phone occasionally seems to be an adequate "solution".

Also, I lied a little. For Direct IP to IP I do leave a port wide open. However, it's not 5060 through 5070 which are the common VoIP ports. In my example above, I mentioned 5063 but it's really an obscure port number. While security by obscurity isn't really a good idea, it seems to be sufficient to avoid most of the port scans and crafted packets that seem to crash my SIP phones.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

I would not recommend IP to IP calling outside a local network or a VPN consisting of trusted parties only.

IP to IP calling over the open internet is just a disaster. When I had my port 5060 open (my phone has a public IP, no NAT) there was continuous ringing and "missed calls" on the display.

Not useful to operate it like that. But, it did not crash.

Reply to
Rob

I've used Future Nine (decent service and prices). More recently I've been using Vitelity. They've done quite well, even when I've been calling overseas. Switched my wife's lightly-used business number from a dedicated land-line to Vitelity VoIP a few years ago and haven't ever regretted doing so.

I've noted some incompatibilities between a couple of the consumer-grade ATAs, and older-style (almost heirloom) desk telephones with the old carbon-button mics and mechanical ringers. The phone sounded fine on my land-line, but its "transmit audio" was badly distorted when going through the ATA. I suspect that the ATA simply doesn't deliver enough off-hook current for the older circuits to operate properly.

It's a shame... I'll probably have to give up my dream of having a lightly-adapted original-model Elliot Ness "candlestick" phone hooked up to VoIP. :-)

I've had no such problems when using a modern phone (which all seem to have electret mics and low-REN electronic "ringers") with any ATA.

Reply to
Dave Platt

So, with NAT, you can create a connection from inside (with a LAN-only address like 192.168.x.x) and it will go out through the firewall/router as a WAN address. The router remembers the connection number and translates responses and sends them back to the internal node that created them. (I'm probably not using the right terminology for all this.) This works for making a connection outward to a node with a WAN address. But, the LAN address cannot be reached from the WAN side, as it does not have a WAN address. Addresses such as 192.168.x.x, 10.x.x.x and such are private-only addresses, and will not be routed through the WAN net.

So, two of these devices behind firewall/routers with NAT can not talk to each other. Either one could create an outbound connection request to some WAN address, but unless the other unit had been assigned a WAN address, they could not connect to each other.

Now, there are a million ways one could use a server somewhere as a proxy to carry the traffic. There are VPNs, proxy servers and such schemes that are normally used for this type of purpose, allowing two LAN-only machines to make connections. But, this takes some prior setup to allow it.

Filling in a web form is all done through HTTP, you use a GET request to view a page, and a POST request with the info in the rest of the packet to send the info out. This is all done through the one connection you established when you first connected to the HTTP server. I suggest you read up on TCP/IP and HTTP to see how this is all done.

Jon

Reply to
Jon Elson

Well, it is complicated, but it can do a LOT.

I got some SNOM 300 VOIP phones. I'm using them with Asterisk/FreePBX, but if you can establish net connectivity between two points, I'm pretty sure two of them could make a connection and allow you to talk between them. This would be like making an intercom call between two separated offices. If you can't make a direct connection between them, then there are ways to use a proxy to mediate the connection. Or use a VOIP provider, some of them are VERY cheap. Buy two lines, set up the phones to each connect to one of the VOIP "lines" and you can call from anywhere in the world from one to the other.

There's a guy selling the Snom 300s on eBay for $5 each plus shipping.

Jon

Reply to
Jon Elson

They're the absolute cheapest SIP service I could find that offered a reasonable set of features. I've used their service for about 6 years. However, I've had a few bizarre outages lately. Like all good things, don't assume the "decent service" will last forever.

I have logins and extensions on about 5 Asterisk switches and 3 other VoIP service providers. I use them as needed mostly for testing. I don't know if I'm really good at finding bugs and incompatibilities, or if the various vendors are really good at producing bugs and incompatibilities.

Ok, they're an unbundler, where you can order as much or as little service as you need. I did a quick back of the envelope estimate of what they will cost monthly and found it's about the same as Future-Nine for the services I use. I'll need a spreadsheet to do it right, which means later.

It's a common problem, especially when someone expects a tiny FXO/FXS box to drive a dozen phone ringers at the same time. That's not going to happen. What you need is a ring voltage booster: Inside the box is a 20Hz audio amplifier and hybrid to pass audio around the 20Hz amp. I designed and built a prototype (since they looked like a product with a high profit margin) but my customer evaporated before I was ready.

Linksys/Sipura were shipping their ATA boxes set to 25Hz instead of

20Hz. For a modern phone, either frequency works fine. However, for your antique dinosaur of a phone, which was probably designed for party line ringing which required a narrow bandwidth ringer, it has to be properly programmed. This setting is usually NOT user accessible in ATA boxes provided by locked in service providers.

Sigh. I once had a bunch of original antique candlestick phones. I sold them all to a "friend" who turned around and resold them on eBay for about 8-10 times what he paid me. Lesson learned. In telephone, one has no friends.

Put a 20Hz function generator on a modern phone and notice how little

20Hz is required to trigger the ringer. Last time I checked, it was something like 10Vrms on a Radio Shock something phone. Meanwhile the ring generator puts out 80-100Vrms. I think the idea is for the RS phone to ring on just about anything that resembles 20Hz AC.
--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
 Click to see the full signature
Reply to
Jeff Liebermann

Something like a MJ has the hardware, but the software normally works through a provider which connects you to the POTS network. You would need to rewrite the software to make it work directly to another unit as you describe.

I have a Nettalk DUO which I paid $50 for including a year of service. Now I see they are $15 with three months service. It would have all the electronics you would need, but contains a ARM most likely that you would need to program your way. RJ-45, RJ-11 and USB for power.

I'm not sure how well a direct IP connection would work. Otherwise people would be doing it. I seem to recall reading that some services support direct IP to IP connection... but it's still through them. Do you understand the protocols enough to figure it all out?

--

Rick C
Reply to
rickman

Here you go. Duo to Duo free comms.

formatting link

Don't know if you still need to pay for an annual plan. Nettalk is one of those companies that are very stingy with info.

--

Rick C
Reply to
rickman

Lots of people have trouble with their service, but I don't know how much of that is the service and how much is their Internet connection. I couldn't use my Nettalk DUO very well, but that's because of my Internet connection.

--

Rick C
Reply to
rickman

There are two problems with it:

  1. it requires that the phone is on an address reachable from the caller, so not behind a NAT router. LAN or VPN is fine.
  2. when the phone is exposed to the world (internet), it will receive so many phantom calls that it is not fun to use.
Reply to
Rob

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.