Chapter 2. Delivering Broadband Access Today: An Access Technologies Primer
In this chapter, you learn about the following topics:
Technologies and Protocols for DSL, Cable, and Ethernet Broadband Networks Bridged and PPP Access Mechanisms, with an Evaluation of how well They Solve the Requirements for Broadband, Such as Quality of service, Address Assignment, Service Selection, and so on
A VPN is a service that can carry pure data or multiservice traffic. When you design or implement a VPN for broadband access, you need to understand how the different access architectures can impact design decisions and can actually have some interesting repercussions on the VPN service itself, because of quality of service (QoS) or security trade-offs, to name but two examples.
This chapter reviews the two principal Layer 2 access architectures in use today: bridging and PPP. It looks at how each is implemented on different Layer 1 broadband media, such as digital subscriber line (DSL) and cable. Then it describes how each architecture solves some of the basic requirements of a network service, such as security, QoS support, routing, and address assignment. There are lots of permutations to go through: For example, security on a bridged cable broadband network is different from security on a bridged Ethernet broadband network, so it is worthwhile to look at each case.
If you sometimes feel lost going through all of these different scenarios, remind yourself that you are looking at how common problems are solved on different types of broadband networks. The set of problems is important, because you will want to make sure that a broadband VPN service solves it too. The major topics that are covered are as follows:
Bear in mind that this is a review chapter. If you are comfortable with PPP and bridging, then you can safely skip ahead to the next chapter.
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