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TRANSCRIPT
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BKTP.HCM
2008
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K Thut Truyn S Liu
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2008
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2008, Dr. Dinh Duc Anh Vu 2Data Communication and Computer Networks
Mn hc
M s: 504003
S tn ch: 4
Mn hc trc: khng
Ging vin
Nguyn Ho Hng
Khoa Khoa hc v K thut my tnh
(38647256 ext. 6227 or 5843)
http://cse.hcmut.edu.vn/~hungnguyen
Gii thiu
mailto:[email protected]://cse.hcmut.edu.vn/~hungnguyen
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2008
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2008, Dr. Dinh Duc Anh Vu 3Data Communication and Computer Networks
Gii thiu mn hc
ng lc S pht trin v bo ca cc ng dng my tnh
S cn thit ca vic trao i thng tin gia cc ni, gia cc my tnh
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2008
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2008, Dr. Dinh Duc Anh Vu 4Data Communication and Computer Networks
Gii thiu mn hc
Mc ch Gii thiu cc khi nim, thut ng v cc phng php tip cn
c dng trong cc h thng truyn d liu
Hiu vic truyn s liu gia 2 thit b v cc vn lin quan
Hiu vic truyn d liu qua mng gia 2 thit b thng qua mt nghi thc giao tip
Gii thiu mt s mng truyn s liu c s dng hin nay
i tng Sinh vin chuyn ngnh c kin thc v thit k mch, cu trc my
tnh, ngn ng lp trnh cp cao
K s chuyn ngnh
nh gi Kim tra gia k: 20%
Thc hnh: 20%
Kim tra cui k: 60%
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2008
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2008, Dr. Dinh Duc Anh Vu 5Data Communication and Computer Networks
Ni dung mn hc
Tng quan v truyn s liu v mng truyn s liu
Truyn dn s liu
K thut m ha tn hiu
K thut truyn d liu s
iu khin lp lin kt d liu
Ghp/tch knh
Chuyn mch mch v chuyn mch gi
Ch truyn bt ng b
Tm ng trong mng chuyn mch
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2008
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2008, Dr. Dinh Duc Anh Vu 6Data Communication and Computer Networks
Ti liu tham kho [1] Tp slide bi ging, TS. inh c Anh V, 2008
[2] Data and Computer Communications William Stallings (12 chng u)
[3] Data Communications and Computer Networks
ISDN & B-ISDN William Stallings
ATM Foundations for Broadband Networks Uyless Black
Data Communications William L. Schweber
Data communications and teleprocessing systems Trevor Housley
Data communication technology James Martin
Cng ngh ATM v CDMA LG Information & Communications
Lecture notes for M.Sc. Data Communication Networks and Distributed Systems D51 -- Basic Communications and Networks - Saleem N. Bhatti - Department of Computer Science - University College London - October 1994
Lecture notes for DATA COMMUNICATIONS, v4.0 Brian Brown, 1995-2001.
Fiber Optics Communication and Other Applications Henry Zanger & Cynthia Zanger.
Wireless Networked Communications Concepts, Technology and Implementation Regis J. Bates.
Practical digital and data communications with LSI applications Paul Bates
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BKTP.HCM
2008
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Chng 1
Tng quan v truyn s liu v
mng truyn s liu
M hnh h thng truyn d liu
Truyn s liu
Mng truyn s liu
Kin trc truyn s liu dng my tnh
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2008
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2008, Dr. Dinh Duc Anh Vu 8Data Communication and Computer Networks
M hnh h thng truyn d liu
ng dng d liu
ng dng m thanh, ting ni
ng dng video
ng dng thi gian thc
S khi tng qut (m hnh Shannon)
V d
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2008
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2008, Dr. Dinh Duc Anh Vu 9Data Communication and Computer Networks
M hnh h thng truyn d liu
H thng truyn d liu l g? D liu: biu din s liu, khi nim, di dng thch hp cho vic
giao tip, x l, din gii
Thng tin: ngha c gn cho d liu
Tn hiu: mt dng biu din ca d liu
Tp hp cc thit b c kt ni thng qua mt mi trng truyn dn
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2008
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2008, Dr. Dinh Duc Anh Vu 10Data Communication and Computer Networks
Cc tc v chnh
Ti u h thng truyn dn Chia s ng truyn hiu qu gia nhiu thit b, chng
nghn mch
Giao tip gia thit b vi h thng truyn
To tn hiu C kh nng truyn dn trong mi trng truyn
Bn nhn phi hiu c d liu
ng b gia bn truyn v bn nhn im bt u v im kt thc ca tn hiu
Qun l vic trao i d liu Cc giao thc truyn d liu
V d: thc hin cuc gi in thoi
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2008, Dr. Dinh Duc Anh Vu 11Data Communication and Computer Networks
Cc tc v chnh
iu khin dng d liu Tc truyn h thng ch khng b qu ti
Pht hin v sa li
nh v a ch v tm ng a ch l duy nht
Tm ng trong mt mng v gia cc mng
Khi phc Khi phc li trng thi c ca h thng khi c li lm ngt qung
nh dng thng tin (vd: binary code ca m k t)
Bo mt D liu ch c gi n i tng nhn xc nh
Qun tr mng Ci t h thng, qun l trng thi, x l li, c k hoch nng cp
trong tng lai
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2008, Dr. Dinh Duc Anh Vu 12Data Communication and Computer Networks
H thng truyn d liu
Ti sao phi dng h thng truyn d liu Chia s ti nguyn
My in
a/bng t
Cng sut tnh ton
Tp hp d liu
Phn tn ti Tnh ton song song
Tnh ton theo m hnh client-server
Fault tolerance
Chuyn thng tin Giao dch c s d liu
Th in t
Game
Phn tn d liu trn mng lu tr
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2008, Dr. Dinh Duc Anh Vu 13Data Communication and Computer Networks
Truyn s liu
Lin quan n cc vn truyn d liu s dng th Truyn dn d liu (data transmission)
M ha d liu (data encoding)
K thut trao i d liu s (digital data communication)
iu khin lin kt d liu (data link control)
Phn hp (multiplexing) Lin kt (link) hoc mch (circuit)
Knh (channel)
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2008, Dr. Dinh Duc Anh Vu 14Data Communication and Computer Networks
Mng truyn s liu
Giao tip im-im
thng khng thc t
Cc thit b cch xa
nhau
S kt ni tng ng k
khi s cc thit b cn
giao tip ln
Mng truyn s liu
Phn loi da vo
phm vi hot ng
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2008, Dr. Dinh Duc Anh Vu 15Data Communication and Computer Networks
Mng truyn s liu
Mng cc b (Local-Area Networks LAN)
c tnh
Tm vc nh (ta nh, nhiu ta nh)
Thng c s hu bi 1 cng ty, t chc
Tc cao hn WAN
Phn loi
Switch LAN (Ethernet)
Wireless LAN
ATM LAN
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2008, Dr. Dinh Duc Anh Vu 16Data Communication and Computer Networks
Mng truyn s liu
= Brige (cau)
LAN 1
LAN 2
LAN 3
= PC, Work station
a) ng dng trong vn phng
Building A
Building B
Building C
Site-wide (backbone) LAN
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2008, Dr. Dinh Duc Anh Vu 17Data Communication and Computer Networks
Mng truyn s liu Mng din rng (Wide-Area Networks WAN)
Khc nh th no so vi mng LAN? Trin khai theo din rng
Da vo cc mch truyn dn cng cng
Cng ngh Chuyn mch mch in (circuit-switching)
ng truyn dn logic dnh ring gia 2 node mng
Chuyn mch gi (packet-switching) Khng c dnh ring ng truyn dn
Mi gi i theo ng khc nhau
Chi ph ng truyn cao khc phc cc li truyn dn
Frame Relay c dng trong chuyn mch gi c tc li thp
Tc ln n 2 Mbps
ATM Ch truyn bt ng b (Asynchronous Transfer Mode)
Dng cc gi c kch thc c nh (gi l cell)
Tc ln n Gbps
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2008, Dr. Dinh Duc Anh Vu 18Data Communication and Computer Networks
Mng truyn s liu
Mt cch phn loi khc
Da vo kin trc v k thut dng trao i d
liu
Mng chuyn mch (switched networks)
Mng chuyn mch mch in
Mng chuyn mch gi
Mng pht tn (broadcast networks)
Mng radio gi (packet radio net.)
Mng v tinh (satellite net.)
Mng cc b (local net.)
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BKTP.HCM
2008
dce
Chng 1
Tng quan v truyn s liu v
mng truyn s liu
M hnh h thng truyn d liu
Truyn s liu
Mng truyn s liu
Kin trc truyn s liu dng my tnh
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2008, Dr. Dinh Duc Anh Vu 20Data Communication and Computer Networks
V d kin trc phn cp
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2008, Dr. Dinh Duc Anh Vu 21Data Communication and Computer Networks
Kin trc truyn thng my tnh
Trong ng dng truyn file, nhng cng vic phi lm l Ngun thit lp kt ni (bo cho mng bit u l ch)
Ngun m bo ch sn sng nhn d liu
ng dng truyn file trn h/t ngun phi m bo chng trnh qun l file trn h/t ch sn sng nhn v lu tr file
Nu nh dng file dng trn 2 h/t khng tng thch, mt hoc c 2 h/t phi thc hin chc nng chuyn i
Tc v giao tip c phn nh thnh cc mun
V d, truyn file c th c phn thnh 3 mun Truyn file
Dch v giao tip
Truy xut mng
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2008, Dr. Dinh Duc Anh Vu 22Data Communication and Computer Networks
Nghi thc giao tip (protocol)
Dng giao tip gia cc thc th trong mt h thng Thc th
C kh nng gi/nhn thng tin
ng dng ngi dng
Th in t
Thit b u cui
H thng
i tng vt l, cha mt hoc nhiu thc th
My tnh
Thit b u cui
Cm bin t xa
Phi cng ni mt ngn ng
Cc thnh phn chnh ca mt nghi thc giao tip Ng php (syntax)
nh dng d liu
Mc tn hiu
Ng ngha (semantic)
Thng tin iu khin
X l li
nh thi (timing)
ng b
Tun t
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2008, Dr. Dinh Duc Anh Vu 23Data Communication and Computer Networks
M hnh n gin 3 lp
Lp truy xut mng
Lp vn chuyn
Lp ng dng
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2008, Dr. Dinh Duc Anh Vu 24Data Communication and Computer Networks
Lp truy xut mng
Trao i d liu gia my tnh v mi trng
mng
Cung cp a ch my nhn, tm ng i
Yu cu cc dch v t mi trng mng
(priority)
Ph thuc vo loi mng ang s dng (LAN,
chuyn mch gi, mch)
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2008, Dr. Dinh Duc Anh Vu 25Data Communication and Computer Networks
Lp vn chuyn
m nhn vic truyn d liu tin cy
D liu n ng a ch
Theo th t gi
Khng ph thuc vo loi kt ni mng bn
di
Khng ph thuc vo ng dng
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2008, Dr. Dinh Duc Anh Vu 26Data Communication and Computer Networks
Lp ng dng
Cung cp cho cc ng dng cc dch v
truy cp mng
Web browser: HTTP
Email: SMTP
File: FTP
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2008, Dr. Dinh Duc Anh Vu 27Data Communication and Computer Networks
Kin trc 3 lp
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2008, Dr. Dinh Duc Anh Vu 28Data Communication and Computer Networks
Protocol data unit (PDU)
Ti mi lp c nhiu protocol c s dng
D liu ngi dng phi c thm vo cc thng tin iu
khin ti mi lp
Lp vn chuyn c th chia nh d liu ngi dng
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2008, Dr. Dinh Duc Anh Vu 29Data Communication and Computer Networks
Hot ng ca kin trc 3 lp
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2008, Dr. Dinh Duc Anh Vu 30Data Communication and Computer Networks
Tiu chun ha Cn thit cho cc tc v lin thng gia cc
thit b
u im Bo m th trng ln cho cc thit b v cc
phn mm
Cho php cc sn phm ca cc nh cung cp c th giao tip vi nhau
Nhc im Hn ch s pht trin cng ngh
C th c nhiu chun cho cng mt cng ngh
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2008, Dr. Dinh Duc Anh Vu 31Data Communication and Computer Networks
Tiu chun ha Cc t chc chun ha
Electronics Industries Association EIA: hip hi cc nh sn xut M, a ra chun RS232 v cc chun tng t
Institute of Electrical and Electronic Engineers IEEE (http://www.ieee.org): t chc nh ngh ca cc k s in-in t (IEEE-802: chun cho LAN/MAN)
International Telecommunications Union ITU (http://www.itu.ch): iu phi cc chun tm quc t, cp pht tn s vin thng v tinh (X.25 protocol: WAN communication)
ISOC: Internet society (http://www.isoc.org): l mt cng ng chuyn nghip gm nhiu t chc con (Internet architecture Board: IAB), a ra rt nhiu cc chun v internet (TCP/IP)
International Organization for Standards ISO (http://www.iso.ch): c nhiu chun lin quan n my tnh (OSI: Open system interconnection)
http://www.ieee.org/http://www.itu.ch/http://www.isoc.org/http://www.iso.ch/
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2008, Dr. Dinh Duc Anh Vu 32Data Communication and Computer Networks
M hnh DoD Pht trin bi DARPA (Defense Advanced Research Projects Agency) cho mng chuyn
mch gi ARPANET (sau ny l Internet)
Sp xp phn cp ca cc thc th c kh nng giao tip vi cc thc th ngang cp trong
mt h thng khc
Trong mt h thng, mt thc th cung cp dch v cho cc thc th khc v cng s dng
dch v ca cc thc th khc
Nhn mnh vo internetworking, ngha l, khi 2 thc th giao tip khng ni chung mt mng
Quan tm c h thng hng n kt ni v khng kt ni
Bao gm cc ng dng: trao i file (FTP, RCP), m phng terminal (telnet, rlogin), chia s
v truy cp file phn tn (NFS), thc thi lnh t xa (rsh, rexec), in n t xa (lpr), 802.X, X.25,
mail (SMTP), qun tr mng (NSP, SNMP)
TCP/IP c pht trin ng thi vi m hnh ISO
Khng cha cc nghi thc lin quan n cc lp trong m hnh ISO
Hu ht cc chc nng ca m hnh ISO c tch hp trong TCP/IP
Khng phi m hnh chnh thc, nhng l mt m hnh thc tin
Lp ng dng
Lp transport (giao tip gia cc thit b)
Lp Internet
Lp truy xut mng
Lp vt l
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2008, Dr. Dinh Duc Anh Vu 33Data Communication and Computer Networks
M hnh kin trc nghi thc TCP/IP
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2008, Dr. Dinh Duc Anh Vu 34Data Communication and Computer Networks
Lp vt l Giao tip vt l gia thit b v mi trng truyn
Tnh cht ca mi trng truyn, mc tn hiu, tc truyn
Lp truy xut mng Trao i d liu gia thit b v mng truyn
Cung cp chc nng tm ng gia 2 thit b trong cng 1 network
Yu cu cc dch v t mng truyn (priority)
Lp Internet Cung cp chc nng tm ng gia 2 thit b thuc 2 mng khc
nhau
Cn c hin thc trong cc router
Lp transport m nhn vic truyn d liu tin cy gia 2 ng dng
Chc chn d liu i n ch, cc gi d liu n ng th t gi
Lp ng dng Cung cp cho cc ng dng cc dch v truy cp mng
M hnh kin trc nghi thc TCP/IP
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2008, Dr. Dinh Duc Anh Vu 35Data Communication and Computer Networks
D liu c truyn qua TCP/IP
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2008, Dr. Dinh Duc Anh Vu 36Data Communication and Computer Networks
M hnh kin trc nghi thc TCP/IP
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M hnh mng ISO/OSI
L mt m hnh tham kho
ISO 7498, nm 1984
M hnh tng ng ca ITU-T l X.200
H thng l thuyt ra i qu tr
TCP/IP ang l tiu chun thc tin (de facto
standard)
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2008, Dr. Dinh Duc Anh Vu 38Data Communication and Computer Networks
M hnh mng ISO/OSI
7 lp ng dng (application)
Trnh by (presentation)
Giao dch (session)
Vn chuyn (transport)
Mng (network)
Lin kt d liu (data link)
Vt l (physical)
Application Layer
Transport Layer
Presentation Layer
Session Layer
Network Layer
Datalink Layer
Physical Layer
Netw
ork
environm
ent
OSI
environm
ent
Real system environment
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2008, Dr. Dinh Duc Anh Vu 39Data Communication and Computer Networks
M hnh mng ISO/OSI
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2008, Dr. Dinh Duc Anh Vu 40Data Communication and Computer Networks
Lp vt l iu khin vic truyn d liu (chui cc bit) thc s trn cp/mng
nh ngha tn hiu in, trng thi ng truyn, m ha thng tin v kiu kt ni c s dng
Thi gian tr truyn Thi gian t/h truyn t ngun n ch
T/h truyn vi vn tc xp x vn tc nh sng C=3x108 m/s
V d
v tinh GEO d=40.000km tr truyn 1/8 s;
cp Ethernet d=1km tr truyn 3s
Li truyn Suy gim cng sut t/h
Suy gim do nhiu
Cc c trng chnh c trng c hc: connector, loi vt liu truyn dn
c trng in: dng biu din ca bit (vd: mc volt), v tc truyn bit
c trng chc nng: chc nng ca cc mch gia h thng v ng truyn
c trng th tc: quy nh cc s kin trong qu trnh truyn bit stream qua ng truyn
Lp ph thuc mi trng truyn dn
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2008, Dr. Dinh Duc Anh Vu 41Data Communication and Computer Networks
Lp ph thuc mi trng truyn dn
Lp lin kt d liu
Chu trch nhim truyn dn mt cch tin cy
(error-free) cc gi d liu ca lp mng trn mt
lin kt n
Khi ng, duy tr v ngt ng truyn
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2008, Dr. Dinh Duc Anh Vu 42Data Communication and Computer Networks
Lp ph thuc mi trng truyn dn
Lp mng
Trung chuyn cc gi gia lp
vn chuyn v lp lin kt d
liu
nh a ch gi v dch a
ch lun l thnh a ch vt l
Tm ng kt ni vi my
tnh khc thng qua mng
Mi node cha mt moun
lp mng cng vi mt moun
lp lin kt d liu cho mt
lin kt
Khng cn thit nu kt ni 2
my trc tip
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2008, Dr. Dinh Duc Anh Vu 43Data Communication and Computer Networks
Lp hng ti ng dng
Lp vn chuyn Cung cp c ch trao i d liu gia 2 h thng
Cung cp dch v gi thng ip (message service) end-to-end cho cc lp trn
Bo m d liu c truyn khng c li, theo th t v khng mt mt, ngt qung hoc d tha
Chu trch nhim ng gi d liu t mt message ln thnh nhiu message kch thc nh hn gi i v tp hp cc message nh thnh mt message ban u khi nhn c (c kh nng a hp)
Ngt thng bo thnh cc gi nh (c kch thc thch hp) v tp hp cc gi cho lp mng
Kt hp cc giao dch vi cng cc node ngun/ch
Ti lp th t cc gi ti ch n
Khi phc li, h hng
iu khin dng t ngun n ch v ngc li
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2008, Dr. Dinh Duc Anh Vu 44Data Communication and Computer Networks
Lp hng ti ng dng
Lp giao dch Cung cp c ch iu khin vic truyn thng ip gia
cc ng dng (tr gip danh b, quyn truy cp, chc nng tnh cc, )
Cho php 2 ng dng to, s dng v xa kt ni
C kh nng nhn dng tn v cung cp cc dch v khc (security, checkpoint, recovery) cn thit cho 2 my tnh ni kt qua mng
Lp trnh by Cung cp nh dng d liu c dng truyn d liu
gia cc my tnh ni mng (chuyn i m k t, m ha d liu, nn d liu)
Lp ng dng Cung cp cho cc ng dng cc dch v truy cp mng
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2008, Dr. Dinh Duc Anh Vu 45Data Communication and Computer Networks
Truyn d liu qua m hnh mng OSI
Presentation layer
Session layer
Application layer
Transport layer
Network layer
Datalink layer
Physical layer
Application process
Presentation layer
Session layer
Application layer
Transport layer
Network layer
Datalink layer
Physical layer
Application process
Data network
Network environment
OSI environment
Real systems environment
Computer I Computer II
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2008, Dr. Dinh Duc Anh Vu 46Data Communication and Computer Networks
D liu c truyn qua mng OSI
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2008, Dr. Dinh Duc Anh Vu 47Data Communication and Computer Networks
So snh m hnh OSI v TCP/IP
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2008, Dr. Dinh Duc Anh Vu 48Data Communication and Computer Networks
So snh m hnh OSI v TCP/IP
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Cc giao thc trong m hnh TCP/IP
Ethernet IEEE 802.3.
L chun ph bin nht cho PHY v MAC.
Token Ring iu khin quyn gi nhn message bng token.
IP: Internet Protocol Protocol dng chuyn gi d liu t my ngun n my ch da
trn a ch
ICMP: Internet Control Message Protocol Hin thc da trn IP
Dng gi error message t router hay my ch n my ngun
ARP: Address Resolution Protocol Phn gii a ch IP ra a ch vt l
RARP: Reverse Address Resolution Protocol Xin cp a ch IP cho my. -> DHCP (Dynamic Host Configuration
Protocol)
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Cc giao thc trong m hnh TCP/IP
TCP: Transmission control protocol Giao thc truyn nhn d liu tin cy gia cc ng dng
S dng ng truyn lun l tm thi
UDP: User-datagram protocol Truyn d liu khng tin cy
Telnet ng nhp t xa
FTP, TFTP Truyn nhn file
SMTP ng dng gi nhn mail
DNS i tn min thnh a ch IP
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2008, Dr. Dinh Duc Anh Vu 51Data Communication and Computer Networks
Bt li ca m hnh nhiu lp
Processing overhead: d liu phi i qua
nhiu lp t trn xung di
Data overhead: d liu gc c gn thm
cc header ca cc lp
Mt nhiu thi gian xy dng h thng cc
protocol chun cho tng lp
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2008, Dr. Dinh Duc Anh Vu 52Data Communication and Computer Networks
c thm
W. Stallings, Data and Computer
Communications (7th edition), Prentice Hall
2004, chapter 1, 2
Web sites for IETF, IEEE, ITU-T, ISO
Internet Requests for Comment (RFCs)
Usenet News groups
comp.dcom.*
comp.protocols.tcp-ip
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Chng 2
Truyn dn s liu Khi nim v thut ng
Truyn dn d liu tng t v d liu s
Suy hao ng truyn
Dung lng knh truyn
Mi trng truyn dn c nh hng
Truyn dn khng dy
Lan truyn khng dy
Truyn ng thng (line-of-sight)
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2008, Dr. Dinh Duc Anh Vu 2 Data Communication and Computer Networks
Thut ng
Thit b
Thit b pht (Transmitter)
Thit b thu (Receiver)
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2008, Dr. Dinh Duc Anh Vu 3 Data Communication and Computer Networks
Thut ng
Mi trng truyn (Medium)
Hu tuyn (guided)
V tuyn (unguided, wireless)
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2008, Dr. Dinh Duc Anh Vu 4 Data Communication and Computer Networks
Thut ng
Kt ni
Kt ni trc tip (Direct link)
Khng cn cc thit b trung gian
Kt ni im-im (Point-to-point)
Kt ni trc tip
Ch c 2 thit b dng chung kt ni
Kt ni nhiu im (Multi-point)
2 thit b dng chung kt ni
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2008, Dr. Dinh Duc Anh Vu 5 Data Communication and Computer Networks
Ch truyn
Simplex mode Khng dng rng ri v khng th gi ngc li li hoc tn
hiu iu khin cho bn pht
Television, teletext, radio
Half-duplex mode
B m
Full-duplex mode
in thoi
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2008, Dr. Dinh Duc Anh Vu 6 Data Communication and Computer Networks
Tn hiu Khi nim min thi gian
T/h lin tc
Thay i mn theo thi
gian
T/h ri rc
Thay i tng mc theo
thi gian
T/h tun hon
Mu lp li theo thi gian
C bn nht l sng sin
(Bin , tn s v pha)
T/h khng tun hon
Mu khng lp li theo thi
gian
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2008, Dr. Dinh Duc Anh Vu 7 Data Communication and Computer Networks
Biu din tn hiu min tn s
Tn hiu thc t c
cu to bi nhiu thnh
phn c tn s khc nhau
Cc tn hiu thnh phn
l cc sng hnh sin
Tn s nh nht: tn s c
bn
Chu k ca tn hiu tng
hp bng chu k ca tn
s c bn
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2008
dce
2008, Dr. Dinh Duc Anh Vu 8 Data Communication and Computer Networks
Biu din tn hiu min tn s
Tt c cc tn hiu (tng
t ln s) u c th c
phn tch thnh tng ca
nhiu sng sin (khai trin
Fourier)
=> C th biu din tn hiu
theo min tn s
Trc honh: cc tn s c
trong tn hiu
Trc tung: bin nh ca
tn hiu tng ng vi mi
tn s
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2008
dce
2008, Dr. Dinh Duc Anh Vu 9 Data Communication and Computer Networks
Tn s, ph v bng thng
Ph Tm tn s cha trong tn hiu
Bng thng tuyt i rng ph (c o bng s
chnh lch tn s cao nht v thp nht)
Bng thng knh truyn cng ln, tc truyn cng cao
Bng thng hiu dng Gi tt l bng thng
Di tm tn s hp cha hu ht nng lng ca tn hiu
Thnh phn mt chiu Thnh phn c tn s bng 0
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2008
dce
2008, Dr. Dinh Duc Anh Vu 10 Data Communication and Computer Networks
Tn hiu c thnh phn DC
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 11 Data Communication and Computer Networks
Tn hiu s
Tn s f
Chu k T = ?
Thi gian truyn 1 bit Tbit = ?
Tc truyn d liu?
Bng thng???
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 12 Data Communication and Computer Networks
Tng hp tn hiu s
-
2008
dce
Tng hp tn hiu s
Khi cng nhiu tn s kf bng bi s l ca
tn s c bn: tn hiu cng gn vi tn hiu
s
Dng biu din ca tn hiu s
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 14 Data Communication and Computer Networks
Bng thng v tc truyn
Trng hp 1:
ng truyn c bng thng 4MHz
Tn hiu c thnh phn f, 3f, 5f vi f = 1MHz
Trng hp 2:
ng truyn c bng thng 8MHz
Tn hiu c thnh phn f, 3f, 5f, vi f = 2MHz
Trng hp 3
ng truyn c bng thng 4MHz
Tn hiu c thnh phn f, 3f vi f = 2MHz
Kt lun?
(chi ph, bng thng, mo tn hiu, tc d liu)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 15 Data Communication and Computer Networks
Truyn dn d liu tng t v s
D liu Cc thc th cha ng thng tin
D liu tng t: gi tr lin tc trong 1 thi khong
D liu s: gi tr ri rc theo thi gian
Tn hiu D liu c biu din dng tn hiu in hoc in t
Tn hiu tng t Thay i lin tc theo thi gian
Truyn trn nhiu mi trng: hu tuyn, quang, khng gian
Tn hiu s S dng 2 thnh phn DC
Truyn dn Trao i d liu bng cch lan truyn v x l tn hiu
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2008
dce
2008, Dr. Dinh Duc Anh Vu 16 Data Communication and Computer Networks
Truyn dn d liu tng t v s
Thng thng Tn hiu tng t
truyn d liu tng t
Tn hiu s truyn d liu s
Trong mt s trng hp Tn hiu tng t
mang d liu s
Tn hiu s mang d liu tng t
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2008
dce
2008, Dr. Dinh Duc Anh Vu 17 Data Communication and Computer Networks
Truyn dn tn hiu tng t v s
Truyn tn hiu tng t Khng quan tm ni dung d liu cha ng bn trong
Suy gim tn hiu theo khong cch
Dng amplifier khuch i tn hiu (k c nhiu)
Truyn tn hiu s Cn ch ni dung d liu cha ng bn trong
Khong cch truyn ngn
Dng repeater tng khong cch truyn
Nhiu khng b khuch i
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2008
dce
2008, Dr. Dinh Duc Anh Vu 18 Data Communication and Computer Networks
Truyn dn s
u im
Cng ngh s
Cng ngh LSI/VLSI lm gim gi thnh
Ton vn d liu
Nhiu v suy gim tn hiu khng b tch ly bi cc repeater
Truyn khong cch xa hn trn cc ng truyn km cht lng
Hiu qu knh truyn
TDM > FDM
Bo mt
Cc k thut m ha bo mt d liu d p dng
Tch hp
D liu s v analog c x l tng t nhau
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 19 Data Communication and Computer Networks
Suy gim tn hiu
T/h nhn c khc vi t/h truyn i
Analog suy gim cht lng t/h
Digital li trn bit
Nguyn nhn
Suy yu v mo do suy yu trn ng truyn
Mo do tr truyn
Nhiu
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2008
dce
2008, Dr. Dinh Duc Anh Vu 20 Data Communication and Computer Networks
suy yu tn hiu trn ng truyn
Khi mt tn hiu lan truyn qua mt mi trng truyn, cng (bin ) ca tn hiu b suy gim theo khong cch
Ty thuc vo mi trng truyn dn i vi mi trng hu tuyn: l hm m theo khong cch
i vi mi trng v tuyn, suy gim cng t/h l mt hm phc tp theo khong cch v thnh phn kh quyn
Vn cn quan tm Tn hiu nhn phi mnh thit b nhn nhn bit c
Tn hiu phi c gi cao so vi nhiu t/h khng b li
Phi dng amplifier v repeater vi khong cch nht nh
Tn hiu khng c mnh qu mc gy qu ti, mo cho receiver
Vn i vi khong cch trong kt ni a im
Suy yu l mt hm tng theo tn s
Dng b khuch ai (khuch i tn s cao nhiu hn)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 21 Data Communication and Computer Networks
suy yu tn hiu trn ng truyn
o bng n v decibel (dB)
Cng t/h suy gim theo hm m
li/ hao ht ca cc tng ni tip c th
c tnh bng php ton n gin (+/-)
Cng thc
Attenuation = 10log10(P1/P2) (dB)
P1, P2: cng sut (watts)
Decibel (dB) l gi tr sai bit tng i
Cng sut suy gim hao ht l 3dB
Cng sut tng gp i li l 3dB
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2008
dce
2008, Dr. Dinh Duc Anh Vu 22 Data Communication and Computer Networks
Tr lan truyn tn hiu
Mo tr lan truyn Ch xy ra trong mi trng truyn dn hu tuyn
Vn tc lan truyn thay i theo tn s Vn tc cao nht gn tn s trung tm
Cc thnh phn tn s khc nhau s n ch cc thi im khc nhau
Cng thc Transmission propagation delay
Tp = S/V S : khong cch vt l (meter)
V : vn tc lan truyn tn hiu trn mi trng truyn, vi sng in t: v = 2 x 106 (m/s)
Round trip delay
Tx = N/R N : khi lng d liu truyn (bit)
R : tc truyn bit trn ng truyn.
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2008
dce
2008, Dr. Dinh Duc Anh Vu 23 Data Communication and Computer Networks
Nhiu
T/h thm vo gia thit b pht v thit b thu
Nhiu nhit
Do dao ng nhit ca cc electron trong cht dn
Hm ca nhit
Phn tn ng nht trn ph tn s => Nhiu trng
Khng th loi b gii hn hiu sut ca h thng
Nhiu trong bng thng 1Hz ca bt k cht dn no
N0 = kT
N0: mt cng sut nhiu (watt/Hz)
k: hng s Boltzmann (= 1.38 x 10-23 J/K)
T: nhit (K)
Nhiu trong bng thng B (Hz) N = kTB
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2008
dce
2008, Dr. Dinh Duc Anh Vu 24 Data Communication and Computer Networks
Nhiu Nhiu iu ch (intermodulation)
T/h nhiu c tn s l tng hoc hiu tn s ca cc t/h dng chung mi trng truyn
Do tnh phi tuyn ca thit b thu/pht
Nhiu xuyn knh (crosstalk) T/h t ng truyn ny nh hng sang cc ng
truyn khc
Cng ln (hoc nh hn) nhiu nhit
Nhiu xung Xung bt thng (spike)
e.g. nh hng in t bn ngoi
Thi khong ngn
Cng cao
nh hng nhiu n qu trnh trao i d liu s Xung 0.01s lm mt 50 bit d liu nu truyn tc 4800bps
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2008
dce
2008, Dr. Dinh Duc Anh Vu 25 Data Communication and Computer Networks
c im C th truyn nhiu hn mt bit ng vi mi thay i ca
tn hiu trn ng truyn.
Tc truyn thng tin cc i b gii hn bi bng thng ca knh truyn
Cng thc Nyquist Nu tc truyn t/h l 2W th t/h vi cc tn s nh hn
v bng W l ; ngc li nu bng thng l W th tc t/h cao nht l 2W
C = 2W x log2M C : tc truyn t/h cc i (bps) khi knh truyn khng c
nhiu
W : bng thng ca knh truyn (Hz)
M : s mc thay i tn hiu trn ng truyn
Tc knh truyn (kh nng knh truyn)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 26 Data Communication and Computer Networks
Tc d liu Baud rate (baud)
Nghch o ca phn t d liu ngn nht (s ln thay i tn hiu ng truyn mi giy)
Tn hiu nh phn tc 20Hz: 20 baud (20 thay i mi giy)
Bit rate (bps hoc bit/s) c trng cho kh nng ca knh truyn
Tc truyn d liu cc i trong trng hp khng c nhiu
Bng baud rate trong trng hp tn hiu nh phn
Khi mi thay i ng truyn c biu din bng 2 hay nhiu bit, tc bit khc vi tc baud
Quan h gia Baud rate v Bit rate
R = Rs x log2M = Rs x m R : tc bit (bit/s)
Rs : tc baud (baud/s)
M : s mc thay i tn hiu trn ng truyn
m : s bit m ha cho mt tn hiu
hu hiu bng thng: B = R/W (bps Hz-1)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 27 Data Communication and Computer Networks
Thut ng
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2008
dce
2008, Dr. Dinh Duc Anh Vu 28 Data Communication and Computer Networks
Signal to Noise ratio SNRdB = 10 x log10( ) (dB)
S : cng sut tn hiu nhn
N: cng sut nhiu
Cng thc Shannon-Hartley
C = W x log2(1 + ) (bps)
C: tc truyn t/h cc i khi knh truyn c nhiu
T s nng lng t/h ca 1 bit so vi nng lng nhiu ca 1 Hz Eb/N0 Tb: thi gian truyn 1 bit
R: tc bit ca d liu nh phn
Eb = STb = S/R
Eb/N0 = S/(RN0) = S/(kTR)
Tc sai bit l hm gim ca t s ny
T l tn hiu trn nhiu
N
S
N
S
-
BK TP.HCM
2008
dce
Chng 2
Truyn dn s liu Khi nim v thut ng
Truyn dn d liu tng t v d liu s
Suy hao ng truyn
Dung lng knh truyn
Mi trng truyn dn c nh hng
Truyn dn khng dy
Lan truyn khng dy
Truyn ng thng (line-of-sight)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 30 Data Communication and Computer Networks
Bc sng
Khong cch sng truyn c trong mt chu
k
Khong cch gia 2 im pha tng ng
trong 2 chu k lin tip
K hiu
Gi s vn tc t/h v
= vT
= v/f
c = 3*108 ms-1 (tc nh sng)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 31 Data Communication and Computer Networks
Mi trng truyn dn Hu tuyn (guided media wire)
Cp ng
Cp quang
V tuyn (unguided media wireless) V tinh
H thng sng radio: troposcatter, microwave, ...
c tnh v cht lng truyn d liu c xc nh bi mi trng v tn hiu i vi hu tuyn, mi trng nh hng ln hn
i vi v tuyn, bng thng to ra bi anten pht nh hng ln hn
Yu t nh hng trong vic thit k: tc d liu v khong cch Bng thng
Bng thng cao th tc d liu cao
Suy yu truyn dn Nhiu (nhiu nhit, nhiu iu ch, nhiu xuyn knh, nhiu xung)
S thit b nhn (receiver) Trong mi trng hu tuyn, cng nhiu thit b nhn, tn hiu truyn cng
mau suy gim
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2008
dce
2008, Dr. Dinh Duc Anh Vu 32 Data Communication and Computer Networks
Cp ng: two-wire open line
Single pair
Flat ribon
Terminating Connector
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2008
dce
2008, Dr. Dinh Duc Anh Vu 33 Data Communication and Computer Networks
Cp ng: twisted-pair
Insulating outer cover
Multi core
Insulating outer cover
Protective screen (shield)
Cch in trn mi dy Xon li vi nhau Thng c b li Chng nhiu crosstalk
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2008
dce
2008, Dr. Dinh Duc Anh Vu 34 Data Communication and Computer Networks
Cp ng: twisted-pair
ng dng Mi trng truyn dn thng dng nht
Mng in thoi Gia cc thu bao v hp cp (subscriber loop)
Kt ni gia cc ta nh Tng i ni b (Private Branch eXchange PBX)
Mng cc b (LAN) 10Mbps hoc 100Mbps
u nhc im R
D dng lp t, thao tc
Tc d liu thp
Tm ngn
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2008
dce
2008, Dr. Dinh Duc Anh Vu 35 Data Communication and Computer Networks
Cp ng: twisted-pair
c tnh truyn dn
Analog
Cn b khuch i mi 5km ti 6km ( suy gim t/h:
~1dB/km, chun trong T: 6dB)
Digital
Dng tn hiu tng t hoc tn hiu s
Cn b lp (repeater) mi 2km hoc 3km
Khong cch gii hn
Bng thng gii hn (1MHz)
Tc d liu gii hn (100Mbps)
D b nhiu v tc ng ca mi trng ngoi
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2008
dce
2008, Dr. Dinh Duc Anh Vu 36 Data Communication and Computer Networks
Cp ng: twisted-pair Khng v bc gip Unshielded Twisted Pair (UTP)
Dy T bnh thng
R nht
D lp t
D b nhiu trng in t bn ngoi
V bc gip Shielded Twisted Pair (STP) V gip bn gip gim nhiu v tc ng bn ngoi
t hn
Kh lp t (cng, nng)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 37 Data Communication and Computer Networks
Cp ng: twisted-pair
UTP Cat 3 Ln n 16MHz
c dng trong lin lc thoi hu ht cc vn phng
Chiu di xon (twist length): 7.5cm ti 10cm
UTP Cat 4 Ln n 20 MHz
UTP Cat 5 Ln n 100MHz
c dng ph bin hin nay trong cc vn phng
Chiu di xon: 0.6cm n 0.85cm
Thch hp cho tc truyn ln n 100 Mbps (LAN)
STP Cat 3: thch hp cho tc truyn
ln n 10 Mbps
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2008
dce
2008, Dr. Dinh Duc Anh Vu 38 Data Communication and Computer Networks
Cp ng: twisted-pair cable
Cable standards
Tn Loi Mbps Thng c dng
Category 1 UTP 1 Modem
Category 2 UTP 4 Token Ring-4
Category 3 UTP 10 10Base-T Ethernet
Category 4 STP 16 Token Ring-16
Category 5 UTP 100 100Base-T Ethernet
Category 5 STP 100 100Base-T Ethernet
Category 5e UTP 100 1000Base-T Ethernet
Category 6 UTP 200 1000Base-T Ethernet
Category 7 STP 600 1000Base-T Ethernet
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2008
dce
2008, Dr. Dinh Duc Anh Vu 39 Data Communication and Computer Networks
Cp ng: coaxial
-
2008
dce
Cp ng: coaxial
2008, Dr. Dinh Duc Anh Vu 40 Data Communication and Computer Networks
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2008
dce
2008, Dr. Dinh Duc Anh Vu 41 Data Communication and Computer Networks
Cp ng: coxial
ng dng Mi trng truyn linh hot nht
Cp truyn hnh
Truyn dn T khong cch xa FDM
C th mang ng thi 10.000 cuc gi
S b thay th bi cp quang
Kt ni cc thit b khong cch gn
Mng cc b
c tnh truyn dn Hiu ng b mt (skin effect)
Analog Cn b khuch i mi vi km
Khong cch cng ngn nu tn s cng cao
Ln n 500MHz
Digital Cn b lp (repeater) mi km
Khong cch cng ngn nu tc d liu cng tng
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2008
dce
2008, Dr. Dinh Duc Anh Vu 42 Data Communication and Computer Networks
Cp ng: c im chung
T l bit li trn ng truyn (Bit Error Rate
BER) vo khong 10-6.
D b nh hng ca nhiu (crosstalk,
thermal,...) v mi trng xung quanh.
Tc truyn thng tin thay i ty theo phm
vi h thng c trin khai :
LAN: tc 10Mbps ~ 100Mbps, khong cch
khong vi trm mt (UTP: length < 100 m).
WAN: tc truyn thp hn, t vi chc Kbps
n vi Mbps. V d: T1 ~ 1,5Mbps, E1 ~ 2Mbps,
telephone line: 64Kbps
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2008
dce
2008, Dr. Dinh Duc Anh Vu 43 Data Communication and Computer Networks
Cp quang: cu trc
Single core
Multicore
Plastic
coating
Optical core Optical cladding
Single core
Multicore
Plastic
coating
Optical core Optical cladding
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2008
dce
2008, Dr. Dinh Duc Anh Vu 44 Data Communication and Computer Networks
Cp quang: li ch v ng dng Li ch
Dung lng cao Tc d liu hng trm Gbps (so vi 100Mbps trn 1km coaxial cable v thp
hn ca twisted-pair cable)
Kch thc v trng lng nh
suy hao ca tn hiu trn ng truyn thp.
Cch ly trng in t (khng b nh hng ca nhiu v mi trng xung quanh, kh cu trm)
Khong cch gia cc b repeater xa
T l bit li trn ng truyn vo khong 10-9 10-12
ng dng Phm vi trin khai rt a dng: LAN (vi km), WAN (hng chc km).
Mi trng truyn thch hp trin khai cc ng dng mng s a dch v tch hp bng rng (Broadband Integrated Services Digital Networks)
ng trung k khong cch xa
Trung k th
Trung k tng i nng thn
Thu bao
LAN
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2008
dce
2008, Dr. Dinh Duc Anh Vu 45 Data Communication and Computer Networks
Cp quang: c tnh truyn dn
Sng lan truyn c hng 1014 n 1015 Hz
Mt phn ph hng ngoi v ph nhn thy c
Light Emitting Diode (LED)
R
Tm nhit hot ng rng
Tui th cao
Injection Laser Diode (ILD)
Hiu qu hn
Tc d liu cao hn
Wavelength Division Multiplexing
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2008
dce
2008, Dr. Dinh Duc Anh Vu 46 Data Communication and Computer Networks
Cp quang : ch truyn multimode: several paths/time delays
narrow: 1 wavelength no time delays
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2008
dce
2008, Dr. Dinh Duc Anh Vu 47 Data Communication and Computer Networks
Cp quang : ch truyn
Step-index
multimode
Graded-index multimode Single-mode
Ngun sng LED/ILD LED/ILD ILD
Bng thng Rng (ln n
200MHz/km)
Rt rng (200MHz-
3GHz/km)
Cc rng (3GHz-
50GHz/km)
Ghp ni Kh Kh Kh
ng dng Truyn d liu
my tnh
ng in thoi
(khong cch trung bnh)
Vin thng ng
di
Gi thnh R nht Trung bnh t nht
ng knh li
(m)
50-125 50-125 2-8
ng knh v
(m)
125-440 125-440 15-60
suy gim
(db/km)
10-50 7-15 0.2-2
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2008
dce
2008, Dr. Dinh Duc Anh Vu 48 Data Communication and Computer Networks
Cp quang
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 49 Data Communication and Computer Networks
Mi trng truyn dn hu tuyn
c tnh truyn dn im-im
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2008
dce
2008, Dr. Dinh Duc Anh Vu 50 Data Communication and Computer Networks
V tuyn
Truyn v nhn thng qua anten
C hng
Chm nh hng (focused beam)
i hi s canh chnh hng
V hng
Tn hiu lan truyn theo mi hng
C th c nhn bi nhiu anten
Tm tn s
30MHz n 1GHz
V hng
radio
2GHz n 40GHz
Vi sng (microwave)
nh hng cao
im-im, V tinh
3 x 1011 n 2 x 1014 (Hz)
Hng ngoi
Cc b
Khc phc nhng kh khn v a l khi trin khai h thng
T l bit li trn ng truyn (BER) thay i ty theo h thng c trin khai. V d: BER of satellite ~ 10-10
Tc truyn thng tin t c thay i, t vi Mbps n hng trm Mbps
Phm vi trin khai a dng: LAN (vi km), WAN (hng chc km)
Chi ph trin khai h thng ban u rt cao
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2008
dce
2008, Dr. Dinh Duc Anh Vu 51 Data Communication and Computer Networks
V tuyn: cc bng tn truyn thng
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2008
dce
2008, Dr. Dinh Duc Anh Vu 52 Data Communication and Computer Networks
V tuyn: sng viba mt t Cho parabol (thng bn knh 3m)
Chm sng nh hng theo ng ngm (line of sight)
suy gim t/h
d: khong cch
: bc sng
suy gim t l thun bnh phng khong cch cn
amplifier/repeater mi 10-100km
suy gim thay i theo mi trng (cng tng khi c ma)
ng dng:
Thay th cho cp ng trc trong vin thng khong cch xa (cn t b
amp/repeater, nhng phi nm trn ng thng)
Truyn im - im khong cch ngn
in thoi di ng
Tn s cng cao th tc d liu cng cao
dBL d 24log10
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2008
dce
2008, Dr. Dinh Duc Anh Vu 53 Data Communication and Computer Networks
V tuyn: sng viba mt t
Band (GHz) Bandwidth (MHz) Data rate (Mbps)
2 7 12
6 30 90
11 40 90
18 220 274
Hiu sut sng viba s
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2008
dce
2008, Dr. Dinh Duc Anh Vu 54 Data Communication and Computer Networks
V tuyn: sng v tinh V tinh l trm trung chuyn
V tinh nhn trn mt tn s, khuch i (lp li tn hiu) v pht trn mt tn s khc
Cn qu o a tnh Cao 35.863 km
ng dng Truyn hnh
in thoi ng di
Mng ring (VSAT)
c tnh Thng trong khong tn s 1-10 GHz
< 1 GHz: qu nhiu nhiu t mi trng t nhin
>10 GHz: hp th bi tng kh quyn
Cp tn s thu/pht
(3.7-4.2 downlink, 5.925-6.425 uplink) 4/6 GHz band
(11.7-12.2 downlink, 14-14.5 uplink) 12/14 GHz band
Tn s cao hn i hi tn hiu phi mnh khng b suy gim
Tr 240-300ms, ng ch trong vin thng
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2008
dce
2008, Dr. Dinh Duc Anh Vu 55 Data Communication and Computer Networks
V tuyn: v tinh
Satellite
Footprint
Earth
Earth ground
station
Up
link down
link
point-to-point
Satellite
Hub station
point-to-multipoint
Up
link
down
link
down
link
VSAT VSAT
VSAT : very small aperture terminal
Eq
uato
rial O
rbit
22,3
00 m
iles
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2008
dce
2008, Dr. Dinh Duc Anh Vu 56 Data Communication and Computer Networks
V tuyn: sng radio
V hng, 30MHz 1GHz Antena khng cn c hnh a v khng cn chnh hng
Sng FM, truyn hnh UHF v VHF
t b suy gim do ma, xuyn qua kh quyn
Truyn theo ng ngm (line of sight)
B nh hng bi nhiu a knh (multipath) Phn x
Radio towerRadio tower
Ionosphere
TroposphereRefracted
wave
Reflected
wave
Direct wave
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2008
dce
2008, Dr. Dinh Duc Anh Vu 57 Data Communication and Computer Networks
V tuyn: sng hng ngoi
Truyn theo ng thng (hoc phn x)
Cn bi cc bc tng
B iu khin TV t xa, cng iu khin bng
hng ngoi (IRD port)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 58 Data Communication and Computer Networks
Mi trng truyn dn
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2008
dce
2008, Dr. Dinh Duc Anh Vu 59 Data Communication and Computer Networks
Lan truyn khng dy
Lan truyn sng mt t (ground wave)
Tn hiu i theo b mt cong ca tri t
Do to ra dng in b mt tri t
Do s nhiu x khi qua cc chng ngi vt
Tn s ln n 2MHz
AM radio
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2008
dce
2008, Dr. Dinh Duc Anh Vu 60 Data Communication and Computer Networks
Lan truyn khng dy
Sng khng gian (sky wave)
Radio nghip d, BBC world, VoA
Tn hiu b tng in ly phn x li mt t
(thc t l b khc x)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 61 Data Communication and Computer Networks
Lan truyn khng dy
Truyn theo ng ngm
Tn s trn 30Mhz
C th truyn xa hn ng ngm nh sng v b
hiu ng khc x
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 62 Data Communication and Computer Networks
Truyn theo ng ngm
Khong cch max ca ng ngm
h: chiu cao ca anten
k: hng s hiu chnh khc x ca sng (k=4/3)
V d: thp anten cao 100m c th truyn n mt
im trn mt t cch xa 41km
Khong cch max gia 2 anten
h1, h2:chiu cao cc anten
khd 57.3
)21(57.3 khkhd
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 63 Data Communication and Computer Networks
Truyn theo ng ngm
Suy gim tn hiu trong khng gian (free
space loss)
Tn hiu b phn tn theo khong cch
i vi cng 1 anten, suy gim cng nhiu i vi
tn s thp (bc sng di)
dBdfLc
fd56.147)log(20)log(20log10
24
2424c
fdd
r
t
P
P
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 64 Data Communication and Computer Networks
Truyn theo ng ngm
Hp th ca kh quyn Hi nc v oxy hp th sng v tuyn
Hi nc nh hng ln nht ti 22GHz, t hn i vi tn s
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 65 Data Communication and Computer Networks
Multipath
-
2008
dce
Bi tp
3.14, 15, 16, 17, 19, 20, 21
4.2, 7, 13, 16
2008, Dr. Dinh Duc Anh Vu 66 Data Communication and Computer Networks
-
BKTP.HCM
2008
dce
Chng 3
K thut m ha tn hiu
D liu s, tn hiu s
D liu s, tn hiu tng t
D liu tng t, tn hiu s
D liu tng t, tn hiu tng t
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 2Data Communication and Computer Networks
Tn hiu analog
Ba c im chnh ca tn hiu analog bao gm Bin (Amplitute)
Tn s (Frequency)
Pha (Phase)
Bin ca tn hiu analog o mnh ca tn hiu, n v: decibel
(dB) hay volts
Bin cng ln, tn hiu cng c cng mnh
Tn hiu ting ni - t hello
Ting ni (speech) l mt tn hiu rt phc tp
Ting ni cha hng ngn t hp khc nhau ca nhiu tn hiu
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 3Data Communication and Computer Networks
Tn s ca tn hiu analog
Tc thay i ca tn hiu
trong mt giy, n v Hz
hay s chu k trong mt
giy (cycles per second)
T/h 30Hz thay i 30 ln trong
mt giy
Mt chu k l s di chuyn
sng ca tn hiu t im
ngun bt u cho n khi
quay tr v li im ngun
.
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 4Data Communication and Computer Networks
Pha ca tn hiu analog
Tc thay i quan h ca tn hiu i vi thi gian, c m t theo (degree)
S dch pha xy ra khi chu k ca tn hiu cha kt thc, v mt chu k mi ca tn hiu bt u trc khi chu k trc cha hon tt Tai ngi khng cm nhn
c s dch pha
T/h mang d liu b nh hng bi s dch pha
V d cc mi ni khng hon ho s gy ra dch pha
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 5Data Communication and Computer Networks
Tn hiu digital
Tn hiu s bao gm ch hai trng thi, c din t
vi hai trng thi ON hay OFF hoc l 0 hay 1
Tn hiu s yu cu kh nng bng thng ln hn tn
hiu analog.
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 6Data Communication and Computer Networks
Tn hiu digital
Cc vn khi s dng knh thoi (voice channel) trong vic truyn tn hiu s
Mt tn hiu s l mt t hp ca cc tn hiu khc. c bit, tn
hiu s c th c biu din nh sau
Signal = f + f3 + f5 +f7 +f9 +f11 +f13 ....f
Do mt tn hiu s gm 1 tn s c bn (f), cng thm tn s 3f
(hi tn bc 3), cng thm tn s 5f (hi tn bc 5),
Nu bin ca tn s f, f3, f5, l a, a3, a5, th a = 3a3 = 5a5
gi tn hiu s qua knh truyn thoi, bng thng ca knh
truyn phi cho php tn s c bn f, tn s 3f v tn s 5f i qua
m khng nh hng nhiu n cc tn s ny
y l yu cu ti thiu bn nhn nhn ng c tn hiu s
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 7Data Communication and Computer Networks
Tn hiu digital
Truyn 1 tn hiu s nh phn tc 2400bps trn knh thoi c bng thng 3.1kHz Tn s c bn: 1200Hz (thng thng bng tc bit)
Ch c tn s c bn i qua m khng b thay i
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 8Data Communication and Computer Networks
D liu, tn hiu v truyn dn Analog data/Analog Signal
Gi bnh thng hoc m ha vo phn ph khc
Analog data/Digital Signal M ha dng b codec to ra chui bit s
Digital Data/Analog Signal c m ha dng modem to ra t/h tng t
Digital Data/Digital Signal Biu din trc tip d liu hoc m ha to ra t/h s c
c tnh mong mun
Analog Signal/Analog Transmission Lan truyn thng qua cc b khuch i, x l t/h nh
nhau bt k d liu l s hoc tng t
Analog Signal/Digital Transmission Gi s t/h biu din d liu s, lan truyn qua cc b
repeater
Digital Signal/Analog Transmission Khng dng
Digital Signal/Digital Transmission T/h l chui nh phn lan truyn qua cc b repeater
Analog and digital
transmission
Analog
data
Analog
signal
Digital
signal
Digital
data
Analog
signal
Digital
signal
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 9Data Communication and Computer Networks
D liu s, tn hiu sAnalog and digital
transmission
Analog
data
Analog
signal
Digital
signal
Digital
data
Analog
signal
Digital
signal
Tn hiu s Xung in p ri rc, khng lin tc
Mi xung l mt phn t tn hiu
D liu nh phn c m ha thnh cc phn t tn hiu
-
2008
dce
Thut ng
2008, Dr. Dinh Duc Anh Vu 10Data Communication and Computer Networks
Baseband signal
Carrier signal
Bandpass
Lowpass
Highpass
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 11Data Communication and Computer Networks
Thut ng
Unipolar Tt c cc phn t t/h c cng du
Polar Mt trng thi logic c biu din bng mc in p dng, trng
thi logic khc c biu din bng mc in p m
Tc d liu Tc truyn dn d liu theo bps (bit per second)
rng (chiu di 1 bit) Thi gian thit b pht dng truyn 1 bit
Tc iu ch (tc tn hiu) Tc mc t/h thay i
n v l baud = s phn t t/h trong 1 giy
Mark v Space Tng ng vi 1 v 0 nh phn
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 12Data Communication and Computer Networks
Din gii tn hiu
Cn bit
nh thi ca cc bit (khi no chng bt u v
kt thc)
Mc tn hiu tng ng vi bit 0, 1
Yu t nh hng n vic din gii t/h
T s SNR: cng ln th BER cng gim
Tc d liu (bps): cng tng th BER cng tng
Bng thng: cng ln th tc d liu cng tng
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 13Data Communication and Computer Networks
Nonreturn to Zero (NRZ) Nonreturn to Zero-Level (NRZ-L)
2 mc in p khc nhau cho bit 1 v bit 0
Thng thng, in p m dng cho bit 1 v in p dng dng cho bit 0
in p khng thay i trong thi khong bit Khng c transition (no return to 0V level)
NRZ: bit 0 khng c in p; bit 1 in p dng
Nonreturn to Zero Inverted (NRZI) NRZI cho cc bit 1
Xung in p hng s sut thi khong bit
D liu c m cn c vo vic c hay khng s thay i t/h u thi khong bit
Thay i t/h (LH hoc HL) m ha nh phn 1
Khng c thay i t/h m ha nh phn 0
Mt v d cho m ha sai phn (differential encoding)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 14Data Communication and Computer Networks
Nonreturn to Zero (NRZ)
M ha sai phn D liu c biu din bng s thay i mc t/h (thay v
bng mc t/h)
Nhn bit s thay i d dng hn so vi nhn bit mc
Trong cc h thng truyn dn phc tp, cm gic cc tnh d dng b mt
u v nhc im ca m ha NRZ u
D dng nm bt
Bng thng dng hiu qu
Nhc C thnh phn mt chiu
Thiu kh nng ng b
Dng trong vic ghi bng t, USB, CD
t dng trong vic truyn t/h
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 15Data Communication and Computer Networks
Multilevel Binary
Dng nhiu hn 2 mc tn hiu
Bipolar-AMI (Alternate Mark Inversion) 0 c biu din bng khng c t/h
1 c biu din bng xung dng hay xung m
Cc xung 1 thay i cc tnh xen k
Khng mt ng b khi d liu l mt dy 1 di (dy 0 vn b vn ng b)
Khng c thnh phn mt chiu
Bng thng thp
Pht hin li d dng
Pseudoternary 1 c biu din bng khng c t/h
0 c biu din bng xung dng m xen k nhau
Khng c u im v nhc im so vi bipolar-AMI
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 16Data Communication and Computer Networks
Multilevel Binary
Trade Off
Khng hiu qu bng NRZ
Mi phn t t/h ch biu din 1 bit
H thng 3 mc c th biu din log23 = 1.58 bit
B thu phi c kh nng phn bit 3 mc (+A, -A, 0)
Cn thm khong 3dB cng sut t c cng xc
sut bit li ca binary code
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 17Data Communication and Computer Networks
Biphase: Manchester
Manchester Thay i gia thi khong bit
Thay i c dng nh t/h ng b (clock) v d liu
LH biu din 1
HL biu din 0
Dng trong IEEE 802.3 (ethernet), RFID
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 18Data Communication and Computer Networks
Biphase: Differential Manchester
Differential Manchester Thay i gia thi khong bit ch dng cho ng b
Thay i u thi khong biu din 0
Khng c thay i u thi khong biu din 1
Dng trong IEEE 802.5 (token ring)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 19Data Communication and Computer Networks
Biphase
u v nhc im Nhc
Ti thiu c 1 thay i trong thi khong 1 bit v c th c 2
Tc iu ch ti a bng 2 ln NRZ
Cn bng thng rng hn
u ng b da vo s thay i gia
thi khong bit (self clocking)
Khng c thnh phn mt chiu
Pht hin li Khi thiu s thay i mong i
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 20Data Communication and Computer Networks
Bi tp
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 21Data Communication and Computer Networks
Scrambling
Dng k thut scrambling thay th cc chui to ra hng s in p
Chui thay th Phi to ra s thay i t/h, dng cho vic ng b ha
Phi c nhn din bi b thu v thay th tr li chui ban u
Cng di nh chui ban u
Khng c thnh phn mt chiu
Khng to ra chui di cc t/h mc 0
Khng gim tc d liu
C kh nng pht hin li
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 22Data Communication and Computer Networks
B8ZS v HDB3
B8ZS (Bipolar With 8 Zeros Substitution) Da trn bipolar-AMI
Nu c 8 s 0 v xung in p cui cng trc l dng, m thnh 000+0+
Nu c 8 s 0 v xung in p cui cng trc l m, m thnh 000+0+
Gy ra 2 vi phm m AMI
C th lm ln vi tc ng gy ra bi nhiu
B thu pht hin v din gii chng nh 8 s 0
HDB3 (High Density Bipolar 3 Zeros) Da trn bipolar-AMI
Chui 4 s 0 c thay th bng chui c 1 hoc 2 xung theo quy tc:
Nu s bit 1 k t ln thay th cui cng l l: 0000 -> 000V
Nu s bit 1 k t ln thay th cui cng l chn: 0000 -> B00V
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 23Data Communication and Computer Networks
B8ZS v HDB3
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 24Data Communication and Computer Networks
Bi tp
-
2008
dce
Mua bus 1 thc hnh
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 26Data Communication and Computer Networks
D liu s, tn hiu tng t
ng dng Dng truyn d liu s trn
mng in thoi cng cng 300Hz 3400Hz
Thit b MODEM (MOdulator-DEMulator)
K thut iu bin: Amplitude-Shift Keying
(ASK)
iu tn: Frequency-Shift Keying (FSK)
iu pha: Phase-Shift Keying (PSK)
Digital Analog
FSK PSKASK
QAM
Analog and digital
transmission
Analog
data
Analog
signal
Digital
signal
Digital
data
Analog
signal
Digital
signal
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 27Data Communication and Computer Networks
iu bin (ASK)
Dng 2 bin khc nhau ca sng mang biu din 0 v 1 (thng thng mt bin bng 0)
S dng mt tn s sng mang duy nht
Phng php ny ch ph hp trong truyn s liu tc thp (~1200bps trn knh truyn thoi)
Tn s ca tn hiu mang c dng ph thuc vo chun giao tip ang c s dng
K thut c dng trong cp quang LED: sng, khng sng
ILD: 2 mc sng khc nhau
00
1)2cos()(
binary
binarytfAts
cc
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 28Data Communication and Computer Networks
iu bin (ASK)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 29Data Communication and Computer Networks
iu tn (FSK)
S dng hai tn s sng mang: tn s f1 tng ng mc 1,
tn s f2 tng ng mc 0.
t li hn so vi ASK
c s dng truyn d liu tc 1200bps hay thp hn
trn mng in thoi
C th dng tn s cao (3-30MHz) truyn trn sng radio
hoc cp ng trc
0)2cos(
1)2cos()(
2
1
binarytfA
binarytfAts
c
c
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 30Data Communication and Computer Networks
iu tn (FSK)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 31Data Communication and Computer Networks
iu pha (PSK)
S dng mt tn s sng mang v thay i pha ca sng mang ny
PSK sai phn (differential PSK) thay i pha tng i so vi sng trc (thay v so vi sng tham chiu c nh)
Cho php m ha nhiu bit trn mi thay i tn hiu sng mang (Phase
Amplitude Modulation)
Phng php ny thng c dng trong truyn d liu tc
2400bps (2 bits per phase change - CCITT V.26) hoc 4800bps (3 bits
encoding per phase change - CCITT V.27) hoc 9600bps (4 bits encoding
per phase/amplitude change)
Tng qut cho m ha NRZ-L
0)2cos(
1)2cos()(
binarytfA
binarytfAts
c
c
elements signaldifferent ofnumber :L
element signalper bits ofnumber :
(bps) rate data :R
(bauds) rate modulation :D
Llog
RRD
2 ll
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 32Data Communication and Computer Networks
iu pha (PSK)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 33Data Communication and Computer Networks
iu pha (PSK)
Quadrature PSK (QPSK)
Multilevel PSK H thng 64 v 256 trng thi
Ci thin tc d liu vi bng thng khng i
Tng kh nng tim n li
11)2702cos(
10)1802cos(
01)902cos(
00)02cos(
)(
tfA
tfA
tfA
tfA
ts
c
c
c
c
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 34Data Communication and Computer Networks
Hiu sut
Bng thng
Bng thng ASK v PSK lin quan trc tip vi tc bit
BT = (1+r)R
Bng thng FSK c quan h vi tc d liu i vi cc
tn s thp, c quan h vi sai lch ca cc tn s iu
ch i vi tn s cao
BT = 2F + (1+r)R
Tn hiu nhiu mc
BT = (1+r)R/l = (1+r)R/log2M
Trong trng hp c li, tc li ca PSK v
QPSK cao hn khong 3dB so vi ASK v FSK
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 35Data Communication and Computer Networks
Quadrature Amplitude Modulation (QAM)
QAM c dng trong ADSL v mt s h thng wireless
Kt hp gia ASK v PSK
M rng logic ca QPSK
Gi ng thi 2 tn hiu khc nhau cng tn s mang Dng 2 bn sao ca sng mang, mt ci c dch i 90
Mi sng mang c iu ch ASK
2 tn hiu c lp trn cng mi trng
Gii iu ch v kt hp cho d liu nh phn ban u
-
2008
dce
Quadrature Amplitude Modulation (QAM)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 37Data Communication and Computer Networks
D liu tng t, tn hiu s ng dng
Dng truyn d liu tng t trn mng truyn d liu s
Tn dng cc u im ca truyn dn s (thit b r, dng repeater, TDM, )
S ha D liu s c th truyn dng NRZ-L hay cc
loi m khc
Thit b CODEC (COder-DECoder)
K thut iu ch xung m: Pulse Code Modulation
(PCM)
iu ch Delta: Delta Modulation (DM)
Analog Digital
DMPCM
Analog and digital
transmission
Analog
data
Analog
signal
Digital
signal
Digital
data
Analog
signal
Digital
signal
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 38Data Communication and Computer Networks
iu ch xung m (PCM) L thuyt ly mu
Nu tn hiu f(t) c ly mu u vi tc ly mu cao
hn ti thiu 2 ln tn s cao nht ca tn hiu, th cc
mu thu c cha thng tin ca tn hiu ban u. T/h
f(t) c th c ti to, dng b lc thng thp
Cng thc Nyquist: N >= 2f
N: tc ly mu
f: tn s ca tn hiu c ly mu
D liu ting ni
Gii hn tn s
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 39Data Communication and Computer Networks
iu ch xung m (PCM)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 40Data Communication and Computer Networks
iu ch xung m (PCM)
PAM (Pulse Amplitude Modulation) Cc xung c ly mu tn s R=2B
Lng t ha cc xung PAM Xc nh gi tr ca im c ly mu, ri vo khong no th ly gi tr
khong
Ty thuc vo cc mc lng t 2n (n l s bit cn thit s ha 1 xung)
M ha d liu Thc hin cc thao tc m ha thng tin trc khi truyn i
Nhiu lng t (quantizing noise) SNR = 6.02n + 1.76 (dB)
Mi bit dng thm cho lng t ha s tng SNR 6dB
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 41Data Communication and Computer Networks
iu ch xung m (PCM)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 42Data Communication and Computer Networks
Non-Linear encoding
Mc lng t khng u
Gim mo tn hiu
Companding (compressing-expanding)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 43Data Communication and Computer Networks
Companding
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 44Data Communication and Computer Networks
iu ch Delta (DM)
Tn hiu tng t c xp x bi hm cu thang
(staircase)
Hnh vi nh phn
i ln hay xung 1 mc () ti mi thi khong ly mu
Hiu sut
ti to ting ni tt
PCM - 128 mc (7 bit)
Bng thng thoi 4khz
Cn 8000 x 7 = 56kbps i vi PCM
K thut nn d liu c th lm gim tc bit
V d: k thut m xen khung (interframe coding) cho video lm
gim tc bit t 92Mbps xung 15Mbps
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 45Data Communication and Computer Networks
iu ch Delta (DM)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 46Data Communication and Computer Networks
D liu tng t, tn hiu tng t ng dng
Dng iu ch d liu tng t: thay i tn s truyn (tn s cao hn truyn dn tt hn)
Dng cho FDM
K thut iu ch bin: Amplitude
Modulation (AM)
iu ch gc (Angle Modulation) iu ch tn s: Frequency
Modulation (FM)
iu ch pha: Phase Modulation (PM)
Analog Analog
AngleAM
PMFM
Analog and digital
transmission
Analog
data
Analog
signal
Digital
signal
Digital
data
Analog
signal
Digital
signal
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 47Data Communication and Computer Networks
iu ch bin (AM)
Bin ca sng mang c thay i bi bin ca tn hiu c truyn is(t) = [1+nax(t)]cos(2fct)
To ra t/h 2 bn (DSBTC), trong ch cn c mt bn
na1 t/h bao ct trc thi gian (thng tin b mt)
Pt = Pc(1+na2/2)
Pt v Pc cng sut t/h c truyn i v t/h sng mang
na ch s iu ch, t s bin t/h c truyn v sng mang
Single sideband (SSB) v double sideband suppress carier (DSBSC)
u im D hin thc (iu ch v gii iu ch)
D bin i tn hiu sang cc gii bng tn khc nhau
Khuyt im D b nh hng ca nhiu
Khng s dng hiu qu nng lng
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 48Data Communication and Computer Networks
iu ch bin (AM)
M(f)
fB
M(f)
ffc B fc + Bfc
Upper sideband
Lower sideband
Discrete carrierterm
-
2008
dce
iu ch bin (AM)
-
2008
dce
iu ch bin (AM)
na < 1 (V trong Matlab)
-
2008
dce
iu ch bin (AM)
na > 1
-
2008
dce
iu ch bin (AM)
na < 1 (V trong Matlab
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 53Data Communication and Computer Networks
iu ch gc
s(t) = Accos[2fct + (t)]
Phng php iu tn s (FM) o hm ca pha (t) t l thun vi tn hiu c truyn i
(t) = nfm(t)
u im Kh b nh hng ca nhiu
S dng hiu qu nng lng
Khuyt im Tn hiu c iu ch yu cu bng thng rng hn nhiu tn hiu
truyn i ban u (d liu)
Hin thc mch iu ch v gii iu ch phc tp hn so vi phng php iu bin
)('2
1)( tftf ci
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 54Data Communication and Computer Networks
iu ch gc
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 55Data Communication and Computer Networks
iu ch gc
Phng php iu ch pha (PM) (t) = npm(t)
Tn hiu truyn i khng nh hng n thnh phn bin v tn s m ch lm thay i pha ca sng mang
Ph tn s ca tn hiu c iu ch theo phng php iu pha tng t nh phng php iu tn phng php iu pha cng c cc c im tng t phng php iu tn
Tuy nhin, c hai l do phng php iu pha c d chp nhn hn
i vi bn nhn: tn s ca tn hiu nhn c l c nh, ch c pha thay i nn ch cn thit k b lc tn s ch cho mt tn s duy nht thay v nhiu tn s nh trong phng php iu tn gim chi ph thit k v hin thc mch
Trong trng hp tn hiu iu ch ch nhn mt s gi tr (nh tn hiu s), mch iu ch v gii iu ch hin thc theo phng php iu pha c n gin rt nhiu
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 56Data Communication and Computer Networks
Hiu sut
Bng thng
AM
BT = 2B
FM&PM
BT = 2(+1)B
FM&PM cn bng thng ln hn so vi AM
FMB
An
B
F
PMAn
mf
mp
2
-
2008
dce
Bi tp
5.4, 5, 6, 10, 12, 15, 16, 20, 23, 24, 25, 26
2008, Dr. Dinh Duc Anh Vu 57Data Communication and Computer Networks
-
BKTP.HCM
2008
dce
Chng 4
Cc k thut truyn d liu s
Truyn bt ng b v truyn ng b
Cc loi li
Pht hin li
Sa li
Cu hnh ng truyn
Giao tip
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2008
dce
2008, Dr. Dinh Duc Anh Vu 2Data Communication and Computer Networks
Truyn d liu song song
Mi bit dng mt ng truyn ring, truyn ng thi.
Cc ng truyn khc
Clock signal: thng bo cho bn nhn bit khi no c d liu
GND: so snh in p
Direction: hng ca ng truyn
Hand-shaking: tn hiu bt tay (sn sng nhn)
VD: ISA, ATA, PCI
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 3Data Communication and Computer Networks
Truyn d liu tun t
Tt c cc bit u c truyn trn cng mt ng truyn
Khng cn cc ng truyn ring cho tn hiu ng b v tn hiu bt tay(cc tn hiu ny c m ha vo d liu truyn i)
Vn nh thi (timing) i hi phi c c ch ng b gia bn truyn v bn nhn
VD: RS232, SPI, I2C
2 cch gii quyt
Bt ng b: mi k t c ng b bi start v stop bit
ng b: mi khi k t c ng b dng c
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 4Data Communication and Computer Networks
Truyn bt ng b
D liu c truyn theo tng k t trnh vic mt ng b khi nhn c chui bit qu di 5 8 bits
Ch cn gi ng b trong mt k t
Ti ng b cho mi k t mi
Hnh vi i vi dng d liu u, khong cch gia cc k t l ng nht (bng
chiu di ca phn t stop)
trng thi rnh, b thu pht hin s chuyn 1 0
Ly mu 7 khong k tip (chiu di k t)
i vic chuyn 1 0 cho k t k tip
Hiu sut n gin
R
Ph tn 2 hoc 3 bit cho mt k t (~20%)
Thch hp cho d liu vi khong trng gia cc k t ln (d liu nhp t bn phm)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 5Data Communication and Computer Networks
Truyn bt ng b
LSB
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 6Data Communication and Computer Networks
Truyn ng b
Truyn khng cn start/stop
Phi c tn hiu ng b
ng b bit (bit synchronization) Tch hp xung clock vo d liu truyn i
Tch hp thng tin ng b (clock) vo trong d liu truyn
u nhn s tch thng tin ng b da vo d liu nhn c
Manchester, differential Manchester, tn s sng mang (analog)
S dng ng clock ring Dng mt ng tn hiu ng b ring bit
Mt bn (pht hoc nhn) to ra cc xung clock ng b vi cc bit truyn i trn ng clock ring
Bn cn li dng tn hiu trn ng clock ring lm clock
Thch hp khi truyn trong khong cch ngn
Tn hiu ng b d b suy gim trn ng truyn
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 7Data Communication and Computer Networks
Truyn ng b
ng b frame
Mi block d liu c bt u bng mt c gi l preamble, kt
thc bng mt c gi l postamble
Preamble v postamble l mt mu bit (bit pattern) c quy nh
sn
Mt chui cc k t SYN (16h trong bng m ASCII)
Mu bit 11111110
Frame: d liu + preamble + postamble + thng tin iu khin
Hiu qu hn so vi truyn bt ng b (ph tn thp hn cho cc
bit iu khin)
HDLC: 48 bit iu khin cho mi block 1000 k t (8000 bit)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 8Data Communication and Computer Networks
Cc loi li xy ra trn ng truyn Mi trng truyn dn b nhiu (in, t, ) d liu nhn c li (cc bit
b thay i)
2 cch khc phc khi pht hin c li Forward error control: thng tin sa sai c thm vo cc k t hoc cc
frame truyn i, bn nhn c th pht hin khi no c li v li nm u sa (c kh nng sa li)
Feedback (backward) error control: thng tin sa sai c thm vo cc k t hoc cc frame truyn i ch pht hin khi no c li (khng c kh nng sa li). C ch yu cu truyn li k t/frame sai c dng trong trng hp ny
Phn loi li Li 1 bit
Ch 1 bit b li, khng nh hng cc bit xung quanh
Thng xy ra do nhiu trng
Li chm (busrt error) Mt chui lin tc B bit trong bit u, bit cui v cc bit bt k nm gia chui
u b li
Thng xy ra do nhiu xung
nh hng cng ln i vi tc truyn cao
Bit error rate (BER): xc sut mt bit nhn c b li
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 9Data Communication and Computer Networks
C ch pht hin li
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 10Data Communication and Computer Networks
Pht hin li bng bit parity
1 bit parity c thm vo 1 khi d liu cn truyn i
Bit parity Parity chn: tng s bit 1
c trong khi d liu, k c bit parity, l s chn
Parity l: tng s bit 1 c trong khi d liu, k c bit parity, l s l
D a t aD a t a ( ASCII ) B0 B1 B2 B3 B4 B5 B6
Parity bit( odd )
h 0 0 0 1 0 1 1 0e 0 1 0 1 0 1 1 1
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2008
dce
2008, Dr. Dinh Duc Anh Vu 11Data Communication and Computer Networks
Parity
c im
Ch d c li sai mt
s l bit, khng d c
li sai mt s chn bit
Khng sa c li
t c dng trong truyn
d liu i xa, c bit
tc cao
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 12Data Communication and Computer Networks
Block Sum Check
Block Sum Check (BSC): s dng parity hng v ct
Khng sa c sai, ch sa c sai khi s bit sai trong d
liu l mt
D tm c tt c cc li sai mt s l bit v hu ht cc li
sai mt s chn bit.
Khng d c li sai mt s chn bit xy ra ng thi trn
c hng v ct.
D a t a Start D a t a Parity
(even)
Stop
B 1 B 2 B 3 B 4 B 5 B 6 B 7
H 1 0 0 0 1 0 0 1 0 0
E 1 1 0 1 0 0 0 1 0 0
L 1 0 0 1 1 0 0 1 1 0
L 1 0 0 1 1 0 0 1 1 0
O 1 1 1 1 1 0 0 1 1 0
BCC
(odd)
1 1 0 1 1 1 1 0 0 0
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2008
dce
2008, Dr. Dinh Duc Anh Vu 13Data Communication and Computer Networks
Cyclic Redundancy Check (CRC)
Nguyn l k-bit message
Bn pht to ra chui n bit FCS (Frame Check Sequence) sao cho frame gi i (n+k bit) chia ht cho 1 s xc nh trc
Bn thu chia frame nhn c cho cng 1 s v nu khng c phn d th c kh nng khng c li
S hc modulo 2 Exlusive-or
1010
0101-
1111
1 1 0 0 1
x 1 1
1 1 0 0 1
1 1 0 0 1
1 0 1 0 1 1
1010
0101+
1111
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2008
dce
2008, Dr. Dinh Duc Anh Vu 14Data Communication and Computer Networks
CRC dng s hc
Xc nh FCS T: frame c truyn (k+n bit)
D: message, d liu cn truyn (k bit u ca T)
F: FCS (n bit sau ca T)
P: s chia c xc nh trc (n+1 bit)
Gi s
Suy ra nu ly th T chia ht P
Kim tra li?
P
RQ
P
Dn2
FDn2 T
R F
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 15Data Communication and Computer Networks
CRC dng s hc
V d:
D = 1010001101 (10 bit)
P = 110101 (6 bit)
F =? (? bit)
n = 6-1 = 5 bit, k = 10 bit, n+k = 15 bit
p s: F = 01110
D liu T = 101000110101110
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2008
dce
2008, Dr. Dinh Duc Anh Vu 16Data Communication and Computer Networks
CRC dng s hc
S chia P Di hn 1 bit so vi FCS mong mun
c chn ty thuc vo loi li mong mun pht hin
Yu cu ti thiu: msb v lsb phi l 1
Biu din li Li = nghch o bit (i.e. xor ca bit vi 1)
Tr = T + E T: frame c truyn
Tr: frame nhn c
E: error pattern vi 1 ti nhng v tr li xy ra
Nu c li xy ra (E 0) th b thu khng pht hin ra li khi v ch khi Tr chia ht cho P, ngha l E chia ht cho P kh c kh nng xy ra
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 17Data Communication and Computer Networks
CRC dng a thc
Cch khc xc nh FCS: a thcD=110011 D(x) = x5+x4+x+1
P=11001 P(x) = x4+x3+1
V d D liu cn truyn: 1001001 (k = 7 bits) a thc biu din:
D(x) = x6 + x3 + 1
Cho a thc sinh: P(x) =x3 + 1 (n = 3 bits)
D liu D dch tri n bits:
xn D(x) = X9 + X6 + X3
FCS = 001
D liu T c truyn: 1001001001
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 18Data Communication and Computer Networks
Cyclic Redundancy Check
Cc li c pht hin Tt c cc li bit n
Tt c cc li kp nu P(x) c t nht 3 ton hng
Mt s l li bt k nu P(x) cha 1 tha s (x+1)
Bt k li chm no m chiu di ca chm nh hn hoc bng chiu di FCS
Hu ht cc li chm ln hn
CRC l mt trong nhng phng php thng dng v hiu qu nht pht hin li
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 19Data Communication and Computer Networks
Cyclic Redundancy Check
4 a thc sinh c s dng rng ri CRC-12 = X12 + X11 + X3 + X2 + X + 1
12-bit FCS
Dng truyn chui cc k t c di 6-bit
CRC-16 = X16 + X15 + X2 + 1 16-bit FCS
Dng truyn chui cc k t c di 8-bit
USA
CRC-CCITT = X16 + X12 + X5 +1 Europe
CRC-32 = X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 + X8
+ X7 + X5 + X4 + X2 + X + 1 32-bit FCS
Point-point synchronous transmission, DVB-T
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 20Data Communication and Computer Networks
CRC dng mch sD=1010001101P=110101
1010001101
x2
1
x4
x5
C4
C3
+
C2
C1
C0
+
+
C4* C3 C2* C1 C0* Input
Initial 0 0 0 0 0 1
Step 1 1 0 1 0 1 0
Step 2 1 1 1 1 1 1
Step 3 1 1 1 1 0 0
Step 4 0 1 0 0 1 0
Step 5 1 0 0 1 0 0
Step 6 1 0 0 0 1 1
Step 7 0 0 0 1 0 1
Step 8 1 0 0 0 1 0
Step 9 1 0 1 1 1 1
Step 10 0 1 1 1 0
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2008
dce
2008, Dr. Dinh Duc Anh Vu 21Data Communication and Computer Networks
Sa li
Cch sa li thng thng l yu cu truyn li khi
d liu b li
Khng thch hp cho cc ng dng trao i d liu
khng dy
Xc sut li cao, dn n vic phi truyn li nhiu
Thi gian tr truyn ln hn nhiu thi gian truyn 1 khi
d liu
C ch truyn li l truyn li khi d liu b li v nhiu
khi d liu khc tip theo
Cn thit sa li da vo cc d liu nhn c
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 22Data Communication and Computer Networks
C ch sa li
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 23Data Communication and Computer Networks
C ch sa li
Thm mt s m d tha vo d liu truyn i
B thu c kh nng suy lun ra d liu gc ban u
khi c li xy ra
V d: m sa li block
Tng qut l thm n bit vo sau k bit d liu cn truyn
To thnh block d liu (n+k) bit (codeword)
Trong t m c cha k bit d liu gc
Mt s k thut FEC chuyn k bit d liu gc thnh n (n>k)
bit t m trong khng xut hin k bit d liu gc
Lm gim tc d liu hiu dng
Code rate: k/(n+k)
-
2008
dce
C ch sa li
VD:
Data block/Codeword
00: 00000
01: 00111
10: 11001
11: 11110
D liu nhn c 00100 -> ? Sa sai c?
(Khong cch Hamming)
D liu khng sa sai c?
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 25Data Communication and Computer Networks
Giao tip
Giao tip Thit b x l d liu (DTE) thng khng c cc phng tin pht d liu, v
ch pht cc t/h s n gin nh NRZ-L
Cn mt thit b giao tip (DCE) v d: modem, NIC,
DCE pht cc bit d liu trn mi trng truyn dn
DCE trao i d liu v thng tin iu khin vi DTE c thc hin thng qua mch trao i
Cn mt chun giao tip r rng
c tnh C kh
Kt ni vt l, cc u kt ni
in in p, nh thi thay i cc mc in th, m ha,
Chc nng ngha ca mi chn kt ni
D liu, iu khin, nh thi, GND,
Th tc Chui cc s kin xy ra khi truyn d liu
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 26Data Communication and Computer Networks
Giao tip
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 27Data Communication and Computer Networks
Chun V.24/EIA-232-F Chun giao tip c s dng rng ri, quy nh bi
ITU-T
ITU-T ch c t chc nng v th tc V.24 tham kho cc chun khc cho cc c tnh c kh v
c tnh in
EIA-232-F (USA) RS-232
c tnh c kh: ISO 2110
c tnh in: v.28
Chc nng: v.24
Th tc: v.24
Dng kt ni DCE vi modem s dng trn ng dy in thoi
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 28Data Communication and Computer Networks
c tnh c kh
DB-25 female
(DTE)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 29Data Communication and Computer Networks
c tnh in
Dng tn hiu s
Cc gi tr c hiu l d liu hoc iu khin ty thuc vo mch
NRZ-L >+3V 0
+3V on
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2008
dce
2008, Dr. Dinh Duc Anh Vu 30Data Communication and Computer Networks
c tnh chc nngV.24 EIA-232 Name Direction to Function
Data signals
103 BA Transmitted data DCE Transmitted by DTE
104 BB Received data DTE Received by DTE
Control signals
105 CA Request to send DCE DTE wishes to transmit
106 CB Clear to send DTE DCE is ready to receive, response to RTS
107 CC DCE ready DTE DCE is ready to operate
108.2 CD DTE ready DCE DTE is ready to operate
125 CE Ring indicator DTE DCE is receiving a ringing signal on the
channel line
109 CF Received line signal detector DTE DCE is receiving a signal within
appropriate limits on the channel line
Timing signals
113 DA Transmitter sig. elm. timing DCE Clocking signal
114 DB Transmitter sig. elm. timing DTE Clocking signal;
115 DD Receiver sig. elm. timing DTE Clocking signal for circuit 104
Ground
102 AB Signal ground/common return Common ground reference for all circuits
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2008
dce
2008, Dr. Dinh Duc Anh Vu 31Data Communication and Computer Networks
Local/Remote loopback testing
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 32Data Communication and Computer Networks
Th tc
V d modem ring bt ng b, kt ni 2 thit b khong cch ngn
Ch cn mt s tn hiu Signal ground (102)
Transmitted data (103)
Received data (104)
Request to send (105)
Clear to send (106)
DCE ready (107)
Received line signal detector (109)
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2008
dce
2008, Dr. Dinh Duc Anh Vu 33Data Communication and Computer Networks
Modem ring bt ng b
DCE ready
Request to send
Clear to send
D liu
Received line
signal detector
D liu
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 35Data Communication and Computer Networks
Khong cch di
Hai modem ni vi nhau qua mng in thoi
Cn thm 2 tn hiu
DTE ready (108.2)
Ring indicator (125)
Tng t nh vic s dng in thoi
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 36Data Communication and Computer Networks
Hot ng quay s (1)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 37Data Communication and Computer Networks
Hot ng quay s (2)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 38Data Communication and Computer Networks
Hot ng quay s (3)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 39Data Communication and Computer Networks
Null modem
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 41Data Communication and Computer Networks
ISDN interface
Chun EIA-232-F cn qu nhiu chn trong giao tip
Chun X.21 a ra chun giao tip 15 chn -> 8 chn -> ISDN
ISDN (Intergrated Services Digital Network): thay th mng li in thoi v truyn t/h tng t bng h thng truyn t/h s
Giao tip gia TE (terminal equipment tng t DTE) v NT (network-terminating equipment)
ISO 8877 giao tip thng qua 8 chn
Transmit/receive truyn d liu ln iu khin
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 42Data Communication and Computer Networks
ISDN interface
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 43Data Communication and Computer Networks
ISDN interface
Tn hiu c truyn trn cp xon
Balanced transmission
Gi tr nh phn ph thuc vo s sai khc mc
in th gia 2 dy dn
t nhiu: nhiu nh nhau trn 2 dy
M ha ph thuc tc d liu
Basic rate (192 kb/s): pseudotenary (750mV)
Primary rate
1.544 Mb/s: B8ZS
2.048 Mb/s: HDB3
-
BKTP.HCM
2008
dce
Chng 5
iu khin lp lin kt d liu
iu khin dng d liu
iu khin li
Giao thc iu khin lin kt d liu cp
cao HDLC
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 2Data Communication and Computer Networks
Vn khi trao i d liu Mt s vn khi hai thit b kt ni trc tip truyn
nhn d liu
ng b khung
D liu c gi di dng cc frame
Thi im bt u v kt thc mt frame
iu khin tc truyn d liu
X l li gp phi trn ng truyn
nh v a ch trong cu hnh multipoint
Phn bit d liu v thng tin iu khin
D liu v thng tin iu khin truyn chung
Qun l kt ni
Thit lp, duy tr, ngt kt ni
Lp vt l khng th thc hin cc chc nng trn
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 3Data Communication and Computer Networks
iu khin dng d liu
Bn nhn thng c b m nhn d liu
Khi d liu n, bn nhn thng thc hin mt s x l trc khi gi ln lp cao hn
iu khin dng nhm m bo bn pht khng gi d liu qu nhanh
Ngn nga vic trn b m
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 4Data Communication and Computer Networks
M hnh truyn khung
Dng phn tch qu trnh truyn nhn d liu thnh tng khung (frame)
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 5Data Communication and Computer Networks
Khi nim
Thi gian truyn (tframe): thi gian cn thit gi tt c cc bit ca frame d liu ln ng truyn
Thi gian lan truyn (tprop): thi gian cn thit d liu i t ngun n ch
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 6Data Communication and Computer Networks
iu kin gi nh
Tt c frame u n ch, khng b mt
Khng c frame li
Cc frame n ng th t
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 7Data Communication and Computer Networks
Idle RQ (StopandWait) C ch hot ng
Ngun pht d liu (di dng cc frame)
ch nhn d liu v tr li bng ACK (acknowledgement)
Ngun phi i ACK trc khi pht tip d liu
ch c th dng qu trnh bng cch khng gi ACK
c im
Phng php n gin nht
c dng ch yu trong cc ng dng character-oriented.(byte-oriented)
S dng knh truyn hot ng trong ch half-duplex
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 8Data Communication and Computer Networks
Thi gian tng cng TD= n(2tprop + tframe)
Hiu sut ng truyn
Idle RQ Hiu sut
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 9Data Communication and Computer Networks
Vn kch thc frame
Phng php Stop-and-wait s dng ng truyn hiu qu nu kch thc (chiu di) frame ln
Nhng thc t d liu ln c chia thnh cc frame c kch thc nh
Kch thc b m c gii hn
Frame kch thc nh kh xy ra li
Li c pht hin sm
Khi c li, ch cn truyn li frame nh
Ngn nga tnh trng 1 trm lm vic chim ng truyn lu
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2008
dce
2008, Dr. Dinh Duc Anh Vu 10Data Communication and Computer Networks
Sliding windows
Cho php nhiu frame c th truyn ng thi
Bn thu c b m vi kch thc W frame (c th nhn W frame)
Bn pht c th truyn ti a W frame m khng cn i ACK
Cc frame c nh s th t
ACK c cha s th t ca frame k tip c th truyn
S th t thng c gii hn bi k bit trong frame
nh s quay vng modulo 2k
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2008
dce
2008, Dr. Dinh Duc Anh Vu 11Data Communication and Computer Networks
Sliding windows
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 12Data Communication and Computer Networks
Sliding windows V d
-
2008
dce
2008, Dr. Dinh Duc Anh Vu 13Data Communication and Computer Networks
Sliding windows Ci tin
ch c th gi ACK khng cho php Ngun gi tip d liu (Receive Not Ready)
Trong trng hp ny, sau