  UNIX/Linux       -
   (promiscuous)     .  UNIX 
Linux 6  ,  1024,  . 
,        
 .  ,     
  ,   NIS, NFS, RSH  LPD.  
  LAN     , 
   .  ,    , 
   ,      .  -
    ,    ,
     .     -
         . -
,      ,   -
  ,     .

  

         -
 ,   .     -
  IPSec (Internet Protocol Security      Internet).
        ,
 VPN (. ),     
     Internet. IPSec  -
, ,    , 
 .

IPSec     (IPsec =  + ESP + IPComp + IKE):

   (Authentication Header  ). 
,    (. )  . 
  .

     (Encapsulating Security Payload 
ESP).  ,     .

  IP- (IP Payload Compression  IPComp).  .
    , a IPComp   -
 .

    Internet (Internet Key Exchange  IKE). 
     .   
 ,            -
         
(.  3    ).

IPSec     IPv4,    IPv6 (.  "IPv6" -
 10).     IPv6    - . -
 IPSec   2.6    "IPSecurity (IPSec)"  .

    .    ,  . 
      . ,  21  
 ftp,   23  telnet.

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