HP OpenVMS Systems

Determining TCP/IP (UCX) Time To Live (TTL)?

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The Question is:

 
What is the command to see the value of the TCP/IP parameter TIME_TO_LIVE ?
 

The Answer is :

 
  The default Time To Live (TTL) value is a hard-coded value under TCP/IP
  Services for OpenVMS (UCX) V4, though you can change it -- via a call to
  setsockopt -- for specific connections.  As there is no way to change the
  system-wide default setting, no mechanism to view the current (hardcoded)
  setting was implemented.
 
  All recent versions of UCX use a TTL of 128, for both TCP and UDP
  outgoing packets -- the value was increased from 30 to 128 back
  around 1993.  The Wizard suspects that most networks will operate
  quite nicely with a TTL circa 60 -- few exceed 30 and only very seldom
  is 50 reached -- and that the current value of 128 is too large.
 
  Inordinately large values for TTL will simply leave the packets churning
  around the network (unnecessarily) in the event of a routing loop.
 
  The upcoming V5 release includes the ability to change the TTL value
  on a system-wide basis, see the output from "sysconfig -q inet".  In
  the V5 release, the new TTL default is 60.
 

  

     

     
answer written or last revised on ( 7-DEC-1998 )
     
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