In recent years networking in enterprise data centers has undergone dramatic changes and following today’s discussions about FCoE and data center convergence it is obvious the speed of change will even increase. But it seems to me not even the recent advancements in technology have made it to the minds of all users.
Traditionally everything that had to be transported over distance had to be converted in order to fit into a carriers Sonet/SDH transport infrastructure. But new technologies like WDM, MPLS or even Ethernet have emerged replacing Sonet/SDH and still it seems some people out there love the “old” technology so much – they want to convert everything into it.
This might be acceptable for applications like voice but definitely not for latency and bandwidth critical requirements as they are common in disaster recovery or business continuity environments. There are better alternatives out there and for distances up to 200km those technologies offer lower latency and higher bandwidth than Sonet/SDH could ever do.
In scenarios where dark fiber is available WDM technology should be the solution of choice. Not only does it offer almost unlimited bandwidth (up to 120 wavelengths, each carrying 10G) but it also enables native transport of all relevant protocols in the data center space. Ethernet, ESCON, Fibre Channel, InfiniBand – almost everything can be transported natively thus eliminating the need for expensive FC-over-Sonet protocol converters. This does not only mean significant cost savings but also latency savings since each additional signal processing step causes latency. This development is enforced by the fact that most of today’s switches or routers at the end of the link have powerful distance extension capabilities built-in (e.g. buffer-to buffer credits with FC) to go the distance plus fewer of those buffers are required since latency is lower.
One might respond that today it is anyhow a better choice to use IP (or Ethernet) to go the distance, but the problem of converting everything into and the fact of limited bandwidth scalability does not go away. And even for new applications like Grid- or Cloud Computing the latency problem will continue to exist (see here).
For distances beyond 200km or for customer that don’t have access to dark fiber those technologies might still be the only option.