CertiGuide to Network+  9  Chapter 0111: Wide Area Networking       9  VI  TCP/IP Encapsulation for High-Speed Internet Connections

VI  TCP/IP Encapsulation for High-Speed Internet Connections 1 PPPoE

With the low-speed remote access technologies, you are not always connected to the network. Instead, you choose when you connect by dialing up on demand (when you need to use the network), and disconnect when you are finished. Also, you choose each time you dial up, the network access point to which you connect – it doesn’t have to be the same location each time. With high-speed technologies, you have dedicated (always-on) connectivity to the network, and your connection always goes from the same location (your home) into the same location at the DSL-equipped ISP or Cable Company (unless they change their configuration). In this way, DSL and cable modem connections are much more like traditional Ethernet.

ISP’s, however, desired the same sorts of access control and connect/disconnect processing provided by the PPP log in / log out operations for lower speed lines. These functions are useful as they allow ISP’s to track statistics, such as number of hours used, on a per-user basis and limit access to the network to only those who needed to use it at the time, which was good from a security point of view. Another benefit ISP’s gain by allowing users to connect and disconnect is that they don’t have to have one IP address for each subscriber – instead, IP addresses are shared among currently-connected users via DHCP. If a user isn’t connected, the ISP doesn’t need to reserve an IP address for them, thus reducing the total number of IP addresses that the ISP needs to have available. What could be done, to give these technologies already using Ethernet, connect / disconnect functionality?

VI  TCP/IP Encapsulation for High-Speed Internet Connections 1 PPPoE