Dk Thiet Bi Qua Mang Internet 8989

8/2/2019 Dk Thiet Bi Qua Mang Internet 8989

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M C L C LU N VN T T NGHI P


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CH NG 1. GI I THI U

1.1. Gi i thi u

i u khi n t xa v ang l m t xu h ng pht tri n mang tnh quy lu t. S

pht tri n nhanh chng c a khoa h c k thu t ni chung v ngnh i n t -vi n thng

ni ring l n n t ng cho xu h ng ny. V s ti n l i c a n, i u khi n t xa c

th c s d ng b t k n i no. Ng i s d ng c th b t k u trn th gi i

cng c th i u khi n c nh ng b ph n ngo i vi nh, cng s hay m t n i

no c nh s n.Lc ny khng cn gi i h n v kho ng cch n a.

Trong k thu t i u khi n t xa, mi tr ng truy n d n c th l dy d n i n

hay khng kh v i tn hi u truy n c th l tn hi u i n h ng ngo i hay sng v

tuy n.... c bi t, k thu t h ng ngo i hay v tuy n c khai thc tri t trong

vi c ch t o cc thi t b u xa. Tuy nhin k thu t i u khi n dng tia h ng ngo i

v v tuy n b h n ch v kho ng cch v bng thng. kh c ph c nh c i m

trn c th s dng ph ng php khc l i u khi n t xa qua m ng ethernet, Internet ho c LAN. t ng c a n l s d ng m ng c s n truy n tn hi u i u khi n,

nh m v n kho ng cch c kh c ph c.

Nh ta bi t, ngy nay m ng l i Internet-Ethernet pht tri n v ph bi n

kh p n i trn th gi i. C th xem s bng n c a Internet ngy nay cng gi ng nh

s bng n c a tivi vo nh ng nm 40-50 c a th k tr c. Chnh i u ny cng lm

cho Internet ng tr trong m i ngc ngch c a cu c s ng, v do vi c i u khi n t

xa qua m ng tr nn d dng, thu n ti n h n v l m t nhu c u t t y u c a cu c

s ng hi n i ngy nay.

i u khi n t xa qua m ng c 2 u i m n i b c:

Th nh t chng ta c th s d ng m ng Internet c s n.


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Th hai c th s d ng nhi u n i v c nhi u ng d ng m con ng i

khng th ti p c n m t cch tr c ti p c.

Cc thi t b i u khi n t xa qua m ng ang t ng b c xm nh p vo trong cc

sinh ho t gia nh do tnh n gi n ti n d ng, tin c y t ng i n nh. B i u

khi n c th lm m t s cng vi c trong gia nh khi ta ang xa nh nh : m my

b m n c, t t b p i n, t t m bng n...

1.2. Ph ng n th c hi n

Thi t k c a ti nh m xy d ng h th ng i u khi n t xa thng qua m ng

internet. M hnh c a h th ng c m t nh hnh sau.

Internet

SwitchIP

tnh

Device1

Device 2

IPtnh

.

.

.

remote

client

Device N

IPtn

h


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Thi t k g m 2 ph n chnh:

Ph n th nh t: l ph n giao ti p ng i dng t i my u xa i u

khi n thi t b . Trong ti, ph n ny c thi t k l m t software s

c ci t trn my tnh u xa (remote host) t o giao di n cho

ng i dng, truy n cc l nh i u khi n qua m ng t i thi t b v nh n

cc khung d li u bo tr ng thi t thi t b n ng i dng. Ph n m m

ny c vi t b ng ngn ng Visual Basic trn mi tr ng h i u hnh

Window, h tr l p trnh m ng v giao di n p. Ph n thi t k software

s c ni k cc ch ng sau. Ph n th hai: l Thi t b giao ti p m ng v i u khi n. giao ti p

c m ng Ethernet. Thi t b c thi t k g m 1 chip Ethernet

controller dng t o khung Ethernet, truy xu t m ng, i u khi n thi t

b giao ti p v i chip v t l giao ti p m ng ( y ta s d ng IC

ENC28J60 c a Microchip h tr chu n IEEE 802.3).


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CH NG 2. L THUY T M NG ETHERNET

2.1. T ng quan v Ethernet

Ngu n g c c a Ethernet c pht tri n t nh ng th nghi m i v i cp ng

tr c c th c hi n t c 3 Mbps v s d ng nghi th c CSMA/CD (carrier sense

multiple access collision detect) cho m ng LAN vo nm 1970 b i t p on Xerox. S

thnh cng c a n ny s m gy s ch v d n n s pht tri n c a

Ethernet 10 Mps b i ba t p on: Digital Equipment, Intel, Xerox.

Thnh ng Ethernet c ngu n g c v i m ng LAN ( Local-Area Network) v vi c

s d ng chu n IEEE 802.3. Chu n ny c bi t v i nghi th c CSMA/CD. C ba t c

c c dng cho m ng Ethernet v i ng truy n l cp ng tr c, cp i

hay s i quang.

10Mbps10 base-T Ethernet.

100Mbps Ethernet t c cao (Fast Ethernet).

1000MbpsGigabit Ethernet.

Ethernet 10-Gigabit pht tri n v c a ra cng chu n IEEE 802.3ae cu i

2001 v u 2002. N cng t ng thch v i chu n IEEE 802.3.

Ethernet c t o ra ph n l n t k thu t m ng LAN (hi n t i ang c s

d ng cho g n 85% cho m ng LAN n i PC v cc my tr m-workstations). B i v

ghi th c c a n c m t s c i m sau:

D dng s d ng, th c hi n, qu n l v b o tr.

Cho php th c hi n m ng t c th p.

Cung c p r t a d ng m hnh m ng (topology).

B o m t thnh cng vi c k t n i chung.


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2.2. M hnh tham chi u OSI

M t hnh OSI (Open Systems Interconnection) l m t m hnh cho php hai h

th ng khc nhau b t k thng tin v i nhau b t ch p c u trc bn d i. M c ch c a

m hnh OSI l m r ng thng tin gi a hai h th ng khc nhau m khng c n thay i

logic ph n c ng v ph n m n bn d i c a m i h th ng. M hnh OSI khng ph i

l m t nghi th c, n ch l m t m hnh hi u v thi t k ki n trc m ng cho linh

ng, v ng ch c v lin thng.

M hnh OSI l c u trc phn l p thi t k cc h th ng m ng cho php thng

tin qua t t c cc lo i h th ng my tnh. N bao g m 7 l p ring bi t nh ng c m i lin quan v i nhau, m i l p nh ngha m t phn o n x l khi chuy n d ch thng tin

qua m ng. Hnh sau m t m hnh 7 l p c a OSI.

Hnh 2-1 m hnh OSI 7 l p

Qu trnh x l t i l p 7, k ti p chuy n t l p ny sang l p khc theo th t .

T i m i l p (ngo i tr l p 7 v l p 1), header c a l p t ng ng s c c ng vo

n v d li u tr c khi chuy n xu ng cho l p d i k ti p. Khi n v d li u

c nh d ng i qua l p v t l, n i thnh tn hi u i n t v v n chuy n d c

theo lin k t v t l.

Khi t n ch, tn hi u i vo l p 1 v c i ng c thnh bit. Cc n v

d li u k ti p c chuy n ln qua cc l p OSI. Khi m i kh i d li u t i l p k


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cao h n, cc u v ui c g n lc tr c s c lo i b t i cc l p t ng ng.

Khi n n l p 7 th thng i p tr thnh d ng thch h p cho ng d ng.

2.2.1. L p v t l (Physical Layer)

Ch c nng l p v t l l truy n m t dng bit trn m t mi tr ng v t l. N lin

quan n cc qui nh v i n v c c a giao ti p v mi tr ng truy n. N cng

nh ngha cc th t c v cc ch c nng m cc thi t b v t l v cc giaor ti p ph i

th c thi.

2.2.2. L p lin k t d li u (Data Link Layer) L p ny c nhi m v chia nh d li u a xu ng t l p m ng thnh cc frame

d li u (m t frame th ng di t vi trm byte n hng ngn byte) truy n i v

t ch c nh n sao cho ng th t cc frame. L p ny cng cung c p kh nng truy n

khng l i trn ng truy n v t l cho cc l p cao h n. V n t ra y l ph i

xc nh c ch xc nh n 1 frame c truy n thnh cng hay khng ? (Acknowledge

frame) v x l nhi u (truy n l i).

L p lin k t d li u lin quan n s truy n, ki m tra l i v i u khi n lu ng

d li u. Ch c nng chnh c a l p lin k t d li u h at ng nh m t l i ch n b o

v cho cc l p cao h n, i u khi n qu trnh truy n v nh n. Ki m tra l i v i u

khi n l p v t l nh l ch c nng chnh m b o cc l p trn nh n d li u t l p

m ng khng c l i. Chu n IEEE 802 chia l p lien k t d li u thnh hai l p con l:

Logical Link Control (LLC) v Media Access Control (MAC).

L p con Logical Link Control (LLC) c nhi m v b o v l p trn t b t c

ph ng php truy c p c th no ho c truy c p ng truy n c th no. Cc l p

trn khng lo l ng v cch k t n i c a chng t i m ng Ethernet b i v LLC i u

khi n giao di n ny.

L p con Media Acess Control (MAC) c nhi m v cho m t vi h at ng. Trn

ng truy n l p con MAC c trch nhi m trong vi c nh n d li u t l p l p con

Logical Link Control v ng cc gi s n sng cho vi c truy n. L p MAC xc nh


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cc knh ng truy n r nh. N u ng truy n r nh MAC s truy n d li u trn

cp v lun gim st tr ng thi c a l p v t l cho vi c bo hi u c xung t. N u c

xung t, MAC cng i u khi n qu trnh thu h i d li u v truy n l i. MAC gi i quy t tranh ch p cho mi tr ng dung chung. N bao g m cc quy nh ng b , c

v ki m sot l i c n thi t truy n thng tin t v tr ny n v tr khc, cng nh

cc a ch v t l c a tr m nh n. Cc nghi th c MAC c dung c th v i t ng

LAN (Ethernet, Token ring, Token bus).

2.2.3. L p m ng (Network Layer)

i u khi n ho t ng c a cc subnet, t c l tm ng cho m t packet i t

ngu n n ch (truy n d li u gi a 2 my b t k trong m ng).

V n l n nh t c a l p ny l tm ng (Routing), gi i quy t xung t

(Collsision Detect), gi i quy t v n a ch (Addressing), v n tnh chi ph

(Accounting).

L p m ng m nh n d li u t l p giao v n v thm cc thng tin ph h p cho

gi v cung c p ng truy n ph h p cng nh nh ng m c ki m tra l i. D li u

c nh d ng cho ph h p v i ng truy n.

2.2.4. L p giao v n (Transport Layer)

Ch c nng c b n c a l p ny l chia nh gi d li u c a t l p bn trn

xu ng thnh nh ng n v nh h n truy n qua m ng v i s m b o l d li u

s t i n i m t cch chnh xc (ki m tra s sepuence, error detection pht hi n l i,

flow control i u khi n lu ng). L p ny cung c p cho cc l p bn trn ph ng ti n

truy n cc message c l p v i cc l p bn d i (end to end hai h th ng th c s

k t n i v i nhau).

L p giao v n m b o s t i u cho vi c truy n d li u t ngu n n ch

b ng cch i u khi n lu ng d li u c a m ng v th c hi n s yu c u m b o

d ch v cho l p phin. L p giao v n xc nh kch c c a gi d a trn s l ng d

li u c g i v kch th t gi l n nh t cho php truy n trn ng truy n. N u d


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li u g i l n h n gi c kch th t t i a, n s th c hi n chia d li u thnh cc thch

th t ph h p m t cch tu n t . N ng th i thm cc thng tin nh i u khi n l i

ph h p v i t l d li u c a m t gi.

Khi nh n d li u t l p m ng, l p giao v n s m b o r ng d li u nh n

c ng th t v ki m tra l p v m t khung.

2.2.5. L p phin (Session Layer)

Cung c p nh ng ph ng ti n cho php 2 th c th c a l p ng d ng c th t

ch c v ng b cu c i tho i v qu n l s trao i thing tin gi a chng (cc d ch

v cc qu trnh c th trao i v i nhau, t o v k t thc k t n i gi a cc qu

trnh trn cc my khc nhau). L p phin lin quan n s giao ti p gi a hai thi t b

vi n thng. L p ny t o ra nh ng qui lu t cho vi c kh i ng v k t thc giao ti p

gi a hai thi t b , cng nh s ph c h i l i. N u c l i v s giao ti p l i c pht

hi n, l p phin s truy n l i d li u hon thnh qu trnh giao ti p. L p phin yu

c u m t s ph c v t t t l p giao v n khng yu c u truy n l i, ho c truy n

hai h ng, yu c u nhi u s gim st (monitoring) v h i ti p (feedback).

2.2.6. L p trnh by (Presentation Layer)

L p ny bi u di n nh ng thng tin c truy n ( c hi u l c php v ng

ngha). N ng nh t cc thng tin gi a cc h th ng v i nhau. L p trnh by gi i

quy t cc v n lin quan n thng d ch d li u v thay i m gi a cc thi t b ,

m chng nh d ng d li u khc nhau. Ngoi ra, l p ny cng i u khi n s thng

d ch s khc nhau gi a cc thi t b v cc t p tin nh d ng (file formats), cng nh cung c p d ch v thao tc trn d li u nh nn v m ha (compression &

cryptography).

2.2.7. L p ng d ng (Application Layer)

a cc ng d ng thi t th c cho ng i s d ng, ng v i m i ng d ng c m t

nghi th c khc nhau. L p ng d ng l l p giao ti p gi a ng i dng v m ng. L p

ny nh h ng tr c ti p n nh ng ch ng trnh ng d ng dnh cho ng i s d ng


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(user application programs) cung c p cch th c truy c p m ng. L p ng d ng

th ng lin quan v i cc ng d ng nh : FTP (truy n nh n file), Telnet (gi i quy t s

khc nhau ph n c ng cng nh ph n li gi a cc terminal), e-mail (truy n nh n mail), file sharing

2.3. S l c v chu n IEEE 802.3

Chu n IEEE 802.3 l m t ph n c a h chu n cho m ng c c b v metropolitan.

M i quan h gi a cc thnh vin c a chu n c trnh by bn d i.

Hnh 2-2 H chu n c a m ng c c b .

Cc chu n ny lin quan n l p v t l v l p data link c nh ngha b i

International Organization Standardization (ISO).

2.4. C u trc khung Ethernet IEEE 802.3

Chu n IEEE 802.3 nh ngha m t khung nh d ng d li u c b n cho t t c

cng vi c m MAC th c hi n. Thm vo , m t vi ch c nng l a ch n c thm

vo cho khung d li u. M t khung d li u g m c 7 tr ng nh hnh v .


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Hnh 2-3 C u trc Frame Ethernet

Ph n u khung Preamble

Preamble ch ra s b t u c a m t khung truy n. N g m m t dy cc gi tr

bit 0 v 1 xen k nhau bo hi u cho tr m nh n (receiving stations) r ng c khung

ang t i. V n cng cung c p m t ph ng ti n ng b ha nh ng ph n khung

nh n c a l p v t l nh n v i m t lu ng bits vo.

Preamble bao g m 7 bytes nh sau:

10101010 - 10101010 - 10101010 - 10101010 - 10101010 - 10101010 - 10101010

Start Frame Delimiter (DFD)

SFD l m t chu i 8 bit (1 byte) 10101011. N theo sau Preamble v ch ra s b t

u c a chu i thng tin v i hai bit cu i l 11. Sau byte ny chnh l a ch .

Destination Address (DA) a ch ch

a ch ch bao g m 6 bytes xc nh n tr m s nh n khung. N ch a a ch

v t l (physical address) c a ch s p n c a gi. a ch v t l c a h th ng l m t

m u bit c m ha trn NIC (Network Interface Card). N u gi ph i i qua m ng

LAN ny n m ng LAN khc n ch c a n, tr ng DA ch a a ch v t l

c a router n i m ng LAN hi n hnh v m ng LAN k . Khi gi t n m ng ch,

tr ng DA ch a i ch v t l c a thi t b ch.


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Trong chu i bits ny, bit pha bn tri c a tr ng DA ch ra a ch n

(individual address) n u l bit 0 ho c a ch nhm (group address) n u l bit 1. Bit th

hai bn tri ch ra DA c qu n l c c b hay qu n l ton c c. Nh ng bit cn l i c gn xc nh n m t tr m n, nhm tr m ho c t t c tr m trn m ng

(network).

Source Address (SA) a ch ngu n

a ch ngu n bao g m 6 bytes ch a a ch v t l c a thi t b cu i cng chuy n

ti p gi. Thi t b c th l tr m ang g i ho c router m i x y ra nh t nh n v

chuy n ti p gi. a ch ngu n th lun lun l a ch n v bit pha tri th lun l bit 0.

Length/type of PDU field

Lengh/type field g m 2 bytes. Ch ra s byte trong PDU (Protocol Data Unit)

ang n. N u chi u di c a PDU l c nh, tr ng ny c dung ch ra lo i ho c

n n c a cc giao th c khc. V d , Novel v Internet dng n lm r nghi th c

m ng ang dung PDU. Data field Tr ng d li u (802.2 frame)

Tr ng d li u g m tu n t n bytes. Chi u di t i thi u v l n nh t c a d

li u l t 46 bytes n 1500 bytes. D li u c g i qua l p m ng v i m t vi thng

tin i u khi n. N u d li u c chi u di t h n 46 byte trong m t gi, m t c ch t

bi t s m t i thi u 46 bytes. PDU c t o ra b i l p ph trn (LLC) r i

lien k t n khung 802.3. Frame Check Sequence (CRC)

Frame Check Sequence bao g m 4 bytes. M t vng ch a 32 bits m ki m tra l i

v pht hi n sai theo m CRC-32 v tnh trn t t c cc tr ng (fields) ngo i tr

Preamble, SFD, FCS.


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2.5. L p con MAC v ph ng th c truy c p CSMA/CD

2.5.1. Media Access Control (MAC)L p con MAC n m l p 2 trong m hnh OSI. C ch c nng l gi i quy t tranh

ch p cho mi tr ng dng chung. N bao g m cc quy nh ng b , ki m sot l i

c n thi t chuy n thng tin t v tr ny n v tr khc, cng nh cc a ch v t l

c a tr m m b o khung d li u c truy n nh n ng tr m.

Hnh 2-4 V tr l p con MAC trong m hnh OSI

MAC Control l 1 l p con (sublayer) ty ch n n m trong l p Data link (trong m

hnh 7 l p c a OSI). N c s d ng chung v i l p con CSMA/CD MAC. MAC

Control cung c p kh nng i u khi n th i gian th c v thao tc ho t ng c a l p

con MAC. L p con MAC Control s d ng cc d ch v khng k t n i (connectionless)

c a l p con MAC pha d i truy n khung i u khi n v khung d li u. MAC

Control khng cung c p b t k c ch no m b o khung truy n khng b m t

mt. Cc c ch m b o truy n khung khng b m t mt, nh truy n l i cc

khung b l i, b h y b , s c MAC Control Client (Logic link control) h tr .

V ho t ng c a MAC Control l ty ch n, nn MAC Control Client khng th nh n

bi t c s t n t i c a th c th MAC Control trong m t tr m.

Ho t ng c a l p con MAC control trong su t i v i CSMA/CD MAC.

m ng Ethernet l p con MAC s d ng ph ng th c truy c p CSMA/CD (Carrier


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Sense multiple access with collision detect) truy c p knh truy n v i 2 ch

truy n l: song cng (full duplex) v bn song cng (half duplex).

2.5.2. Ph ng th c truy c p CSMA/CD

Khi c nhi u ng i s d ng cng truy c p 1 knh truy n dng chung m khng

c quy lu t th s d n n xung t. i u ny s d n n d li u s b sai v tr

thnh nhi u. Do m t m ng LAN c n c m t c ch qu n l l u l ng, t i

thi u ha cc xung t v c c i ha cc khung c phn ph i thnh cng. C ch

truy c p c dng trong m ng Ethernet theo chu n IEEE-802.3 l Carrier Sense

Multiple Access with Collision Detect (CSMD/CD), t m d ch l a truy c p c m

nh n sng mang c pht hi n xung t.

Thi t k ban u l ph ng th c a truy c p (Multiple Access - MA) trong

m i tr m truy c p n m t lin k t l ngang b ng nhau v bnh quy n. V i MA th

khng c qu n l l u l ng, b t c tr m no mu n truy n th s truy n v d a vo

xc nh n ki m tra khung truy n l thnh cng hay khng.

Trong m t h th ng CSMA, b t c tr m no mu n truy n tr c tin ph i l ng

nghe sng mang b ng cch ki m tra i n p. N u khng c i n p trn ng truy n

th ng truy n xem nh l r nh v n c th b t u truy n. CSMA c th gi m

thi u s xung t nh ng t t nhin khng th lo i b chng m t cch hon ton. Xung

t v n x y ra n u m t tr m ch a c m nh n c tn hi u sng mang t m t tr m

khc no trn ng truy n do hi n t ng tr c a truy n sng.

kh c ph c tnh tr ng nh trn c n ph i c b pht hi n xung t Collision Detect CD. Trong CSMA/CD m t tr m mu n pht th ph i ch c ch n l ng

truy n r nh, r i m i truy n d li u. Trong lc truy n d li u, tr m lun ki m tra

xem c i n p cao v t tr i hay khng, n u c t c l c xung t x y ra. N u pht

hi n c xung t, tr m s ng ng truy n v i m t l ng th i gian ng u nhin n u

ng truy n r nh n s th c hi n truy n l i.


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2.5.3. Ch bn song cng (Half Duplex Ethernet)

Half Duplex Ethernet l m hnh truy n th ng c a Ethernet s d ng giao th c

CSMA/CD (Carrier Sense Multiple Access/Collision Detect). V i CSMA/CD hay

nhi u h n cc tr m chia s m t ng truy n chung. truy n m t frame, m t

tr m ph i ch cho m t kho ng th i gian r nh trn ng truy n khi khng c m t

tr m khc ang truy n. Sau n truy n frame b ng cch thng bo (broadcast) n

trn ng truy n m n nghe t t c cc tr m trn m ng. N u m t tr m khc c

g ng truy n truy n d li u t i cng m t th i i m, m t ng xu t hi n.

Tr m truy n sau c truy n m t Jam b o m t t c cc tr m c thng bo frame truy n b l i v m t ng . Tr m sau gi cho m t kho ng th i gian

ng u nhin tr c khi n l c truy n l i. Ti n trnh c l p l i cho n khi frame

truy n thnh cng.

Cc nguyn t c c b n cho vi c truy n m t frame:

M ng c quan st b i m t carrier, ho c s hi n di n c a m t tr m

truy n. Ti n trnh ny th c bi t nh carrier sense.

N u m t carrier tch c c c pht hi n, sau ng truy n c tr hon.

Tr m ti p t c quan st m ng cho n khi carrier ng ng.

N u m t carrier khng c pht hi n, v kho ng khng c carrier th b ng

ho c l n h n kh ang th i gian chung gi a hai khung d li u (interframe

gap), sau tr m l p t c b t u truy n l i frame.

Trong khi tr m ang truy n frame, n quan st ng truy n c ng hay

khng.

N u m t ng c pht hi n, tr m truy n ng ng g i khung d li u

(frame data) v g i m t chu i jame 32 bits. N u ng c pht hi n r t

s m trong lc truy n frame, th tr m truy n s hon thnh vi c truy n

preamble c a frame tr c khi b t u truy n chu i jame. Chu i jame c

pht i m b o chi u di c a ng thng bo t i cc tr m

khc.


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Sau khi g i chu i jame, tr m truy n ch m t kho ng th i gian ng u nhin

c ch n t b pht random number tr c khi b t u ti n trnh truy n l i.

Ti n trnh ny g i l backoff. C th m t ng c l p l i b gi m i do tr m ang ng ch m t kho ng th i gian ng u nhin tr c khi

truy n l i.

N u ng xu t hi n l i, th vi c truy n c l p l i, nh ng th i gian tr

hon ng u nhin c tng v i m i n l c truy n l i. i u ny lm gi m

kh nng ng c a tr m khc.

Ti n trnh ny l p l i n khi m t tr m truy n m t frame khng c ng . Ngay khi m t tr m thnh cng truy n m t frame, n s reset l i collision

counter n s d ng tng th i gian backoff sau m i l n ng l p l i.

Slot Time

Slot time l m t thng s cho m ng ho t ng half duplex Ethernet. N c

xc nh l 512 bits time cho m ng Ethernet ho t ng t i 10 v 100 Mb/s, v 4096 bit

time cho Gigabit Ethernet. m cho m i n i truy n tin c y trong vi c pht hi n

ng , th i gian truy n nh nh t cho m t frame ph i t nh t l m t slot time, v

th i gian yu c u cho ng truy n n t t c cc tr m trn m ng ph i nh

h n m t slot time. V th , m t tr m khng th hon thnh truy n frame tr c khi pht

hi n r ng m t ng xu t hi n.

Cc tn hi u truy n b i cc kho ng tr hon ng cc tr m Ethernet khi

chng truy n su t trn m ng. Cc kho ng truy n bao g m th i gian yu c u cho tn

hi u truy n qua cc ph n cp, v th i gian tr hon ng logic khi cc tn hi u

chuy n qua cc thnh ph n i n trong Network Interface Cards (NICs) v cc hub. i

v i cc ph n cp di h n v nhi u hub trn tr m, n cho tn hi u truy n t m t m ng

cu i n m ng khc. Th i gian m t tn hi u truy n gi a hai tr m c kho ng cch xa

nh t trong m ng c bi t nh l propagation delay l n nh t c a m ng.

M t tr m pht hi n r ng frame m n ang truy n b t g p m t ng , cc

tn hi u c a n ph i truy n qua m ng n tr m khc pht hi n cc ng . Tr m


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ny ph i truy n m t chu i jame ch m t ng c pht hi n. Chu i jame

ny ph i truy n qua l i m ng tr c khi c pht hi n b i tr m ang truy n. T ng

m t vng truy n t i a (round trip propagation delay) v th i gian yu c u truy n m t chu i jame l cc thnh ph n xc nh chi u di c a Ethernet slot time.

Slot time l m t thng s quan tr ng v:

512 bits slot time thi t l p kch c nh nh t c a m t Ethernet frame l 64

bytes. (4096 bits slot time cho Gigabit Ethernet yu c u m t vng m r ng

c thm vo frame kch c truy n nh nh t l 512 bytes). B t k

frame c chi u di t h n 64 bytes th c xem nh l m t collision fragment hay runt frame, v t ng c b ra b i tr m nh n.

Slot time thi t l p m t gi i h n kch c c a m t m ng trong gi i h n ph n

chi u di cp t i a v s l n l p l i c th trn ng d n. N u kch c

c a m ng qu l n, m t hi n t ng c bi t nh late collisions c th

xu t hi n. ng tr c xem nh m t l i trong m ng b i v ng

n qu tr trong vi c truy n frame t ng i x b i ch c nng

i u khi n truy c p ng truy n Ethernet. Frame ang c truy n s

b b , yu c u m t ph n m m ng d ng pht hi n m t v b t u

truy n l i.

Slot time m b o n u c m t ng s p xu t hi n, n s c pht

hi n trong 512 bits u tin (4096 cho Gigabit Ethernet) c a frame truy n.

M t ph n c ng Ethernet n gi n gi frame truy n l i sau m t ng .

i v i Gigabit Ethernet, slot time ph i c tng t 512 n 4096 bits time. V

Gigabit Ethernet c t c data cao h n, tn hi u truy n ch cho m t kho ng cch r t

nh trong ph m vi 512 bits time. T i t c m t slot time 512 bits s c h tr

m t m ng kch c t i a kho ng 20 mt. M t m ng nh l khng th c t , v th

ch p nh n c a vi c m r ng m t sng mang c gi i thi u tng slot time n 4096

bits. Vi c tng kch c c a slot time v vi c gi i h n s l n l p l i trong m t m ng,

kch c m t m ng 200 mt c th c h tr b i Gigabit Ethernet.


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Backoff

Backoff l qu trnh x l m t tr m ang truy n tnh ton ch bao lu sau m t

ng tr c khi n l c truy n l i frame. N u t t c cc tr m ch cng kho ng

th i gian tr c khi truy n l i, sau ng khc s ch c ch n xu t hi n. i u

ny c trnh b ng cch m i tr m pht m t s ng u nhin tn kho ng th i gian

n ph i ch tr c khi ki m tra sng mang. Kho ng th i gian ny c bi t nh l

backoff delay c a tr m.

Thu t backoff th c hi n trong Ethernet l truncated binary exponential backoff.

Sau m t ng , m i tr m pht m t s ng u nhin n m trong t m ch r c a gi tr . Sau n ch s slot time tr c khi n l c truy n l i. T m gi tr tng theo s m

sau m i l n truy n l i b h ng. N l c l n u c t m l 0 n 1, l n th hai l 0

n 3, l n ba l 0 n 7 v c th ti p t c. N u ng l p l i, th t m ti p t c m

r ng n 10 n l c khi n i t 0 n 1023. Sau t m c a gi tr n m gi a t 0

n 1023. N u m t tr m khng thnh cng trong vi c truy n sau 16 l n n l c, th

MAC thng bo excessive collision error. Frame c truy n l i sau b b i, ta

c n ph n m m ng d ng pht hi n m t frame v b t u m t s truy n l i.

Cc k t qu binary exponential backoff trong kho ng tr hon nh nh t tr c khi

truy n l i khi l u l ng trn LAN l th p. Khi l u l ng cao, ng l p l i l

nguyn nhn lm t m tng ln, v th lm gi m c h i ng sau . Trong m t

m ng, n i m l u l ng c m c cao, ng l p l i s b t u gy ra l i qu

ng (excessive collision error) c pht i. L i qu ng ch ra r ng l u

l ng t i tng n i m m n khng th c kh nng c gi trn m t m ng Ethernet n l .

Capture Effect

Khi m ng ang ho t ng d i m t t i l n, thu t ton binary exponential

backoff c th trnh by m t s khng cng b ng c bi t nh capture effect. V n

n y sinh t vi c n m gi c a collision counter. M i tr m s c p nh t b m

ng m t cch c l p c a n v ch sau m t n l c truy n l i. Ch c thnh cng


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b m ng tr v zero sau khi pht m t gi thnh cng. i u ny cho thu n l i

m t tr m n b t cho php n capture m ng c m t kho ng th i gian m r ng.

M t v d c a hi u ng b t g m hai tr m c nhi u data g i v c th g i

data nhanh nh c cho php. C hai ng v i n l c truy n l i u tin v

ch n backoff l 0 ho c 1. Tr m A ch n 0, v tr m B ch n 1. Tr m A truy n l i trong

lc tr m B ch m t slot time. Sau khi tr m A hon thnh vi c truy n c a n v h t

kho ng interframe gap, c hai tr m s n sng truy n l i v ng xu t hi n. y l

ng u tin c a tr m A i v i frame ny, v th n ch n m t backoff l 0 ho c

1. Tuy nhin, y l ng l n th hai c a tr m B cho frame ny, v th n ch n

m t backoff gi a 0 v 3. V v y tr m A c kh nng truy n cao h n trong lc tr m B

ch l i. N u i u ny x y ra th l y s gi ng nh v y v l i ng , cho nn l y

cc s l cho tr m B (l y s ch n th x u h n).

M t k ch b n gi ng nh v y c th l p i l p l i ch c th k t thc khi hng

c a tr m A l n l c cu i cng ho c khi tr m cu i cng tr m B ti n t i n l c th

16. Sau 16 l n n l c tr m B s reset l i b m ng c a n cho php n tr l i

c nh tranh nhi u h n. Nh ng n cng b ra frame n n l c truy n l i, yu c u n

x p hng frame cho vi c truy n l i b ng ph n m m.

Vo nm 1994 m t thu t ton backoff m i c g i l binary logarithm

arbitration method (BLAM) c a ra lm gi m v n hi u ng b t. M t

nhm lm vi c IEEE 802.3w c t o ra thm BLAM nh m t c i m khng

b t bu c cho chu n Ethernet. M c d k t qu m ph ng ch ng minh r ng BLAM

a ra m t c i ti n xc nh trn thu t ton binary exponential backoff, cng vi c k t h p n vo trong chu n Ethernet khng bao gi c hon thnh v m t thay i

(d ch) trong r nt full duplex Ethernet v thi u s ch c p nh t ph n c ng half

duplex.

2.5.4. Ch song cng Ethernet (Full Duplex)

Tiu chu n IEEE 802.3x xc nh m t mode th hai c a ho t ng Ethernet,

c g i l full duplex, b qua nghi th c CSMA/CD. Nghi th c CSMA/CD l


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half duplex. i u ny ch r r ng m t tr m c th truy n data hay nh n data,

nh ng khng cng m t lc. Mode full duplex cho php hai tr m ng th i chuy n

data trn m t lin k t i m i m cung c p ng truy n v nh n c l p. T m i tr m c th truy n v nh n data cng m t lc, thng l ng c a lin k t c

g p i ln. M t tr m 10 Mb/s ho t ng mode full duplex cung c p bng thng

t i a 20 Mb/s. M t tr m 100 Mb/s cung c p bng thng 200 Mb/s.

Ho t ng full duplex b gi i h n n chu n sau:

ng truy n v t l ph i l cp h tr truy n v nh n ng th i m

khng nhi u. Cc ph ng ti n truy n ch r g p yu c u ny l: 10-Base- T, 10Base-FL, 100Base-TX, 100Base-FX, 100Base-T2, 1000Base-CX,

1000Base-SX, 1000Base-LS, v 1000Base-T. Ph ng ti n truy n khng

th h tr full duplex: 10Base5, 10Base2, 10Base-FP, 10Base-FB v

100Base-T4.

Ho t ng full duplex b gi i h n lin k t i m--i m n i chnh xc

hai tr m. T khng c s c nh tr nh cho vi c chia s ng truy n,

ng khng c th xu t hi n v nghi th c CSMA/CD l khng c n

thi t. Frame c th c truy n, gi i h n ch b i yu c u kho ng cch

gi a nh nh t gi a cc frame lin ti p.

C hai tr m trn ln k t ph i c kh nng v c u hnh cho ho t ng full

duplex.

Ho t ng full duplex c m t vi thu n l i:

Thng l ng l g p i cho php truy n v nh n ng th i.

Hi u su t c a lin k t tng b i s lo i b kh nng ng .

Cc phn o n chi u di th khng gi i h n h n b i s yu c u half

duplex Ethernet m b o ng c truy n n t t c cc tr m

trong kho ng yu c u 512 bits time. V d , 100Base-FX c gi i h n


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ph n chi u di 412 mt trong mode half duplex, nh ng c th h tr

ph n chi u di 2km trong mode full duplex.

mode full duplex , chu n Ethernet thm vo ho t ng i u khi n lu ng

(flow control) l PAUSE frame. PAUSE frame cho php m t tr m cu i t m th i

ng ng l u thng t n i khc n tr m.

2.6. Giao th c TCP/IP

2.6.1. Gi i thi u t ng quan

M hnh TCP/IP ch c 4 l p. M hnh tham chi u c a TCP/IP khng tr c ti p

gi ng m hnh c a OSI. M c d m i m hnh m ng u c chung m t m c ch l

truy n thng d dng gi a cc m ng, gi a cc lo i my tnh ch y trn n n h

i u hnh khc nhau. Nh ng m i m hnh m ng u c c i m ring v cch th c

thi cng cht t khc nhau. M hnh OSI do ISO t o ra trong m t th i gian di, n c

dng lm m hnh chu n cho cc m hnh khc. Cn TCP/IP ra i do yu c u c p

thi t c a chnh ph M tr c tnh hnh lc b y gi , do s pht tri n c a TCP/IP

khng b n ng b i nh ng yu c u ch t ch nh OSI.

Do c tnh c a OSI l m t m hnh tham kh o nn vi c p d ng OSI vo th c

t l kh c th th c hi n (hi u su t km v d li u khi truy n trong m ng ph i qua

t t c cc l p c a m hnh OSI). Do , OSI ch l m t tiu chu n cc nh nghin

c u d a vo pht tri n cc m hnh khc t i u h n. C r t nhi u m hnh khc

nhau c pht minh, tuy nhin hi n nay trn th gi i cng v i s pht tri n nh

v bo c a Internet th m hnh TCP/IP l c s d ng ph bi n nh t.

B giao th c TCP/IP l r t quan tr ng trong vi c l a ch n cch th c truy n

thng nh m h n ch l i v tng hi u qu . TCP/IP c cc c i m n i b c sau:

c l p v i c u hnh m ng: TCP/IP c th dung cho m ng bus, start,

ring, cho m ng c c b , m ng di n r ng hay cc lin m ng.


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c l p v i ph n c ng v t l c a m ng: TCP/IP c th dung cho

Ethernet, token-ring hay b t c lo i ph n c ng no.

L m t chu n giao th c m : TCP/IP c th th c hi n trn nhi u h i u

hnh (Operating System OS) khc nhau, nn n thch h p dung cho cc

m ng h n t p cc lo i ph n c ng v ph n m m nh Internet.

nh a ch m t cch t ng qut: m i tr m trn m ng TCP/IP c m t a

ch IP duy nh t c dng lin l c v i b t k tr m no khc trn

m ng.

H tr c l c m ng theo m hnh Client Server.

Cc protocol chu n l p ng d ng: TCP/IP khng nh ng cung c p cho l p

trnh vin ph ng php truy n d li u gi a cc ng d ng m cn

cung c p c s c a nhi u giao th c l p ng d ng.

2.6.2. Ki n trc c a TCP/IP

Pht tri n t m hnh tham chi u OSI, TCP/IP c phn lm 4 l p:

L p truy xu t m ng (Network Access layer).

L p lin m ng (Internet Layer).

L p giao v n (Transport layer).

L p ng d ng (Application layer).

Vi c phn l p ny m b o m t s nguyn t c sau: M t l p c t o ra khi c n n m c tr u t ng ha t ng ng.

M i l p c n th c hi n cc ch c nng c nh ngha r rng.

Vi c ch n ch c nng cho m i l p c n ch t i vi c nh ngha cc quy

t c chu n ha qu c t .

Ranh gi i cc m c c n ch n sao cho thng tin i qua l t nh t ( tham s

cho ch ng trnh con l t).


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S m c ph i l n cc ch c nng tch bi t khng n m trong cng

m t l p v nh m hnh khng qu ph c t p.

M t m c c th c phn thnh cc l p nh c n thi t.

Cc m c con c th l i b lo i b .

Hai h th ng khc nhau c th truy n thng v i nhau n u chng b o

m nh ng nguyn t c chung (ci t cng m t giao th c truy n thng).

Cc ch c nng c t ch c thnh m t t p cc l p ng m c cung c p

ch c nng nh nhau. Cc l p ng m c ph i s d ng giao th c chung.

M t l p khng nh ngha m t giao th c n, n nh ngha m t ch c nng

truy n thng c th thi hnh b i m t s giao th c. Do v y, m i l p c th ch a

nhi u giao th c, m i giao th c cung c p m t d ch v ph h p cho ch c nng c a l p.

M i l p ph i c chu n ha giao ti p v i l p t ng ng v i n. Trn l

thuy t, giao th c ch lin quan t i l p c a n m khng quan tm t i l p trn ho c

d i c a n. Tuy nhin ph i c s ng lm sao chuy n d li u gi a cc l p

trn m t my tnh, b i m i l p l i lin quan t i vi c g i d li u t ng d ng ny t i m t ng d ng t ng ng trn m t my khc. L p cao h n d a vo l p th p h n

chuy n d li u qua m ng pha d i. D li u chuy n xu ng ngn x p t l p ny

xu ng l p th p h n cho t i khi c truy n qua m ng nh giao th c c a l p v t l.

T i n i nh n, d li u i ln ngn x p t i ng d ng nh n. Nh ng l p ring l khng

c n bi t cc l p trn v d i n x l ra sao, n ch c n bi t cch chuy n thng tin

t i l p m thi. S c l p cc hm truy n thng trn cc l p khc nhau gi m thi u

s tch h p cng ngh c a u vo m i b giao th c. Cc ng d ng m i c th thm

vo m khng c n thay i l p v t l c a m ng, ph n c ng c th c b sung m

khng c n vi t l i cc ph n m n ng d ng.

Cc l p ki n trc m hnh TCP/IP v cc nghi th c t ng ng nh sau:

OSI TCP/IP TCP/IP Protocol Stack


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Applicationlayer Process/Application

layer

FTP, SMTP, TELNET,

SNMPPresentationlayer

Session layer

Transport layer Transport layer TCP or UDP

Network layer Internet layer IP, ARP, RARP, ICMP

DataLink layer Network Accesslayer

Network interface cardTransmission mediaPhysical layer

T ng quan hai m hnh OSI model v TCP/IP model

TCP (Transmission Control Protocol): m t nghi th c c c u n i (connection-

oriented) cung c p kh nng truy n dng d li u khng l i, hai chi u song cng (full

duplex) cho cc qu trnh c a ng i s d ng.

UDP (User Datagram Protocol): m t khi th c khng thi t l p c u n i

(connectionless) cho cc qu trnh c a user. Do , n khng d m b o d li u khi

truy n c n n i chnh xc hay khng.

ICMP (Internet Control Message Protocol): nghi th c s l l i v i u khi n

thng tin gi a cc gateway v cc host.

IP (Internet Protocol): y l protocol cung c p d ch v phn ph i cc packet cho

TCP, UDP v ICMP.

ARP (Adress Resolution Protocol): protocol nh x m t a ch Internet vo trong

m t a ch ph n c ng.

RARP (Reverse Address Resolution Protocol): nh x m t a ch ph n c ng

thnh m t a ch Internet.

2.6.3. L p truy xu t m ng (Network Access Layer)

TCP/IP khng nh ngha l p ny m dung chung v i cc chu n khc t n t i

nh IEEE, X25(RS232, Ethernet, X21/X21 bis, X35). B n ch t c a l p ny l


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vi c qui nh cc i l ng tn hi u, cc ph ng cch giao ti p truy n cc dng

bit trn knh truy n.

Khng gi ng nh ng giao th c c a l p cao h n l s d ng d ch v c a l p d i

n v cung c p d ch v cho l p trn, giao th c c a t ng m ng c n ph i bi t chi ti t

c a m ng v t l pha d i (c u trc c a gi, a ch ...) nh d ng ng thng tin

s c truy n tun theo nh ng rng bu c c a m ng. L p m ng c a TCP/IP ch a

ch c nng c a t t c 2 l p th p nh t c a m hnh tham chi u OSI (l p lin k t d

li u v l p v t l). L p m ng th ng khng c ng i dng t i v thi t k

c a TCP/IP che d u nh ng ch c nng c a l p th p nh t ny v nh ng i u c n bi t

cho ng i s d ng cng nh ng i l p trnh ch l nh ng giao th c c a cc l p cao

h n (IP, TCP, UDP...). M i khi c cng ngh ph n c ng m i xu t hi n, nh ng giao

th c c a l p m ng ph i c pht tri n TCP/IP c th s d ng ph n c ng m i

(thng th ng chnh l cc trnh i u khi n c a chnh nh cung c p ph n c ng

). Cc ch c nng trnh di n trong l p ny bao g m ng gi gi thng tin IP thnh

cc Frame c truy n d n trn m ng v chuy n a ch IP thnh a ch v t l s

d ng b i m ng my tnh. M t s cc i m m nh c a TCP/IP l a ch c a n c ph i h p sao cho trn m ng Internet khng c m t thi t b m ng no cng a ch . a

ch ny ph i c chuy n i thch h p v i a ch m ng v t l n i m d li u c

truy n i.

Hai v d RFCs m t giao th c s d ng cho l p m ng l:

RFC 826, giao th c chuy n i a ch chuy n i a ch IP thnh a ch

Ethernet.

RFC 894, m t chu n cho vi c truy n gi tin IP qua m ng Ethernet m t

cch th c ng gi chuy n thng tin qua m ng Ethernet.

Khi ci t trong UNIX, giao th c c a l p ny c xem nh s ph i h p c a

ch ng trnh i u khi n thi t b v cc ch ng trnh lin quan. Nh ng n v

t ng ng v i nh ng thi t b m ng lm nhi m v ng gi d li u v chuy n giao

cho m ng.


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2.6.4. L p lin m ng (Internet Layer)

L p ny nh ngha n v d li u truy n v nh tuy n cho cc n v d

li u . IP l m t protocol quan tr ng nh t c a b TCP/IP v t t c cc protocol trong

b TCP/IP u ph i dng n n v t t c d li u ph i l u chuy n qua n.

2.6.4.1. Gi tin IP (Internet Protocol)

IP l m t nghi th c khng k t n i (connectionless protocol), t c l khng thi t

l p m t giao ti p tr c ti p (end-to-end) tr c khi truy n d li u. IP khng m b o

phn pht chnh xc d li u n ch, cc gi d li u c th n ch khng ng th

t , c th b sao chp hay th t l c (do IP ph i k t h p v i TCP). n v d li u

c a IP l datagram c ch a a ch IP c a ngu n v ch. IP c nhi m v tm ng

cho datagram nn c th phn m nh hay h p nh t cc datagram thch h p v i kch

th c packet l n nh t cho php trn ng truy n.

nh d ng IP datagram header (32 bits header):

Version Header length Type of service Total length of datagramIdentification Flags Fragment

offsetTime to live Protocol Header checksum

Source addressDestination address

Option:Strick source routeLoose source route

Record routeTime stamp

SecurityData (max 65535 bytes)

IP datagram header

Destination Address4 bytes

Source Address4 bytes

Type Field2 byte

IP data46 1500 bytes

CRC4 bytes

Hnh 2-5 M t ng gi IP ln khung Ethernet


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Verision (VER) 4bits: nh s phin b n c a IP, phin b n hi n hnh l 4 (IPv4)

v i gi tr nh phn l 0100.

Header length (HLEN) 4bits: nh ngha chi u di c a IP header ch ra b i s

c a 4 bytes. Dung 4bits t c gi tr t i a l 15 t ng ng 60bytes.

Service type (1 bytes): nh ngha cch m datagram c qu n l. N bao g m

cc bits nh ngha th t u tin c a datagram. N cng ch a cc bit lm r lo i d ch

v pha g i mong mu n tin c y, tr

Total length (2 bytes): nh ngha chi u di t ng th c a m t datagram. T i a

l 65535 bytes.

Identification: c dung v i cc phn o n. M t datagram khi i qua cc

m ng khc nhau c th c chia thnh cc o n ph h p v i kch th c khung

c a m ng. khi x y ra hi n t ng ny th m i o n c nh danh v i m t s th t

trong tr ng ny.

Flags: cc bits trong c c quan h v i phn o n. V d datagram c th ho c

khng c phn o n, c th o n u, o n gi a ho c o n cu i

Fragmentation offset: y l m t con tr ch ra l ch c a d li u trong

datagram g c (n u c phn o n).

Time to live: nh ngha s b c nh y t i a m t datagram c th i qua tr c

khi b drop (lo i b ). My ch ngu n khi t o ra datagram s kh i ng gi tr trong

tr ng ny. K ti p khi datagram qua Internet, m i router m datagram i qua s

gi m gi tr i 1. n u gi tr ny b ng 0 tr c khi n ch cu i cng th datagram s b drop.

Protocol: nh ngha lo i d li u nghi th c no c a l p trn ng gi trong

datagram (TCP, UDP, ICMP).

Header checksum (16 bits): dung ki m tra header ch khng ki m tra ph n cn

l i c a gi.

Source address (4 bytes): a ch IP ngu n c a datagram.


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Destination address (4 bytes): a ch IP c a ch c n g i datagram n.

Options: tr ng ch n l a cho nhi u ch c nng i v i IP datagram. N c th

mang cc thng tin v ki m sot nh tuy n nh : timing, qu n l v cn b ng.

IP l i ch a 4 nghi th c gip l: ARP, RARP, ICMP v IGMP.

ARP (Adrees Resolution Protocol) c dng qu ng b tm a ch v t l t

c ch IP. Protocol ny c dng trong m ng n i b v nh d ng a ch v t l c a

m ng phh thu c vo ph n c ng m ng.

RARP (Reverse Address Resolution Protocol) tm a ch IP khi bi t a

ch v t l.

ICMP (Internet Control Message Protocol) l c ch c dung b i my ch v

router. ICMP cho php IP thng bo pha g i n u datagram khng c pht ng.

c tr ng nh t c a ICMP l ti n ch ping th ng c cc l p trnh vin dng ki m

tra cc node c cn ho t ng hay khng.

IGMP (Internet Group Message Protocol): nghi th c IP lin quan n 2 thng tin

l unicasting v multicasting. Unicasting l thng tin gi a m t ng i g i v m t ng i

nh n. n l thng tin m t m t. Tuy nhin, m t s qu trnh th nh tho ng c n g i

m t thng i p n nhi u ng i nh n ng th i. Tr ng h p ny l multicasting,

t c l thng tin m t nhi u. multicasting c r t nhi u ng d ng.

2.6.4.2. a ch IP

a ch IP g m 32 bits, th ng c m t d ng th p phn v m i byte cch

nhau b i d u . l danh hi u duy nh t trn m ng. a ch ny c 2 ph n: ph n c

ch m ng v a ch n i b . C 3 l p a ch A, B, C dnh cho 3 lo i m ng l n, v a v

nh ; 1 l p a ch multicasting (l p D) v m t l p d tr (E).

Trong c m t l p a ch c bi t dng ki m tra thi t b m ng l:

127.x.x.x (loopback)


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Bit tr ng s

L p(Class)

Ph m vi a ch Kch th ckhng gian a ch

0xxx A 0.0.0.0 127.255.255.255 224 = 1677721610xx B 128.0.0.0 191.255.255.255 216 = 65536110x C 192.0.0.0 223.255.255.255 28 = 2561110 D 224.0.0.0 239.255.255.2551111 E 240.0.0.0 255.255.255.255

Khng gian a ch IP

Khi m t m ng ph c t p c a ch thu c l p A, B ho c C c m t vi subnet

tham d t o c u trc m ng th local s c chia lm 2 ph n: subnet address v

host address. Kch th c v vi c gn tr ng s c a subnet part c qu n l b i t

ch c n i b .

phn bi t cc subnet cho cc host v router th c n dng m t subnetsmask.

l b 32 bits, bit 1 ph ph n network v subnet, bit 0 dng mask out s host

trong a ch IP.

Class A 0 Net ID Host ID

Class B 1 0 Net ID Host ID

Class C 1 1 0 Net ID Host ID

Class D 1 1 1 0 Multicast address

Class E 1 1 1 1 Reserved for future use

Khun d ng a ch lin m ng Subnet address

Cc a ch c bi t:

Nh n d ng m ng: a ch IP tham kh o t i m t m ng co ph n local part

l zero. T ng t i v i m t subnet. Cc a ch ny khng c gn

cho host v router.

Qu ng b trn m ng: a ch 255.255.255.255 c m t m c ch c bi t,

l dung g i m t message t i m i host trn m ng n i b . broadcasts


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th ng dng khi m t host c n nh v t i m t server. Cng c th g i

m t massega t i m i host trn m ng xa b ng cch t local part a

ch ln 1.

Qu ng b trn subnet: M t broadcasts c th nh h ng t i m t subnet

c bi t. Khi host address trong a ch IP c c ln 1; cn n u

mu n pht rn ton nt m ng (node) th c subnet address v host address

c c ln 1.

a ch t kha (loopback address): i ngh ch v i a ch qu ng b l cc

message khng c r i kh i local host. Khi th ng dung m t loopback address, c ngha l node dng ki m tra ph n m m m ng.

l a ch b t u b ng 127.xxx.xxx.xxx.

This host on network: a ch 0.0.0.0 c ngha l b n thn host l ph n t

c a m ng. v i cc host trn cng m t m ng c c b ch c ph n host

address l mang s c a host trn m ng n, cn cc ph n khc l zero.

H th ng tn vng: c th tra tm tn a ch c a m t host no , ng i ta dung h th ng tn vng gi m t server g i l nameserver.

2.6.4.3. Gi tin ARP (Adrees Resolution Protocol)

M t c ch s d ng chuy n a ch IP thnh a ch v t l l ARP (Address

Resolution Protocol). Khi hai my tnh cng n i vo m t m ng v t l, chng bi t

c a ch IP c a nhau nh ng truy n thng gi a hai my, chng ph i bi t c

a ch v t l c a nhau. ARP gi i quy t v n chuy n t a ch IP 32 bits sang a

ch Ethernet 48 bits. Ng i ta s d ng hai c ch l: ARP request v ARP reply.


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Host A Host DHost CHost B

ARP Request

Host A Host DHost CHost B

ARP Reply

Hnh 2-6 M t h at ng c a khung ARP

Chuy n giao tr c ti p: a ch v t l l m t hm c a a ch IP v d s d ng

trn m ng token ring proNET-10 l m ng cho php t a ch IP v a ch v t l

th ai mi. Ng i ta c th t a ch IP l 192.5.48.3 v a ch v t l l 3, khi ta c Pa= f(Ia).

Chuy n giao a ch ng c th c hi n b ng cch my tnh mu n g i thng

tin g i m t thng bo t i tan b cc my tnh trn m ng, trong thng bo c ch a

a ch IP c a my tnh n c n lin l c, m i my s nh n c thng bo v my no

th y a ch IP c a mnh th tr l i m t thng bo ch a a ch v t l. Khi hai my

tnh c th ni chuy n v i nhau.

Ngoi ra, ng i ta cn s d ng b ng ch ng l u tr t m th i cc a ch

s d ng m i nh t ( Address Reslution Cache) tng t c c a vi c chuy n giao

a ch .

M t gi thng tin ARP l m t Ethernet Frame c truy n tr c ti p t my ny

t i my khc. V khng ph i s d ng IP, gi tin ny khng c a ch IP cng nh

khng c n c d n ng, n ph i c g i broadcast t i t t c cc my trn

m ng Ethernet (v i a ch FFFF_FFFF_FFFF).


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Gi thng tin ARP c m t nh sau:

Hardware Type Protocol Type

Sender MAC address (bytes 0-3)

Hareware len ARP operationProtocol len

Sender MAC address (bytes 4-5) Sender IP address (bytes 0-1)

Dest MAC address (bytes 0-1)Sender IP address (bytes 2_3)

Dest MAC address (bytes 2-5)

Dest IP address ( bytes 0-3)

0 7 8 15 16 31

Hnh 2-7 Gi tin c a ARP

Protocol type: 0x0800 cho IP (0000.1000.0000.0000).

Hardware len = 6 bytes cho ethernet.

Protocol len = 4 bytes cho IP.

ARP operation:

o 1= yu c u

o 2 = p l i

o 3/4 = RARP yu c u/p l i

Destination Address6 bytes

Source Address6 bytes

Frame type2 bytes

(ARP) Data28 bytes

CRC4 bytes

Hnh 2-8 Tr ng c a khung ARP

a ch ch (ethernet destination address):

FF:FF:FF:FF:FF:FF l a ch broadcast cho ARP request.

a ch ngu n (ethernet source address) l a ch c a ARP yu c u.


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Frame type:

o ARP yu c u ho c p l i (ARP request/rely) : 0x0806

o RARP yu c u ho c p l i (RARP request/rely): 0x08035

o IP: 0x0800

2.6.5. L p giao v n (Transport Layer)

L p v n chuy n c 2 nhi m v nh sau:

Cung c p d ch v cho l p qu trnh bn trn n v cc ng d ng cng v i

giao di n thch h p cho m ng.

Phn pht message c a cc l p trn gi a cc host.

L p giao th c ngay trn l p Internet l Host to Host Transport Layer hay th ng

g i l Transport Layer. Hai giao th c quan tr ng ny l Transmission Control Protocol

(TCP) v User Datagram Protocol (UDP). TCP cung c p d ch v chuy n giao thng tin

k t n i (connection oriented), n bao g m c ki m tra v s a l i. UDP cung c p d ch

v km tin c y h n (unreliable) v khng th thi t l p lin k t tr c (connectionless).

C hai giao th c u chuy n giao thng tin gi a l p ng d ng v l p Internet.

Ch ng trnh ng d ng c th l a ch n d ch v no thch h p v i ng d ng c a n.

IP phn pht m t datagram t m t my ch ngu n n my ch ch, t o thnh

m t nghi th c my ch -my ch . Cc h u hnh ngy nay tr gip mi tr ng x

l nhi u ng i s d ng. M t ch ng trnh th c thi g i l process. M t my ch ang

nh n m t datagram cng c th ch y nhi u process ng th i. Cc nghi th c giao v n c a b nghi th c TCP/IP nh ngha m t t p k t n i

khi ni m cho cc process ring c g i l cc ports nghi th c, hay n gi n h n l

ports. M t ports nghi th c l m i m n (th ng l m t b m) ch a d li u

dng cho m t process c th . Giao ti p gi a cc processes v cc ports t ng ng

c cung c p b i h i u hnh c a my ch .


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IP l m t nghi th c my ch - my ch , c ngh a l n c th nh n pht gi t

m t thi t b v t l n thi t b v t l khc. Cc nghi th c m c giao v n c a TCP/IP

l cc nghi th c port to port lm vi c pha trn c a cc nghi th c IP phn pht gi t port g c n port ch t i cu i truy n.

M i port c nh ngha b ng m t s nguyn d ng c mang trong header

c a gi l p giao v n. M t khung t i l p giao v n dng a ch port 16 bits, dng

cho cc ports t 0 n 65535.

2.6.5.1. Giao th c UDP (User Datagram Protocol)

UDP (User Datagram Protocol) l m t nghi th c khng tin c y, ch c g ng h t

mnh phn pht d li u. UDP ch cung c p c b n c n thi t cho phn pht end-to-

end. N khng cung c p b t c ch c nng nh s th t no v do khng th lm

r gi no b h ng khi bo co v l i. UDP c th khm ph ra m t l i xu t hi n

t c l ICMP c th thng bo pha g i l m t user datagram h ng v b lo i. Tuy

nhin n khng c kh nng bi t l gi no b m t. UDP cho php truy n d li u trn

m ng v i chi ph th p do s phn pht d li u khng tin c y. Cc d ch v dng UDP l TFTP, DSN, SNMP

Gi thng tin UDP:

M i gi thng tin UDP g i l m t Datagram c phn lm 2 ph n header v

data trong header ch a thng tin v a ch c ng ngu n, a ch c ng ch, di

c a gi v checksum.

Chech sum: 16 bits l s b 1 c a t ng b 1c a cc 2 bytes trong ph n header, d li u v ph n header gi (pseudo header) . N u ph n header v text ch a m t s l

bytes th byte cu i cng c m vo bn ph i v i 0 16 bit cho m c ch

Checksum. Ph n m th khng c truy n nh m t ph n c a header.


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Source port Destination port

Message length Checksum

Data

Data

Data

Destination

Address

Source

Address

Type

field

IP

header

UDP data CRC

Hnh 2-9 ng gi UDP vo khung Ethernet

Phn knh, h p knh v Ports.

Phn knh, h p knh chnh l vi c l a ch n nh ng ti n trnh ng d ng trong

m t s l n cc ti n trnh s d ng giao th c UDP, ng i ta ch n ra nh ng ng d ng

t ng ng v i gi thng tin chuy n n.

Port 1 Port 2 Port 3

UDP: Demultiplexing

Based on Port

IP Layer

UDP Datagram arrives

Hnh 2-10 S phn knh v h p knh c a ARP

Vi c ny gi i quy t b ng c ch c ng Port mechanism c ch ny g n m i

ng d ng v i m t con s g i l port number v m i gi thng tin m n g i i u

mang m t tr ng SOURCE PORT.

T i n i nh n, d a vo thng tin tr ng DESTINATION PORT m gi thng tin

c truy n n c ng t ng ng v i ng d ng. V d m i b ng TCP/IP u c


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d ch v FTP (File Transfer Protocol) g n v i c ng 21 v TFTP (Trivial File Transfer

Protocol) g n v i c ng 69 c a UDP.

Vi c s d ng cc port number cng c nhi u cch.

o Dng nh ng c ng dnh ring cho t ng ng d ng c ng k tr c

(Well-known port assignment).

o M t port number s c sinh ra khi c m t ng d ng i h i (Dynamic

binding).

Cch ti p c n k t h p cc ki u trn (Hybrid) trong ng i ta v a s d ng

Well-known port assignment cho m t s port number v a c th nh ngha cc port

number khc khi c n thi t. M t khung t i l p giao v n dng a ch port 16 bits,

dng cho cc ports t 0 n 65535.

V sao ng i l p trnh ng d ng l a ch n UDP nh m t d ch v giao v n? C

m t s l do:

M t s l ng l n cc gi thng tin nh c truy n, thng tin cho vi c k t n i v

s a l i c th l n h n nhi u so v i thng c n truy n. Trong tr ng h p ny, UDP l

gi i php hi u qu nh t.

Nh ng ng d ng ki u Query-Respon cng r t ph h p v i UDP, cu tr l i

c th dng lm s xc nh n c a m t cu h i. N u khng nh n c s tr l i sau

m t th i gian no , ng d ng ch c n g i i m t cu h i khc.

M t s ng d ng t n cung c p cng ngh ring chuy n giao thng tin

c y, v khng i h i d ch v ny c a transport layer.

y l giao th c n gi n v truy n nhanh, nn n th ng c s d ng trong

cc ng d ng i u khi n th i gian th c. Do trong Lu n Vn ny ch n giao th c

UDP lm giao th c truy n khung i u khi n c a l p trn.


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2.6.5.2. Giao th c TCP (Transmission Control Protocol)

TCP (Transmission Control Protocol) l m t nghi th c tin c y. TCP l m t nghi

th c port-to-port tin c y v nh h ng k t n i. TCP t o ra m t m ch o gi a pha

g i v nh n trong su t qu trnh truy n.TCP b t u truy n b ng cch thng bo cho

pha nh n bi t (thi t l p k t n i) v khi k t thc truy n th g i m t k t thc k t n i.

N c g ng phn pht d li u n ch, ki m tra l i, truy n l i n u c n, thng bo

l i cho l p trn n u truy n khng thnh cng. Do , vi c s d ng TCP cng lm tng

chi ph.

TCP cung c p y cc d ch v l p giao v n i v i p d ng. TCP l m t nghi th c port to port tin c y v nh h ng k t n i. TCP t o ra m t m ch o gi a

pha g i v nh n trong su t qu trnh truy n. TCP b t u truy n b ng cch thng

bo cho pha nh n bi t (thi t l p k t n i) v khi k t thc truy n th g i k t thc k t

n i.

S tin c y c a TCP m b o b ng vi c pht hi n l i v truy n l i cc khung b

h ng: t t c cc an ph i c nh n v xc nh n tr c khi xem nh cu c truy n l

han thnh v m ch o c l ai b .

T i u g i, TCP chia cu c truy n thnh cc n v d li u nh h n v ng

gi thnh cc khung g i l an. M i an bao g m vi c nh s nh m s p l i theo

th t khi nh n. Cc an c t i qua m ng bn trong cc IP datagram. T i u

nh n, TCP gom m i datagram khi chng n v x p l i theo th t d a vo cc s

c nh.

TCP g i trn internet cc datagram. Header c a Internet Protocol mang nh ng

tr ng thng tin bao g m a ch ngu n v ch c a my ch . TCP header theo sau

header c a internet v cung c p thng tin c th t i nghi th c TCP.


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Source port Destination port

Sequence Number

Acknowledgment Number

Checksum Urgent pointer

Option Padding

Data

Data offset reserved URG

ACK

PSH

RST

SYN

FIN

Window

Hnh 2-11 nh d ng Gi TCP

Source port: 16 bits a ch ngu n.

Destination: 16 bits a ch ch.

Sequence Number: 32 bits m t dng d li u t ch ng trnh p d ng c th

c chia thnh hai hay ho c nhi u an TCP. S th t ch ra v tr c a d

li u trong dng d li u g c.

Acknowledgment Number: 32 bits dng xc nh n c nh n d li u t thi t

b khc. S ny ch xc nh n khi bit ACK trong tr ng i u khi n c t.

Trong tr ng h p ny, s th t ch ra mong i k ti p.

Data offset: 4 bits ch ra n i d li u b t u.

Reserved: 6 bits dnh cho t ng lai.

Control bits: 6 bits (t tri sang ph i).

URG: khi c t ch ra tnh h p l c a tr ng urgent pointer. C bit urgent v con tr ch ra r ng d li u trong an l kh n c p.

ACK: khi c t ch ra tnh h p l c a tr ng Acknowledgment number. C

hai u c dng v i nhau v c ch c nng khc nhau ty vo l ai an.

PSH: c dng thng bo pha g i l c n m t t c trung bnh cao h n.

RST: dng xa k t n i khi c nh m l n s th t .


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SYN: dng ng b vi c nh s cho ba l ai an: yu c u k t n i, kh ng

nh k t n i(v i bit ACK), v xc nh n kh ng nh (v i bit ACK c t).

FIN: c dng cho k t thc n i cho ba an v xc nh n c a kh ng nh k t

thc.

Window: 16 bits s d li u c ch ra trong tr ng acknowledgment m pha

g i ang m nh n.

Chech sum: 16 bits l s b 1 c a t ng s b 1 c a 16 bytes trong ph n header

v text. N u ph n header v text ch a m t s l bytes header v text c

ki m tra, th byte cu i cng c m vo bn ph i v i 0 16 bytes cho m c ch Checksum. Ph n m th khng c truy n nh m t ph n c a

header. Trong khi tnh checksum, t b n thn c a tr ng checksum c thay

th v i 0 (c ngha l chechsum s thay th nh ng bit 0 ny).

Chechsum cng bao g m 96 bit header gi (Pseudo header) c thm vo u

header c a TCP. Header gi ny ch a a ch ngu n , a ch ch, nghi th c, chi u di

TCP. Ph n ny c a ra b o v TCP trong vi c truy n l c khung. Nh ng thng tin ny c mang b i Internet Protocol v c truy n qua TCP/Network

interface trong arguments ho c k t qu c a vi c g i b i TCP trn IP.

ss

Source address

Zero PTCL TCP Length

Destination address

Hnh 2-12 Khung TCP

TCP length l chi u di byte c a header v chi u di d li u nh ng n khng

bao g m 12 bytes header gi .

Urgent pointer (16 bits): Tr ng ny giao ti p v i gii tr hi n hnh c a

Urgent pointer nh l m t m c offset t s tu n t trong khung. Urgent pointer


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lun ch n gi tr s bytes d li u kh n. Ga tr c a tr ng ny c tnh khi

tn hi u i u khi n URG c t.

2.6.6. L p ng d ng (Application Layer)

G m cc ng d ng truy n trn m ng nh truy n th (Simple Mail Transfer

Protocol SMTP), truy n file (File Transfer Protocol FTP), truy xu t t xa (Telnet),

qu n l m ng (Simple Network Manegement Protocol SNMP)


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CH NG 3. ENC28J60 MICROCHIP STAND-ALONEETHERNET CONTROLLER WITH SPI INTERFACE

3.1. M t t ng quan

ENC28J60 l IC giao ti p m ng Ethernet l p v t l t ng ng trong m

hnh OSI. N h tr tuy n song cng trn knh truy n c bng thng t 10-

20Mbps. ng th i nh m trnh xung t trn knh truy n, ENC28J60 lm vi c

trn protocol CSMA/CD pht hi n v t i thi u ha xung t. ENC28J60 c giao ti p v i cc thi t b khc theo chu n SPI.

The ENC28J60 is a stand-alone Ethernet controller with an industry standard

Serial Peripheral Interface (SPI). It is designed to serve as an Ethernet network

interface for any controller equipped with SPI. The ENC28J60 meets all of the IEEE

802.3 specifications. It incorporates a number of packet filtering schemes to limit

incoming packets. It also provides an internal DMA module for fast data throughput

and hardware assisted checksum calculation, which is used in various network

protocols. Communication with the host controller is implemented via an interrupt

pin and the SPI, with clock rates of up to 20 MHz. Two dedicated pins are used for

LED link and network activity indication.

ENC28J60 c cc thng s sau:

IEEE 802.3 compatible Ethernet controller Integrated MAC and 10BASE-T PHY Supports one 10BASE-T port with automaticpolarity detection and correction Supports Full and Half-Duplex modes Programmable automatic retransmit on collision Programmable padding and CRC generation Programmable automatic rejection of erroneous

DK Thiet bi qua mang Internet


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packets SPI Interface with clock speeds up to 20 MHz 8-Kbyte transmit/receive packet dual port SRAM Configurable transmit/receive buffer size

Hardware-managed circular receive FIFO Byte-wide random and sequential access withauto-increment Internal DMA for fast data movement Hardware assisted Supports Unicast, Multicast and BroadcastPackets Loopback mode Two programmable LED outputs for LINK, TX,RX, collision and full/half-duplex status Six interrupt sources and one interrupt output pin 25 MHz clock input requirement Clock out pin with programmable prescaler Operating voltage of 3.1V to 3.6V (3.3V typical) 5V tolerant inputs Temperature range: -40C to +85C Industrial,0C to +70C Commercial (SSOP only) 28-pin SPDIP, SSOP, SOIC, QFN packages



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3.2. S chn



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3.3. S kh i



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Chip ENC28J60 c b y kh i ch c nng chnh:

1. An SPI interface that serves as a communication channel between the host

controller and the ENC28J60.

2. Control Registers which are used to control and monitor the ENC28J60.

3. A dual port RAM buffer for received and transmitted data packets.

4. An arbiter to control the access to the RAM buffer when requests are made

from DMA, transmit and receive blocks.

5. The bus interface that interprets data and commands received via the SPI

interface.

6. The MAC (Medium Access Control) module that implements IEEE 802.3

compliant MAC logic.



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7. The PHY (Physical Layer) module that encodes and decodes the analog data

that is present on the twisted pair interface.

3.1.1. Nhm thanh ghi i u khi n



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3.3.1.1. Ch c nng c a thanh ghi



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3.4. Giao ti p v i VK

3.1.1. Truy n gi

3.4.1.1. Thi t l p vi c truy n

3.4.1.2. Ti n trnh g i

3.4.1.3. Tr ng thi truy n

3.1.1. Nh n gi

M hnh bus trong m ng CSMA/CD cho php m i nt nh n m i gi c g i ln m ng. B l c nh n s xc nh gi no c php l u vo b m nh n.

Khng ph i m i gi u c quan tm, ch c nh ng gi c a ch ch th a b

l c nh n m i c chuy n vo b nh . NIC a ra m t s l a ch n cho b l c

nh n v cch qu n l m t gi hon ch nh cho vi c l u tr gi ang n.

3.4.1.4. Ti n trnh nh n

3.4.1.5. B m thu



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1.2. Chu n SPI

The ENC28J60 is designed to interface directly with the Serial Peripheral

Interface (SPI) port available on many microcontrollers. The implementation

used on this device supports SPI mode 0,0 only. In addition, the SPI port

requires that SCK be at Idle in a low state; selectable clock polarity is not

supported. Commands and data are sent to the device via the SI pin, with data

being clocked in on the rising edge of SCK. Data is driven out by the

ENC28J60 on the SO line, on the falling edge of SCK. The CS pin must be

held low while any operation is performed and returned high when finished.



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Dk Thiet Bi Qua Mang Internet 8989