CISSP 12.13 - WAN Technologies

This episode of the ISC2 Certified Information Systems Security Professional (CISSP) exam prep series surveys the technologies that connect networks across long distances, part of Domain 4. It explains why the wide-area link is often the fragile thread holding a distributed business together, and how the technology you choose sets the speed, the cost, and the odds that a single failure isolates a whole site.

Frequently Asked Questions

What splits WAN links into two big families?

A single question: is the connection always reserved for you, or does it have to be dialed up each time? That divides everything into dedicated and nondedicated links. Whatever the type, a long-distance link can boost communication but also expose data, so you need solid connection management and encryption, especially over public paths. Think of it as the difference between owning a private road and merging onto a public one whenever you need to travel.

What is a dedicated line, and where does cable internet fit?

A dedicated line is permanently reserved for one customer, always on and waiting for traffic. Often called a leased line or point-to-point link, it joins two specific endpoints and only those two, which is why businesses use it to tie locations together. Cable internet fits neither family cleanly: it is always on but links your premises to an internet gateway rather than another site, making it point-to-multipoint, and it is shared with neighbors, with privacy preserved by encryption much like a VPN.

What counts as a nondedicated line?

Any link that must establish a connection before data can flow, and that can reach any remote system using the same kind of line. Classic dial-up modems are the old example, and digital subscriber line is the modern one, riding the upgraded telephone network to deliver a wide range of consumer speeds. There are several formats, each offering different download and upload bandwidth. Think of it as a phone you pick up and dial only when you need to talk.

How do you keep a carrier link fault tolerant?

By refusing to depend on a single connection. For real fault tolerance you deploy two redundant links, and for stronger protection you buy them from two different providers. But check the fine print: if both providers ride the same regional backbone or share a major pipeline, you have not gained much, and even the physical routing out of your building matters. If a full duplicate leased line is too costly, a cheaper nondedicated connection can still give partial availability.

What carries the long haul in the backbone today?

The segment linking local networks to a central hub or the wider internet is the backhaul, and a few technologies dominate it. A label-based routing approach tags packets for fast, scalable routing across many locations with quality-of-service controls, and Ethernet-based options like carrier-grade metro Ethernet offer high bandwidth and flexibility. Satellite fills the gaps wires cannot reach, with low-orbit networks cutting the delay that plagued the older high-orbit approach.

Reference: This article is based on concepts discussed in CISSP 12.13 - WAN Technologies.