How do dialup ISPs allow multiple clients under one access number?

Choprboy choprboy at
Mon Nov 24 10:03:41 UTC 2008

On Monday 24 November 2008 00:14, John Musbach wrote:
> I'm interested in figuring out how dialup ISPs work and have found
> plenty of info on dialin server setup but not much on how ISPs allow
> multiple clients under one access number, how do they do it?

One phone number != one phone line.

Each phone circuit has a single associated billing/account number. Notice I 
say circuit, not line, which is 1 or more channels over some medium. It may 
be a single line POTS, a 2 channel ISDN, a 23/24 channel T1, a 600+ channel 
T3, etc. In addition to the account number, one or more additional phone 
numbers can be directed at that account or agroup of accounts, either as a 
direct routing to a particular channel(s) or a roll-over between groups of 
various accounts. A call to a phone number is therefore is directed at a 
particular account number which, if all channels are busy, may roll on to 
other account numbers in the group.


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