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A telephony carrier industry perspective


As an introduction, my name is Roy Bynum. I work for MCI WorldCom in
the Data and Optical Network Technology Development organization. I am
late coming to this discussion because of a failure by the telephony
industry to recognize GbE as a defacto optical networking technology.
My charter was to work on a native optical networking standard for IP
services over carrier systems. I came across GbE by accident and
friends that work for data systems vendors.

Over the last several months, I have been involved in evaluating
Gigabit Ethernet (GbE) as a viable data service. The outcome of that
is the following observations (I apologize for the length of this

1. Depending on whom you talk to, 80% to 85% of all data
communications traffic in the world originates on "Ethernet" (802.3).
The reason for this is a combination of almost commodity prices on the
interfaces and very simple operational support requirements, which
translates into very low cost of ownership for the return on investment. 

2. Internet Protocol (IP) can operate on most any layer two protocol,
and does. However, (again depending on whom you talk to) up to 95% of
all IP communications traffic originates on Ethernet. This makes
Ethernet the defacto native data communications protocol for IP. The
reason for this is economics, as stated above.

3. GbE is following the precedence of Ethernet in that it is very cost
effective to deploy compared to other high bandwidth technologies. The
cost for GbE, per bandwidth, is anywhere from one forth to one tenth
of that of ATM or Packet Over SONET (POS).

4. Dense Wavelength Division Multiplexing (DWDM) is being developed
and deployed in the Metropolitan carrier and other fiber optic
systems. These DWDM systems have up to 32 wavelengths, with path
protection for each. Metro DWDM uses single mode fiber (SMF) over
"short" distances, 200km or less. The economics for these systems is
turning out to be very favorable as well.

5. Another technology standard is being proposed in the telephony
industry that provides for transportation of native data, such as
Ethernet, directly over SONET facilities. Data Aware Transmission over
SONET (DATS) is the name of that proposal. DATS comes in two types,
transparent data, and Native data. The transparent data technology
puts ATM SAR switches directly on SONET transport nodes. Native data
technology puts Ethernet switches directly on SONET nodes. Native data
over SONET was demonstrated last year at Interopt and is also turning
out to have some economic benefits.

6. Telephony carrier data communications standards (WAN) today are
very different from Information Technology (IT) data communications
(LAN/MAN) standards. Telephony standards are circuit based and are
concerned with maintaining traffic connection path integrity and
quality. IT standards are based on connectionless data with a major
emphasis on cost of ownership. Telephony standards have been based on
Time Division Multiplexing (TDM) of voice rate (modulo 64kbs)
circuits. IT Ethernet standards have developed independently and are
based on native data requirements (modulo 10Mbs). Up until recently,
the two standards only came together at a router/gateway device that
removed the different standards at layer two, leaving the upper layer
(layer three and above) data to be communicated. It also means that
data traffic path restoration has been dealt with differently by the
two industries and standards. This is changing.

7. Telephony carriers have recognized that in a few years the massive
bulk of the traffic on their systems will be connectionless oriented
native data, not connection oriented voice. Some have also recognized
that the services on this traffic are abstracted from software on the
end systems, not the facilities based services that provides the
profits of today. This means that telephony carriers are looking for a
very cost-effective alternative to the TDM systems that they have been
using. Many are working, along with vendors on what they refer to as
"Optical Networking". This is a combination of very high DWDM
wavelength systems (up to 160 wavelengths) and optical switching which
provides for direct optical transport of data. I will not go into the
economics of what has been developed so far, but it is sufficient to
know that this work is being done.

8. SONET/SDH is a very resilient communications standard. It provides
for very tightly coupled traffic path restoration, which prevents the
unnecessary loss of data traffic connectivity. It provides for very
high bandwidth of channelized and concatenated traffic. It provides
for operational and maintenance support for 365 day x 24 hour
communications services. It is also very expensive, but justified in
the many customers, much circuit oriented, bulk traffic services
provided by the telephony carrier industry.

9. The loss of traffic path connectivity for high bandwidth, bulk data
communications has a much more massive impact than it does with lower
or moderate bandwidth communications. As more and more applications
utilize more and more data communications bandwidth, the loss of
traffic path connectivity will have a business, economic, and personal
impact that it did not have on lower or moderate bandwidth data

10. The nature of wide area networking protocols such as IP's OSPF
changes when you move from a telephony circuit based WAN to a common
virtual circuit based, layer two switching/bridging WAN. The
implications of traffic restoration timers and timing requirements
change when moved from a non-broadcast, multiple circuit path
architecture to a broadcast domain, single segment architecture. This
is not very well understood at the present time. It will take a while
for WAN data communications engineers to work out these changes. This
will delay, for a short while, the deployment of GbE or 10GbE for
enterprise WAN systems.

These observations should help provide some insight into the some of
the issues being discussed by the HSSG. Whatever is developed must be
economical for it to survive. 10GbE is approaching the bandwidth and
functionality requirements of the telephony carrier systems. Where it
is deployed will have a major impact on what the requirements for it
will be. Depending on where it is deployed, it needs to be traffic
path resilient and have operational and maintenance support
functionality directly within 10GbE. This does not mean that 10GbE
could not defined with two standards, one for LAN/MAN, and another
that encapsulates the LAN/MAN framing in a WAN transport standard. A
LAN standard does not have the requirements of a WAN standard. Many of
the WAN requirements can be incorporated in the Metro DWDM systems for
MAN services. This could simplify many of the issues of wavelength,
power, distance, synchronous or block coding, fiber type, and others. 

I hope that I can be of some help with the development of this or
these standards. It is very critical to the future economics of the
carrier data communications industry.

Thank you,
Roy Bynum   roy.bynum@xxxxxxx
Sr. Engineer, Data and Optical Networking Technology Development
MCI WorldCom
(972) 729-7249