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Re: Long distance links


At 01:17 PM 8/30/99 -0700, Rohit Mittal wrote:
>Rich et al,
>One of the things you need to consider is that SONET has extensive error
>"built-in" the overhead to allow speedy detection of failures before they
>to serious levels. SONET provides rapid fault isolation.
>Now, if you use TCP/IP for the same tasks, you are going to add latency etc.
>because the frame/data will have to pass through many layers before any
fault is
>detected. That is the problem in moving up the protocol stack.
>For instance, SONET allows less than 50ms time for signal restoration (due
to cut
>fiber etc.). I do not see anything in Ethernet which can provide
equivalent support
>- maybe Far end fault detector but doesn't that takes a long time to detect?
>IMO, the best solution is just to encapsulate ethernet frames as data bits
in a
>SONET frame. That way SONET can provide the management features for
>expensive mantainence and Ethernet can travel as is. Am I overlooking

To carry Ethernet frames on a SONET system:

1)Ethernet must match the payload rate of 9.584640 Gbps
2)Ethernet frames must be encoded with NRZ efficiency
3)Ethernet frame delimiting must operate without special symbols

>Rohit Mittal
>Engineering, Microlinear Corp.
>> Mark,
>> I believe you're on the right track insofar as digging to the root of the
>> management issue. The fact of the matter is that Ethernet does it one
way, and
>> SONET does it another. My sense is the same as yours: "...instead of
>> transporting management info on dedicated
>> circuits, use TCP/IP and packets.  It's the histroric trend, moving up the
>> protocol stack."
>> I have asked numerous questions over this reflector trying to get at the
core of
>> requirements for WAN management. I've seen no responses to those
questions. BTW,
>> I'm sill very much interested in hearing the responses to these questions.
>> Without knowing the requirements for SONET WAN management, I have to
>> that Ethernet Management, ULP (e.g. Ping, SNMP, Browser) management
>> Etherenet PHY capabilities for determining things like the BER of each
>> represent sufficient architecture to implement WAN management equivalent or
>> superior to that of SONET.
>> Best Regards,
>> Rich
>> --
>> "Gerhold, Mark" wrote:
>> > All,
>> >
>> > It sounds as if one of the biggest issues here is with the optical
>> > repeaters.  If I understand correctly, Sonet repeaters are
instrumented so
>> > that the administrator can isolate problems without sending out a truck.
>> >
>> > Consider using a 2-port "LAN" switch instead of a repeater.  Switches
>> > provide lots of remote maintenance features, including
>> >
>> > o Ping (for I'm alive)
>> > o SNMP (for tons of performance statistics, and alarms)
>> > o Browser management (for ease of use)
>> >
>> > With a switch, instead of transporting management info on dedicated
>> > circuits, use TCP/IP and packets.  It's the histroric trend, moving up
>> > protocol stack.
>> >
>> > Here's a question on a similar vein.  Are WDM amplifiers instrumented to
>> > isolate BER problems?  I thought they did optical amplification.
>> > BER info sounds tough.
>> >
>> > Thanks,(signing off)
>> >
>> > Mark Gerhold
>> > Unisys
>> >
>> >
Paul A. Bottorff, Director Switching Architecture
Enterprise Solutions Technology Center
Nortel Networks, Inc.
4401 Great America Parkway
Santa Clara, CA 95052-8185
Tel: 408 495 3365 Fax: 408 495 1299 ESN: 265 3365