How Does an Emulator Work?

SLIP/PPP Emulator mini-HOWTO
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# 2. How Does an Emulator Work?

It is important to understand how a SLIP/PPP emulator works in general, to be aware of its limitations. First, you do not need to install the emulator on your machine. It runs on your remote host only. What you need on your machine is the TCP/IP and SLIP or PPP protocols installed in your kernel (more on that in a bit), and some clients.

Here's what happens: you send network requests from your machine to your remote host over the SLIP/PPP link. The emulator grabs them and sends them out to the Net at large. Then, incoming data is sent back from the Net to your account on the remote host, where the emulator grabs it and sends it back over the SLIP/PPP link to your machine. So, to the Net it appears as if you are working out of your account on the remote host, but to you it looks like you are really connected right to the Net.

As you can see, this can confuse stuff that is incoming from the Net. For example, talk doesn't work via an emulator, because the incoming talk request tries to start the remote hosts talk daemon, not yours.

The other big difference between an emulator and real SLIP/PPP is you are NOT assigned your own IP address; remember, you are only converting a dialup account to a SLIP/PPP connection.

## 2.1. What is TIA?

The Intenet Adaptor was written by the fine folks at marketplace.com. They have quit working on it now, and consider it a 'mature' product. The last version is 2.05; if you are going to use TIA, please get this version.

> Note: At last report, marketplace.com have gone out of business.

## 2.2. What is SLiRP?

This is a freeware application, covered under the GNU Public License. It is out of beta, and is real stable. It sports a few more features than TIA, and is (reportedly) easier on host resources. Available at fine Linux FTP sites everywhere.

## 2.3. What about Term?

If you don't have root access to your machine for one reason or another, and you can't persuade someone who does to install SLIP and dip, then you won't have much choice except to use Term. If you want to know more about Term, please read the HOWTO on Sunsite.

## 2.4. What about real SLIP/PPP?

Hey, a lot of places are offering real SLIP/PPP at reasonable prices for non-dedicated dialup nowadays. If you can afford it, or feel the need, go for it. The Real Thing is always better than emulation. However, one of the things an emulator provides is security; it acts as an impregnable firewall, and with it you are pretty much as bulletproof as your provider is. You'll pay for it though, emulation is slower, and does not fully support every protocol. Still and all, emulation is good enough for most people, and is a fine way to connect to the Net.

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