Scott, Thanks for taking the time to put that together. From some of your observations, it's clear to see that many of Vinod's views are now contemporary, although some of them are disputed in some venues. I will have more to say in a later posting after having had the opportunity to digest it.
----------
STS stands for synchronous transport signal. For all intents and purposes, a STS can be viewed as the electrical equivalent of an optical carrier, or OC.
STS-n signals are effectively equal to OC-n signals. From a payload handling perspective, each can be viewed as being one and the same (the former is simply mapped to an optical medium and becoes the latter, at which time some of the overhead bytes in the sonet envelope header are changed to reflect the difference), and each is rated in multiples of 51.84 Mb/s. The STS-1 at 51.84 Mb/s is said to be the basic building block of SONET.
Electrical STS signals are manageable up to a certain point (usually up to STS-3 in close settings) for short runs. STSes, when external to the SONET element, ride over coaxial media in central offices and when being "handed off" to the customer at the carrier-customer demarcation point.
It is not uncommon for SONET-derived T3s, or OC-1s to be extended over considerable distances over coax in this manner, although it is less common today to find an STS-3 taking a coaxial medium for any but the shortest distances (for example, between patch panels in adjacent racks or in the same room).
At higher speeds, such as OC-12s/STS-12s, STSes don't have any significance from a "hand-off" perspective to the customer. They are, nonetheless, significant to the internal workings of SONET network elements such as multiplexers, add-drop devices and cross connects, as these are the signals that are mapped and cross-connected within their fabrics (again, at the electrical level).
Beyond OC-1, however, fiber is almost exclusively stipulated for inter-network element connections, due to a variety of reasons. Not the least of which being the attenuation characteristics of metallic media. EMI/RFI also play into the decision, however.
For a good tutorial on SONET by HP go to the International Engineering Consortium site iec.org. This site is a gold mine for those needing a first glance at a plethora of diverse technologies.
The Sonet tutorial is at:
webproforum.com
For a quick look at SONET acronyms, click on the section called 'guide to acronyms' on the right-hand side of the page.
Regards, Frank Coluccio
ps - see my PM |
