Foundations
SIP call flow internals, RTP mechanics, and how VoIP traverses a network from endpoint to carrier.
The VoIP Engineer's Library · Vol I Network Analysis
Network Analysis
for VoIP Engineers
A practical guide to capturing, diagnosing, and resolving VoIP problems.
The book
Most VoIP engineers learn to troubleshoot by trial and error — rebooting SBCs, restarting registrations, and hoping the problem resolves itself. Most network engineers understand packets deeply but have never seen a SIP INVITE and aren't sure why one-way audio happens. This book is for both of them.
Network Analysis for VoIP Engineers bridges the gap between protocol theory and real-world production troubleshooting. By the time you finish, you won't just know that there's a problem — you'll know exactly where in the call flow it broke, why it broke, and what to do about it. You'll be reading packet captures the way an experienced clinician reads an X-ray: quickly, confidently, and with a clear diagnosis.
Who this is for
- The VoIP engineer who understands UCaaS platforms, dial plans, and SIP trunking — but who gets lost when a Wireshark capture lands in their inbox.
- The network engineer who can read BGP tables and trace a routing loop, but who doesn't yet understand how SIP and RTP behave differently from normal TCP/IP traffic.
- The senior engineer who knows both worlds but wants a structured reference for diagnosing complex issues quickly — the one-way audio at 4am, the codec mismatch no one can explain, the carrier drop that only happens under load.
What's inside
Capture Methodology
Where and how to capture traffic, the Wireshark VoIP workflow, sngrep for live SIP, and Homer/VoIPmonitor for persistent capture.
Diagnosing Real Problems
One-way audio, choppy calls, dropped calls, registration failures, DTMF issues — each as a worked case with annotated companion captures.
Network-Layer Factors
QoS, NAT traversal, firewall/SBC interaction, and how BGP and routing decisions affect call quality.
Monitoring at Scale
Building a VoIP observability stack: MOS tracking, CDR analytics, alerting on quality degradation before your customers do.
Companion resources
The book ships with hands-on companions for every Part 3 case file and the broader Wireshark workflow.
Pcap library
A curated collection of annotated .pcap files — one for every scenario in Part 3. Load them in Wireshark and follow along.
Download →Wireshark cheat sheet
Single-page reference for the most useful display filters, color rules, and decode-as settings for SIP and RTP analysis.
Download →VoIP Analysis profile
Ready-to-import Wireshark profile — color rules for SIP/RTP/RTCP/DTMF/T.38/STUN, tuned column layout, ~20 pre-loaded filters.
Download →Errata
Corrections and updates discovered after publication. Bookmark this page if you're working through the book closely.
View →The VoIP Engineer's Library · Vol I
Pick up the book
The companions on this site are free and freely redistributable, but they're designed to be read alongside the book. The paperback ties the captures, filters, and case files into a structured walkthrough you can read once and then keep as a reference.
Buy on AmazonAvailable in paperback and Kindle eBook