B3Configuration on Receiver-side

[Lothar Kimmeringer]

Hello,

is there a way to get the B3-Configuration the caller is setting
in CONNECT_REQ on the receiver side, e.g. the station-id of a
G3-Fax or the X.25-Windows-size?

I'd need both informations and like to avoid performing OCR
on a received Fax ;-)


Best regards,

Lothar

[Danilo Kempf]

Hi,

Am 02.07.2008, 11:23 Uhr, schrieb Lothar Kimmeringer

Post by Lothar Kimmeringer
is there a way to get the B3-Configuration the caller is setting
in CONNECT_REQ on the receiver side, e.g. the station-id of a
G3-Fax or the X.25-Windows-size?

In general: There isn't. The B-Protocol parameter and with it the
contained B1, B2, and B3 protocol and configuration parameters aren't
something that's communicated to the remote party during a call. These
parameters are used only in order to set up the local protocol stack that
sits above the B channel.

Effectively, ISDN signalling is used to establish a 64 kbit/s bearer
channel to a remote party. Neither the local software stack nor the remote
party initially knows what you intend to do with that channel. You can,
however, during call set up, exchange "Bearer Capability", "Low Layer
Compatibility" and "High Layer Compatibility" information elements which
give the remote party (and intermediate hops) some sort of clue towards
your goal.

When you've set up the B channel, you still have random data come out of
it with a rate of 64 kbit/s a second. The B-Protocol parameter now only
controls how your local CAPI interprets that data and how it's mangled
before being delivered to your application.

The parameters you set inside the B-Protocol aren't necessarily
communicated to the remote party at all. I think that's the case with X.25
window size, as that parameter merely controls some properties of the
local implementation. (But I surely might be wrong here, the closest I
ever came to X.25 was reading the X.75 specification -- which I admit is
not very close at all.)

Some other paramters in fact _are_ communicated to the remote party over
the B channel. That's, for example, the case with a T.30 station id which
is transmitted during initial T.30 handshake. On the remote side (if it's
a CAPI, of course) this station id will come up (wrapped in an NCPI
structure) in either a CONNECT_B3_IND, CONNECT_B3_ACTIVE_IND or
DISCONNECT_B3_IND. You will need to interpret the NCPI parameter to find
out.

Mind you that theoretically a (remote) station id might change during fax
transmission/reception, so you may actually see different IDs in each
NCPI. There's only a remote chance to that, but still...

Post by Lothar Kimmeringer
I'd need both informations and like to avoid performing OCR
on a received Fax ;-)

Just out of curiosity: How's an X.25 window size involved in both fax
reception and OCR processing?

Best regards,

Danilo

[Lothar Kimmeringer]

Hi Danilo,

thanks for your answer.

Post by Danilo Kempf
Am 02.07.2008, 11:23 Uhr, schrieb Lothar Kimmeringer

Post by Lothar Kimmeringer
is there a way to get the B3-Configuration the caller is setting
in CONNECT_REQ on the receiver side, e.g. the station-id of a
G3-Fax or the X.25-Windows-size?

In general: There isn't. The B-Protocol parameter and with it the
contained B1, B2, and B3 protocol and configuration parameters aren't
something that's communicated to the remote party during a call.

I feared that you will say that. That it's not transmitted I already
saw with the CAPI-traces I read, but hoped that there might be some
way to get them anyway.

Post by Danilo Kempf
You can,
however, during call set up, exchange "Bearer Capability", "Low Layer
Compatibility" and "High Layer Compatibility" information elements which
give the remote party (and intermediate hops) some sort of clue towards
your goal.

Problem is that I'm dependent on the "good-will" of the remote-
party and that's nothing I can count on.

Post by Danilo Kempf
The parameters you set inside the B-Protocol aren't necessarily
communicated to the remote party at all. I think that's the case with X.25
window size, as that parameter merely controls some properties of the
local implementation.

The X.25-window-size must be communicated in some way, at least on
the X.25-layer itself. Problem is that when using CAPI I haven't
found a way to get the X.25-data being sent and received. All that
happens inside the ISDN-hardware or CAPI-driver and end up in
DATA_B3_INDs.

Post by Danilo Kempf
Some other paramters in fact _are_ communicated to the remote party over
the B channel. That's, for example, the case with a T.30 station id which
is transmitted during initial T.30 handshake. On the remote side (if it's
a CAPI, of course) this station id will come up (wrapped in an NCPI
structure) in either a CONNECT_B3_IND, CONNECT_B3_ACTIVE_IND or
DISCONNECT_B3_IND. You will need to interpret the NCPI parameter to find
out.

Not only that, you have to send NCPI-data when doing CONNECT_B3_REQ
containing the X.25-source- and destination-address. Because you have
to do that before you receive a CONNECT_B3_IND, NCPI-informations inside
there in general don't bring up new informations ;-)

Post by Danilo Kempf
Mind you that theoretically a (remote) station id might change during fax
transmission/reception, so you may actually see different IDs in each
NCPI. There's only a remote chance to that, but still...

... it's nothing you can count on ;-)

Post by Danilo Kempf

Post by Lothar Kimmeringer
I'd need both informations and like to avoid performing OCR
on a received Fax ;-)

Just out of curiosity: How's an X.25 window size involved in both fax
reception and OCR processing?

In no way at all. The posting contains questions concrening two
different topics:

1. The ability to add more informations to the class FaxDocument in
http://jcapi.cvs.sourceforge.net/jcapi/net/sourceforge/jcapi/connection/fax/FaxDocument.java?view=markup
2. A problem while performing OFTP-communication with a car-manu-
facturer that claims it's my fault but I'm sure it's theirs.
The X.25-window-size is one informatoin I would be glad to get,
the complete X.25-data would be perfect.

I've got another question concerning B3-Data with the more-data-
flag but I think I will put that into another post ;-)


Regards, Lothar