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Ethernet as a WAN Technology

For the first several decades of the existence of Ethernet, Ethernet was only appropriate
for LANs. The restrictions on cable lengths and devices might allow a LAN that stretched a
kilometer or two, to support a campus LAN, but that was the limit.

As time passed, the IEEE improved Ethernet standards in ways that made Ethernet a reasonable
WAN technology. For example, the 1000BASE-LX standard uses single-mode fiber
cabling, with support for a 5-km cable length; the 1000BASE-ZX standard supports an even
longer 70-km cable length. As time went by, and as the IEEE improved cabling distances for
fiber Ethernet links, Ethernet became a reasonable WAN technology.

Today, in this second decade of the twenty-first century, many WAN service providers
(SP) offer WAN services that take advantage of Ethernet. SPs offer a wide variety of these
Ethernet WAN services, with many different names. But all of them use a similar model,
with Ethernet used between the customer site and the SP’s network, as shown in Figure 3-9.
Free CISCO CCNA Routing and Switching ICND1 Study Guide
Figure 3-9 Fiber Ethernet Link to Connect a CPE Router to a Service Provider’s WAN
The model shown in Figure 3-9 has many of the same ideas of how a telco creates a
leased line, as shown earlier in Figure 3-3, but now with Ethernet links and devices. The
customer connects to an Ethernet link using a router interface. The (fiber) Ethernet link
leaves the customer building and connects to some nearby SP location called a point of
presence (PoP). Instead of a telco switch as shown in Figure 3-3, the SP uses an Ethernet
switch. Inside the SP’s network, the SP uses any technology that it wants to create the
specific Ethernet WAN services.

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