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Re: [802.3BA] query regarding Alignment markers transmission


Figure 82.7/8 of 802.3ba-D20Pre suggests clearly that initially no alignment markers are inserted. First set of alignment markers are inserted after 16383 66-bit blocks on each lane.

As far as collection of BIP bits is concerned, In the first case (when first block is not a alignment block), the first 16383 66-bit blocks will have no alignment marker block and the BIP will be calculated based on bits from first block to 16383rd block. In the second case, BIP will be calculated based on bits from last alignment block to 16383rd block.

So, in all there has to be 8 X 16383bits, first 66-bit block may be a alignment marker block or a data/control block.

Thanks and Regards,
SK Rana
IIT Bombay

On Wed, May 20, 2009 at 3:47 PM, Tarun Aggarwal <tarun_agarwal@xxxxxxxxxx> wrote:

I am reading following clauses of 802.3ba draft 2.0:

Paragraph 1 of 82.2.8 :
"The alignment markers are inserted after every 16383 66-bit blocks on each lane"

Paragraph 2  of 82.2.9 :
"Each bit in the BIP field is an even parity calculation over all of the previous selected bits of a
given PCS Lane, from and including the previous alignment marker, but not including the current alignment

I am not clear that when should the Alignment markers be sent for the first time? That is, should
they be sent at very beginning or after transmisting initial 16383 66-bit blocks. In both cases, how should BIP field calculation
be done for the first time?

Any clarifications on this would be greatly helpful.