I tend to be a fairly funny guy. Well, at least I think I'm funny. My kids might disagree. The thing is, it's hard to find a group of people to understand obscure networking jokes. At a non-tech conference, for example, if I say to the person next to me, “Jeez, that speaker must have delivered his presentation with UDP packets, because he never stopped to see if any of us were getting what he was talking about!”—exactly zero people laugh. In fact, I usually get really weird looks. At a Linux conference, however, the same comment usually gets an eye-roll. (As a father of teenagers, I consider an eye-roll the equivalent to amusement.) That's why I love Linux Journal so much. This month, we're talking about Networking, and everyone in our little “room” understands what we're talking about! So let's peel this issue apart one OSI layer at a time.
Reuven M. Lerner starts us out with URLs. That ubiquitous string of text that takes you to a location (usually a Web site) is something we often take for granted. As the Internet matures, however, an understanding of how URLs work is vital. Reuven teaches us everything from protocol designations to URL fragments. If you've ever wondered about those seemingly out of place # characters in a URL, you'll want to read his column. Dave Taylor follows with a great look at the evolution of scripting. Just like we no longer have to hand-crank our car engine to get it running (mine doesn't even have a key anymore, just a button), shell scripting has changed through the years. Supporting legacy systems (or legacy code) is a problem we all need to deal with, as Dave shows us with one of his real-world experiences.
Kyle Rankin continues his theme this month and teaches how to encrypt our e-mail—specifically text-based Mutt e-mail. Kyle remains true to his command-line preferences, and rather than switch to a GUI e-mail app, he describes how to use GPG with Mutt. If you're a Mutt user like Kyle, or just want to learn about implementing GPG, don't miss his column. I follow Kyle with a continuation on last month's scripting basics article. Rather than leaving you with a simple set of tools, I tried to come up with some examples of using those tools in real-world situations. My scripts are basic and my techniques are simple, but that's the point. Don't be intimidated by the command line. It's powerful and not terribly difficult to master.
Sniffing network traffic is often a critical part of diagnosing a problem or detecting a potential one. Brian Trapp explains how to sniff the packets of our smartphones. That seems like a simple enough task, until you realize capturing traffic from a wireless device to the network can be challenging. (Using Firesheep will garner you tons of Web information, but if you want every packet, that gets a little rougher.) Brian shows how to capture the traffic, and then how to dissect it with Wireshark. Marco Alamanni follows Brian with an in-depth article on OSSIM, a server-based program for detecting problems on your local network. With its Web interface and powerful collection of snooping tools, OSSIM can be incredibly useful for early detection of problems or threats.
Any network user or administrator is familiar with firewalling tools. Most of us, however, aren't nearly as familiar with Berkeley Packet Filters. Valentine Sinitsyn walks through using BPF to do some very low-level traffic filtering. This powerful system can add an incredible set of tools to your network filtering needs. And finally, Mark Dotson gives us an in-depth tutorial on Ansible. Managing multiple systems is becoming more and more complex, but thankfully with tools like Ansible, we can deploy and configure countless machines quickly and, most importantly, securely.
Like every issue of Linux Journal, this one is chock full of tech tips, product announcements and recommendations. The networking issue touches on so many disciplines and interest areas in the Linux community, that it's always one of our favorites. The large majority of folks still won't understand our networking jokes, but that's okay, they can sit around as bored as a teenager in a Faraday cage while we all enjoy this issue. (Thank you, thank you, I'll be here all night....)