FREE MOBILE CLOUD COMPUTING
CONCEPTS - TRAINING_MODULES_WITH_ TONS_OF_VIDEOS
Post by Lawrence Terry Calley with Oklahoma Broadband
The Synchronous Optical NETwork (SONET) standard for fiber optic networks
was developed in the mid-1980s. It remains in widespread use today. In a nutshell, SONET allows multiple technologies and
vendor products to interoperate by defining standard physical network interfaces.
In Europe, the term Synchronous Digital
Hierarchy (SDH) refers to essentially the same standard as SONET. This article uses the term "SONET" to refer to
the common characteristics of SONET/SDH.
SONET was originally designed for the public telephone network.
In the early 1980's, the forced breakup of AT&T in the United States created numerous regional telephone companies, and
these companies quickly encountered difficulties in networking with each other. Fiber optic cabling already prevailed for
long distance voice traffic transmissions, but the existing networks proved unnecessarily expensive to build and difficult
to extend for so-called long haul data and/or video traffic.
The American National Standards Institute (ANSI) successfully devised SONET as the new standard for these applications.
Like Ethernet, SONET provides a "layer 1" or interface layer technology (also termed physical layer
in the OSI model.) As such, SONET acts a carrier of
multiple higher-level application protocols. For example, Internet Protocol (IP) packets can be configured to flow over SONET.
transmits data at speeds between 155 megabits per second (Mbps) and 2.5 gigabits per second (Gbps). To build these high-bandwidth
data streams, SONET multiplexes together channels having bandwidth as low as 64 kilobits per second (Kpbs) into data
frames sent at fixed intervals.
Compared to Ethernet cabling that spans distances up to100 meters (328 feet), SONET fiber
typically runs much further. Even short reach links span up to 2 kilometers (1.2 miles); intermediate and
long reach links cover dozens of kilometers.
One of SONET's most interesting characteristics is its support for a ring topology. Normally, one piece
of fiber -- the working ring -- handles all data traffic, but a second piece of fiber -- the protection ring
remains on standby. Should the working ring fail, SONET includes the capability to automatically detect the failure and transfer
control to the protection ring in a very short period of time... often in a fraction of a second. For this reason, SONET can
be described as a self-healing network technology.
Figure 1: Conceptual SONET ring
will help SONET service to reach the "five nines" availability level. However, the usefulness of rings also depends on their physical location. There are two instances of
SONET ring topology. The cables take distinctly different routes to reach the same destination. Geographically speaking, one
path turns north first and then east, the other first turns easy Being physically separated, the likelihood of an excavation
or natural disaster breaking both cables lessens dramatically.
However, the cables follow essentially the same route. Imagine
in this case two strands of fiber set only a few feet apart from each other... possibly even in the same trench! The likelihood
of one problem disabling both fiber strands increases dramatically, effectively defeating the advantage of SONET rings. Note
that SONET does not require rings: many SONET networks have been deployed in single-strand linear architectures.
Management and Maintenance
The term OAM&P
often appears in conjunction with optical network technologies like SONET (and ATM). OAM&P -- Operations, Administration,
Maintenance, and Provisioning -- refers to the support built into the technology for ease of network management. In the case
of SONET, a significant number of bytes inside the data frame have been reserved for this "management overhead."
At the expense of some bandwidth, problems can be more quickly detected, isolated, and repaired.
The Future of SONET
Because SONET can carry very large
amounts of traffic, it would seem on the surface to be an ideal technology for future voice and data broadband networks. SONET competes with several other viable technologies including ATM and Gigabit Ethernet for this role....and the cloud progression