Traffic Engineering

What this chapter covers

This chapter explains how MPLS traffic engineering places traffic on chosen paths instead of the shortest one.

It is the shortest chapter of the three, but it builds directly on the MPLS chapter. You need MPLS running on the links before a TE tunnel makes sense. Examples use the RouterOS v6 console.

How the topics fit together

The chapter follows the life of a tunnel, from the reason for it to the resources it uses.

Three pages cover the chapter:

• Traffic engineering basics explain the problem, the tunnel as an interface, and how traffic is steered into it.
• RSVP and paths show how the tunnel is signalled and how a static path differs from a dynamic path calculated with CSPF.
• Bandwidth shows how capacity is reserved and how real traffic is limited, which are separate things.

How to use these pages

Each topic page has the same shape, so you can skim for what you need.

• What it is: the idea in plain words.
• How it works: the mechanism, with diagrams and example commands.
• What to remember for the exam: the facts to memorise.
• Common mistakes: the classic traps.
• Check yourself: three questions to test your understanding.

Practise on a lab with two possible paths between a head end and a tail end. Build a static tunnel first and move it from one path to the other. Then switch to a dynamic path and watch how the head end reacts when you fail a link.

Be careful with the settings that are written differently in RouterOS v7. These pages describe the v6 console, so confirm the syntax on the version you are using.

Read the pages in order. The second page uses the tunnel interface from the first, and the third page uses both.

After each page, write the commands from memory and compare them with the examples.

When a lab tunnel fails, check in the same order each time. First confirm that MPLS works. Then check the TE interface list and the path, and finally the route into the tunnel.