HP OpenVMS Systems

DECnet-Plus Late Collision CSMA/CD Error?

» close window

The Question is:

 
I have found something similar to this titled 'Meaning of Carrier Check
 Failure?'; is this a similar problem?
All services and application processes are running fine.
Operator log is filling with the given error message which is repeating
 regularly between 5 seconds and 1 minute.
Are there any system parameters to adjust to compensate or is this a hardware
 problem?
 
 

The Answer is :

 
  Your TCP/IP Services version is not supported and is not supported
  on this OpenVMS release, and in need of an upgrade.  Please move
  to V5.1 with ECO or later (as available).  Please also upgrade your
  OpenVMS Alpha version to V7.1-2, V7.2-2, V7.3 or later (as available).
 
  A "late collision" is a packet collision that occurs after the window
  for a network collision closes.  CSMA/CD (Carrier Sense Multiple Access
  with Collision Detection) networks function based on signal propogation
  across the network; CSMA/CD networks require that the length of the
  shortest network packet be long enough to span the entire cabling plant
  when transmitted.  The width of the permissible collision window is
  defined by the maximum permitted span of the Ethernet or IEEE 802.3
  network configuration and the length of the shortest permissible packet,
  and the late collision error indicates there is too much of a signalling
  delay in the configuration, or that there is a network station that is
  not correctly detecting signals and thus is not backing off for a retry.
 
  That these collisions are occuring (late) implies that the physical
  network cabling is too long, that there are too many repeaters, that
  there exists failed network hardware, or some combination of these
  factors.
 
  The typical approach toward resolving these errors involves TDR-based
  (time domain reflectometer; a device which measures signal reflection)
  determination of the cable run lengths and any cable faults that might
  lurk, determining the physical lengths of individual cabling runs,
  looking for correct terminations and correct cabling, counting the
  numbers of repeaters, and similar tasks.  You are specifically looking
  for any and all violations of the Ethernet or IEEE 802.3 network
  requirements.
 
  As should now be quite obvious, there are no OpenVMS system parameters to
  adjust nor to compensate for this -- your network has a hardware error.
 
  Related topics include (7105), (3500), (3516), (3632), and (4439).
 

  

     

     
answer written or last revised on ( 8-NOV-2001 )
     
» close window