Chapter 6. Navigate the VoIP Network
Hacks 72–87: Introduction
Switching to Voice over IP—especially in an enterprise environment—is wrought with perils that you won’t experience on a non-VoIP network. Real-time applications like voice require a high-quality, real-time network. And, at least by itself, traditional Internet Protocol (IP) networking gear doesn’t fully deliver on that promise. Fortunately, you can apply some old tools—such as Perl and Ethereal—to VoIP networking to troubleshoot and improve your IP network.
When problems occur, your trusty old network troubleshooting apps will come to the rescue. In this chapter, you’ll use Ethereal to sniff Session Initiation Protocol (SIP) signaling messages as they traverse the network inside of User Datagram Protocol (UDP) packets. If you’re a seasoned hacker or a timid script kiddie, you can start with this chapter’s Perl scripts, which graph and monitor VoIP activity on the network. You’ll also be able to monitor latency and jitter—the two things VoIP admins want to avoid like the plague—using standard IP networking commands.
If you play your cards right, you might even learn how to beat a SIP-mangling firewall. (OK, you don’t have to play cards at all. Just read “Explore NAT Traversal” [Hack #76] .) I’ll also show you how to clandestinely monitor and record actual VoIP phone calls—the IP equivalent of a phone tap.
Monitor VoIP Devices
The only thing worse than having a VoIP service outage is being the last to know about it.