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DECserver 200, DELNI, and echo pauses?

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The Question is:

I am having a strange performance issue with DECserver 200's on an Alphaserver
 1000A running VMS 7.2-1.  The user's can connect to the host and work with
 everything normal except that there is a 2 to 4 second delay in the typed
 character display.  Yhis co
nfiguration also includes PC's connected using telnet that do not have any
 problems.  File transfers using FTP also perform as expected.  I have replaced
 each server, DELNI and cable to no avail. The problem goes away as soon and as
 long as someone connec
ts to the (each) server using MC LANCP.  I have talked to Compaq support and
 they had never seen anything like this.  Any thoughts you might have would be

The Answer is :

  The most obvious question: what has changed since this (old hardware)
  was last functioning.
  The OpenVMS Wizard has seen similar behaviour when there are network
  errors lurking -- the echo is provided by OpenVMS, which would imply
  a connectivity or response problem between the DECserver 200 series
  device and the OpenVMS host.  Accordingly, please apply the available
  mandatory ECO kits for OpenVMS, and also any that include updates for
  LAT and for the network drivers.
  It is also possible that there is a babbling device on the network.
  (This is comparatively unlikely, but odd behaviours have been seen
  with network hardware of this vintage.)
  Please also check for connectivity errors -- use the LANCP counters,
  and check the cabling and transceiver connections -- between the OpenVMS
  host and the DECserver device, and check for such details as the
  transceiver AUI and heartbeat settings, the Ethernet switch (if any)
  settings, etc.   (This assumes the DELNI is connected to an Ethernet
  segment using a transceiver.)
  The DELNI itself is also little more than an electronic simulation of
  a long Ethernet cable within a box, and particularly has very specific
  Ethernet network configuration requirements -- details on the DELNI
  configuration include the local-remote switch setting, the number of
  DELNI devices connected together, and the use of the network AUI port.
  If the DELNI is connected to a repeater and the DELNI global port is
  enabled, heartbeat MUST be disabled on the transceiver, either via a
  switch on the particular transceiver for more "recently-ancient" Ethernet
  transceivers, or via the H4000-BA series "no heartbeat" transceiver.
  Propogation of heartbeat through a DELNI device has been known to cause
  problems and sluggishness among repeaters and other devices -- heartbeat
  is a collision presence detection mechanism, and the reported behaviour
  could be caused by misinterpreted collisions.  Newer devices generally
  also expect heartbeat to be enabled, and will generate errors if not.
  DELNI and DECserver 200 series devices are comparatively rare and rather
  old devices, as well.  This might well be a hardware problem with these
  devices.  (Given prices of current-generation terminal server and network
  hardware, does continued diagnosing of this problem make economic sense?)

answer written or last revised on ( 20-MAY-2002 )

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