MoIP: How do we make modem calls over IP? (and general chat about phone networks and modems, T1, E1, BRI 56k etc)

[Cloudschatze]

Nice. Thank-you for testing! That was through an ATA on your end even?

I can probably improve on the round trip latency somewhat. Both the 4960 and 2800 are connected to my main router via ethernet-to-WiFi bridging, so direct connections would likely help to a degree. That said, I'm fairly pleased with the results of even just the current setup/configuration.

This has all been a something of a lark, and I don't necessarily have any plans going forward, but it's been a great learning opportunity. Notwithstanding the similar functionality/services of 2600.network, it's cool to think that if I ever get around to creating a BBS that I'll be able to locally offer multiple lines of dial-up into it with just two older pieces of gear.

 

[maxtherabbit]

Nice. Thank-you for testing! That was through an ATA on your end even?

Yes, my Adtran Total Access 912.

I can probably improve on the round trip latency somewhat. Both the 4960 and 2800 are connected to my main router via ethernet-to-WiFi bridging

WiFi for VoIP? oof

 

[MiaM]

WiFi for VoIP? oof

Related tangent: I have a WiFi VoIP telephone somewhere. Can't remember which manufacturer/brand or which protocols it supports. (Unfortunately the battery pack is bad...)
Looks and probably feels like a DECT handset. I think that for any place where you already have WiFi coverage it's a good idea.

 

[maxtherabbit]

Something I've found, which surprised me, is that I get better RTP stream reliability by using siproxd in the openwrt router to relay the media stream vs. forwarding the inbound RTP ports directly to the ATA and spoofing the external NAT address in the SDP payload.

Both approaches "work" but using the media relay is providing a more reliable stream with less jitter and lost/dropped packets.

The call quality log in the adtran is very helpful for gauging performance here.

 

[Neoa_56]

Yes, my Adtran Total Access 912.

Hi ! I already have a PBX with 8 analog ports (Siemens HiPath 1120) and it works really well with V.34, but I would like to try out 56K (V.90 or V.92)
As I understand, I either need a PBX that both does analog and BRI/PRI, or gateways that do these.
PRI RASes and modem banks seem really expensive, is it possible to use ISDN BRI (128K) "modems" ?
They seem way more affordable than their PRI counterparts, so that's why I would like to try that
For the analog end, I would like to use a Cisco VG224, is it good for 56K ? Is the Adtran better ?

 

[maxtherabbit]

I have no experience with the cisco stuff, but the adtran is excellent for V.90.

I'm not sure with you're asking about on the ISDN side. Are you asking if an ISDN modem can terminate an incoming V.90 call? I believe the USR Courier I-modem can do this but I haven't tried personally.

 

[MiaM]

Since the ISDN side is fully digital, at least in theory it would be possible to do V.90 or whatnot in software.
(Can't remember if we already discussed this, perhaps I already brought it up in this thread and someone replied with a link to some already existing implementation...).
If so then you could likely use any digital interface, I.E. instead of ISDN you could likely use any IP telephony thing that has some mode that uses uncompressed audio.

 

[Neoa_56]

I have no experience with the cisco stuff, but the adtran is excellent for V.90.

I'm not sure with you're asking about on the ISDN side. Are you asking if an ISDN modem can terminate an incoming V.90 call? I believe the USR Courier I-modem can do this but I haven't tried personally.

I was asking if I could terminate a V.90 / V.92 call with a BRI ISDN modem
There are a few Patton SN4120/SN4630 floating around in Leboncoin (French alternative to eBay), might pick one up along with a SN4112 or Cisco SPA
I've also seen a HiPath 540 PBX with 8 analog lines and a BRI S0 port, could be simpler than doing everything on VoIP

 

[Neoa_56]

Since the ISDN side is fully digital, at least in theory it would be possible to do V.90 or whatnot in software.
(Can't remember if we already discussed this, perhaps I already brought it up in this thread and someone replied with a link to some already existing implementation...).
If so then you could likely use any digital interface, I.E. instead of ISDN you could likely use any IP telephony thing that has some mode that uses uncompressed audio.

A PCMCIA ISDN modem should work then, my dial-up server is a Windows XP/Server 2003 laptop

 

[davidrg]

A PCMCIA ISDN modem should work then, my dial-up server is a Windows XP/Server 2003 laptop

I'm not sure just any ISDN modem can do it. The ISDN BRI interfaces I've seen that support terminating V.90 calls have a DSP chip per channel dedicated to the job and were available in variants that didn't have those DSP chips and so couldn't terminate V.90 calls.

 

[maxtherabbit]

I'm not sure just any ISDN modem can do it. The ISDN BRI interfaces I've seen that support terminating V.90 calls have a DSP chip per channel dedicated to the job and were available in variants that didn't have those DSP chips and so couldn't terminate V.90 calls.

Yes. Some ISDN BRI TAs can do it, but not all. You're gonna have to check the specs for whichever specific TA you're considering.

 

[Istarian]

Just my two cents: While it would definitely be challenging, reinventing the wheel might make sense here.

I.e. simulate the phone line/call (like you would for tcpser or a similar situation), answer it, and then do the demodulation step yourself. Then you can forward purely digital data over the regular internet to a similar setup on the other end (whatever that happens to be).

Although UDP/IP might be a better starting point than TCP/IP because of all the extra overhead doing send/resend and error correction.

Since it isn't a true voice call you shouldn't need to capture and reproduce the whole spectrum of frequencies.

Using ATA and VoIP forces you to understand a lot of complex stuff that is/was used to provide functionally similar telephone service via the internet.

While that does make some things easier it also introduces it's fair share of problems and dilemmas

 

[Cloudschatze]

So, here's a "Version 2" setup. An Adtran Total Access 908e (3rd gen) now fulfills the IAD role, supplanting both the Patton SmartNode 4960 and Virtual Console PSTN Simulator. A Patton 2960 RAS has been added to (eventually) replace the Patton 2800 that sits outside of the photo, but both are currently connected to the TA908e for a combined 72 digital modems.

I have five DIDs trunked to the TA908e that anyone is free to test out and use:

385-596-1770 - 10 channel trunk, Patton 2800, V.34 -> Telnet Gateway
385-596-1771 - 10 channel trunk, Patton 2960, V.92 -> Telnet Gateway
385-596-1772 - 10 channel trunk, Patton 2960, V.92 -> Telnet Gateway
385-596-1773 - 10 channel trunk, Patton 2960, V.92 -> Telnet/PPP
385-596-1774 - 10 channel trunk, Patton 2960, V.92 -> Telnet/PPP

The Patton 2800, while V.90-capable, has been intentionally constrained to V.34 (33.6 kbps) because V.90 (and V.92) connections are difficult to maintain across VoIP links. The Patton 2960 is currently uncapped (full V.92) for now, though I may cap it at 43.4 kbps later.

The "Telnet Gateway" service will accept any Telnet-accessible host and, optionally, a port value. This is similar to the service that https://2600.network provides, but differs in that I didn't want to manage a list of BBSes and credentials on the RAS itself and am instead just forwarding to a Raspberry Pi for both the gateway script and Telnet host resolution. The maximum session time is set to 120 minutes.

 

[Neoa_56]

I'm stuck between 2 options for my dial-up server: either going V.90 with a Dialogic Diva card (BRI/PRI, doesn't really matter), or going V.34+ with a Multitech analog modem card.
So, which is better ? On one hand, 56K would be a marginal advancement from V.34 since only the download speed is affected (the Dialogic is V.90-capable, but not V.92, software limatation). And also, as Cloudschatze stated, V.90/V.92 connections are hard to sustain over VoIP (I plan to connect the card to an Asterisk server in the same computer). On the other hand, the Multitech card has V.92-capable modems which benefit from V.44 compression in both ways, upload and download !

	Dialogic Diva	Multitech ISIxxxx
Download	56K, V.42bis compression	33.6K, V.34 compression
Upload	33.6K, V.42bis compression	33.6K, V.34 compression

 

[Cloudschatze]

I'm stuck between 2 options for my dial-up server: either going V.90 with a Dialogic Diva card (BRI/PRI, doesn't really matter), or going V.34+ with a Multitech analog modem card.

If you plan on using your dial-up server "locally," in addition to VoIP connectivity, the V.90/V.92 option can be worthwhile.

In my own setup, calls from the FXS ports on the Adtran (my “local POTS”) to either RAS are TDM-hairpinned, so those V.92 connections against the 2960 are solidly 54666 bps.

 

[Neoa_56]

If you plan on using your dial-up server "locally," in addition to VoIP connectivity, the V.90/V.92 option can be worthwhile.

In my own setup, calls from the FXS ports on the Adtran (my “local POTS”) to either RAS are TDM-hairpinned, so those V.92 connections against the 2960 are solidly 54666 bps.

The problem is that Patton Dialfires are really rare
How did you get both of them ?

 

[Cloudschatze]

The problem is that Patton Dialfires are really rare
How did you get both of them ?

Data Connect for the 2810 ($350), and a private sale for the 2960 (which was "priced per the last eBay listing" at $750).

Neither price was great. It's difficult to quantify the value of a completely silent setup though, which the Adtran TA908e and Patton 2960 combination provides. (The Patton 2800, while not silent, is still reasonably quiet after swapping its fans with Noctua variants.)

 

[Neoa_56]

Data Connect for the 2810 ($350), and a private sale for the 2960 (which was "priced per the last eBay listing" at $750).

Neither price was great. It's difficult to quantify the value of a completely silent setup though, which the Adtran TA908e and Patton 2960 combination provides. (The Patton 2800, while not silent, is still reasonably quiet after swapping its fans with Noctua variants.)

I'll probably stick to V.90 with Diva cards then. It's a shame that they never got V.92, because they're pretty cheap compared to Pattons and should be capable hardware-wise (DSPs).
One of the only Patton Dialfire I see available on eBay is a 2977 PCI card, at ~420USD.

 

[RCourtney]

One method where software written for serial ports: virtual-modem-com Windows 32 / 64 and ARM64
software needed at both ends. $135/per seat and is TCP connection no physical modems or serial ports.

Second when using leased line modems https://xds.amtelco.com/boards/em-voip-gateway-appliance (note the 3D printed case)

Third (my favorite) cloud based modems where VoIP calls are answered by DSP routines. Where one physical modem is used by the caller over VoIP.
vocal.com/voip/moip/ (MoIP and SAMS) Very pricey because $17k for license for 32 modem pool.

I have a few old school physical modems myself using G.711 codec on a Grandstream ATA.




(image from vocal.com)



(my modem stack plus a few uncased 212A cards)

 

[famicomaster2]

Hi ! I already have a PBX with 8 analog ports (Siemens HiPath 1120) and it works really well with V.34, but I would like to try out 56K (V.90 or V.92)
As I understand, I either need a PBX that both does analog and BRI/PRI, or gateways that do these.

You can use plain CT1 as well

PRI RASes and modem banks seem really expensive, is it possible to use ISDN BRI (128K) "modems" ?
They seem way more affordable than their PRI counterparts, so that's why I would like to try that

Very, very few BRI devices contain the brains to answer an analog call. The US Robotics Courier I-Modems (rare and expensive in many cases) can do v.90 and X2 with a proprietary license someone had to buy before the service went down, the Eicon Diva BRI cards have the DSPs to do analog calls, and the Tyan Netscalibur can do v.34.

For the analog end, I would like to use a Cisco VG224, is it good for 56K ? Is the Adtran better ?

The Adtran makes it dirt simple to set up and it's extremely reliable. They're also fanless, run pretty cool, and pretty cheap. I don't know about the Ciscos but I've heard they often have noisy fans and are rather power hungry. The Adtrans have a GUI setup as well, if you don't like a CLI.