[cisco-voip] Fwd: Cisco ATA Fax Confusion

Rhodium rhodium_uk at yahoo.co.uk
Mon Jan 25 09:22:43 EST 2010 

Thanks all for the reply.

Appreciate the feedback from this very knowledgeable crowd.

Regards,

Jason

--- On Mon, 1/25/10, Ryan Ratliff <rratliff at cisco.com> wrote:

> From: Ryan Ratliff <rratliff at cisco.com>
> Subject: Re: [cisco-voip] Fwd: Cisco ATA Fax Confusion
> To: "Nick Matthews" <matthnick at gmail.com>
> Cc: "Rhodium" <rhodium_uk at yahoo.co.uk>, "cisco-voip at puck.nether.net Group" <cisco-voip at puck.nether.net>
> Date: Monday, January 25, 2010, 2:17 PM
> Nick is correct, I meant the call was
> being handled as a normal g.711 (audio) call and you were
> getting lucky that the ecan, etc wasn't breaking the fax.
> 
> -Ryan
> 
> On Jan 24, 2010, at 7:17 PM, Nick Matthews wrote:
> 
> He was commenting on the difference of passthrough and
> normal G.711
> operation.  In theory, you should be able to place
> fax/modem calls
> over G.711 since it's not compressed.  This turns out
> not to be the
> case because the way echo cancellers and the jitter buffers
> used for
> voice don't work perfect for modems/faxes.  It can
> still be done
> however, which is why faxes and modems will work sometimes
> without
> doing any configuration.  Passthrough really just
> disables the ECAN,
> disables DTMF, and modifies the jitter buffer, and it's
> G.711 under
> that.
> 
> -nick
> 
> On Sun, Jan 24, 2010 at 4:00 PM, Rhodium <rhodium_uk at yahoo.co.uk>
> wrote:
> > I appreciate what you are saying and understand the
> difference between the protocols and how they function.
> > 
> > I do not know of any other protocol apart from the
> ones you and I mentioned so I was perplexed by an earlier
> statement made by Ryan as regards low speed fax. Which led
> to my question on that:
> > 
> > "It's basically the same as the straight g.711 fax
> pass-through.  I think the only difference with this
> and modem passthrough is that when we detect the fax tones
> we'll turn off some of the DSP features (ecan, etc) that are
> useful for voice but not for fax.
> > 
> > -Ryan"
> > 
> > As far as I am aware, low speed fax is just a term for
> any fax pass-through, passthrough, relay that uses less than
> 9600bps, it is not a separate method of fax transmission.
> > 
> > That is my question?
> > 
> > 
> > 
> > --- On Sun, 1/24/10, Nick Matthews <matthnick at gmail.com>
> wrote:
> > 
> >> From: Nick Matthews <matthnick at gmail.com>
> >> Subject: Re: [cisco-voip] Fwd: Cisco ATA Fax
> Confusion
> >> To: "Rhodium" <rhodium_uk at yahoo.co.uk>
> >> Cc: "Ryan Ratliff" <rratliff at cisco..com>,
> "cisco-voip at puck.nether.net
> Group" <cisco-voip at puck.nether.net>
> >> Date: Sunday, January 24, 2010, 8:04 PM
> >> passthrough and pass-through get you
> >> to the same place, just with two
> >> different methods.
> >> 
> >> just like protocol based T38 and NSE based T38 get
> you to
> >> the same
> >> place, just in two different ways.  The end
> >> destination is the same
> >> for protocol based or NSE based.  I'm not
> entirely
> >> sure what your
> >> question is.  What I'm saying is that there
> was a new
> >> project to make
> >> that 'destination' or protocol be able to handle
> higher
> >> speeds.  At
> >> the moment I can't remember if it was a 15.0M
> release or
> >> 15.1T
> >> release.
> >> 
> >> 
> >> -nick
> >> 
> >> On Sun, Jan 24, 2010 at 1:06 PM, Rhodium <rhodium_uk at yahoo.co.uk>
> >> wrote:
> >>> In relation to Ryan's comments, it would be
> NSE based
> >> fax passthrough with the fax negotiating low
> speed, not
> >> something inherently differently to the
> passthrough
> >> protocol. So it is not a different type of FaxoIP
> method but
> >> uses an existing method which is NSE passthrough.
> >>> 
> >>> Am I right?
> >>> 
> >>> --- On Sun, 1/24/10, Nick Matthews <matthnick at gmail.com>
> >> wrote:
> >>> 
> >>>> From: Nick Matthews <matthnick at gmail.com>
> >>>> Subject: Re: [cisco-voip] Fwd: Cisco ATA
> Fax
> >> Confusion
> >>>> To: "Rhodium" <rhodium_uk at yahoo.co.uk>
> >>>> Cc: "Ryan Ratliff" <rratliff at cisco.com>,
> >> "cisco-voip at puck.nether.net
> >> Group" <cisco-voip at puck.nether.net>
> >>>> Date: Sunday, January 24, 2010, 5:50 PM
> >>>> both passthrough, pass-through, and
> >>>> relay can handle up to 14.4.  Some
> >>>> of the newer 15.0 code is supposed to
> allow 56k,
> >> but I
> >>>> haven't heard
> >>>> the results of the testing.
> >>>> 
> >>>> -nick
> >>>> 
> >>>> On Sun, Jan 24, 2010 at 9:41 AM, Rhodium
> <rhodium_uk at yahoo.co.uk>
> >>>> wrote:
> >>>>> Hi Nick,
> >>>>> 
> >>>>> Thanks for replying.
> >>>>> 
> >>>>> So low speed fax as mentioned by Ryan
> is just
> >> fax
> >>>> "passthrough" (NSE based) with the fax
> negotiating
> >> a speed
> >>>> of <=9600 bps.
> >>>>> 
> >>>>> Regards,
> >>>>> 
> >>>>> Jason
> >>>>> 
> >>>>> --- On Sun, 1/24/10, Nick Matthews
> <matthnick at gmail.com>
> >>>> wrote:
> >>>>> 
> >>>>>> From: Nick Matthews <matthnick at gmail.com>
> >>>>>> Subject: Re: [cisco-voip] Fwd:
> Cisco ATA
> >> Fax
> >>>> Confusion
> >>>>>> To: "Rhodium" <rhodium_uk at yahoo.co.uk>
> >>>>>> Cc: "Ryan Ratliff" <rratliff at cisco.com>,
> >>>> "cisco-voip at puck.nether.net
> >>>> Group" <cisco-voip at puck.nether.net>
> >>>>>> Date: Sunday, January 24, 2010,
> 5:50 AM
> >>>>>> To clarify:
> >>>>>> 
> >>>>>> fax pass-through:  protocol
> based pass
> >> through.
> >>>>>> Supported in SIP/H323.
> >>>>>> fax passthrough: nse based
> passthrough.
> >> Same
> >>>> thing as
> >>>>>> modem passthrough
> >>>>>> fax relay:  a method of
> turning g711
> >> packets
> >>>> into
> >>>>>> specific fax
> >>>>>> packets.  Options are T38 and
> Cisco.
> >>>>>> Cisco fax relay:  The default
> method in
> >> IOS
> >>>> versions
> >>>>>> before 15.0, and
> >>>>>> uses Cisco NSEs for transport and
> >> negotiation.
> >>>> This
> >>>>>> is not the
> >>>>>> suggested option, as it is
> legacy.
> >>>>>> T38 NSE switchover:  this is
> cisco
> >> proprietary,
> >>>> and is
> >>>>>> supported with
> >>>>>> SCCP, SIP, MGCP, and H323
> >>>>>> T38 protocol switchover: 
> This is
> >> standards based
> >>>> and
> >>>>>> what you will
> >>>>>> use with 3rd party devices. 
> Supported
> >> in SIP,
> >>>> H323,
> >>>>>> and MGCP.
> >>>>>> NSE:  A cisco proprietary
> packet value
> >> for RTP
> >>>>>> (normally 101) that is
> >>>>>> used between Cisco devices to
> signal
> >> certain fax
> >>>> events.
> >>>>>> 
> >>>>>> modem passthrough: used for both
> fax and
> >> modem
> >>>> passthrough
> >>>>>> using G711.
> >>>>>>  Available in the 4
> protocols.  Only
> >> thing that
> >>>> ATAs
> >>>>>> officially
> >>>>>> support.  It turns off the
> echo
> >> canceller, and
> >>>> changes
> >>>>>> the playout
> >>>>>> buffer (for jitter).  Cisco
> proprietary
> >> since it
> >>>> uses
> >>>>>> NSEs.
> >>>>>> 
> >>>>>> Faxes can work on G711, but that
> is if
> >> the echo
> >>>> canceller
> >>>>>> and playout
> >>>>>> buffer work for that particular
> stream
> >> and
> >>>> associated fax
> >>>>>> machines.
> >>>>>> It's very likely that high speed
> faxes
> >> (speed >
> >>>> 14.4)
> >>>>>> will not work on
> >>>>>> normal G711.
> >>>>>> 
> >>>>>> 
> >>>>>> Faxing is confusing :)
> >>>>>> 
> >>>>>> -nick
> >>>>>> 
> >>>>>> On Fri, Jan 22, 2010 at 4:52 PM,
> Rhodium
> >> <rhodium_uk at yahoo.co.uk>
> >>>>>> wrote:
> >>>>>>> Can't find anything about
> that
> >> particular fax
> >>>> oIP
> >>>>>> method from googling or on CCO??
> >>>>>>> 
> >>>>>>> All I can find are the relay
> types,
> >> and the
> >>>>>> pass-through/passthrough types..
> >>>>>>> 
> >>>>>>> Regards,
> >>>>>>> 
> >>>>>>> Jason
> >>>>>>> 
> >>>>>>> --- On Fri, 1/22/10, Ryan
> Ratliff
> >> <rratliff at cisco.com>
> >>>>>> wrote:
> >>>>>>> 
> >>>>>>>> From: Ryan Ratliff <rratliff at cisco.com>
> >>>>>>>> Subject: Re: [cisco-voip]
> Fwd:
> >>  Cisco
> >>>> ATA Fax
> >>>>>> Confusion
> >>>>>>>> To: "Rhodium" <rhodium_uk at yahoo.co.uk>
> >>>>>>>> Cc: "cisco-voip at puck.nether.net
> >>>>>> Group" <cisco-voip at puck..nether.net>
> >>>>>>>> Date: Friday, January 22,
> 2010,
> >> 9:40 PM
> >>>>>>>> It's basically the same as
> the
> >>>>>>>> straight g.711 fax
> >> pass-through.  I
> >>>> think the
> >>>>>> only
> >>>>>>>> difference with this and
> modem
> >>>> passthrough is that
> >>>>>> when we
> >>>>>>>> detect the fax tones we'll
> turn
> >> off some
> >>>> of the
> >>>>>> DSP features
> >>>>>>>> (ecan, etc) that are
> useful for
> >> voice but
> >>>> not for
> >>>>>> fax.
> >>>>>>>> 
> >>>>>>>> -Ryan
> >>>>>>>> 
> >>>>>>>> On Jan 22, 2010, at 4:34
> PM,
> >> Rhodium
> >>>> wrote:
> >>>>>>>> 
> >>>>>>>> Thanks for following it
> up
> >> internally.
> >>>> :)
> >>>>>>>> 
> >>>>>>>> What is this by the way in
> terms
> >> of fax
> >>>>>> protocols:
> >>>>>>>> 
> >>>>>>>>> The other option is
> that it
> >> has
> >>>> fallen back
> >>>>>> to g.711
> >>>>>>>> low
> >>>>>>>>> speed fax and you are
> >> getting
> >>>> lucky.
> >>>>>>>> 
> >>>>>>>> 
> >>>>>>>> --- On Fri, 1/22/10, Ryan
> >> Ratliff <rratliff at cisco.com>
> >>>>>>>> wrote:
> >>>>>>>> 
> >>>>>>>>> From: Ryan Ratliff
> <rratliff at cisco.com>
> >>>>>>>>> Subject: Re:
> [cisco-voip]
> >> Fwd:
> >>>> Cisco ATA
> >>>>>> Fax
> >>>>>>>> Confusion
> >>>>>>>>> To: "Rhodium" <rhodium_uk at yahoo.co.uk>
> >>>>>>>>> Cc: "cisco-voip at puck.nether.net
> >>>>>>>> Group" <cisco-voip at puck.nether.net>
> >>>>>>>>> Date: Friday, January
> 22,
> >> 2010, 9:26
> >>>> PM
> >>>>>>>>> I ran this by
> somebody
> >> that
> >>>> actually
> >>>>>>>>> works fax issues every
> day
> >> and there
> >>>> are two
> >>>>>> ways your
> >>>>>>>> call
> >>>>>>>>> can be working.
> >>>>>>>>> 
> >>>>>>>>> The first is that
> modem
> >> passthrough
> >>>> is
> >>>>>> actually being
> >>>>>>>>> used.  This can
> be
> >> confirmed by
> >>>> waiting 10
> >>>>>>>> seconds
> >>>>>>>>> after the call is
> answered
> >> and
> >>>> looking at the
> >>>>>> output
> >>>>>>>> of
> >>>>>>>>> 'show call active
> voice
> >> brief'.  If
> >>>> you see
> >>>>>>>> modem-pass
> >>>>>>>>> here then it's
> switched to
> >> modem
> >>>>>> passthrough.
> >>>>>>>>> 
> >>>>>>>>> The other option is
> that it
> >> has
> >>>> fallen back
> >>>>>> to g.711
> >>>>>>>> low
> >>>>>>>>> speed fax and you are
> >> getting
> >>>> lucky.
> >>>>>>>>> 
> >>>>>>>>> -Ryan
> >>>>>>>>> 
> >>>>>>>>> On Jan 22, 2010, at
> 4:15
> >> PM, Ryan
> >>>> Ratliff
> >>>>>> wrote:
> >>>>>>>>> 
> >>>>>>>>> Are your calls working
> in
> >> one
> >>>> direction only
> >>>>>> or both
> >>>>>>>>> ways?  We are all
> in
> >> agreement that
> >>>> the ATA
> >>>>>> only
> >>>>>>>>> supports NSE based
> >> passthrough and I
> >>>> do know
> >>>>>> that the
> >>>>>>>>> default fax protocol
> on
> >> cisco
> >>>> routers is
> >>>>>> modem
> >>>>>>>> passthrough
> >>>>>>>>> so maybe there's
> another
> >> bit of your
> >>>> config
> >>>>>> that's
> >>>>>>>> allowing
> >>>>>>>>> the call to proceed.
> >>>>>>>>> 
> >>>>>>>>> In the doc you
> referenced
> >> it
> >>>> mentions that
> >>>>>> no
> >>>>>>>> fall-back
> >>>>>>>>> will still allow for
> the
> >> fax to
> >>>> proceed if
> >>>>>> modem
> >>>>>>>> passthrough
> >>>>>>>>> is configured.. 
> Maybe
> >> this also
> >>>> applies if
> >>>>>> fax
> >>>>>>>>> pass-through fallback
> >> isn't
> >>>> successful.
> >>>>>>>>> 
> >>>>>>>>> -Ryan
> >>>>>>>>> 
> >>>>>>>>> On Jan 22, 2010, at
> 3:50
> >> PM, Rhodium
> >>>> wrote:
> >>>>>>>>> 
> >>>>>>>>> Yep, I am aware of
> the
> >> hyphenations.
> >>>> Been
> >>>>>> trying to
> >>>>>>>> use
> >>>>>>>>> them in the right
> context
> >> if you
> >>>> look at my
> >>>>>> emails.
> >>>>>>>> ;o)
> >>>>>>>>> 
> >>>>>>>>> I don't think the fall
> back
> >> command
> >>>> applies
> >>>>>> to NSE
> >>>>>>>>> passthrough but
> protocol
> >> based
> >>>> pass-through:
> >>>>>>>>> 
> >>>>>>>>> http://www.cisco..biz/en/US/docs/ios/12_3/vvf_c/cisco_ios_fax_services_over_ip_application_guide/t38.html#wp1156682
> >>>>>>>>> 
> >>>>>>>>> Also, the written
> >> documentation I
> >>>> have shows
> >>>>>> it under
> >>>>>>>>> protocol based
> >> pass-through.
> >>>>>>>>> 
> >>>>>>>>> Which led me to ask
> the
> >> question,
> >>>> why is it
> >>>>>> working?
> >>>>>>>> Are
> >>>>>>>>> you sure that it
> refers to
> >> protocol
> >>>> based
> >>>>>> pass-through
> >>>>>>>> and
> >>>>>>>>> not NSE?
> >>>>>>>>> 
> >>>>>>>>> Regards,
> >>>>>>>>> 
> >>>>>>>>> Jason
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>> 
> >> _______________________________________________
> >>>>>>>>> cisco-voip mailing
> list
> >>>>>>>>> cisco-voip at puck.nether.net
> >>>>>>>>> https://puck.nether.net/mailman/listinfo/cisco-voip
> >>>>>>>>> 
> >>>>>>>>> 
> >>>>>>>> 
> >>>>>>>> 
> >>>>>>>> 
> >>>>>>>> 
> >>>>>>>> 
> >>>>>>>> 
> >>>>>>> 
> >>>>>>> 
> >>>>>>> 
> >>>>>>> 
> >>>>>>> 
> >>>>
> _______________________________________________
> >>>>>>> cisco-voip mailing list
> >>>>>>> cisco-voip at puck.nether.net
> >>>>>>> https://puck..nether.net/mailman/listinfo/cisco-voip
> >>>>>>> 
> >>>>>> 
> >>>>> 
> >>>>> 
> >>>>> 
> >>>>> 
> >>>>> 
> >>>> 
> >>> 
> >>> 
> >>> 
> >>> 
> >> 
> > 
> > 
> > 
> > 
> > 
> 
>

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