O'Reilly logo
live online training icon Live Online training

How Networks Really Work

Russ White

There are many elements to a networking system, including hosts, virtual hosts, routers, virtual routers, routing protocols, discovery protocols, etc. Each protocol and device (whether virtual or physical) is generally studied as an individual "thing." It is not common to consider all of these parts as components of a system that works together to carry traffic through a network. To show how all these components work together to form a complete system, I will present a series of walk throughs, showing the processing involved in various kinds of network events.

The session begins with the data plane, including the discovery of the information a host needs to send traffic, and the forwarding process within a network device. The first walk through will be simple, but they will build in complexity until traffic carried in an overlay through a hardware optimized forwarding plane is carried.

The second part of the session begins with a simple network configured to use a single routing protocol to find a set of loop free paths. In this simple scenario, the information created by the control plane will be related to the information required to forward traffic described in the simple data plane walk through. The following walk through will consider convergence based on link and node failures in increasingly complex network topologies.

This training is important because it shows how all the various protocols and pieces fit together to build a working network.

What you'll learn-and how you can apply it

By the end of this course, participants will not only understand how several sets of protocols work together as a system to carry traffic through a network, but also how to relate multiple protocols together into a single larger system on their own.

This training course is for you because...

  • You want to understand how the various protocols and systems in a network work together to forward packets
  • You want to really understand how packets are forwarded through a network
  • You want to really understand how routing protocols converge in various network situations in order to predict network performance, know what various failure modes will look like before a failure occurs, and understand how to plan network design around potential failures
  • You want to understand how to put the various protocols and systems in a network together into a mental model of packet forwarding and other operations
  • You want to be able to troubleshoot networks more quickly by understanding how routing protocols converge, and how packets are forwarded through a network; this is particularly important in finding the “signal path” to apply the half-split method of troubleshooting


  • Basic understanding of the principles of routing
  • A basic idea of the various protocols used in an IPv4/IPv6 network

About your instructor

  • Russ White began working with computers in the mid-1980's and computer networks in 1990. He has co-authored forty-seven software patents, participated in the development of several Internet standards, helped develop the CCDE and the CCAr, and worked in Internet governance with the Internet Society. Russ is a co-host of the History of Networking and Hedge podcasts, serves on the Routing Area Directorate at the IETF, co-chairs the BABEL working group, and serves on the Technical Services Council/as a maintainer on the open source FR Routing project. Russ holds an MSIT from Capella University, an MACM from Shepherds Theological Seminary, and is a PhD Candidate in philosophy at SEBTS.


The timeframes are only estimates and may vary according to how the class is progressing

Segment 1: Introductory Data Plane Walk-throughs

Length: 50 minutes

  • IPv4 initial packet transmission with one router
  • IPv6 initial packet transmission with one router
  • DNS resolution walk-through
  • Combined v4/DNS walk-through
  • GRE tunnel walk-through
  • MPLS Label Switched Path walk-through

10 Minute Break

Segment 2: Advanced Data Plane Walk-throughs

Length: 50 minutes

  • MPLS Segment Routing layer 3 walk-through
  • MPLS Segment Routing layer 2 walk-through (with remote default gateway)
  • Virtual Machine to virtual machine walk-through
  • East-west traffic walk through with layer 2 overlay across DC fabric and DCI
  • Typical forwarding device walk-through

Segment 3: Control Plane Walk-throughs

Length: 50 minutes

  • Ring convergence
  • Nonplanar partial mesh
  • Clos (spine and leaf)

10 minute final Question and Answer Period