SORT BY:

LIST ORDER
THREAD
AUTHOR
SUBJECT


SEARCH

IPS HOME


    [Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

    RE: TCP "reliability"



    Jonathan,
    
    > >(2) Data is correctly delivered in the face of corruption.  TCP's 16-bit
    > >	checksum falls short of a 32-bit CRC in its ability to detect
    > >	corruption, and hence TCP leaves something to be desired here.
    > 
    > stricly, what you say is unquestionably true.
    
    Right ... I put the numbers of bits in for a reason :-).
    
    > But I think you are
    > conflating two quite distinct properties here: 32-bit error-detecting
    > codes (EDCs) and the kinds of errors which a (32-bit) CRC guarantee to
    > catch, versus the errors which to which a transport-level error chehck
    > is, empirically, subjected.
    > 
    > It turns out that, on the best data we (I and Craig Partridge) have on
    > empirically-observed transport-level errors, CRCs are just not a whole
    > lot better than a 32-bit mod-M additive sum (where M ~= 2^32).
    
    I think that's fair, and I certainly don't want to argue with empirical data
    - my wife claims the first rule of engineering is "never argue with results"
    ... and she's always right ;-).
    
    However, when looking at TCP, we have to deal with the 16-bit
    checksum that exists and really cannot be changed at this juncture.
    
    Thanks,
    --David
    
    ---------------------------------------------------
    David L. Black, Senior Technologist
    EMC Corporation, 42 South St., Hopkinton, MA  01748
    +1 (508) 435-1000 x75140     FAX: +1 (508) 497-8500
    black_david@emc.com       Mobile: +1 (978) 394-7754
    ---------------------------------------------------
    
    


Home

Last updated: Tue Sep 04 01:04:19 2001
6315 messages in chronological order