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Article #1388

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#1388

From: "John A. Pershing Jr."
Date: Thu, 22 Sep 1988 13:34

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No, you're not missing anything.  The reliability provided by the SNA DLC
layer is carefully preserved by all higher layers, so that additional
CRCs are probably redundant.  There is probably a tacit "assumption" that
the various nodes are reliable -- that is, that they won't introduce any
bit errors without detecting the fault (e.g., via a machine check).

As I remember (it's been a long time), TCP doesn't make many assumptions
about the reliability of the lower layers; therefore, it needs some sort
of checksum to provide reliable transport.  If, in fact, the lower layers
*are* reliable then TCP probably doesn't need the checksum; however, a
proper TCP implementation cannot make such an assumption.

      John Pershing
      IBM Research, Yorktown Heights

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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!ncrlnk!ncr-sd!hp-sdd!hplabs!ucbvax!YKTVMH.BITNET!PERSHNG
From: PERSHNG@YKTVMH.BITNET ("John A. Pershing Jr.")
Newsgroups: comp.protocols.ibm
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Message-ID: <8809221350.AA14186@jade.berkeley.edu>
Date: 22 Sep 88 13:34:36 GMT
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Reply-To: "John A. Pershing Jr." <PERSHNG%YKTVMH.bitnet@jade.berkeley.edu>
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