7. IP. » &!'() (IS: intermediate system) !"#$% *+'() (ES: end system) Copyright 2000, Suguru Yamaguchi, All right reserved

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1 7. IP»!"#$%» &!'() (IS: intermediate system) *+'() (ES: end system) 1

2 ISES ES: End System!"#$Ethernet%&' ()*+,'-./ Ethernet IS: Intermediate System EF FDDI ES: End System 0 FDDI%&'12!"#$345 67!89:,;,;"#$< Connectionless»» best effort» e.g. IP (Internet Protocol), XNS Connection Oriented»»!"#» e.g. X.25 2

3 (1)» $%&'()*+,» -.$%&'()*/» 0123,-./ (9,-2 3» 456 : MTU (Maximum Transmission Unit) ;<= fragmentation / reassemble (2)» 78 $9:;<.=>"?» $@ABC» DEFGH9AI" $JK» 78 $:;<.@ $:;<.L7 MN» N(a) O N(b) N(a)>DL(a)?01@ DL(b) > N(b)» ARP (Address Resolution Protocol) 3

4 IP IPv4: Internet Protocol (version 4) TCP/IP!"#$! %&» connectionless (IP datagram)» 4 octet address space with its own structure» unicast / multicast / broadcast / anycast» IP + ICMP + ARP » reassemble is done only at the end system» fragmentation is done based on MTU Network Gateway GatewayA&!'()B.C IPDEFGHIJK./ALC01 MNOP Q R$S- 4

$T()PUVWXY(Z[\)]^2$ hgi()p7jk63l"#mn

5 T()PUVWXY(Z[\)]^2 YP_`aY(bcde)BfSYAg hgi()p7jk63l"#mn opqrfgfgoppsxtu vwxyz{ P!"#$% }}~3 1 ƒ C AWXˆsLC Š9P Œ Ž97j mn'()

$Router B Router D LC C [\]^_ Router F Router E Host$ B '() IP&'(# (1) *+,-» 78 ` C ( LC š» a.

6 Router Z& Host A PQRS Router Router C Router B Router D LC C [\]^_ Router F Router E Host B '() IP&'(# (1) *+,-» 78 ` C ( LC š» a.` O9œ AžQŸ C./012345» bcde9a:;<.fg # 6

7 IP&'(# (2) xA3 0xDD 0x4A 0x7F 78 `Ahij /24 IP&'(# (3) 9:;» a.`k all 1 l6m[78 Qno*p q;rs. tvu » [78 Qvw()SxTmyzS*a. QnSN-{ / 7

8 IP&'(# (4)!<:;» %& » N}~F ( (1-2 By: 8( D 1 DP X D ª IPv4 header (1) Ver. IHL Type of Service Total Length (in Octet) Identification Flags Fragment Offset Time to Live Protocol Header Checksum Source Address Destination Address Option (if any) 8

9 IPv4 header (2) Version Internet Header Length Type Of Service Total Length Identification Flags Fragment Offset Time To Live Protocol Header Checksum Source Address Destination Address IP options IP header (3) Version» «Z» (IPv4) IHL» Internet Header Length» 32bit word 9±a/²³ (word±)» IPz' Aqµ 9g /ƒu 9

10 Non-DiffServ (classic) Type Of Service j. SGH,l6Q ƒ k &)*»IPN-{GHQgS ˆ Šx Œ 0D Precedence D T R Ž M Precedence Type of Service (1)» GH» %&Ž» N-{ o EFGHIJK2L5MNOL» j7k!"()s* ˆ» D: low Delay» T: high Throughput» R: high Reliability 10

11 Type of Service (3) P-6QRSTU#IVW X6XYZ7[\]2^_`C» GH V» ~-e H DiffServabc2d@AeWf TOS0g!eWf» 2bitAECN, QžŸ» IPv6 Traffic Class Q 5K precedence low delay DiffServ)*+,- *+,-TOS TOS./' throughput Reliability min cost DSCP (Differentiated Service Code Point) (currently unused) 11

12 Diff-Serv Serv (1) hfi#jklm» 7 ; (edge node) Z e¹ SLA: Service Level Agreement» > ; Z eº»/ ( \D» ; (boundary node)!¼ ƒ?sla)./alcz e ½¾3a Diff-serv (2) ISP-B customer E B B SLA customer E SLA ISP-A 12

13 IP n/jopq ()r> stun/ Total Length Time To Live #vrwxy» IPN-{ (ª*»!«QA >ƒ VS,» > A z{ }1.~» bcdef± Q ²&o» Q\,&N-{³S*» /a.qf (ICMP Time Exceeded) 13

14 Fragmentation & Reassemble (1) n/q2mtui 5» µ<{`» tvu Ethernet 9U)u 1500 š7 IPn/jo» #¹» 64Kbyte (Total Length Field2º) { Yn/MTUƒ 2» fragmentation» bcde Q»¼o*#UT Fragmentation & Reassemble (2) z ]Yˆ#e*» reassemble» >.š{9a reassemble SA½» ¾ À(½* 14

15 Fragmentation & Reassemble (3) Flag 0g!ŠGH» 0, DF, MF» DF: Don t Fragment ÀA¹ ÁÂC DEP fragment Ãª.CPÄ MTUQ ÅIPDEAÆ¾Ç=PÈE» MF: More Fragment EDÉÁÂCC3lÊ% fragment Ag Ç= ¹ Fragmentation & Reassemble (4) Fragment Offset (13bit)» [N-{kÁÂ7Ã Ä`%»MF@ Fragment Offset ÁQ Reassemble DÅ 15

16 Fragmentation & Reassemble (5) Host A MTU=500 Network MTU=1500 Gateway1 Gateway2 `k2000æe ÈÉ7ÊAh š7ë Host B MTU=4000 Fragmentation & Reassemble (6) Host A» H+1480: MF=1, FO=0» H+520: MF=0, FO=1480 Gateway 1» H+480: MF=1, FO=0» H+480: MF=1, FO=480» H+480: MF=1, FO=960» H+40: MF=1, FO=1440» H+480: MF=1, FO=1480» H+40: MF=0, FO=1960 fragment kìg9 Í )umipn-{ Î ÏÐ» ËrÌlA» NFS9PÍÎ 16

17 01 23 Protocol 0g!» ÑÒ~q}ÓÔÕÖo» multiplexing/de-multiplexing GH» TCP (6), UDP (17)» ~q}.e7 Q_*ÑÒ$GHØz IP45 IPn/joIPn/jo#Œ Protocol 0g!2I%ŽY» IP over IP Q (tunneling) Iz #I CA 5» IPsec / VPN (Virtual Private Network)» IP Multicasting» ÙÚ78 (Mbone, 6bone) 17

18 Network Byte Order IPst~ 0g! c RFC791#šW œ.(t IžŸ2Wf» ÛÜQÝkÞ_ÇQo*, Big-Endian»MSBkßà» áâ7µãl79 äo*@åæ Checksum 16bit 1 s complement arithmetic st<1 o» «ço*l6qamchecksum µ };A all 0 9U *è@ù"s«ç» É7Êéêj7 Qëméì«ç» í«ç» îï1ì ˆ #Ist checksum e 18

19 8. &'(#67 (address resolution) Address Resolution $ n/q$» 0123ðë op 1 Ï¾8(op» $: ;<.ôõ 19

20 8989:;< (1) )9!» a.9nö Ho*»!"» øùú(78 9Aûü» a.78 eµd.k¹ý(),l6 QAmÎSa.9šp}ýþkò 8989:;< (2) œ» šp} ÿ» Æ9ƒ Ì H» o*% well-known (56 Ð (56 broadcast ÆkÊc,l6nG AÄÇo*% Ò ÓœÔ 20

21 8989:;< (3) ] W» ARP (Address Resolution Protocol) JK» F Q" Dynamic Binding» 78 $QF kò RFC826 ARP n/q!#ª«a ˆB±Z²«³K X A B Ethernet(A)? 08:ac:fe:90:43:88 21

22 =>? (1) n/q$2arp WL5 µ Z 5» RFC826 AKARP" S* Broadcast Channel Õ«1-Ö (A& Ø (ÙÚA qr» è AÞ* 9AJK9 =>? (2) 9:;³KL5j. Z 5 2I ¹L56» Ethernet Meltdown.» &%QDÑ º¹»- ¼Z ± 2I ¹L56» ßQa.:;<.V*» FÞÍ*#k» Ãrš 22

23 )9! ] W ½ ¾»arp L;Q_*šp} Š»ARP~q}Q_*z"» 6ª²&o, QmARPQ_*z "(),ƒ Ars7()* N Û!OPÜ '\56 N Û!ÊPÝƒCÍ= Þ ß6XÃª 23

IP : Internet Protocol

1/20 IP : Internet Protocol Surasak Sanguanpong nguan@ku.ac.th http://www.cpe.ku.ac.th/~nguan Last updated: July 30, 1999 Agenda 2/20 IP functions IP header format Routing architecture IP layer 3/20 defines