Re: [hylafax-users] large multiport systems

["Darren Nickerson" <darren.nickerson@ifax.com>]

Lee,

Thanks for your reply.

> Ah.  I've miscommunicated.  I didn't mean to imply any conclusion on
> V.8 technology for a single call, but rather as a whole for single-page
> bulk faxing.  Allow me to restate...

Thanks for the clarification, but I believe I understood the conclusion you
were presenting. It's just not what we see here in our production
environments! ;-)

In all cases of 1-page broadcasts to random destinations that we've studied,
enabling V.34 improves overall throughput and shortens time 'on the wire'.
I should add one caveat - we haven't tested it with extremely short pages
(such as a single line of text) but rather with representative documents,
often containing a page of text combined with graphics.


> In my experience the total time consumed with handshaking for a group
> of faxes to random, uncontrolled locations will take longer when using
> V.8 handshaking (done with V.34 faxing) than if handshaking with
> non-V.34 faxing were done.  And therefore V.34 only proves beneficial
> if there is enough total data to send among the group of faxes to
> V.34-capable destinations that the increased bitrate will compensate
> for the V.8 handshaking lag to non-V.34-capable destinations.
> Generally speaking a one-page MMR-compressed page (all V.34-capable
> receivers *should* support MMR due to the common ECM prerequisite
> hurdle), such as this gentlemen is discussing, will not contain enough
> data to make V.34 worthwhile.
>
> So, I don't mean to make a statement regarding how long handshaking
> takes when a V.34-capable sender calls a V.34-capable receiver versus
> how long handshaking takes when a non-V.34-capable sender calls a
> non-V.34-capable receiver, but rather I mean to say that the total
> "wasted" time trying to perform V.8 handshaking when a V.34-capable
> sender calls non-V.34-capable receivers may not be less than the time
> savings for those instances when the receivers are V.34-capable.
>
> When a V.34-capable sender calls it first tries to initiate V.8
> communication (required for all data communication speeds faster than
> 14,400 bps).  If that fails then it falls back to V.21.  That fallback
> takes some time.  If the modem spends some seconds before falling back
> to V.21, then in order for V.34 use to be worthwhile it needs to more
> than "make up" those seconds with another call to a V.34 capable
> receiver.  Most V.34 connections aren't going to be at 33,600 bps, and
> will probably average at 28,800 bps.  So, more than 1800 bytes of data
> will need to be sent at V.34 for every second wasted in failed V.8
> connection attempts.

I may be wrong here Lee, but my research tells me you should look for
another culrprit if you're looking to improve your V.34 broadcast
performance. Your rather surprising conclusion that V.8 (fast) handshaking
actually slows handshaking down when faxing to random destinations (where
V.34 support is not known in advance) troubled me, so I dug a little deeper.
Not only were we NOT! seeing the same behaviour here, but it seems to pretty
much defeat the value of V.8 support in products like the Brooktrout TR1034,
which we're quite fond of. ;-)

As far as I know, V.8 handshaking is not attempted unless we know the remote
supports it. When we're the sender, we listen for the ANSam tone (see [1]
below), which if present, identifies the remote as a fax device with V.34
capability. If we don't hear it, we will not attempt the V.8 exchange but
instead go directly into V.17 mode. No fuss, no muss, and no time lost.

Hope this helps!

-Darren


[1]  International Telecommunication Union, "Procedures for starting
sessions of data transmission over the public switched telephone network,"
Recommendation V.8, Telecommunication Standardization Sector of ITU, Geneva,
Switzerland, Feb. 1998.


--
Darren Nickerson
Senior Sales & Support Engineer
iFax Solutions, Inc. www.ifax.com
darren.nickerson@ifax.com
+1.215.438.4638 office
+1.215.243.8335 fax


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