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RE: [EFM] OAM loop back / echo server function


There will need to be some physical layer command functionality in order 
to  provide management functions that are not data traffic invasive.  That 
is one of the requirements of the OAM.  If it is not done within the EFM 
physical layer, then the service will only be "best effort" and not the 
high margin services that will be required to pay for the infrastructure 
deployment of EFM.

Thank you,
Roy Bynum

At 03:38 PM 9/4/01 -0700, Geoff Thompson wrote:
>I'm not sure that I understand what you mean.
>You seem to be making some assumptions about what constitutes "OAM 
>overhead" that I do not.
>What I meant was that tying the transmit data stream directly to the 
>receive data stream at the physical level is a bad idea when you are part 
>of a live network. Since we don't have the concept of turning circuits up 
>and down that means it  is a bad idea all of the time.
>That has nothing to do with any "Loopback Protocol" which might reflect a 
>payload back at a transmitting entity inside valid Ethernet packets.
>At 03:12 PM 9/4/01 -0500, Roy Bynum wrote:
>>What about a "loop back" within the OAM overhead?  That would be able to 
>>function regardless of the Ethernet traffic and network.  It may not be 
>>what some people are wanting, but it is better than nothing.
>>Thank you,
>>Roy Bynum
>>At 02:11 PM 8/31/01 -0700, Geoff Thompson wrote:
>>>This reminds me how dumb I get sometimes in that I did not jump on this 
>>>I believe that Bob is correct in his statement that looping back 
>>>Ethernet is a really bad idea.
>>>I'll say it again more explicitly:
>>>         Raw physical loopback of Ethernet is a really bad idea.
>>>It breaks/screws up networks that were not designed to tolerate it.
>>>As I have said before, I do believe that we will need a demarcation 
>>>device that has the capability to host OA&M functions.
>>>We have talked about "loop back" from this point in the network.
>>>Let us forevermore make that "PING"
>>>At 12:02 PM 8/30/01 -0700, Denton Gentry wrote:
>>>>>Bob Barrett wrote:
>>>>>Remote loop back of Ethernet packets / 802.3 frames is a really bad idea.
>>>>>No mater how well intentioned it will go wrong sometimes and when it does
>>>>>it is really bad news.
>>>>>I thought we were looking at some form of simple echo server function i.e.
>>>>>take a received packet, swap the SA and DA, then send it back out with a
>>>>>new CRC, same payload ????
>>>>  There was a presentation to that effect at the last meeting, describing
>>>>the merits of the LLC2 TEST frame and how having something like it be
>>>>widely implemented would be a good thing. There will likely be a followup
>>>>presentation in Copenhagen discussing details of the proposed mechanism.
>>>>  I don't think an honest to goodness remote loopback, where the RX is
>>>>logically connected to the TX at the remote end, is even possible in EFM
>>>>for the simple reason that the links we're looking at may be asymmetric.
>>>>PONs and DSL-based copper solutions can provide more bandwidth in one
>>>>direction than another.