[rescue] Static IP! Now what?

John Hudak jjhudak at gmail.com
Wed Apr 5 13:11:30 CDT 2017

> [...], and I'm curious about how well VOIP will work for our fax
> line.
a FAX signal being carried by VOIP  is a very bad combination.  Don't do
it.  FAX protocol dictates that the timing relationships between and among
tone signals and handshaking are tight and deterministic.  Attempting to
run the FAX protocol over a temporal
 non-deterministic transport is asking for trouble.  There are times when
the communication will 'work'.  Most of the time, it will not. By this is
mean, yea, you *may* get one page to FAX successfully, you won't get a doc
of >1 to work.

On Wed, Apr 5, 2017 at 11:45 AM, Mouse <mouse at rodents-montreal.org> wrote:

> > [...]
> > What else is a static IP good for?
> Basically, anything a dynamic IP is good for, plus assorted things
> where you want to be reachable at a fixed IP.  Mostly, in practice,
> this means you can run your own just-about-anything: DNS, mail, web,
> VPN, FTP, what-have-you.  (I'm assuming there aren't still
> provider-imposed restrictions like "can't run servers" or "no outgoing
> TCP to port 25".)
> If you're stuck with only one IP, there are additional headaches, but
> you said you'd have a /29, so those shouldn't be issues.  Depending on
> how much you care about such things, you might want to bug them about
> IPv6, too.
> > [...], and I'm curious about how well VOIP will work for our fax
> > line.
> Based on my tests, either really well (if it gets converted to T.38
> before getting to you) or really crappy (if it is still trying to use
> POTS fax codecs).  The codecs originally used for fax were designed to
> deal with the sorts of errors POTS introduces.  SIP introduces errors
> too, but they tend to be completely different errors (typically
> dropouts rather than corruption, roughly speaking), so different coding
> schemes are called for.  POTS fax works fine provided you have
> absolutely zero data loss, but even a single missed data packet plays
> merry hell with designed-for-POTS fax codecs.
> ...that's assuming your VOI is SIP.  If not, I'm not really competent
> to comment, except that similar remarks _probably_ apply.
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