re: Dial-Ups

["A. Padgett Peterson, P.E. Information Security" <PADGETT @ hobbes . orl . mmc . com>]

>> Well you can get ANI on any line if you want to pay for it. 1-900 & 976 I
>> know can get it, not sure about 700 and 500 series.

>Not *any* line, since ANI is a bypoduct of the phone switching system, 
>it has to come off of the local switch, as it is part of the call routing,
>a normal business drop doesn't have this capability. 

said *line* not *number* and that you would have to pay for it.

>CNID is sent just before the ring signal, but unlike ANI isn't used in 
>routing the call, it's out of band for routing, but in band as far as the 
>signal goes.  Some CNID equipment will only store the last CNID block, making 
>it open to spoofing (pass the new spoofed CNID after the last ring, 
>before the authentication portion of the modem has grabbed it), 

Paul is sort of rite (*please* read the FAQ in the telecom archives at 
lcs.mit.edu, it goes into nausiating deatil and I actually did a couple
of hours research)

>Remember ANI is in-band for routing, but out of band for the call, 
>making it unspoofable.  CNID is not.

Have to disagree here since either is spoofable *at the local switch*
but the real CNID is passed before the circuit is completed, completion
occurs after you pick up the phone. Thus if you use the CNID to decide IF 
you are going to answer the phone, it is as reliable (may not be the same 
info but is as reliable) as ANI particularly if you do not pick up on 
private/blocked.

This is the case was referring to where I may decide not to pick up the 
phone at all and do not care who is calling if not.

Now, if you *must* know the source of *every* call, then ANI is your only
answer and you will need a special connection, just depends on your need.

					Warmly,
						Padgett

ps have been using this for several years now, when my BBS is up, it must
   recognize the incoming number before the modem is authorized to pick up.
   - nothing fancy, just a Supra modem with CNID & Procomm running an .ASP
   I rote (also in the telcom archive).