Jack White ([log in to unmask]) wrote:
: We are looking to replace our X.25 connections and it has been suggested
: that we go with frame relay.
 
- Maybe whoever suggested this meant that you scrap X.25 completely and
  run everything IP-routed over frame-relay backbones?
 
 
:                               My understanding of frame relay is that it
: is much like X.25, only better.
 
- Better...?  Hmmm...  Frame relay is like X.25 in that sense that X.25
  has level 1,2 and 3 and is connection oriented,  guaranteed data dalivery
  protocol with error recovery/correction/re-transmission machanisms built in.
  X.25 is a connection-oriented protocol at levels 2 and 3.
 
  Frame relay is a stripped down version that contains basically the same
  level 1,  small subset of level 2 and none of X.25 level 3 stuff.  It has
  no error recovery/correction nor re-transmission capability.  Frame-relay
  is connectionless protocol.
 
  Where it is better is performance, since it scraps all X.25 level 2 (LAP-B)
  and level 3 acknowledgement mechanisms - it just pushes data thru assuming
  that most of it will go thru and if it doesn't, it'll rely on higher level
  protocols (level 4, like TCP) to recover by re-transmitting when appropriate.
 
 
:                                     If we go with frame relay, will there
: be a problem with the DTC48 that we have.  That is, will I need to
: remove the X.25 card and if so, will this DTC support frame relay?
 
- To my knowledge there is no DTC nor any other card that would support
  frame relay on HP3000 (probably not on HP9000's either).  I would
  expect you to get some sort of 'black box' from frame relay supplier
  to which you can talk one or more protocols of your choise through
  ethernet lan or so and the magic box then talks frame relay on the
  outside network...  you and your systems don't have to know anything
  about frame relay...
 
: I also know that X.25 doesn't support block mode since X.25 PAD
: connections are terminal type 24 ("Configuring System for Terminals ..."
: 5-7,5-8).
 
- Where does this come from?  Of course you can run VPLUS block mode
  applications over X.25 PAD's - should be not an issue.
 
 
:              If frame relay is okay to use, will it allow for the use of
: block mode?
 
- Whether the underlying network type is frame relay, token ring, lan,
  X.25, etc etc etc... it does not matter.  Block mode works in all cases
  when you run over TCP/IP stack.   Even when not running TCP/IP but just
  plain X.25 and PAD, block mode works.  Whether X.25 runs over X.25 or
  frame relay backbone does not make any difference.