My working Cisco ATA191 config and EdgeRouter tweak
reddit / bbs

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bwann · 2023-01-31 02:58

I finally got my Cisco ATA191 working with voip.ms. I've been testing
with a pair of Courier V.Everything connected to a pair of Dosbox
instances running Wildcat! 4 and Qmodem. By dialing via extension so
it goes out to voip.ms and back, I'm getting consistent 26.4-33.6k
carrier speeds. It seems pretty stable navigating around menus,
although Zmodem falls apart which I think is due to serial overruns in
Dosbox.

I had two tweak two things, one was on my Ubiquiti EdgeRouter that I
use as my home router. Along with setting up port forwarding for
SIP/RTP, I had to turn off SIP connection tracking for some reason. At
first I'd get the inbound ring, but no audio. In syslog on the
Edgerouter I saw this at the same time and the iptables log showed it
dropping:

> kernel: nf_ct_sip: dropping packet: cannot parse SDP message

This was a pretty obscure error but I found enough leads to try out
"set system conntrack modules sip disable" to turn off kernel
connection tracking of SIP. I haven't dug into why this came into
play, maybe later investigation.

As for the Cisco ATA191 configuration, this seems very similar to a
SPA112. IIRC this is what I changed from factory settings to get
decent connect speeds. Some of these came from voip.ms's setup
instructions for the SPA112.

I'd be curious how my configs compare to others with SPA112s, if
there's room for improvement.

**SIP configuration**

* RTP Port Min/Max [TCP ports]: 12000-13000 (mainly to shrink the
range for port forwarding)
* RTP Packet Size: 0.02

**Line 1 & 2**

* NAT Mapping Enable, NAT Keep Alive Enable: yes, yes
* Network Jitter Level: extremely high
* Jitter Buffer Adjustment: no
* Preferred Codec: G711u
* Secondary, Third preferred codec: none
* G729a Enable, G726-32 Enable: no, no
* Silence Supp Enable, Echo Canc Enable: no, no
* All FAX options: off
* Modem Line: yes

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Call_Me_Mauve_Bib · 2023-01-31 04:51

Timing is key, these modems aren't able to handle lost audio. You have
to set the buffer size just right and not drop *anything*

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dmine45 · 2023-01-31 09:20

That's about what I had to do with mine. I'm running a single SPA112
serving two USR modems (older Sportster 56k and newer v.92).

The part I had to learn is to turn all the Fax stuff off. You'd think
you want that on, but actually that's worse than leaving it all off.

What VOIP service are you using? I'm using [voip.ms](https://voip.ms),
but also will be experimenting with Skyetel.

If you want someone to test these out, let me know.

Or if you want, feel free to call the Diamond Mine Online BBS at (540)
369-2900.