From: jkors@media03.UUCP (Jacques Kors)
Newsgroups: comp.unix.misc,comp.protocols.tcp-ip,comp.lang.postscript
Subject: problems tfping to a rip
Keywords: tftp,rip,unix
Date: 5 Nov 92 17:07:59 GMT
Organization: Mediasystemen, Netherlands
X-Newsreader: Tin 1.1 PL4



Can anyone give me some advice on the following problem:

One of our customers  has a configuration with an Intel 520 MBII server 
running unix SYSV r3.2 and three Linotype Postscript RIPs (rip30) connected 
via ethernet.
File are sent from the server to the rips using TFTP. These files are 
somewhere between 1Mb and 4Mb in size.
several times a day this communication fails. When this happens the two 
machines (server and rip) keep talking to each other but they don't seem
to make any progress. Usually the operator terminates such a print job,
after about 20 minutes, bij resetting the rip and then retransmits the file.
Since this compagny is in the newspaper business they can't really afford
this loss of time.

Every time this happens it turns out that a given packet is not accepted
by the rip. The server keeps retransmitting this packet and the rip keeps
rejecting it. It then takes them about half an hour to decide that there is 
no use in going on.
The reason seems to be that the UDP checksum is wrong. normally this 
checksum is correct, but the troublesome packets always have 0xFFFF for 
checksum. if my calculations are correct it should be 0x0 instead.

Some testing at our site has shown that Interactive SYSV R3.2 v2.0.2
has the same effects. Our sun servers don't even bother to generate a 
checksum. All unix boxes we tried don't seem to check this UDP checksum
at the receiving end.

now for the questions:
- am i right on the checksum bit
- Does anybody use a simular setup
  what are your experiences 
- Has anybody encountered this problem
- What is your solution
- Is there some workaround possible
  it would be a great improvement if the problem could be detected
  earlier without having to wait for nothing ( and 20 minutes ).
- Hav you got any suggestions

Thanks in advance for any suggestions/help/information etc.....,

Jacques
----
below you'll find an ascii/hex dump of an erroneous packet:

*Packet 5623 (558 bytes) at T + 665.9710 secs, Delta t 0.0209 secs
 Destination = RIP03       , Source = GBD02       , Type = 0800
 VER/IHL = 45, TOS = 00, Len = 0220, ID = 4108, FLG/FRG = 0000, TTL = 1E,  
 Prtcl = 11, IP Chksum = C6F9, IP Srce = C05C8907, IP Dest = C05C890B, 
 Srce Port = 0D38, Dest Port = 065C, Len = 020C, UDP Chksum = FFFF
 0000: 00 03 0C 95 41 31 46 31 45 31 44 32 32 32 31 32     ....A1F1E1D22212
 0010: 30 32 30 32 30 32 30 32 30 31 42 32 32 31 44 31     0202020201B221D1
 0020: 45 31 44 31 43 32 32 31 44 31 44 32 32 32 32 31     E1D1C221D1D22221
 0030: 44 31 43 32 36 31 41 31 43 32 31 32 32 31 43 31     D1C261A1C21221C1
 0040: 44 31 43 32 31 32 30 31 46 0D 0A 32 35 32 30 32     D1C21201F..25202
 0050: 30 32 30 32 30 32 30 32 30 32 33 32 36 32 35 32     0202020202326252
 0060: 31 31 44 32 32 32 32 31 44 32 34 31 44 32 34 31     11D22221D241D241
 0070: 45 32 30 31 46 32 34 32 31 32 36 32 30 32 32 31     E201F24212620221
 0080: 45 31 45 32 33 32 32 32 32 32 32 32 32 32 34 31     E1E2322222222241
 0090: 42 31 31 35 43 39 30 36 30 33 34 0D 0A 33 35 31     B115C906034..351
 00A0: 46 31 45 31 43 31 44 31 44 31 45 31 45 31 45 31     F1E1C1D1D1E1E1E1
 00B0: 45 31 44 32 33 31 44 31 43 32 31 31 43 31 43 32     E1D231D1C211C1C2
 00C0: 31 31 46 32 34 32 32 32 31 32 36 31 42 31 37 32     11F242221261B172
 00D0: 31 45 39 44 34 43 38 43 37 43 38 43 38 43 32 43     1E9D4C8C7C8C8C2C
 00E0: 34 43 36 43 30 43 34 43 34 42 30 42 41 0D 0A 41     4C6C0C4C4B0BA..A
 00F0: 44 36 32 31 32 32 31 32 34 32 33 32 41 32 42 31     D62122124232A2B1
 0100: 46 32 32 32 32 32 32 32 37 32 32 32 32 32 33 32     F222222272222232
 0110: 32 32 31 32 45 32 37 31 45 32 32 31 39 31 41 31     2212E271E22191A1
 0120: 43 31 43 31 43 31 42 32 30 31 41 31 35 31 42 31     C1C1C1B201A151B1
 0130: 41 31 46 31 46 31 39 31 46 31 46 31 41 31 42 0D     A1F1F191F1F1A1B.
 0140: 0A 31 41 32 30 31 41 31 42 32 30 32 30 31 42 31     .1A201A1B20201B1
 0150: 43 31 38 31 38 31 43 31 42 31 42 32 30 31 43 31     C18181C1B1B201C1
 0160: 43 31 43 31 41 31 45 32 32 31 42 31 46 32 33 32     C1C1A1E221B1F232
 0170: 32 32 30 32 33 32 39 32 39 32 34 32 33 31 43 31     22023292924231C1
 0180: 41 31 43 31 43 31 44 31 44 31 38 31 38 31 39 31     A1C1C1D1D1818191
 0190: 38 0D 0A 31 44 31 43 31 43 31 44 31 38 31 44 31     8..1D1C1C1D181D1
 01A0: 44 31 38 31 44 31 43 31 43 31 43 31 42 32 31 31     D181D1C1C1C1B211
 01B0: 43 31 44 31 38 31 38 31 45 31 38 31 39 31 39 31     C1D18181E1819191
 01C0: 38 31 45 31 37 31 44 31 38 31 38 31 44 31 44 31     81E171D18181D1D1
 01D0: 39 31 41 31 38 31 45 31 37 31 44 31 44 31 37 31     91A181E171D1D171
 01E0: 45 31 38 0D 0A 31 39 31 44 31 43 31 36 31 42 32     E18..191D1C161B2
 01F0: 30 31 42 31 44 31 37 31 42 32 34 31 45 31 45 31     01B1D171B241E1E1
 0200: 45 31 45 31                                         E1E1

----

+-----------------+---------------------------------+-------------------+
 \ Jacques Kors    \  email: jkors@media01.UUCP      \  Disclaimer:      \
  \ Mediasystemen   \        ...!sun4nl!media01!jkors \  you would look   \
   \ P.O.Box 4932    \                                 \ funny too, if you \
    \ 2003 EX Haarlem \  voice: + 31-23-319075          \  were RIPped      \
     \ The Netherlands \  fax  : + 31-23-315210          \                   \
      +-----------------+---------------------------------+-------------------+
-- 
+-----------------+---------------------------------+-------------------+
 \ Jacques Kors    \  email: jkors@media01.UUCP      \  Disclaimer:      \
  \ Mediasystemen   \        ...!sun4nl!media01!jkors \  you would look   \
   \ P.O.Box 4932    \                                 \ funny too, if you \
    \ 2003 EX Haarlem \  voice: + 31-23-319075          \  were JPEGged     \
     \ The Netherlands \  fax  : + 31-23-315210          \                   \
      +-----------------+---------------------------------+-------------------+
Newsgroups: comp.unix.misc