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Cell Relay Retreat>List Archive>month:1998-Jan> msg00006



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Re: cell lose due to ATM congestion

  • From: murray@pa.dec.com (Hal Murray)
  • Date: 2 Jan 1998 08:59:30 GMT

In article <34AAADE8.3BC9@ibm.net>, dtcc310@ibm.net writes:

> Can you advise me in detail why link error can cause cell lose?
> is that because of the ATM header HEC failure due to link error? 

If the header gets mashed the cell may get forwarded to the wrong
VP/VC.  The header CRC can fix single bit errors.  Not everybody
turns that feature on and it doesn't solve massive errors which
many links can easily generate.

[Note you can also get added cells as well as lost cells.]


> If a sublayer is put below ATM to handle link error on links other
> than SONET/SDH, this kind of cell lose can be avoided.

Sure.  But that only works if the sublayer is there and it works
well.


People are now running ATM/OC-3 over twisted pairs.  I don't have any
data, but I expect the error rates will be higher than fibers.  No new
extra sublayer was added.