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PDP-10 Archives
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anf703.d14
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EDIT DESCRIPTIONS FOR ANF10-V703
EDIT 12890 FOR ANF
[SYMPTOM]
Downline loading of ANF remote stations does not always work in
configurations containing DUP11s. The following configuration is
known not to work:
KL --- (DTE) DN20 (DUP) --- (DQ) DN80
[DIAGNOSIS]
DUPs treat syncs special in that you don't want to send a BCC
character after the sync characters. This makes sense, since normally
only actual data is checksumed and synchs are inert filler. Clearing
140000 in the byte count is the flag to the DUP driver that these are
syncs, and as such don't get checksummed.
If the two instructions are removed, the DUP driver will instead
get handed a "counted string" (with an address in R0 and a negative
count in R1) be transmitted without a BCC.
In either case, the absence or presence of the two instructions
should make no difference. The net result should be the same, namely
several synchs are sent, although it's not clear why one case works
and the other doesn't.
[CURE]
Remove the two lines of code, thereby causing the synchs to be
checksumed.
********************************************************************************
EDIT 12891 FOR ANF
[SYMPTOM]
The DDCMP driver does not conform to the DDCMP specification.
Out of sequence ACKs cause the line to be declared down and restarted.
Also, the REP timer default of one second is too short for 4800 baud
lines.
[DIAGNOSIS]
When out of sequence ACKs are detected, they should be ignored
and not cause a line restart. A one second REP timer does not allow
enough time to receive an ACK if the remote node begins sending a full
full length packet.
[CURE]
Ignore out of sequence ACKs and increase the default REP timer to
three seconds.
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END OF ANF10-V703