Re: Long distance links
Roy,
I'm aware that the target is 50 ms for correction. That was what I was
implying in the term "management resolution". What I was trying (poorly) to
say was that between detection at several micro seconds and completion of
switchover at 50 milli seconds, we have more than enough time to switch to
an alternate path in an Ethernet environment. We can even do it with
existing standard protocols in the IP world if we configure things the right
way.
regards
Brian
-----Original Message-----
From: Roy Bynum <rabynum@xxxxxxxxxxx>
To: Brian MacLeod <bmacleod@xxxxxxx>
Cc: HSSG <stds-802-3-hssg@xxxxxxxx>
Date: Monday, August 30, 1999 8:47 PM
Subject: Re: Long distance links
>Brian,
>
>There is a misconception that it takes 50 milliseconds to detect a failure
in
>the telecom industry. The 50 milliseconds is the amount of time the
telecom
>industry requires the transmission system to correct for the failure. The
>actual amount of time that it takes to detect the failure can be less than
a
>microsecond, bounded by the speed of light. I have seen a SONET OC192
system
>switch traffic from a cut fiber to an operational fiber in 6 milliseconds.
You
>can imagine the reliability of applications running over such a data
network.
>
>Thank you,
>Roy Bynum
>MCI WorldCom
>
>Brian MacLeod wrote:
>
>> Rohit,
>>
>> Please be aware that there are currently Gigabit Ethernet products in the
>> market that can detect a link failure in several microseconds. Of course
>> detection is different from "management resolution" such as the opening
of
>> an alternative path. However, this is at least three orders of magnitude
>> less than the telecom industry goal of 50 milliseconds. Smart silicon
and
>> software engineers should be able to do lots with that :-)
>>
>> Brian MacLeod
>>
>> -----Original Message-----
>> From: Rohit Mittal <mittal.rohit@xxxxxxxxxxx>
>> To: rtaborek@xxxxxxxxxxxxxxxx <rtaborek@xxxxxxxxxxxxxxxx>
>> Cc: HSSG <stds-802-3-hssg@xxxxxxxx>
>> Date: Monday, August 30, 1999 2:34 PM
>> Subject: Re: Long distance links
>>
>> >
>> >Rich et al,
>> >
>> >One of the things you need to consider is that SONET has extensive error
>> monitoring
>> >"built-in" the overhead to allow speedy detection of failures before
they
>> degrade
>> >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
>> preventing
>> >expensive mantainence and Ethernet can travel as is. Am I overlooking
>> something?
>> >
>> >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
>> believe
>> >> that Ethernet Management, ULP (e.g. Ping, SNMP, Browser) management
>> mechanisms,
>> >> Etherenet PHY capabilities for determining things like the BER of each
>> link,
>> >> 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
>> today
>> >> > 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
>> the
>> >> > protocol stack.
>> >> >
>> >> > Here's a question on a similar vein. Are WDM amplifiers
instrumented
>> to
>> >> > isolate BER problems? I thought they did optical amplification.
>> Capturing
>> >> > BER info sounds tough.
>> >> >
>> >> > Thanks,(signing off)
>> >> >
>> >> > Mark Gerhold
>> >> > Unisys
>> >> >
>> >> >
>> >
>