What Kind of SLIP/PPP Account?

You need an ISP (Internet Service Provider) that provides you internet access via SLIP/PPP. As you browse around several ISP offerings, you may come across the terms "true SLIP" and "pseudo-SLIP".

True SLIP/PPP

True SLIP involes dedicated SLIP hardware (eg., NetBlazer) on the ISP's end. There are also two kinds of IP addresses you can get with true SLIP: a static IP address (so you can announce to the world where you are) and dynamic IP address (you can't announce to the world where you are because your IP address changes with each call you make). As expected, true SLIP services that provide a static IP address general cost more than those that provide only dynamic IP addresses.

The above applies to PPP as well.

Pseudo-SLIP/PPP

Pseudo-SLIP is simply a program (SLIP emulator) that runs out of a login shell account on the remote computer. Because no special hardware is involved on the ISP's end, pseudo-SLIP services normally cost less than true SLIP. With pseudo-SLIP, however, you do not get a real IP address so our computer cannot receive any incoming connections from the internet (it can still make outgoing connections). If you already have a login shell account with host dial-up facilities, you can probably obtain a SLIP emulator (eg., The Internet Adapter) so that your home PC can use to access the internet directly at no additional cost.

PPP emulators are also available. SLiRP is one example. PPP support is planned in version 2.0 upwards of TIA.

Which one to get?

There are some limitations with pseudo-SLIP/PPP. Unless you understand what you are giving up, you should go for true SLIP/PPP accounts.

On a more technical note: Pseudo-SLIP/PPP can be potentially slower because IP packets are first received by the ISP's server, then brought up to the user level program (the SLIP/PPP emulator), processed, then passed on to your computer. True SLIP/PPP passes the IP packets directly to you (via the network software in the server's OS, without being brough up to a user level program). There are some overheads inherent to pseudo-SLIP/PPP.

However, pseudo-SLIP/PPP has an advantage in that, because the network software in the server's OS will bring IP packets up to user level programs, it will perform error checking and correction at its end. With true SLIP/PPP, errorneous IP packets are still passed to your computer for your own network software to resolve. Now, because the ISP's server has a higher bandwidth to the internet, error correction at their end would be faster; Trying to correct errors over your somewhat slower modem link would be less efficient.

In practice, however, the throughput performance between pseudo-SLIP/PPP and true SLIP/PPP should not be significant.

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