Chapter 8. Case Studies for Using MPLS with Broadband VPNs

In this chapter, you learn about the following topics:

• Applying Broadband VPN Design Principles in Two Case Studies

• Migrating an L2TP-Based Wholesale Service to a Managed-LNS Offering Using VRF-Lite, and to a Full MPLS-Based Offering, and a Comparison Between the Two

• Deploying a Residential Ethernet Service for Data, Voice, and Video Services with and Without MPLS in the Access Layer

This chapter looks at how to combine all the different building blocks introduced in the previous chapters to make a working solution. The chapter also introduces some ideas to help you choose products, with the understanding that evolution and natural selection make product characteristics a fast-moving target. To help reinforce how MPLS-based solutions compare to other choices of technology, migration scenarios are included as part of the case studies.

There is also a large component of review in the case studies, with reference to previous chapters for background information or more detailed discussion of the implementation details or alternatives.

The two case studies presented in this chapter are an amalgam of different network designs, based on answers to some fundamental design checks that you can ask yourself pretty much regardless of the network service model:

• Static versus dynamic binding How are subscriber interfaces bound to VRFs? Are the mappings (or bindings) always the same for a particular interface, or is this a kind of run-time decision made only when the subscriber connects?

• Scale and numbers How many VRFs are in the network? How many subscribers exist per VRF? The answers have an impact on both how route tables are managed and the type of PE used.

• VRF compatibility Are the features you need VRF compatible? As discussed in Chapter 7, you cannot just assume that they are VRF compatible, you have to check, sometimes at a very detailed level.

• Isolation of changes across administrative domains Do changes in one customer's network have an impact on another network? Obviously, you should try to design things so that such impact is minimal.

• Review of routing, addressing, and security design Does the end result comply with the best practices of IP network design? You will be surprised to find out how many white board ideas do not comply.