Specifications

22-17

Managing Dial Services

3. If you enable PPP call-back negotiation on a port, DIGITAL strongly

recommends that you also enable some sort of authentication (for example

PAP or CHAP) on the port. Without authentication, any user who happens to

discover the phone number for that port’s modem could potentially request a

call-back and run up unlimited phone charges.

4. To enable authentication on a port, use the SET/DEFINE/CHANGE PORT

LCP AUTHENTICATION PAP/CHAP command.

5. If the PPP client speciﬁed a phone number to which the return call is to be

placed, this phone number is also included in the dial request along with the

name of the dialer service. If the PPP client did not specify a phone number,

the phone number to be used is determined by the dialer service or the user’s

authorization information.

6. If a service name is speciﬁed that does not match an existing dialer service, the

call-back will fail and an accounting event will be generated.

7. Whether the phone number to be dialed comes from the PPP client or the

dialer service deﬁnition, the user making the request must be authorized to

dial that number. Likewise, the user must be allowed to create sessions of the

mode deﬁned by the dialer service, either interactive or framed. If the user is

not authorized to either dial the selected phone number or create sessions of

the mode speciﬁed by the dialer service, the call-back fails and an accounting

event is generated.

8. Unlike interactive dial requests, which require the user to log off the server

and hang up the client’s modem in anticipation of a return call from the

server, successful PPP call-back negotiation results in the initial PPP session

being automatically disconnected. This also breaks the modem’s connection

and results in the PPP client hanging up the phone, making it available for the

return call from the server.