Chuong 2 Sua

7/28/2019 Chuong 2 Sua

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XY DNG H THNG VOIP DA TRN M NGUN M ASTERISK

Lun vn tt nghip Trang 16

CHNG 2: GIAO THC TCP/IP

2.1 Gii thiu v TCP/IPTCP/IP (Transmission Control Protocol/Internet Protocal) l tp hp ca mt

s giao thc, c pht trin ln u tin bi B Quc phng M. TCP/IP l mt bgiao thc c thit k t hai mc tiu chnh:

Cho php truyn qua cc mi trng mng din rng (Wire AreaNetwork Wan).

Cho php truyn gia cc mi trng khc nhau.TCP/IP u tin c pht trin cho mng ARPNet (Advanced Research

Projects Agency Network). ARPNet l tin thn ca mng Internet hin i ngynay v c thit k cung cp s truyn thng phi tp trung ho gia cc hthng my tnh khc nhau. TCP/IP cha mt tp cc tiu chun c t cc my tnhtrong mng giao tip vi nhau v d liu c nh tuyn thng qua nhng mytnh c kt ni vi nhau nh th no. TCP/IP hin l giao thc mng c sdng rng ri nht trn th gii. Cc l do khin giao thc mng ny tr nn ngycng thng dng l:

Khng ph thuc dng hnh hc ca mng: TCP/IP c s dng trn ccmng bus, mng vng v cc mng hnh sao, trong cc mng cc b Lan cng nhtrong cc mng din rng WAN.

Khng ph thuc phn cng vt l ca mng: TCP/IP c th s dngtrn Ethernet, token ring hay bt k cc thit b phn cng no.

Chun giao thc m: Cc chun ca chui giao thc TCP/IP lun snsang thc hin mt cch c lp trn cc h thng phn cng no ca my tnh cngnh trn bt k h iu hnh no.

Nguyn l nh a ch tng th: Mi my tnh trn mng TCP/IP c mta ch xc nh duy nht sao cho bt k thit b no cho php TCP/IP c th giaotip vi cc thit b khc trong mng. Mi gi d liu c gi qua mng TCP /IPbao gm mt header cha a ch ca my tnh n cng nh a ch ca my tnhngun.

Sc mnh ca c cu ClientServer: TCP/IP l c cu cho nhng ngdng Client Server y sc mnh v bn vng, hot dng trong cc mng cc bv mng din rng.

Chun giao thc ng dng: TCP/IP khng ch cung cp cho ngi lptrnh mt phng php di chuyn d liu quanh mt mng trong s nhng ng


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dng. N cng cung cp cho nhiu giao thc cp ng dng thc hin nhng chcnng chung nh email hoc chuyn tip.

Ngy nay, TCP/IP tr thnh mt chun cng nghip c h tr bi phn

ln cc h iu hnh thng dng, bao gm UNIX, DOS, Windows, Macintosh vNetware.

2.2 M hnh TCP/IP hai my tnh c th trao i d liu vi nhau TCP/IP s dng m hnh

truyn thng 4 tng DoD (m hnh ca b quc phng M). Cc tng c cu trcnh sau:

Hnh 2.1: M hnh TCP/IP

Mi giao thc thuc h TCP/IP u thuc mt trong cc tng ny.2.2.1 c im tng qut ca tng tng

Tng ng dng (Application Layer)Cung cp cc ng dng gii quyt s c mng, vn chuyn file, iu khin

t xa, v cc hot ng Internet. ng thi h tr Giao din Lp trnh ng dng(API-Application Program Interface) mng, cho php cc chng trnh c thitk cho mt h iu hnh no c th truy cp mng.

Application layer x l cc giao thc lp cao, a ra cch biu din, m ho viu khin cuc gi, m bo d liu ny c ng gi ng trong lp k tip.

Mt s giao thc c s dng trong tng ny l: DHCP (Dynamic Host Configuration Protocol): Giao thc cu hnh cp

a ch IP ng cho Client.

DNS (Domain Name System): H thng tn min. SNMP (Simple Network Management Protocol): Giao thc qun l mng

n gin. FTP (File Transfer Protocol): Giao thc truyn tp tin.


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TFTP (Trivial File Transfer Protocol): Giao thc truyn tp tin bnhthng

SMTP (Simple Mail Transfer Protocol): Giao thc truyn th n gin Tng giao vn (Transort Layer)

Trch nhim ca tng giao vn l thit lp phin truyn thng gia cc mytnh v quy nh cch truyn d liu, km theo kim sot li (error control), phnmnh (fragmentation) v iu khin lu lng. ng vai tr giao din cho cc ngdng mng.Transport Layer cung cp cc dch v vn chuyn tin cy t host ngunn host ch trn mng (End to End). Hai giao thc chnh trong tng ny gm:

UDP (User Datagram Protocol): cn gi l giao thc gi ngi dng,UDP cung cp cc knh truyn thng phi kt ni nn n khng m bo truyn dliu mt cch tin cy. Cc ng dng dng UDP thng ch truyn nhng gi tin

nh, tin cy d liu ph thuc vo tng ng dng. TCP (Transmission Control Protocol): Ngc vi UDP, TCP cung cpcc knh truyn thng hng kt ni v m bo truyn d liu mt cch tin cy.TCP thng truyn cc gi tin c kch thc ln v yu cu pha nhn xc nhn vcc gi tin nhn.

Tng lin mng (Internet Layer)Nm bn trn tng giao din mng, cung cp a ch logic, c lp vi phn

cng, d liu c th lt qua cc mng con c cu trc vt l khc nhau. Cungcp chc nng nh tuyn giao lu lng giao thng v h tr vic vn chuynlin mng. Thut ng lin mng c dng cp n cc mng rng ln hn,

kt ni t nhiu LAN. To s gn kt gia a ch vt l v a ch logic. LpInternet la chn ng i tt nht truyn gi qua mng. Cc chc nng chnh cth c lit k nh sau:

Cc giao thc lin quan: IP (Internet Protocol): c chc nng gn a ch d liu trc khi truyn

v nh tuyn chng ti ch. ARP (Address Resolution Protocol): c chc nng bin dch a ch IP

thnh a ch MAC. ICMP (Internet Control Message Protocol): c chc nng thng bo li

trong trng hp truyn b hng. IGMP (Internet Group Management Protocol): c chc nng iu khin

a hng (Multicast).


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XY DNG H THN

Lun vn tt nghip

Tng gTng giao din m

tin truyn dn, format

liu cho cc mng con dv cp mng.Cc giao thc tiu biu t

+ ATM (Arsynchr+ Enthernet+ Token Ring+ Frame Relay

2.2.2 Minh ha m h

Hnh

2.3 Nguyn l nh 2.3.1 Gii thiu a ch

Trn mng TCP/IPbng mt a ch IP logicxc nh n. a ch IPvit di mt nh dng

- Phn a ch mng- Phn a ch trm (

Net ID: Dng cn c gi l phn oc cng a ch mng, ph

G VOIP DA TRN M NGUN M AS

ao din mng (Network Interface Layer)g c trch nhim a d liu ti v nhn d liu cho b phn truyn ti trung gian v

a trn a ch phn cng vt l, chng hn

ong tng ny:onuos transfer mode)

h TCP/IP

.2: Cc giao thc s dng trong TCP/IP

ch IPIPhay cn gi l trm TCP/IP, mi my tnh. Mi my tnh trong mng TCP/IP c mtcho bit v tr ca mt h thng trong mthun. a ch IP chia lm hai phn:(Net ID)Host ID)

Hnh 2.3: a ch IP

hn dng nhng h thng trong cng mtn (Segment). Mi h thng trong cng mtn a ch ny phi l duy nht trong s cc

TERISK

Trang 19

liu t phngto a ch d

nh card mng

c xc nha ch duy nhtmng v c

khu vc vt lphn on phimng hin c.


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Host ID: Dng nhn dng m trm lm vic, mt my ch, mt Router,hoc mt trm TCP/IP trong phn on. Phn a ch trm cng phi l duy nhttrong mt mng.

Phn kt hp gia NetID v HostID phi cho php nhn dng duy nht mimy tnh trn mng.2.3.2 c tnh k thut ca a ch IP

a ch IP ang c s dng hin ti (IPv4) c 32 bit chia thnh 4 Octet(mi Octet c 8 bit, tng ng 1 byte) cch m u t tri qua phi bt 1 cho nbt 32, cc Octet tch bit nhau bng du chm (.)

1 byte l mt octet v c gi tr trong khong t 0-255.VD: 203.162.8.19711001011.10100010.00001000.11000101

2.3.3 Cc lp mng

Hnh 2.4: Cc lp mnga ch IP c chia thnh 5 lp to ra cc mng c kch thc khc nhau

k hiu l A, B,C, D, E. Ch c lp A, B, C l c gn cho cc trm.

2.4 Cc giao thc trong TCP/IPLp Internet nh ngha cc datagram v x l nh tuyn cc datagram .

IP l giao thc quan trng nht ca chui TCP/IP v n c s dng bi tt c ccgiao thc TCP/IP khc v tt c d liu phi i qua n. IP cng c xem l khichnh xy dng nn Internet.

2.4.1 Giao thc IPGiao thc IP (Internet Protocol Giao thc lin mng) l mt giao thc

khng nh hng kt ni, c ngha l khng c mt s lin kt u cui no cthnh lp trc khi d liu c truyn. iu ny tri vi giao thc nh hng ktni trao i thng tin iu khin gia cc host thnh lp kt ni trc khi d liu


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c truyn. IP cng khng m bo phn pht d liu mt cch tin cy. Cc gi dliu c th n ch sai th t, trng d liu hay cc trng hp khc. IP da trnnhng lp khc nh lp vn chuyn TCP cung cp c tnh tin cy.

n v c bn xy dng nn IP l cc datagram. Mi datagram c a chngun v a ch ch. nh tuyn d liu c thc hin mc datagram. Khi mtdatagram c nh tuyn t mng ny sang mng khc, n c th chia gi d liuthnh nhiu phn nh hn. Qu trnh ny gi l qu trnh phn mnh v cng lnhim v ca lp IP. Phn mnh c yu cu mt s mng v cc thnh phnphn cng to nn mng c cc kch thc khc nhau. pha thu phi ghp cc giny li vi nhau sao cho hots ch nhn c d liu ban u.

Hnh 2.5: Cu hnh ca header IPv4

IP header gm 32 bit ghp li to thnh mt cu trc nhiu trng (field)

nh sau: Ver: di 4 bit, cha version ca IP. Vng ny c gi tr mc nh l 4. IHL (Header Length): ch ra chiu di gi header l 32 bit (1 t gm 4

bit), n l chiu di tng ca c header gm c vng ny. Type of service: di 8 bit cha cc gi tr quy nh mc tr hon,

thng sut, tin cy ca datagram. Total length: di ch r chiu di ton b gi IP (byte), bao gm data v

header. Gm 16 bit do s c ti a 2^16= 65535 byte, c c chiu di caphn data payload ta ly chiu di tng tr i IHL.

ID: di 16 bit, dng nh s cc gi nh (packet hay fragment) sau khiphn mnh datagram. Nh ID, vic ti hp datagram mi c th thc hin c. Flag: c rng 3 bit, ch phn on ca gi tin Fragment Offset: rng 13 bit, ch r v tr ca phn mnh trong gi tin

tnh theo n v 64 bit.


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Time to live: rng 8 bit, quy nh thi gian tn ti ca gi tin. Slng ny s gim i 1 khi gi qua mt router, do khi b m n 0 th gi s bhy. iu ny ngn chn cc gi b loop (chy lp vng).

Protocol: ch ra giao thc lp cao hn (nh TCP hay UDP) nhn cc gin sau khi tin trnh x l IP hon tt. N gm 8 bit

Header Checksum: m bo s ton vn ca header IP. Source IP Address: a ch IP 32 bit ca host gi datagram. Destination IP Address: a ch IP 32 bit ca host nhn datagram. IP Option: cung cp cc phng tin kim li, o lng. Padding: nhiu s 0 c thm vo vng ny bo m rng header IP

lun l bi s ca 32 bit2.4.2 Giao thc iu khin vic truyn (TCP)

TCP cung cp dch v iu khin lung, bo nhn v truyn song cng honton cho cc giao thc lp bn trn. N di chuyn d liu di dng lung byte lintc khng c cu trc, cc byte c nh danh nh vo cc s tun t.

ti a thng lng, TCP cho php mi trm gi nhiu gi trc khi nhnc mt bo nhn. Sau khi ni gi nhn mt bo nhn cho gi ang ch., n scho ca s gi trt theo lung byte v gi gi k tip. C cu iu khin lung nyc gi l ca s trt.

TCP c th h tr cho nhiu cuc m thoi ca lp trn mt cch ng thi.Cc ch s cng trong phn header ca TCP s nh danh cho mt cuc m thoilp trn. Nhiu cng TCP c dnh cho cc ng dng ni ting nh FPT, HTTP,

SMTP, Telnet..TCP xc nhn rng d liu c truyn n theo th t v khng b ngt.

Cng vi u im ny l khong thi gian tin x l qu lu ca vic to v gi cckt ni.

TCP c xem l c nh hng kt ni v hai h thng cui ca qu trnhgiao tip trao i mt cuc hi thoi thng lng trc khi vic truyn d liu cth bt u. Vic ny m bo vi pha gi rng pha nhn ang rnh v sn sngnhn d liu


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Hnh 2.6: Cu trc header TCP

Cc trng cu trc c m t nh sau: Source Port: cng ngun 16 bit. Destination Port: cng n 16 bit. Sequence number: gm 32 bit, ch s tun t ca octet trong segment ny. Reserved: tr v 0 Code Bits: gm 8 bit

o ACK: Acknowledgment field significanto RST: Reset the connectiono SYN: Synchronize sequence numberso FIN: No more data from sendero PSH = 1: yu cu a tc thi d liu ln lp application.

Data offset: khong cch b qua tnh t segment n bt u d liu (tnhbng n v word), n ch ra ni no d liu bt u.

Window: gm 16 bit, ch ra s lng octet c ch nh trong trngACK m ngi gi s chp nhn.

Checksum: tng kim tra. Urgent pointer: ch ra im cui ca d liu khn Option: thng c nh ngha l kch thc ti a ca mt segment

TCP. Padding: phn thm vo cc bit m bo segment TCP l bi s ca 32

bit.

2.4.3 Giao thc UDPL mt giao thc n gin hn nhiu so vi TCP v hu dng trong cc

trng hp c cu tin cy ca TCP l khng cn thit. UDP l mt giao thc khngto cu ni v c mt header nh.


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Phn header ca UDP ch c 4 fiels: cng ngun, ch, chiu di v kim tra.Cng ngun v ch c chc nng nh TCP, field chiu di cho bit chiu di cac phn d liu v header, phn kim tra cho php kim tra ton b gi, l mt tu

chn.UDP c dng trong VoIP mang lu lng thoi thc (cc knh vn

chuyn). TCP khng c dng v iu khin lung v truyn li cc gi m thanhl khng cn thit. Bi UDP c dng vn chuyn lung m thanh ging ni,nn n lin tc truyn, khng quan tm n vic 5% hay 50% gi b mt.Nu TCP c dng choVoIP, th thi gian phi i cc bo nhn v truyn li sdn n cht lng thoi khng th chp nhn c. Vi VoIP v cc ng dng thigian thc khc, iu khin tr l quan trng hn so vi vic m bo tin cytrong phn phi gi tin.

Cc giao thc dng UDP gm: TFTP (Trivial File Transfer Protocol) SNMP (Simple Network Management Protocol) DHCP (Dynamic Host Control Protocol) DNS (Domain Name System)

Hnh 2.7: Cu trc UDP

o Source port: ch s port gi, gm 16 bit.o Destination port: ch s port b gi, gm 16 bit idleo Length: l s lng byte c header v data.Checksum: vng ny

m bo tnh ton vn, c tnh kim tra kiu tng cho cc vng header v datao Data: l d liu ca giao thc lp trn.

2.5 So snh m hnh TCP/IP v m hnh OSI c th thy c mi lin quan gia 2 m hnh OSI v TCP, ta phi tm

hiu xem chng c c im ging v khc nhau nh th no. Ging nhau:

C hai m hnh u phn chia lp C hai u c lp ng dng, cho d chng c nhiu dch v khc nhau


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u c lp transport v network u p dng k thut chuyn mch gi

Khc nhau: Lp ng dng ca TCP/IP c kt hp thm c lp session v trnh by TCP/IP kt hp lp data link v vt l trong OSI thnh mt lp c tn l

lp truy cp mng. TCP/ IP ch n gin c 4 lp. Giao thc TCP/ IP l mt chun m rng ca Internet, v th m hnh

TCP/IP c tin cy.

Hnh 2.8: M hnh TCP/IP v m hnh OSI

Nn tng ca giao thc TCP/IP l Lp Truy cp mng, tp hp cc dch v

v quy nh qun l vic tip cn phn cng ca mng li. Do vy, ta s tp trungv nhim v ca Lp Truy cp mng v s lin quan ca n vi m hnh OSI.

Lp Truy cp mng l phn phc tp nht trong cc lp ca TCP/IP. V cbn, lp truy cp mng qun l tt c cc dch v v chc nng cn thit cho vicchun b a d liu sang mng vt l. Nhng trch nhim ny gm:

o Tng tc vi b iu hp mng ca my tnh.o iu phi qu trnh truyn d liu theo cc quy c xc nh.o Format d liu thnh cc n v gi l mng (frame) v i mng

thnh dng in t hoc cc xung in, c kh nng di chuyn qua b phn truyntrung gian.

o Kim tra li ca cc mng d liu gi ti.o B sung thng tin kim tra li cho cc mng gi i my tnh nhn

c th pht hin li.o Xc nhn vic nhn mng thng tin v gi li d liu nu nh cha c

xc nhn ca bn kia.


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Lp Truy cp mng quy nh trnh t tng tc vi phn cng mng v tipcn b phn truyn trung gian. Mc d nguyn tc hot ng ca n rt phc tp,nhng ngi s dng thng thng khng th thy n.

Trn nguyn tc, TCP/IP hot ng hon ton c lp vi m hnh mng 7lp OSI (Open System Interconnection), nhng OSI thng c s dng lm tiuchun gii thch cc h thng giao thc khc.

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Chuong 2 Sua