first my humble apologies for my previous, harsh statements about Livingston.
Now let me try to get constructive...
On 1 Nov 97 at 11:28, Heiko Schlittermann wrote:
> On Oct 31, Phil Taylor wrote
> : I'm not really sure what the fuss about D-Channel Call back is anyway,
> : as long as the client supports it just disable call answering, this has
> : the same effect as the PM3 not completing the call except it is client
> : driven.
>
> There may be a situation the other way round. The client want's to be
> called back by you, the ISP. And the client expects to get it's call
> rejected and instantly called back. Impossible if you're using a PM3.
>
D-channel dialback means, that the call originator just "knocks" on the door of the other
side. This is, due to the D-channel protocol definition, free of charge.
The caller and called IDs are both submitted. Now the called router can use the
originatorīs number to lookup a callback number or use this number for callback (the
latter is surely dangerous for security reasons).
The solution would be, as Heiko suggested before, to use the Calling-Station-Id as
username and do a normal RADIUS or usertable loookup.
Now, where do we need this D-channel callback? There are two possibilities
(1) An ISP-customer has an ISDN dialup account to the ISP. The ISP does no charged
dialout. So if an Email arrives for the client, the ISP router just "knocks" the
customerīs machine which then dials to the ISP. There is indeed no charge for the ISP.
What to do if you donīt have D-channel dialback:
- no dialout from the ISP (bad for the customer!)
- Email to customer handled by UUCP or modified SMTP-queuing
- charged dial-out. Then the ISP needs Advice-Of-Charge to distinguish between local and
long-distance calls (and, in Germany the charging structure of the Telekom is very
complicated, so a mere lookup table isnīt accurate, you really need the advice-of-charge
tick provided by the Telco in the D-channel).
If the router manufacturer is able to implement advice-of-charge, he has a sophisticated
understanding of D-channel features and is therefore able to implement D-channel-dialback
as well.
(2) In corporate business, Teleworkers donīt have to pay for their dialup calls to the
company. It is very difficult to distinguish between private calls and corporate calls in
the monthly charge bills. Normally, the Telekom doesnīt provide an accurate call list.
This is an additional feature, which costs additional fees to the Telekom for each
printed call.
Therefore, the companies are *forced* to do dialback to the remote teleworker. They need
the D-channel dialback, because otherwise the originated call charges canīt be precisely
determinded.
Ok, just to clarify: all these features are part of the ISDN protocol. Why not *use*
these protocol features?
In Germany, the ISDN knowledge is really superior. We have ISDN hard- and software with
all this D-channel stuff included from the beginning. But most of these products lack in
case of remote access, routing and so on.
Therefore, I prefer companies with good reputation in remote access business implementing
ISDN features rather than vice versa.
Therefore I want to see Livingston doing that. I love these products, I love to sell
them, I love to do business with Livingston, but I donīt love the ignorance of European
needs. Btw., donīt you also promote ISDN in North-America? So wouldnīt you also like
these features too?
Ok, these were my two Euros (whatīs that cents? ;-)
best regards,
Frank
-- Frank M. Heinzius MMS Communication GmbH mailto:frimp@mms.de Eiffestrasse 598 http://www.mms.de 20537 Hamburg, Germany Phone: +49 40 211105-0 Fax: +49 40 210 32 210 - To unsubscribe, email 'majordomo@livingston.com' with 'unsubscribe portmaster-users' in the body of the message.