WiMax Operator's Manual

136 CHAPTER 6 ■ BEYOND ACCESS
Figure 6-2. Wireless network with Ethernet switch, courtesy of Alvarion
I am mentioning Ethernet switches here in the context of the central office because a considerable
body of opinion says that Ethernet rather than IP is the proper protocol for the MAN.
In fact, no fewer than two industry associations, the Metro Ethernet Forum and the Gigabit
Ethernet Alliance, have arisen to promote such views.
Within the telecommunications world, a high degree of partisan fervor often accompanies
advocacy of one protocol or the other, and indeed the stakes are high and are nothing less than
market success or failure for the party embracing one standard or other. A dispassionate consideration
of all relevant transport protocols is far preferable to rabid partisanship, and the
criteria on which a transport should be judged are the cost effectiveness and flexibility of the
equipment in supporting a given service model as well as the likelihood that the standard itself
will gain wider currency in the future.
That said, you should consider the past and future of metro Ethernet: High-speed metro
Ethernet business class services were introduced by several competitive data services in 2000,
including offerings from Yipes, Cogent, Terabeam, and CAVU-eXpedient, among others, the
last two of which used wireless infrastructure. The initial acceptance for such services was
encouraging, but two, CAVU-eXpedient and Yipes, declared bankruptcy, and neither Cogent
nor Terabeam has succeeded in posing major challenges to the frame relay and T1 incumbents,
though they have managed to survive. Recently large long-distance companies as well as
local incumbent telephone carriers have also begun to introduce both IP and metro Ethernet
services, though as yet such services have very small subscriber bases.
The independent metro Ethernet service providers all followed a similar model, offering
simple high-speed access at high throughput rates and no value-added services whatsoever.
Basic Ethernet is well suited to such a model, but it is much less suitable to a more contemporary
model where the network is used to deliver converged services. An Ethernet substandard
for supporting virtual private networks (VPNs), 802.1q, does exist, as well as another, 802.3x,
which imposes flow control over the network. But far less standards work has been done for the
purpose of enhancing network performance with delay-sensitive traffic than in the case of IP.