( ) - , : (public key), , (private key), . , . , . . , .
, . , .
, - , .. .
, , . .
. : .
, , .
:
1. KUb KRb, .
2. , .. KUb. KRb .
3. , , KUb.
4. , , KRb. , .
VPN, L2TP
Virtual Private Network(VPN)
.
,
,
.
,
.
VPN, , , - ,
,
, ,
.
, . VPN
-
, ,
. ( , ,
|
|
,
.)
VPN-. ,
,
. -
- ,
. ?
, ,-
, -
, ,-, .
,
. VPN
,
.
, VPN , ,
.
2. VPN.
VPN : trusted() VPNs, secure
() VPNs, hybrid() VPNs.
,
.
, : , IP
..(
).
( ), ,
. ,
,
.
,
. , , trusted VPN
,
"" ,
""
( ). , ,
,
, -
.
. VPN,
, secure VPN.
, trusted VPN secure VPN
, hybrid VPN.
,
secure VPN.
3., secure VPN.
90-
() VPN-: Microsoft PPTP Cisco L2F.
,
L2TP, .
, PPTP,
|
|
Microsoft,
VPN . ,
PPTP L2TP.
3.a PPTP.
Point to Point Tunneling Protocol (PPTP) -
- - secure VPN
TCP/IP PPP.
( TCP,
1723). ,
, Generic Routing
Encapsulation (GRE).,
, .
-, OSI Network
, Data Link
PPP . .
PPTP
PPP ., PPP-
GRE-. GRE- IP-, PPP-
.
, PPTP GRE,
(IPX, AppleTalk, ..)
IP-, PPTP -
TCP/IP .
3.b L2TP.
Layer 2 Tunneling Protocol (L2TP) -
- (PPTP -
TCP/IP- L2F - X.25,
ATM, Frame Relay).
L2TP UDP(
, ).
(Data Link), PPP- L2TP
. L2TP- UDP, ,
, IPSec.
L2TP
, UDP- (
L2TP Next-Received Next-Sent
Acknowledgement Number Sequence Number
TCP). - IPSec.
.
OSI. , ( ) . , OSI,
: ;
, , . , ( ) . , ,
, , . , , . . : ; ; ; . , . : ( ) .
|
|
, , , , . , : ; ;
, . . , . ,
. , , . . ,
, | |
. | |
. , , . ; , . , (, .400) , .400, ,
, , ,
, , Microsoft Windows NT Server Systems Network Architecture IBM. ,
, . (, Windows NT Server To SNA Gateway)
, : , ; ,
OSI, .
. , , . - , ,
|
|
: ;
: ; ;
(router) ; , , , . : , , ; , . .
(gateway) , , OSI ; OSI. , .
, , , .
13. TCP/IP. IP-. InterNIC.
(network layer), , . . ip (- internet), icmp (- internet) igmp (- internet) tcp/ip.
( ) IP-. . , , , IP-.
IP- . (NIC), . , , IP-. NIC, IP-. , IP, IP-.
IP- . .
IP
IP- 32 ( ). IP- . 32 8- , . , IP- . , IP- . . - .
IP- , , 192.168.1.5. , 32- 11000000101010000000000100000101. , , , , .
32- IP- 4- (IPv4). IP-. 32- 4 IP-.
IP
IP- 5 : A, B, C, D, E. A, B C : .
, , ( ), TCP/IP. IP- , , . .
, , TCP/IP ( , , TCP/IP-) . , .
|
|
A 0 (.1). _ 8 . 3 (24 ). , A 126 (27 - 2, ). 16777214 (224 - 2). A 231 , IP 4 232 . A 50% IP 4.
A , . A .
.1
B 1 0 (. 2). - 16 . 16 . , B 16384 (214); B 65534 (216 - 2). B 230 , 25% .
B (, ).
.2
C 1, 1 0 (. 3). 24 , - 8 . C 2097152 (221). 254 (28 - 2). C 229 , 12,5% .
C .
.3
D
D , . 4 1110 (. 4). , 224 239. D , . Cisco (CiscoDiscovery Protocol CDP), ICMP, Internet (Internet Group Management Protocol IGMP), , , Cisco IOS 11.2.
. , . , IP- 224.0.0.5, ( OSPF),
Ethernet.
.4 D
240.0.0.0255.255.255.255 E. 1111 (.5). IP. , - , , 6 IP (IPv6).
.5
( " Internet ") . 90- InterNIC (NIC Internet -- Network Informational Center Internet), NSF ( ). InterNIC " Internet ", .
InterNIC :
InterNIC . NIC .
. , Internet (IP-), , - 500 , .
, - . .
Internet. . , (whois ). , , .
, ,
Internet. ( , , - telnet). Gopher, WAIS, World Wide Web FTP.
; , ( ), , , , Internet.