One word - money. Ethernet gear is cheaper to buy and cheaper to run.
So what's the problem? Reliability and availability. The installed base of traditional SONET is huge and SONET technology has been engineered for excellent reliability and fault-tolerance, albeit at a high cost. Ethernet is improving on reliability, but is still lagging. Ethernet is also gaining popularity but its presence in the metro/WAN is still miniscule.
SONET is inherently channelized, into fixed rates of 1.5, 50, 155 Mbps, etc. SONET is layer one exclusively, switching implies a second layer. In Ethernet or ATM, the channels are virtual allowing oversubscription of a given shared pipe. When the customers traffic patterns are diverse, the packet switched systems can carry alot more customers in a given carriers network, compared to a pure SONET network. Manufacturers have combined the two, allowing shared channels of a SONET distribution network to carry ethernet traffic to multiple 10/100BaseT ports, confusing your equipment choices.
I do agree with $$$ aspect as mentioned. If you consider the ML Series in the 15454, a Metro Ethernet solution is very viable. Part of the reason is that the ML has 12 10/100 port or 2 GE ports and allows traffic to be stat muxed around an RPR ring to offer metro services. The stat mux ability allows the customer the ability to get more bang for their buck vs. using a nailed up STS between locations that really only serves that one customer.
It is also an important point to use Etherchanneling over 100/1000 Mbps Ethernet links. This is useful for midrange fiber lines or point-to-point copper links between aggregation devices. This ability extends the useability of F-/G-Ethernet in MAN-environments.
Introduction: The "external-out enable" command is available for
configuration under the "router ospf process" in case of the IOS-XR
operating system. This command basically enables advertisement of
intra-area routes on the device as external routes in th...
IntroductionIn this article we'll discuss how to troubleshoot packet
loss in the asr9000 and specifically understanding the NP drop counters,
what they mean and what you can do to mitigate them. This document will
be an ongoing effort to improve troublesh...