Framing packets over the link

[Hon Wah Chin <HWChin@xxxxxxxxxxxxxxxxxxx>]

We still have to consider how to format and frame the packets
once we get the speed of the MAC/PLS settled.  Here is a start for a
comparison
table (read with a fixed width font) for some schemes.

                Fixing the Signalling           Fixing the Throughput Rate
                rate at OC-192                  at 10Gb/s
                (get to use regenerators)       (Might have to do new
PHY/PMD)


FRAMING


Manchester      approx 5Gb/s throughput         Must signal at 20Gb/s
                        (sucks)                         (really hard)

          -- tradeoff about fast locking PLLs (hard)
                vs some scheme like running quarter speed transitions
                to indicate "no carrier"
          -- This would not be a serious contender


8B/10B          approx 8 Gb/s throughput        must signal at 12.5 Gb/s


PPP/POS         variable throughput             variable througput
                        10Gb/s - some delta             10Gb/s +- some delta
                                                (depending on signalling
rate)

          -- some kind of scrambling required to reduce chance
                of long runs


Header/Length   10 Gb/s - epsilon throughput    Can be 10 Gb/s throughput
(SDL et al)
          -- would require changing MAC/PLS definition to provide
                packet length early
          -- framing acquisition logic required - parallel CRC
                checkers to search for byte/packet alignment
          -- some kind of scrambling required to reduce chance
                of long runs


Multilevel                     NA                       ?
  signalling


Multichannel                   NA                       ?
  signalling