The Joy (and Agony) of SLIP
Have you ever wanted to connect your computer to a network? Perhaps you have two computers that you want to run Mosaic, ftp, or X11 between? Do you want to let your friends experience the full power of your magnificent new Linux box? SLIP is one way you can do all these things.
by Warren Baird
SLIP (Serial Line Internet Protocol) is a protocol that allows you to make a TCP/IP connection over a serial line. TCP/IP stands for Transmission Control Protocol/Internet Protocol, and is the protocol used on the Internet and on most local ethernets. Many common Unix programs (like X11, Mosaic, gopher, IRC, talk, telnet and ftp) use TCP/IP to communicate. If you want to use programs like this to talk to the rest of the world over the Internet, or if you want to connect two (or more) local machines, SLIP is a good option.
There are actually two variants of SLIP: normal SLIP, and CSLIP (which stands for Compressed SLIP). CSLIP compresses various TCP/IP headers to give a higher throughput on a serial line. (Note: CSLIP doesn't compress the data that is being transmitted, just the headers added by TCP/IP.) Unfortunately not all systems support it. Even with CSLIP, the throughput on a serial line is quite low compared to ethernet and other Local Area Networks (LANs). It's possible to run high bandwidth applications like Mosaic and xv over a SLIP link, but the response times may be quite low.
One of the most common uses of SLIP is to connect to a commercial Internet provider. There are many companies that provide full access to the Internet by allowing you to make a SLIP connection using a modem.
Another use of SLIP is to connect two or more machines using a null-modem cable. Since SLIP is implemented for many different platforms, you can connect your Linux box to many different types of systems. For example, I have an Amiga 2000 connected to my 386 running Linux 1.0.8.
If you are really ambitious, you can even set up your Linux box as a SLIP server. You could do this to give your friends access to your machine, or as part of a BBS setup.
Configuring something like SLIP under Unix is always very dependent on the flavor and version of Unix that you are running. The details given here are for the Slackware 1.2.0 (Linux 1.0.8) distribution. The exact details may vary somewhat with other versions of Linux and other distributions.
There is a whole host (no pun intended) of files that control the behavior of a Unix system, and a number of them need to be modified to set up SLIP.
Looking up host names: /etc/hosts, /etc/resolv.conf, and /etc/host.conf
The /etc/hosts file maps hostnames (for example acme.gadgets.com) to IP addresses (for example 18.104.22.168). If you are using SLIP to connect two local machines, your /etc/hosts file only needs to contain the hostnames and IP addresses of your two machines. If you are connected to a larger network, but talk to only a few sites, you can put their names and IP addresses in your /etc/hosts file.
If you are connecting to many hosts (or using a program like Mosaic that connects to many hosts), you'll need to tell your system who it should ask to find IP addresses for unknown hostnames. There are systems called nameservers that will lookup an IP address for a given hostname. The /etc/resolv.conf file tells your system which nameserver(s) to use. It also tells your system what your domain name is. The domain name is your full hostname with the machine name removed—for example, if your hostname is acme.gadgets.com, your domain name would be gadgets.com.
If your domain name is gadgets.com, and you have a nameserver at the IP address 22.214.171.124, your /etc/resolve.conf file could read:
domain gadgets.com nameserver 126.96.36.199
It's possible to list multiple nameservers in a resolve.conf file. The /etc/host.conf file tells the system what order it should use to lookup hostnames. Normally this file contains
order hosts,bind multi on
which tells the system to check the /etc/hosts file first, and then to try any nameservers it knows about.
The names of the Internet startup files vary even between different Linux distributions. On most Linux systems the files used are /etc/rc.d/rc.inet1 and /etc/rc.d/rc.inet2. Whichever startup file is used, there are a number of daemons that must be running for any TCP/IP program to work. The NET-2 HOWTO describes which daemons are available, and what they do. Minimally, you need to have the inetd daemon running. The inetd daemon coordinates the startup of many other TCP/IP daemons.
Additionally, if you are setting up a permanent link to another computer over a dedicated line, you may want to actually initialize the SLIP link in the startup files.
|Designing Electronics with Linux||May 22, 2013|
|Dynamic DNS—an Object Lesson in Problem Solving||May 21, 2013|
|Using Salt Stack and Vagrant for Drupal Development||May 20, 2013|
|Making Linux and Android Get Along (It's Not as Hard as It Sounds)||May 16, 2013|
|Drupal Is a Framework: Why Everyone Needs to Understand This||May 15, 2013|
|Home, My Backup Data Center||May 13, 2013|
- Nice article, thanks for the
49 min 12 sec ago
- I once had a better way I
6 hours 35 min ago
- Not only you I too assumed
6 hours 52 min ago
- another very interesting
8 hours 45 min ago
- Reply to comment | Linux Journal
10 hours 39 min ago
- Reply to comment | Linux Journal
17 hours 33 min ago
- Reply to comment | Linux Journal
17 hours 49 min ago
- Favorite (and easily brute-forced) pw's
19 hours 40 min ago
- Have you tried Boxen? It's a
1 day 1 hour ago
- seo services in india
1 day 6 hours ago
Enter to Win an Adafruit Pi Cobbler Breakout Kit for Raspberry Pi
It's Raspberry Pi month at Linux Journal. Each week in May, Adafruit will be giving away a Pi-related prize to a lucky, randomly drawn LJ reader. Winners will be announced weekly.
Fill out the fields below to enter to win this week's prize-- a Pi Cobbler Breakout Kit for Raspberry Pi.
Congratulations to our winners so far:
- 5-8-13, Pi Starter Pack: Jack Davis
- 5-15-13, Pi Model B 512MB RAM: Patrick Dunn
- 5-21-13, Prototyping Pi Plate Kit: Philip Kirby
- Next winner announced on 5-27-13!
Free Webinar: Hadoop
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers
Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.
Some of key questions to be discussed are:
- What is the “typical” Hadoop cluster and what should be installed on the different machine types?
- Why should you consider the typical workload patterns when making your hardware decisions?
- Are all microservers created equal for Hadoop deployments?
- How do I plan for expansion if I require more compute, memory, storage or networking?