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Re: Chapter 46: preamble length

Hi Ben,

At 01:00 PM 03/29/2001 -0500, Ben Brown wrote:

>I think this same idea exists in 10G. No implementation should
>ever remove any bytes of preamble so a MAC designed to expect no
>fewer than 8 (or even exactly 8) should be fine. If it stops working
>because someone else's PHY removes bytes of preamble, than it should
>be easy to show that PHY is non compliant.

I completely agree with you.


>> As for where in the draft, I don't think there is any text that directly
>> tells you how to do preamble shrinkage. There is text that describes the
>> occurrence of preamble shrinkage (hence this thread).  Another question
>> would be: is there any text in the draft that strictly forbids preamble
>> shrinkage?
>There is also no text in the draft that says a PHY can't perform
>clock tolerance by discarding data from the packet. However, a PHY
>that did so, even if it corrected the CRC somehow, would immediately
>be considered non compliant. The way we're handling preamble in
>these PHYs is identical to the way we're handling data. It should
>never be touched. Therefore, a MAC designed to only expect 8
>bytes of preamble should never be deemed non compliant.
>> Cheers,
>> Brad
>>                 -----Original Message-----
>>                 From:   Ben Brown [mailto:bbrown@xxxxxxxx]
>>                 Sent:   Wednesday, March 28, 2001 10:44 PM
>>                 To:     stds-802-3-hssg@xxxxxxxx
>>                 Subject:        Re: Chapter 46: preamble length
>>                 Brad,
>>                 In my opinion, after reading the drafts, I would say that an
>>                 implementation which chose to change the length of the
>> preamble,
>>                 for any reason, would be non compliant. I think you would
>>                 disagree with this statement. I wonder how many others would
>>                 disagree with it. Also, where in the draft does it allow an
>>                 implementation to change the length of the preamble?
>>                 Ben
>Benjamin Brown
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