Overview

DSL will be around for the next 100 years

JOHN CIOFFI

When discussing Ethernet in the First Mile s (EFM s) point-to-point copper solutions, there are two misconceptions that I encounter very frequently, representing two opposite and incorrect views of the Task Force s accomplishments. Before starting the detailed discussion of the EFM copper architecture in this chapter, and the 10PASS-TS and 2BASE-TL specifics in the next two chapters, let us get these misconceptions out of the way.

The first view is that the EFM copper Physical Layer entity sublayers (PHYs) 2BASE-TL and 10PASS-TS are limited to bitrates of 2 Mbps and 10 Mbps, respectively. This false idea probably results from mistaking the Task Force s objectives (specifically the last two bullets of objective 2 in Annex A) for the standard. The objectives were set to guide the work of the Task Force, and if the port types that were eventually standardized meet these objectives, they are by no means limited by them.

The second view is that the EFM copper PHY specifications are identical to the existing Single-Pair High-Speed Digital Subscriber Line (SHDSL) and Very-High-Speed Digital Subscriber Line (VDSL) standards with Ethernet on top. This view sticks to the Task Force s baseline proposals too closely, and ignores the fact that the Task Force has actually done a lot of work on top of what already existed in DSL standards. Not only are the frame encapsulation and bonding methods used by EFM original, but there are a...