Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!ucsd!ucbvax!hsi.UUCP!stevens From: stevens@hsi.UUCP (Richard Stevens) Newsgroups: comp.protocols.ibm Subject: SNA reliability above DLC Message-ID: <8809220906.AA11914@jade.berkeley.edu> Date: 21 Sep 88 20:01:16 GMT Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: Richard StevensOrganization: The Internet Lines: 16 After going through a many SNA manuals, including the friendly FAPLs, I've come to realize that SNA provides no reliability in terms of a checksum at any level above the data link. Obviously you'll have the data link reliability (16-bit CRC for SDLC, 32-bit FCS for the token ring, etc.), but unlike TCP, UDP or Xerox's IDP, there is no "checksum". Am I missing something ?? I'll assume the designers of SNA assumed that a DLC check was adequate. Do TCP or UDP really need a checksum, especially when running over an Ethernet, say ? I see that ISO only specifies the use of a checksum for TP-4. Richard Stevens Health Systems International, New Haven, CT stevens@hsi.uu.net ... { uunet | yale } ! hsi ! stevens