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Cell Relay Retreat>List Archive>month:1995-Oct> msg00037



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Multicasting with ATM - a concern

  • From: Jon Crowcroft <J.Crowcroft@cs.ucl.ac.uk>
  • Date: Tue, 17 Oct 95 11:26:57 +0100
  • CC: ip-atm@hplb.hpl.hp.com



 >> it is not entirely clear that you can easily construct a mpt-mpt
 >> VC service (to avoid the need for pt to mpt VC meshes).
 
 >A mpt-mpt VC doesn't work.  Consider what happens if two machines 
 >each send a packet at the same time.  How does the receiver sort 
 >the cell stream into 2 packets if they arrive on the same VC? 

 >(AAL3/4 might work if you cooridinated allocation of the multiplexing 
 >info.)

yes, two solutions
1/ constrain VCI/VPI allocation for multipoint (i.e. make it a non
local choice)
2/ extend the addrtessing thru MIDs or other multiplexing id info....

the former is broken because the ITU never understood the scale and
number of groups  (they didn;t think about community TV:-(

the latter is broken because it needs extra logic outside the normal
cell header processing and wil lcost some vendors dear....

sad...

 jon