6.4.            541

        -
: IP, SNA, Ethernet, ISDN.

        -
       Bell Labs   1968 . -
      TDM  
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.    TDM,    -
   STM (Synchronous Transfer Mode),   -
      
.    ,      -
 ,        ,
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     .   
STDM (Statistical TDM),      -
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    ,     .

         
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    ,       
 ,         -
.     ,  
       -
         
      . .  ISDN  -
         , -
       .   
    ,    
     ,

    B-ISDN     , 
   ISDN    ,   -
,  ,  ,   , -
  .     
      ,    
  ISDN  ,     -
      30 /.  ISDN
    ,        -
.

       
 Forum     IEEE,    ITU-T 
ANSI.      ,    
 , ,        1993 -
,     .    ,