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RE: Clause 49, Figure 49-7 - //T// followed by //O//


If one is in a packet and the Phy starts putting out LF, it probably is
because errors were being detected so the packet is already hosed.
Transitions to states where we send LF are not conditioned on finishing
sending the current packet. If we are in the middle of a packet, we switch
right to LF and destroy the packet. Data to LF transition within a block
also causes an E block. We don't mind losing the first Ordered set to an
error. There will be plenty more.
Similarly for the RS when it sends RF.

If we delayed the ordered set until the end of packet, then we would have to
put in some kind of watch dog timer in case we got a stream that looked like
endless data. It is simpler to start sending ordered sets when a fault is

If we were going to add codings for a block containg a T plus an ordered
set, we would need 4 additional codings and there is only one type field
left that preserves the Hamming distance. Therefore, we would weaken our
code by adding this feature and we don't need it.

Where ordered sets are introduced in clause 46, it would be appropriate to
note that an ordered set beginning less than 5 characters after a Terminate
may cause loss of the packet and may be lost. We don't need this for current
RF/LF usage but it would be appropriate because there might sometime be
other uses for the ordered sets.


-----Original Message-----
From: Tuan Hoang []
Sent: Friday, February 16, 2001 10:17 AM
To: ''
Subject: Clause 49, Figure 49-7 - //T// followed by //O//


Figure 49-7 does not include input data frames, containing XGXS's T column
(T0, T1, T2, or T3) followed by an O column (O4), are valid frames. From
what I've gathered from the D2.1, I just don't see how occurrences of the
above frames at the PCS input are not considered as normal. 


Tuan Hoang


Tuan Hoang
Optical Transport Unit

49 Discovery
Irvine, CA 92618
Phone: (949) 585-6888