492     6   

 20-  TCP- ( 40 ).  CSLIP -
  40-   3-5 .    -
   SLIP   CSLIP.

 ,  SLIP      -
       IP-. -
      ,  
  ,    .

  HDLC

        HDLC (High-
level Data Link Control),    ISO.  HDLC  -
     ,    
: LAP-B,     .25, LAP-D  -
   ISDN, LAP-M    -
, LAP-F     frame relay.

    HDLC:   ,
         ,
      RNR  RR,   
         3   
   HDLC   LLC2.

   HDLC     
-, Point-to-Point Protocol, PPP.

  ,       HDLC   -
    . ,   HDLC
     (BER)  10"3,  
   ,  10'9.

   _^ _  -
^     ( BER -
 lO^-lO"9).        
HDLC  .       
     HDLC (   HDLC,
 -     LAP-M,  
  HDLC).   HDLC   -
    .

 PPP

    IETF (Internet Engineering Task Force)  
 TCP/IP       
     SLIP (Serial Line IP).  PPP
         -
         -
   .    PPP    
  HDLC    .   PPP
     HDLC.    , -
   PPP   frame relay    -
 .