Lightwave Extra! 4/98 Report on SONET, SDH & ATM
[Many excellent articles at the following site]
broadband-guide.com
Special Report, April 1998
SONET, SDH & ATM - Q&A
Question: Once viewed as potential competitors,
SONET/SDH and ATM are now frequently seen as working
together to increase the efficiency of fiber-optic networks.
What's driving this change in philosophy?
Answer: It's generally a combination of practicality and market
forces. At one time, voice, data, and video services were often
carried on separate networks - frequently by different companies.
Then things began to change, particularly in the United States.
First, voice companies like the RBOCs - who were big fans of
SONET networking - decided to get in the data and video
delivery business, and they wanted to do so using their existing
SONET-based networks. Meanwhile, other kinds of companies
who were looking to expand their offerings, both in terms of
service variety and geographical coverage, realized that in many
cases it was better to use existing networks, most of which were
SONET based, than build brand new ones. So it became
advantageous to find some way of melding SONET and ATM.
And SONET has proven amazingly flexible in terms of the
payloads it can carry. ATM payloads are just one example -
SONET is also proving capable of carrying IP payloads. In fact,
the battle to watch won't be SONET versus ATM - it will be
ATM versus IP.
Q: What are some examples of SONET and IP working
together?
A: The best example right now is Sprint, which is installing Cisco's
Gigabit Switch Routers to boost the efficiency of its fiber-based
Internet transport network. GTE Internetworking also will use
Cisco routers in a similar fashion. Cisco explains this approach -
which it calls "Packet over SONET" - in an article in our April
issue. While Cisco is making the most noise in this area, you can
be sure its competitors aren't far behind. IP over SONET makes a
lot of sense for existing carriers who want to add Internet
provision to their service portfolio; these carriers should represent
a healthy market for IP over SONET routers. However, it will be
interesting to see how new carriers, such as Level 3
Communications, approach the design of their IP-centric
networks. Will they also opt for SONET or will they try some
other tack?
Q: Speaking of SONET's flexibility, I understand Microsoft
is implementing the technology in a new way.
A: Yes. You'd expect Bill Gates would do nothing in a small way,
and Microsoft's new corporate network in Redmond, WA, does
nothing to change this perception. The company is touting the
network as "the largest corporate ATM network in the world,
possibly riding over the largest private SONET backbone in the
world." Few companies other than Microsoft would need the
capacity afforded by OC-3 and OC-12 rings in their corporate
network these days (and a source at Microsoft said they'd have
installed OC-192 if they could have gotten it!). However,
bandwidth demands are increasing all the time, and while
Microsoft is undoubtedly a trailblazer in SONET-based ATM
enterprise networks, I wouldn't be surprised if other companies
followed a similar trail in the future. Again, you can read all about it
in our April issue.
Additional Resources
Check out these feature articles on SONET/SDH & ATM:
Packet Over SONET Fuels New IP Transport Paradigm
Microsoft Chooses SONET for Corporate Network
Clocking SONET Equipment
Reshaping Fiber's Last Mile
Integrating SONET- and Ethernet-based Service Provision
Evaluating ATM Network Topologies
Upgrading FDDI backbones to ATM
Have a question? Contact the editor
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