Chapter 9. Network Design with MPLS TE

This chapter covers the following topics:

• Sample Network for Case Studies

• Different Types of TE Design

• Tactical TE Design

• Online Strategic TE Design

• Offline Strategic TE Design

• Protection Scalability

• Forwarding Adjacency Scalability

So far, this book has covered the detailed aspects of MPLS TE; how it works, and how you configure and manage it. But how do you use MPLS TE in your network design? That's what this chapter covers.

Chapter 1, "Understanding Traffic Engineering with MPLS," discussed the two main ways to think about deploying MPLS TE—tactically and strategically:

• Tactical MPLS TE is building MPLS TE LSPs as you need them, to work around congestion.

• Strategic MPLS TE is a full mesh of TE tunnels between a given set of routers. Strategic MPLS TE can be further broken down into two pieces:

  - Online path calculation— The routers themselves are allowed to determine the path their TE LSPs take.
  
  

  - Offline path calculation— The path that TE LSPs take is chosen by an external device that has a better view of the network topology and traffic demands than a router does.
  
  

This chapter discusses network design using both tactical and strategic approaches.

A design chapter could concentrate on many things. The entire topic of network design can't be covered in a single chapter. Therefore, this chapter focuses on the scalability of various approaches and tools.

Why scalability? Scalability is one of the most important things to think about when designing a network. You need to understand not only how well a particular solution scales and the factors that influence this scalability, but also the limits within which you are trying to scale. A solution that scales wonderfully for a ten-router network might not scale for 100 nodes, and a solution that scales for a 100-node network or a 1000-node network might not scale for 1,000,000 nodes. On the other hand, who has a million routers in their network? This chapter discusses scalability with real-life networks in mind—anywhere from dozens to hundreds of routers in the TE portion of the network.

Also discussed is the scalability of various protection techniques. Protection was covered in Chapter 7, "Protection and Restoration." All that's covered in this chapter is scaling MPLS TE with protection.