Re: HARI: Question regarding byte (column?) versus word striping
I am getting somewhat confused on this isse. Could someone give a pointer
to where the
concept of "lane", "column" and "striping" are detailed ?
Regards,
Tripathi.
At 08:06 PM 1/6/00 -0800, you wrote:
>
>Rich,
>
>I believe you are missing the point of how word striping works.
>As the number of lanes scales up, word striped data still uses
>ONLY ONE WORD to be added/deleted for clock tolerance compensation.
>That is, for n lanes, byte striping must delete n characters (ie,
>a column) while word striping must delete only 4 characters (ie,
>a word) from any one of the n lanes.
>
>Without the constraint that the packet begin in a particular lane,
>I believe that the IPG is CONSTANT for word striping, but must
>grow linearly with the number of lanes for byte striping.
>
> [Please note that the number of bytes (characters) in a "word"
> in word striping is chosen to span the expected skew, yielding
> its great simplicity of implementation. For HARI, it is merely
> coincidence that the word size is the same as the number of lanes.
> The word size and the number of lanes are independent things.]
>
>
>Simon,
>
>I appreciate your comments on this issue, and I agree completely.
>Please let me know if I've missed anything above, or if I need to
>improve on my explanation.
>
>Regards,
>Mike
>
>
>Rich Taborek wrote:
>>
>> Simon,
>>
> (text deleted)
>>
>> When Hari is scaled to higher speeds, Column-Striping can function with a
>> smaller IPG than can Word-Striping. Two requirements of the IPG are:
>>
>> 1) Link synchronization - commas required
>> 2) Clock tolerance compensation - insert/remove protocol required
>>
>> Column-Striping requires only a single column of commas (K) for link
>> synchronization and utilizes a single column of skips (R) for clock
tolerance
>> compensation. The minimum IPG size based on starting a new packet in
lane 0 is
>> 3n, where n=number of lanes. That's one n for the K column, another for
the R
>> column and a third possibly complete column containing the End-of-Packet
>> delimiter plus pad characters.
>>
>> Word-Striping uses words containing commas which may be inserted/deleted
during
>> the IPG. The minimum IPG size is 5n, where n=number of lanes. That's 4n
for 4
>> deletable Idles and one more word containing the End-of-Packet delimiter
plus
>> pad characters.
>>
>> Best Regards,
>> Rich
>
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Devendra Tripathi
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