Alt+Connect is a program to manage dialup connections: it allows a group of networked machines to share a single internet connection through their server. Users use special client software to start or stop their internet connection, and the server (connectd) ensures that the connection remains up only while someone's using it.
For example, you might have a Linux server, with a modem, networked to some Windows and Linux machines. Install connectd on your internet gateway and any of those machines can start or stop the server's modem connection.
Microsoft call this Internet Connection Sharing (ICS). I'd describe it as a proxy dialer--you need ip-forwarding (a feature of the linux kernel) or a web/ftp proxy (like Apache or Squid) to fully share an internet connection, and Alt+Connect doesn't try to provide these services. But the windows connectd can make use of Window 2000's ICS.
Doesn't dial on demand and disconnects instantly rather than relying on idle detection.
Effortlessly handles multiple ISPs, letting you chose your connection from a menu of providers. There's a wizard to add ISPs. (unix only)
Supports multiple links (for example several modems or ISDN channels.)
Connectd records the time a user spends online, and can charge them for it; splitting the cost of the connection between all users who are using it.
You can cancel the connection for everyone, or for individual users.
Scripts are run on specific events, and at regular intervals. These are in the right place to reconfigure your firewall.
Inactive links are detected and terminated.
There's per-user name space (sessions)
Supports user authentication: either explicitly (by password) or implicitly (via /proc/net/tcp or identd).
Connectd specific users can be added to /etc/connect/users, and they can change their password. Or you can turn off authentication and valid usernames altogether.
Dialup connections can be blocked by user, ip-address provider, time-of-day, or day-of-week. (Connection Control Lists)
Restrict access to connectd via the unix-standard /etc/hosts.allow and /etc/hosts.deny files.
The install procedure's fully automated. There are .spec files included and instructions on how to can roll your own RPMs.
Can manage the ppp username and secret.
All the clients can automatically locate the server.