We live in a virtual world where most of us have network access in
our homes -- the Internet -- which is a virtual network. We access
the virtual network with some form of
TCP/IP connection that is almost always a
type of Ethernet.
@30670 That access gets to your home or office behind the scenes
through the virtual network. For example, you might be using an
asynchronous digital subscriber line (ADSL), dial up or some other
mechanism leading you into that "network cloud" where technologies
like
synchronous optical network (SONET),
synchronous digital hierarchy (SDH), wave
division multiplexing (WDM),
dense wave division multiplexing (DWDM),
coarse wave division multiplexing (CWDM), optical carrier
networks (OCx) and other technologies exist.
Why not just use TCP? Well you probably are but TCP is just a
protocol that has to run on some sort of network transport. SONET
is a network transport that carries TCP-based traffic. Ethernet,
InfiniBand and
Fibre Channel (FC) are all interfaces.
Telephone carrier-based networks have been built for many years
on SONET technology that typically employs optical fiber --
particularly for spanning great distances.
So, to summarize, you have optical fiber (maybe copper) at the
lowest level. The cabling then supports a network like SONET with
Ethernet, FC or InfiniBand mapped directly onto it. You increase
bandwidth using some form of multiplexing. On a SONET network, you
can also allocate bandwidth into OCx, such as OC3, OC12 or other
subdivisions, and those, in turn, can carry different traffic.
While TCP (or TCP/IP) is your virtual network, you still need the
physical network -- what's inside that "cloud" -- to support the
protocols.
Listen to the
SAN FAQ audiocast here.
Go back to the beginning of the
Storage Area Network FAQ Guide.