计算机网络

4 4.1 4.2 IP4.3 4.4 ICMP4.5 4.6 IP 4.7 VPN NAT

(1) (2) IP (3) IP CIDR(4)

(internet)Internetinternet.TCP/IPTCP/IPinternetInternet ITCP/IPARPANET

LAN-LAN LAN-MANWAN-WANLAN-WAN-LAN

IEEE 802

ISO(relay):(repeater);(bridge);(router);(gateway)

4.1 : : ::QoS(Quality of service)

:(a)H1H5A-B-EA-C-EA-C-B-E:(b)H1H5H1-A-B-E-H5

(Virtual Circuit)

H1H1 H2

H1IP H1 H2

4.2 IP IP TCP/IP IP ARP (Address Resolution Protocol) RARP (Reverse Address Resolution Protocol) ICMP (Internet Control Message Protocol) IGMP (Internet Group Management Protocol)

IP (HTTP, FTP, SMTP )TCP, UDPICMPIPRARPARPIGMP

TCP/IP

123123123123

321

I1I3I2O1O2I1I3I2O1O2I1I3I2O1O3(a) (c) (b) O3O3

(a) (b)

IP IP IP

54321H1 H2 R1 R4 R5 R2 R3 R1 R2 R3H1 R5 H2 R4

IP IP IP H1R1R2R3R4R5H2

4.2.2 IP 1. IP IP 32 IP ICANN (Internet Corporation for Assigned Names and Numbers)

IP IP 1981 [RFC 950] 1985 1993

IP net-id host-id IP IP ::= { , } (4-1)::=

IP net-id24 host-id24 net-id16 net-id8 0A host-id16 B C 011D 1 1 1 0 E 1 1 1 101

128.11.3.31 128 11 3 31 8

2. IP IP A 126 (27 2) 1 126 16,777,214 B 16,383(214 1) 128.1 191.255 65,534 C 2,097,151 (221 1) 192.0.1 223.255.255 254

IP (1) IP IP IP IP

IP (2) IP IP net-id (multihomed host) IP IP

IP (3) net-id(4) net-id

IP B222.1.1.222.1.1.1222.1.1.2222.1.1.3222.1.1.4R1222.1.2.5222.1.2.2222.1.2.1222.1.2.3222.1.2.4222.1.2.222.1.6.1222.1.5.1222.1.5.2222.1.6.2222.1.4.1222.1.4.2222.1.3.3222.1.3.2222.1.3.1R3R2222.1.3.LAN3N3N2222.1.4.222.1.5.222.1.6.N1LAN2LAN1

4.2.3 IP TCP IP MAC

HA1HA5HA4HA3HA6 H1 H2 R1 R2HA2IP1IP2H1 R1 R2 H2

HA1HA5HA4HA3HA6 H1 H2 R1 R2HA2IP1IP2IP1HA1HA5HA4HA3HA6HA2IP6 H1 H2 R1IP MAC IP2IP4IP3IP5 R2MAC MAC IP

HA1HA5HA4HA3HA6 H1 H2 R1 R2HA2IP1IP2IP1HA1HA5HA4HA3HA6HA2IP6 H1 H2 R1IP MAC IP2IP4IP3IP5 R2MAC MAC IP IP IP

HA1HA5HA4HA3HA6 H1 H2 R1 R2HA2IP1IP2IP1HA1HA5HA4HA3HA6HA2IP6 H1 H2 R1IP MAC IP2IP4IP3IP5 R2MAC MAC IP MAC

IP1HA1HA5HA4HA3HA6HA2IP6 H1 H2 R1IP MAC IP2IP4IP3IP5 R2MAC MAC IP IP IP IP1IP2 IP1 IP2 IP IP

4.2.4 ARP RARP IP ARPIP RARP

ARP ARP (ARP cache) IP A B IP ARP B IP MAC MAC

AYXBZ B A ARP A ARP ARP ARP ARP 209.0.0.5209.0.0.600-00-C0-15-AD-1808-00-2B-00-EE-0A 209.0.0.5 00-00-C0-15-AD-18 209.0.0.6 209.0.0.6 08-00-2B-00-EE-0AAYXBZ209.0.0.5209.0.0.600-00-C0-15-AD-18

ARP A ARP IP ARP B A ARP A B ARP B A

ARP IP ARP

IP IP ARP IP

ARP IP ARP IP ARP IP ARP IP ARP

IP ARP

RARP RARP IP RARP

4.2.5 IP IP 20 IP

204004816192431 IP

IP(4bit): IP,IP version4(4bit): 604 (8bit): (16bit): 216-1=65535(16bit): (3bit): ()MF=1;MF=0;DF=0: : (8bit): : : IP(4);IP(4) : 140()

4-1 IP = 0/8 = 0 = 0/8= 0 = 1400/8 = 175 = 2800/8 = 350140028003799279913993799 1 3800 1 2 3 0 2 314002800 0

TCPUDPICMPIGMPOSPF IP

04816192431

2. IP IP 1 40 IP IP

4.2.6 IP A 4

110.0.0.0 440.0.0.0 330.0.0.0 220.0.0.010.0.0.440.0.0.430.0.0.220.0.0.920.0.0.720.0.0.030.0.0.010.0.0.040.0.0.020.0.0.730.0.0.1 1 0 R2 30.0.0.110.0.0.440.0.0.430.0.0.220.0.0.920.0.0.730.0.0.1 4 3 2 1R2R3R101R2R3R1

(default route) 1243 1 2 33 34 3 1 1 2

1243 1 3 1

1243 1 32 3 34 4 2

1243 2 4 4 3 2

IP IP IP IP ARP IP MAC

4.3 4.3.1 1. IP IP ARPANET IP ,AIPIP IP

IP 1985 IP IP IP (subnetting)

subnet-id host-id IP ::= {, , } (4-2)

IP IP net-id IP net-id subnet-id IP

B 145.13.0.0145.13.3.10145.13.3.11145.13.3.101145.13.7.34145.13.7.35145.13.7.56145.13.21.23145.13.21.9145.13.21.8 145.13.0.0 145.13.0.0R1R3R2

145.13.3.10145.13.3.11145.13.3.101145.13.7.34145.13.7.35145.13.7.56145.13.21.23145.13.21.9145.13.21.8 145.13.21.0 145.13.3.0 145.13.7.0 145.13.0.0145.13.0.0R1R3R2

IP IPIP=+ IP

IP host-id IP net-id

2. IP (subnet mask) IP

IP 145 . 13 .3 . 10 IP 3 IP net-idhost-id0net-idsubnet-idhost-id145 . 13 .145 . 13 . 33 . 10

(IP ) AND () = net-id host-id IP IP net-idsubnet-id0 AND

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10 0 0 0 0 0 0 00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 01 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0net-idnet-idhost-id 0net-idA255.0.0.0B255.255.0.0C255.255.255.0host-id 0host-id 0

4-2 IP 141.14.72.24 255.255.192.0 141 . 14 . 0 1 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0(a) IP (c) 255.255.192.00 0 0 0 0 0 0 0141 . 14 . 72 . 24141 . 14 .64 . 0. 00 1 0 0 1 0 0 0141 . 14 .. 24(b) IP 3 (d) IP (e)

(mask)(subnet) B162.105.0.0255.255.224.08162.105.0.0 162.105.32.0 162.105.64.0 162.105.96.0162.105.128.0 162.105.160.0 162.105.192.0 162.105.224.0 2**13=8192010162.105.130.0

(mask)(subnet)162.105.69.12255.255.254.0 162.105.68.0 0.0.1.12 IPIP 130.50.15.6 130.50.15.6 15.600001111.00000110255.255.252.0252.011111100.00000000130.50.12.0B,130.50130.50.12.0(22)3.6 ()11.00000110

4.3.2 IP IP IP

4-4 R1 H1 H2 R1 H1 H2 128.30.33.10128.30.33.13H11 128.30.33.0 255.255.255.128128.30.33.1301R22 128.30.33.128 255.255.255.128H2128.30.33.13801128.30.33.129H3128.30.36.23 128.30.36.0 255.255.255.0128.30.36.12

128.30.33.0128.30.33.128128.30.36.0255.255.255.128255.255.255.128255.255.255.0 0 1R2

H1 H2 128.30.33.10R1 128.30.33.13H11 128.30.33.0 255.255.255.128128.30.33.130R11R22 128.30.33.128 255.255.255.128H2128.30.33.13801128.30.33.129H3128.30.36.23 128.30.36.0 255.255.255.0128.30.36.12 IP 128.30.33.138H1 H2 H1 H2 IP 128.30.33.138 H1 128.30.33.138 R1

128.30.33.0128.30.33.128128.30.36.0255.255.255.128255.255.255.128255.255.255.0 0 1R2

H1 255.255.255.128 IP 128.30.33.138 (AND ) 128.30.33.10H11 128.30.33.0 255.255.255.128128.30.33.130R11R22 128.30.33.128 255.255.255.128H2128.30.33.13128.30.33.13801128.30.33.129H3128.30.36.23 128.30.36.0 255.255.255.0128.30.36.12255.255.255.128 AND 128.30.33.138 255 1 255 AND xyz = xyz 128 AND 138 128 10000000138 10001010 AND 10000000 128 H1

128.30.33.0128.30.33.128128.30.36.0255.255.255.128255.255.255.128255.255.255.0 0 1R2

H1 R1128.30.33.10R1 128.30.33.13H11 128.30.33.0 255.255.255.128128.30.33.130R11R22 128.30.33.128 255.255.255.128H2128.30.33.13801128.30.33.129H3128.30.36.23 128.30.36.0 255.255.255.0128.30.36.12

128.30.33.0128.30.33.128128.30.36.0255.255.255.128255.255.255.128255.255.255.0 0 1R2

R1 1 128.30.33.138 AND 128.30.33.10R1 128.30.33.13H11 128.30.33.0 255.255.255.128128.30.33.130R11R22 128.30.33.128 255.255.255.128H2128.30.33.13801128.30.33.129H3128.30.36.23 128.30.36.0 255.255.255.0128.30.36.12255.255.255.128 AND 128.30.33.138 = 128.30.33.128!128.30.33.128 128.30.33.0 R1 IP 128.30.33.138

128.30.33.0128.30.33.128128.30.36.0255.255.255.128255.255.255.128255.255.255.0 0 1R2

R1 2 128.30.33.138 AND 128.30.33.10R1 128.30.33.13H11 128.30.33.0 255.255.255.128128.30.33.130R11R22 128.30.33.128 255.255.255.128H2128.30.33.13801128.30.33.129H3128.30.36.23 128.30.36.0 255.255.255.0128.30.36.12255.255.255.128 AND 128.30.33.138 = 128.30.33.128! 2 R1 IP 128.30.33.138

128.30.33.0128.30.33.128128.30.36.0255.255.255.128255.255.255.128255.255.255.0 0 1R2

4.3.3 CIDR1. 1987 RFC 1009 VLSM (Variable Length Subnet Mask) IP VLSM CIDR (Classless Inter-Domain Routing) CIDR(network-prefix)IP

IP ::= {, } (4-3) CIDR (slash notation)CIDR IP / 1 CIDR IP CIDR

CIDR 128.14.32.0/20 212 20 12 128.14.32.0/20 128.14.32.0/20 128.14.32.0128.14.32.0/20 128.14.47.255 0 1

(route aggregation) CIDR (supernetting)CIDR /20 20 1 1

CIDR 10.0.0.0/10 10/10 0 10.0.0.0/10 IP 10.0.0.0 255.192.0.0 11111111 11000000 00000000 00000000

23 CIDR C C CIDR 2 IP

CIDR 206.0.68.0/22206.0.64.0/18ISP X206.0.71.128/26206.0.71.192/26206.0.68.0/25206.0.68.128/25206.0.69.0/25206.0.69.128/25206.0.70.0/26206.0.70.64/26206.0.70.128/26206.0.70.192/26206.0.70.0/24206.0.71.0/25206.0.71.0/26206.0.71.64/26206.0.71.128/25206.0.68.0/23 ISP 206.0.64.0/18 11001110.00000000.01* 16384 206.0.68.0/22 11001110.00000000.010001* 1024 206.0.68.0/23 11001110.00000000.0100010* 512 206.0.70.0/24 11001110.00000000.01000110.* 256 206.0.71.0/25 11001110.00000000.01000111.0* 128 206.0.71.128/25 11001110.00000000.01000111.1* 128

CIDR 206.0.68.0/22206.0.64.0/18ISP X206.0.71.128/26206.0.71.192/26206.0.68.0/25206.0.68.128/25206.0.69.0/25206.0.69.128/25206.0.70.0/26206.0.70.64/26206.0.70.128/26206.0.70.192/26206.0.70.0/24206.0.71.0/25206.0.71.0/26206.0.71.64/26206.0.71.128/25206.0.68.0/23 ISP 64 C CIDR ISP 64 1 206.0.64.0/18 ISP

2. CIDR (longest-prefix matching)(more specific)

D = 206.0.71.128206.0.68.0/22 ISP 206.0.71.128/25 1 AND D = 206. 0. 01000100. 0 1 206.0.68.0/22 M 22 1M = 11111111 11111111 11111100 00000000 D 3 M = 11111111 11111111 11111100 00000000206. 0. 01000100. 0 206.0.68.0/22

D = 206.0.71.128206.0.68.0/22 ISP 206.0.71.128/25 2 AND D = 206. 0. 71. 10000000 2 206.0.71.128/25 M 25 1M = 11111111 11111111 11111111 10000000 D 4 M = 11111111 11111111 11111111 10000000206. 0. 71. 10000000 206.0.71.128/25

D AND (11111111 11111111 11111100 00000000) = 206.0.68.0/22 D AND (11111111 11111111 11111111 10000000) = 206.0.71.128/25

3. (binary trie)IP

5 32 IP 01000110 00000000 00000000 00000000 010001010110 00000000 00000000 00000000 010101100001 00000000 00000000 00000000 01110110000 00000010 00000000 00000000 1011010111011 00001010 00000000 00000000 10111

4.4 ICMP IP ICMP (Internet Control Message Protocol)ICMP ICMP IP ICMP IP IP

ICMP ICMP 0 4 ICMP 81631IP 4 ICMP

4.4.1 ICMP ICMP ICMP ICMP ICMP 4 4 ICMP :,P141.:

ICMP 5 (Source quench) (Redirect)

ICMP IP ICMP 8 ICMP IP IP ICMP 8 IP IP 8ICMP IP

ICMP ICMP ICMP ICMP ICMP 127.0.0.0 0.0.0.0 ICMP

ICMP : : ICMP

4.4.2 ICMPPING (Packet InterNet Groper) PING PING ICMP PING ICMP TCP UDP

Traceroute

4.5 4.5.1 1.

AS(Autonomous System) AS AS AS AS AS AS AS AS AS

IGP (Interior Gateway Protocol) RIP OSPF EGP (External Gateway Protocol) EGP BGP-4

RIP B ABGP-4R1R2 OSPF(interdomain routing)(intradomain routing)

4.5.2 RIP (Routing Information Protocol)1. RIP IGPRIP RIP

1 1RIP (hop count) 1

RIP RIP 15 16 RIP RIP RIP ()

RIP 30

1RIP (convergence)

3. RIP2 4 RIP 20 / 25 IP (1-16) IP UDP 0 4 UDP

RIP2 4: :1,2; RIP 20 IP2.RIP

RIP RIP RIP RIP 1516

4.5.3 OSPF (Open Shortest Path First)1. OSPF (Open) OSPF Dijkstra SPFOSPF

5,:

Dijkstra

DijkstraG,D(v)sL(v,w)w.Dijkstra1N={s}Nv,2Nw,D(w)wNND(v): D(v):=min{D(v),D(w)+l(w,v)} 2N

Dijkstra:P5.

(metric)

(link-state database) OSPF OSPF

OSPF (area) OSPF OSPF 32 200

OSPF 0.0.0.1 0.0.0.3 0.0.0.0R9R7R6R5R4R3R2R1 8 6 3 2 1 7 0.0.0.2 4 5R8

,OSPF (backbone area)0.0.0.0

0.0.0.1 0.0.0.3 0.0.0.0R9R7R6R5R4R3R2R1 8 6 3 2 1 7 0.0.0.2 4 5R8

OSPF IP OSPF UDP IP OSPF

OSPF IP IPOSPF OSPF 1 5 OSPF 24 081631

2. OSPF 1(Hello)2(Database Description)3(Link State Request)4(Link State Update) 5(Link State Acknowledgment)

OSPF tACKRRRRt1

t2

t3

t4

OSPF OSPF 30 OSPF RIP OSPF 100 ms

4.5.4 : BGP(Border Gateway Protocol)BGP BGP 2006 1 BGP-4BGP 4 RFC 4271 ~ 4278 BGP-4 BGP

BGP AS AS BGP

BGP AS BGP BGPBGP BGP BGPAS1AS3AS2AS5AS4

BGP-4 (1) (OPEN)BGP(2) (UPDATE)(3) (KEEPALIVE)(4) (NOTIFICATION) RFC 2918 ROUTE-REFRESH

BGP BGP 16 2 1BGP TCPIP BGP TCP

4.6 IP 4.6.1 IP 90 R1R3R4R2 M30 30 30 30 3030 90 90

1 1 90 R1R3R4R2 M1 1 1 1 1 1

IP (1) IP D (2) IANA (3) (4)

4.6.2 IANA 24 00-00-5E TCP/IP 00-00-5E-00-00-00 00-00-5E-FF-FF-FF D IP 28 28 5

D IP 0000000000000001010111100111008162431D IP 5 48 0 1 0 0 5 E 23 D IP

4.6.3 IGMP 1. IP IGMP (Internet Group Management Protocol)

IGMP 128.56.24.34135.27.74.52130.12.14.56130.12.14.43226.15.37.123IGMPIGMPIGMPIGMPR1R4R3R2

IGMP IGMP IGMP IP IGMP

2. IGMP IGMP IP .IGMP IP IGMP :IGMP IGMP

IGMP IP 125

IGMP IGMP N 10 0 N

(1) RPB (Reverse Path Broadcasting)

RPB IP

R3R4R6R7R8R1R5R2 RPB

(2) (tunneling) IP 1 2 IP R2R1 1 2

(3) G (core) IP G

DVMRP (Distance Vector Multicast Routing Protocol) CBT (Core Based Tree) MOSPF (Multicast Extensions to OSPF) - PIM-SM (Protocol Independent Multicast-Sparse Mode) - PIM-DM (Protocol Independent Multicast-Dense Mode)

4.7 VPN NAT IP IP 4.7.1 VPN(Virtual Private Network)

RFC 1918 (private address) 10.0.0.0 10.255.255.255172.16.0.0 172.31.255.255192.168.0.0 192.168.255.2551A,16B56C,

A BR1R2 = 10.1.0.0 = 10.2.0.0

A BR1R2 X Y 125.1.2.3194.4.5.6

intranet extranet TCP/IP A B VPN (intranet) A B VPN (extranet)

VPN(remote access VPN) VPN PC VPN PC VPN

4.7.2 NAT (Network Address Translation) NAT 1994 NAT NAT NAT IPG NAT IPG

X IPX Y NAT NAT IPX IPG IPY NAT Y IPY IPG NAT NAT IPG IPX X

NAT192.168.1.xInternetIP202.107.212.10192.168.1.12InternetWeb ServerA202.107.212.1061.56.18.176TCP:80Web Server192.168.1.10192.168.1.12WebTCP1025

NAT202.107.212.1061.56.18.176TCP:80192.168.1.12WebTCP1025Web Server192.168.1.10IP61.56.18.176IP 192.168.1.12 80 1025IP61.56.18.176IP 202.107.212.10 80 5000IP202.107.212.10IP 61.56.18.176 5000 80IP192.168.1.12IP 61.56.18.176 1025 80192.168.1.12,1025202.107.212.10,5000 61.56.18.176,80

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