11-06, 13:00–14:00 (Europe/Vienna), Palais Sachsen Coburg I-III
This talk is an introduction to intuiting where non-network latency comes from. While it's usually quite clear how to determine what is network latency and what isn't, it's less clear how to dig into the timing differences between packets at different stages of a TCP conversation to direct troubleshooting at different layers of the stack.
Using a Linux-based web server as an example platform, this talk will demonstrate what network latency looks like, what host latency looks like, and what application/backend latency looks like. To explain what we see in the demonstration, we will also examine the web server to show how packets and requests propagate through the Linux OS to the web server application.
Attendees to this talk will leave with a greater understanding of how to identify latency at different stages of a web request. They will understand the basic Linux kernel and OS structure and how different stresses on a system show up in packet captures.
"The website is slow, so the network must be having an issue."
Network engineers skilled with Wireshark are masters of responding to statements like this one. With one peek at the iRTT, one scroll through the TCP stream, and one long-running ping to the web server, network latency can be disproven. But how do we take the next step? How do we help a server admin or application owner identify exactly what is happening?
Packets can isolate latency at the network, the server, and the application, and this talk will walk through how to find and understand those latencies.
Expect a review of identifying network latency. Expect to learn how to isolate both server and application latency. Expect to learn how network data propagates through a Linux server and where it makes pit stops along the way.
Josh has both academic and real-world experience in the world of protocol analysis. He holds an M.S. degree in Computer Engineering with a focus in network engineering and has spent the past 8 years designing, troubleshooting, and optimizing networks and applications.