FAQ

What's the difference between SONET/SDH, DWDM and OCx -- Why not just use TCP?

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

    Requires Free Membership to View

type of Ethernet.

SAN information
IP storage: Five tips in five minutes

Multipath I/O and failover: The differences

ISCSI gains strength from servers
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.


This was first published in January 2007

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to: