tim hieu cong nghe ip muliticast 4291

TRNG . KHOA.

----------

Bo co tt nghip

ti:

TM HIU CNG NGH IP MULITICAST

LI CM N

Ti xin chn thnh cm n TS. Ng Khnh Vn, ngi tn tnh hng

dn, ch bo ti trong sut thi gian di thc hin ti.

Ti xin chn thnh cm n PGS.TS Nguyn Vn Tam, cng tc ti Vin

cng ngh thng tin, ch bo v cho ti nhng li khuyn qu bu hon

thin lun vn.

Ti xin chn thnh cm n cc thy c trong trng i Hc Cng Ngh,

i Hc Quc Gia H Ni ging dy, truyn t v to iu kin hc tp tt

nht cho ti trong sut thi gian hc tp cng nh trong qu trnh thc hin lun

vn.

H Ni, thng 08 nm 2009

Trng Cng i

I

MC LC

LI CM N

MC LC

DANH MC CC T VIT TT

DANH SCH HNH V

DANH SCH CC BNG

M U................................................................................................................ 1

1. t vn .................................................................................................. 1

2. i tng v mc tiu lun vn................................................................. 1

3. Hng tip cn ........................................................................................... 2

4. Kt cu ca lun vn .................................................................................. 2

CHNG 1 ........................................................................................................... 3

C BN V IP MULTICAST.............................................................................. 3

1.1 M u ......................................................................................................... 3

1.2 Cc thnh phn tham gia vo truyn thng multicast .................................. 5

1.3 a ch multicast .......................................................................................... 7

1.4 Cy phn phi multicast............................................................................... 9

1.4.1 Cy ngun ............................................................................................. 9

1.4.2 Cy chia s .......................................................................................... 10

1.5 Chuyn tip multicast................................................................................. 13

1.6 ng trc multicast.................................................................................. 15

1.7 Giao thc qun l nhm Internet ............................................................... 17

1.7.1 Giao thc IGMPv1.............................................................................. 17

1.7.1.1 Thng ip Host Membership Report.......................................... 18

1.7.1.2 Thng ip Host Membership Query........................................... 19

1.7.2 Giao thc IGMPv2.............................................................................. 19

1.7.2.1 La chn router truy vn.............................................................. 20

1.7.2.2 Thng ip ri nhm.................................................................... 21

1.7.2.3 Truy vn cho tng nhm.............................................................. 21

1.7.3 Giao thc IGMPv3.............................................................................. 21

I

1.7.3.1 Lc d liu ................................................................................... 21

1.7.3.2 Thng ip IGMPv3 Host Membership Query ........................... 22

1.7.3.3 Thng ip IGMPv3 Host Membership Report........................... 23

CHNG 2 ......................................................................................................... 25

NH TUYN MULTICAST ............................................................................. 25

2.1 Giao thc nh tuyn multicast vct khong cch ................................... 25

2.1.1 Tm kim hng xm ............................................................................ 25

2.1.2 Trao i thng bo nh tuyn ............................................................ 26

2.1.3 Ct nhnh ............................................................................................ 29

2.1.4 Ghp nhnh ......................................................................................... 31

2.2 Giao thc PIM Dense Mode ...................................................................... 33

2.2.1 Tm kim hng xm ............................................................................ 33

2.2.1.1 Thng ip Hello ......................................................................... 33

2.2.1.2 Router c ch nh.................................................................... 33

2.2.1.3 Cy phn phi multicast............................................................... 34

2.2.2 Ct nhnh ............................................................................................ 35

2.2.3 C ch xc nhn .................................................................................. 37

2.2.4 Ghp nhnh ......................................................................................... 38

2.3 PIM Sparse Mode....................................................................................... 39

2.3.1 M hnh tham gia ................................................................................ 39

2.3.2 Cy chia s .......................................................................................... 40

2.3.2.1 Tham gia cy chia s .................................................................... 40

2.3.2.2 Ct nhnh trn cy chia s............................................................ 43

2.3.3 Cy ng i ngn nht ...................................................................... 45

2.3.3.1 Tham gia cy ng i ngn nht................................................ 45

2.3.3.2 Ct nhnh trn cy ng i ngn nht ....................................... 47

2.3.4 Thng ip Join/Prune ........................................................................ 48

2.3.5 ng k ngun d liu........................................................................ 49

2.3.5.1 Thng ip PIM Register............................................................. 49

2.3.5.2 Thng ip PIM Register Stop.................................................. 50

2.3.6 Chuyn t cy chia s sang cy ng i ngn nht .......................... 50

I

2.4 Giao thc Multicast Open Shortest Path First ........................................... 54

2.4.1 nh tuyn multicast trong vng......................................................... 54

2.4.2 nh tuyn multicast trn nhiu vng ................................................. 56

2.4.3 nh tuyn multicast trn cc vng t tr............................................ 59

CHNG 3 ......................................................................................................... 61

S DNG ACCESS GRID XY DNG .......................................................... 61

H THNG HI NGH TRUYN HNH DA TRN IP MULTICAST ........ 61

3.1 Cc khi nim chung v dch v hi ngh truyn hnh .............................. 61

3.1.1 H thng hi ngh truyn hnh ............................................................ 62

3.1.2 Cc thnh phn c bn ca hi ngh truyn hnh ................................ 63

3.2 Giao thc RTP............................................................................................ 64

3.2.1 Khun dng RTP header ..................................................................... 64

3.2.2 Cc ng dng s dng RTP ............................................................... 65

3.2.2.1 Thoi hi ngh n gin ............................................................... 65

3.2.2.2 Thoi v truyn hnh hi ngh ...................................................... 67

3.2.2.3 B trn v b bin dch ................................................................ 67

3.3 ng b lung hnh nh v m thanh ........................................................ 68

3.4 S dng Access Grid xy dng mt hi ngh truyn hnh......................... 70

3.4.1 Cc thnh phn ca Access Grid......................................................... 70

3.4.2 S dng Access Grid client tham gia vo hi ngh truyn hnh..... 73

KT LUN.......................................................................................................... 76

HNG PHT TRIN CA TI ............................................................... 77

TI LIU THAM KHO

II

DANH MC CC T VIT TT

T vit tt Vit y Ngha ting Vit

ABR Area Border Router Router bin vng

AG Access Grid Phn mm h tr xy dng ng dng

hi ngh truyn hnh

AS Autonomous System Vng t tr

ASBR Autonomous System

Border Routers

Router trn bin vng t tr

DR Designated Router Router c la chn

DVMRP Distance Vector Multicast

Routing Protocol

Giao thc nh tuyn multicast vc-

t khong cch

IGMP Internet Group

Management Protocol

Giao thc qun l nhm Internet

LAN Local Area Network Mng ni b

LSA Link-State Advertisement Thng ip qung b trng thi lin

kt

MABR Multicast Area Border

Router

Router bin vng multicast

MBONE Multicast Backbone ng trc multicast

MOSPF Multicast Open Shortest

Path First

Giao thc nh tuyn multicast da

trn thut ton ng i ngn nht

MCU Multipoint Control Unit B iu khin a im

OSPF Open Shortest Path First Giao thc nh tuyn unicast da

trn thut ton ng i ngn nht

II PIM Protocol Independent

Multicast

Giao thc nh tuyn multicast c

lp

PIM-DM Protocol Independent

Multicast Dense Mode


lp theo m hnh tp trung

PIM-SM Protocol Independent

Multicast Sparse Mode


lp theo m hnh phn tn

RAT Robust Audio Tool Cng c truyn m thanh trong ng

dng hi ngh truyn hnh

RIP Routing Information

Protocol

Giao thc thng tin nh tuyn

RPF Reverse Path Forwarding Kim tra ng dn ngc

RP Rendezvous Point im hn

RTCP Real Time Transport

Control Protocol

Giao thc iu khin truyn thng

thi gian thc

RTP Realtime Transport

Protocol

Giao thc truyn thng thi gian

thc

SPT Shortest Path Tree Cy ng i ngn nht

TTL Time To Live Thi gian tn ti gi tin

VIC Video Conference ng dng video trong hi ngh

truyn hnh

III

DANH SCH HNH V

Hnh 1.1: Truyn thng unicast v multicast ......................................................... 3

Hnh 1.2: Cc thnh phn tham gia vo truyn thng multicast ............................ 6

Hnh 1.3: nh dng ca a ch IP lp D.............................................................. 7

Hnh 1.4: nh x a ch IP multicast sang a ch MAC...................................... 8

Hnh 1.5: Cy ng i ngn nht ca host A....................................................... 9

Hnh 1.6: Cy ng i ngn nht ca host B ..................................................... 10

Hnh 1.7: Cy chia s ........................................................................................... 11

Hnh 1.8: Cy chia s hai chiu............................................................................ 12

Hnh 1.9: Cy chia s mt chiu s dng cy SPT .............................................. 12

Hnh 1.10: Cy chia s mt chiu s dng nh tuyn unicast ............................ 13

Hnh 1.11: Gii hn TTL ..................................................................................... 14

Hnh 1.12: C ch ng hm lin kt cc c o multicast............................... 15

Hnh 1.13: ng gi IP multicast theo c ch tunneling..................................... 16

Hnh 1.14: C ch ng hm lin kt cc MRouter .......................................... 16

Hnh 1.15: Thng ip IGMPv1 .......................................................................... 18

Hnh 1.16: Thng ip IGMPv2 .......................................................................... 19

Hnh 2.1: Tm hng xm trong DVMRP ............................................................. 26

Hnh 2.2: Trao i nh tuyn DVMRP bc 1................................................... 27



Hnh 2.5: Ct nhnh trong DVMRP bc 1 ........................................................ 30

Hnh 2.6: Ct nhnh trong DVMRP bc 2 ........................................................ 31

Hnh 2.7: Ghp nhnh trong DVMRP bc 1 ..................................................... 32

Hnh 2.8: Ghp nhnh trong DVMRP bc 2 ..................................................... 32

Hnh 2.9: Cy phn phi PIM-DM ...................................................................... 35

Hnh 2.10: Ct nhnh trong PIM-DM bc 1...................................................... 36



Hnh 2.13: Xc nhn trong PIM-DM................................................................... 38

III Hnh 2.14: Ghp nhnh trong PIM-DM............................................................... 39

Hnh 2.15: Tham gia cy chia s PIM bc 1...................................................... 40


Hinh 2.17: Tham gia cy chia s PIM bc 3...................................................... 42




Hnh 2.21: Ct nhnh trn cy chia s bc 1 ..................................................... 44



Hnh 2.24: Tham gia cy ng i ngn nht bc 1.......................................... 46



Hnh 2.27: Ct nhnh trn cy ng i ngn nht bc 1 ................................. 47



Hnh 2.30: Chuyn sang cy SPT bc 1 ............................................................ 51

Hnh 2.31: Chuyn sang cy SPT bc 2 ............................................................ 51

Hnh 2.32: Ct b ngun khi cy chia s bc 3 ............................................... 52



Hnh 2.35: Vng MOSPF cha ngun v thnh vin nhm G ............................ 55

Hnh 2.36: Cy ng i ngn nht MOSPF SPT cho mng N3 v N4.............. 56

Hnh 2.37: Thng ip nhm tm tt trong vng ng trc.............................. 57

Hnh 2.38: Cy ng i ngn nht SPT trong vng ng trc ........................ 58

Hnh 2.39: Ngun trong vng khng phi ng trc......................................... 59

Hnh 2.40: Lu lng multicast xung cc min MOSPF .................................. 60

Hnh 3.1: Thnh phn ca hi ngh truyn hnh .................................................. 63

Hnh 3.2: Khun dng RTP header ...................................................................... 64

Hnh 3.3: Cc thnh phn ca Access Grid ......................................................... 70

Hnh 3.4: Desktop node........................................................................................ 71

III Hnh 3.5: Office node........................................................................................... 72

Hnh 3.6: Room node ........................................................................................... 72

Hnh 3.7: Mi quan h gia multicast v Access Grid ........................................ 73

Hnh 3.8: Profile Dialog....................................................................................... 73

Hnh 3.9: in a ch virtual venue kt ni ................................................... 73

Hnh 3.10: Venue client ....................................................................................... 74

Hnh 3.11: Ca s video....................................................................................... 74

Hnh 3.12: Ca s audio....................................................................................... 75

IV

DANH SCH CC BNG

Bng 1.1: Cc trng trong thng ip IGMPv1................................................. 18

Bng 1.2: Cc trng trong thng ip IGMPv2................................................. 20

Bng 1.3: Cc trng trong thng ip IGMPv3 Host Membership Query........ 22

Bng 1.4: Cc trng trong thng ip IGMPv3 Host Membership Report ....... 24

1

M U

1. t vn

Ngy nay mng Internet v cc ng dng trn mng ngy cng tr nn

thng dng, v th c mt lng rt ln cc thng tin cn phi chuyn tip n

nhiu ni trong cng mt thi gian. Phn ln cc ng dng trn mng hin nay

s dng phng php truyn d liu unicast, y l phng php truyn d liu

t im ti im, tc l d c truyn t mt ngi gi ti mt ngi nhn.

Tuy nhin vi mt s ng dng yu cu phi thng xuyn gi d liu t mt

im ti nhiu im, d liu c gi t mt ngi gi ti nhiu ngi nhn,

phng php truyn d liu unicast tr nn khng hiu qu. Trong trng hp

ny, cc ng dng s dng unicast phi ng gi cng mt d liu nhiu ln v

ln lt gi chng t im ti im. Mt cch khc thc hin vic truyn d

liu t im n nhiu im l s dng broadcast, y l phng php gi d

liu t mt im n tt c cc im. D thy rng c hai phng php trn u

gy nn nhng s lng ph ti nguyn mng, khi multicast l mt s thay th

tt nht, phng php ny gip ta tit kim c bng thng mng cng nh ci

thin c tc truyn d liu. Multicast l phng php truyn d liu t

im ti nhiu im, trong mt ngun gi s gi lu lng ti mt nhm

ngun nhn thng qua a ch nhm multicast. Trong phng php multicast c

cc giao thc cho php cc my tnh c th gia nhp vo nhm nhn d liu

hay ri b nhm mt cch d dng, cc giao thc nh tuyn cng c xy dng

cho php cc ng dng c th gi d liu mt cch hiu qu trn mng.

2. i tng v mc tiu lun vn

Xut pht t vn nu trn, lun vn xc nh IP multicast l i tng

nghin cu vi nhng vn tp trung ch yu nh sau:

Tm hiu cc thnh phn c bn ca qu trnh truyn d liu multicast gm: a ch multicast, cy multicast, chuyn tip multicast cng nh qu trnh

2

tham gia nhm multicast thng qua giao thc Internet Group Management

Protocol.

Tm hiu cc giao thc nh tuyn c bn c s dng trong truyn thng multicast nh giao thc nh tuyn Distance Vector Multicast Routing

Protocol, giao thc nh tuyn Protocol Independent Multicast v giao thc

nh tuyn Multicast Open Shortest Path First.

Tm hiu kh nng p dng ca multicast trong ng dng thi gian thc. 3. Hng tip cn

Vi mc tiu l tm hiu cng ngh IP multicast, lun vn c tip cn

theo hng tp trung nghin cu cc khi nim, tm hiu cc giao thc ph bin

ca multicast t ch ra c cc u im, nhc im cng nh kh nng p

dng ca IP multicast vo cc ng dng.

4. Kt cu ca lun vn

Lun vn gm phn m u, 03 chng v kt lun. Chng 1: Trnh by cc vn c bn ca IP multicast nh a ch

multicast, cy phn phi multicast, chuyn tip multicast v qu trnh tham

gia nhm multicast.

Chng 2: Trnh by cc giao thc nh tuyn c s dng trong truyn thng multicast gm giao thc nh tuyn Distance Vector Multicast

Routing Protocol, giao thc nh tuyn Protocol Independent Multicast theo

hai m hnh tp trung v phn tn v giao thc nh tuyn Multicast Open

Shortest Path First.

Chng 3: Tm hiu v hi ngh truyn hnh, ng dng phn mm Access Grid xy dng h thng hi ngh truyn hnh da trn IP multicast.

Cui cng l kt lun v hng nghin cu tip theo ca lun vn.

3

CHNG 1

C BN V IP MULTICAST

1.1 M u

IP multicast l mt nhm cc cng ngh v tiu chun cho php vic truyn

ti a im a im nh hi ngh, hay truyn ti im a im nh vic

qung b m thanh, video trn Internet. Vic ng dng cng ngh ny ngy cng

pht trin do nhu cu ngy cng cao i vi cc ng dng a phng tin v s

ci tin cng ngh IP multicast.

Multicast l thut ng k thut, c ngha mt gi tin c th c gi n

nhiu ni trong cng thi im. Cch thc thng thng trong vic truyn thng

tin trn Internet l s dng cc giao thc unicast, cc giao thc ny gi cc gi

tin n mi im thu ti mt thi im. Trn mng multicast, mt gi tin c th

c gi t mt my tnh n mt vi my tnh khc, thay v gi gi tin ln

lt n tng my tnh. Do 5, 10 hay 100 my c th nhn c cng gi tin nn

bng thng c tit kim. Khi s dng multicast gi i gi tin th khng cn

thit phi bit a ch ca nhng ngi cn nhn lung tin multicast : d liu

c qung b theo mt phng thc m nhng ngi quan tm n n c th

nhn c.

Hnh 1.1: Truyn thng unicast v multicast

Cc mng h tr multicast cung cp nhiu dch v v cc ng dng cho

ngi s dng u cui. Nhiu ng dng h tr multicast l cc ng dng a

4 phng tin, tuy nhin cn c nhiu loi ng dng khc nhau s dng cng ngh

IP multicast cho cc mc ch khng phi a phng tin. Cc ng dng thi

gian thc bao gm: truyn hnh trc tip, i pht thanh, hi ngh truyn hnh,

cc ng dng khng phi thi gian thc nh truyn file, d liu, video theo yu

cu

Truyn ti multicast a li nhiu u im so vi unicast truyn thng.

Bng thng ca mng c tn dng hiu qu hn do nhiu lung d liu c

thay th bi mt lung d liu multicast. Cng ngh ny em li cht lng ti

u do cn t bn sao d liu chuyn i v x l ti cc nt mng. c th c

c cc u im ca IP multicast, th kh nng nh tuyn multicast phi c

h tr ti cc nt mng. Ty thuc vo chnh sch s dng v nhu cu ca ngi

s dng, th cc vn lin quan n nh tuyn, tin cy, nh a ch mng

v cc giao thc truyn ti a phng tin c tm quan trng i vi nh vn

hnh mng.

Multicast khng ch em li li ch cho ngi s dng u cui. Hu ht

cc ng dng multicast l da trn UDP, vic s dng giao thc ny c th dn

n cc nh hng ph khng mong mun (cc gi tin c th b hy) so vi cc

ng dng unicast tng t da trn TCP. Tuy nhin, vic thiu kim sot nghn

c th dn n vic suy gim cht lng mng tng th. Cc gi tin trng c th

thnh thong c to ra khi cc topo mng multicast thay i. Trong tng lai

vic trin khai IPv6 s em li multicast c sn cho ngi s dng mng. Phn

mm nh tuyn tin cy hn vi cc giao thc mi s tn dng c h tng

mng. Vi multicast c sn, cc vn nh tuyn s c gii quyt d dng

hn v bng thng s c tit kim hn.

Multicast l mt cng ngh tng i mi cho php cc khch hng c

hng li t cc ng dng thi gian thc m ng ra phi yu cu mt lng

bng thng cc ln. Cng ngh ny cho php nhiu loi cng ty a cc sn

phm ca h n cc nhm ngi vi chi ph thp so vi unicast. Multicast gim

lu lng mng v tit kim bng thng cho php ngi dng khai thc kh nng

s dng cc i c th ca Internet. Multicast cung cp cho cc ngi s dng

lin quan n Internet (cc ngi s dng u cui, nh vn hnh mng, ISP v

5 cc cng ty lin quan khc) gii php kh thi kinh t v k thut cho vn

truyn ti khi lng thng tin ln n cc nhm ngi dng c la chn.

c c multicast trn Internet hay cc mng Intranet, cch u tin l

kt ni cc c o mng h tr multicast vi cc ng hm IP multicast. Do cc

ng hm ny khng kh phn cp v khng a li cc u im k tha ca

multicast, bc k tip l thay th h tng ng hm vi h tng nh tuyn

multicast thc s. Cng ngh multicast hin ti a ra cc thch thc khc nhau

cho vic nh tuyn v nh a ch, hin nay th thch ln nht l thit lp h

tng ton cu c tnh tin cy v c tnh kh phn cp tng t nh h tng mng

Internet unicast ngy nay.

Trong khi giao thc mng IP t bn thn n cung cp cc c ch k tha

i vi IP multicast, cc giao thc lp cao hn khng h tr n. Mc d cc giao

thc khng tin cy nh UDP, RTP c th s dng trn nc ca IP multicast, TCP

v cc giao thc truyn ti tin cy hn trong cc mi trng unicast khng h tr

multicast. Do vy cc giao thc truyn ti multicast phi c pht trin v v th

khng c giao thc truyn ti mc ch chung cho mi trng hp, tuy nhin li

xut hin cc giao thc kh cu hnh cao v cc giao thc c chuyn bit cao

cho cc mc ch truyn ti tin cy c bit trong mi trng IP multicast.

1.2 Cc thnh phn tham gia vo truyn thng multicast

tham gia vo qu trnh trao i d liu cc my tnh v router cn h tr

giao thc multicast, khi cc my c th gi hay nhn lu lng multicast.

My ngun gi d liu multicast ti mt a ch nhm, y l mt a ch lp D.

Cc my trm mun nhn cc gi tin multicast s lin h vi router cc b

ng k tham gia nhm v nhn d liu. Cc router s s dng mt giao thc

nh tuyn multicast xc nh cc mng con c cc thnh vin ca nhm v

chuyn d liu multicast ti cc my nhn. Nu mng con khng c thnh vin

ca nhm, router s khng chuyn d liu ti mng . Ta s tm hiu cc thnh

thnh phn tham gia vo truyn thng multicast v hot ng ca chng trong

mng qua minh ho trn hnh 1.2:

6

Hnh 1.2: Cc thnh phn tham gia vo truyn thng multicast

Trong m phng trn hnh 1.2 cc hot ng din ra nh sau:

Host A trong Subnet 1 l mt ngun multicast v gi d liu multicast ti a ch nhm.

Host B trong Subnet 1 gi yu cu tham gia nhm ti router cc b ca n. Bi v Host B gia nhp vo nhm nn giao din mng ca n s lng

nghe cc gi d liu gi ti a ch nhm. Cc my tnh cn li trong

Subnet 1 khng tham gia nhm nn chng s lc b cc lu lng gi ti

a ch nhm multicast.

Router s chuyn d liu multicast ti tt c cc mng con c thnh vin ca nhm. Trong trng hp ny, router s chuyn d liu t Subnet 1 ti

Subnet 3.

Host C trong Subnet 3 tham gia vo nhm do n s nhn d liu multicast.

Host D trong Subnet 3 gi yu cu ti router tham gia nhm, sau khi tham gia nhm giao din mng ca n s lng nghe v nhn cc d liu gi

ti a ch nhm.

Cc thnh phn tham gia vo truyn thng multicast:

7 Host (bao gm ngun hoc ch): l cc l cc my tnh tham gia kt ni

vo mng v h tr qu trnh gi v nhn d liu multicast.

Router: l cc router h tr giao thc multicast, n c kh nng x l cc yu cu tham gia hay ri nhm v c giao thc nh tuyn multicast xc

nh v chuyn d liu ti cc mng con.

a ch multicast: l a ch lp D, n chnh l a ch ca nhm multicast. Nhm multicast: l mt tp cc thit b u cui lng nghe d liu gi ti

mt a ch multicast.

MBone: vit tt ca t Internet multicast backbone l mt phn ca Internet h tr qu trnh nh tuyn v gi d liu multicast.

1.3 a ch multicast

Cc router phi c phng thc phn bit d liu dng multicast vi

dng unicast hay broadcast. iu ny thc hin thng qua vic gn a ch IP,

bng cch dng a ch lp D t 224.0.0.0 n 239.255.255.255 cho multicast cc

thit b mng c th nhanh chng lc ra cc a ch multicast bng cch c 4 bit

bn tri ca mt a ch. Bn bit ny ca mt a ch multicast lun lun bng

1110, hnh 1.3 th hin nh dng ca mt a ch lp D.

Hnh 1.3: nh dng ca a ch IP lp D

Lm th no mt router kt hp mt a ch multicast ca IP vi mt a

ch MAC. Do khng c c ch tng ng vi giao thc phn gii a ch nh

trong truyn thng unicast, mt dng gi tr c bit dnh ring cho a ch MAC

ca multicast s c dng. Cc a ch ny bt u bng 01005E, phn 28 bit

sau ca a ch IP multicast s c nh x vo 23 bit thp ca a ch MAC

bng mt gii thut n gin.

Multicast Group ID 0 1 1 1 Class D

28 bits

8

Hnh 1.4: nh x a ch IP multicast sang a ch MAC

Hnh 1.4 cho thy c ch nh x a ch, ch c 23 bit cui ca a ch l

c chp t a ch IP sang a ch MAC. Tuy nhin ch rng c 5 bit ca a

ch IP khng c chuyn sang a ch MAC. nh x ny lm ny sinh mt vn

l c th c 32 a ch multicast khc nhau c th nh x vo cng mt a ch

MAC. S nhp nhng ny dn n mt vn nh khi host multicast nhn mt

Ethernet frame ca a ch multicast. Mt a ch MAC c th tng ng vi 32

a ch IP multicast khc nhau. V vy, khi mt host nhn d liu n kim tra tt

c cc frame c MAC m n quan tm. Sau host ny phi kim tra phn a

ch IP bn trong mi frame nhn ra phn a ch ca tng nhm multicast. Sau

y l mt s khng gian a ch c dnh ring ca multicast:

Ton b khng gian a ch multicast: 224.0.0.0 - 239.255.255.255. a ch link-local: 224.0.0.0 - 224.0.0.255 c dng bi cc giao thc nh

tuyn. Router s khng chuyn cc gi tin c a ch ny. Cc a ch bao

gm a ch tt c cc host 224.0.0.1, tt c cc router 224.0.0.2, tt c cc

OSPF router 224.0.0.5 y l a ch cc nhm c nh v cc a ch ny

c xc nh trc.

Khong a ch dnh cho qun tr 239.0.0.0 - 239.255.255.255 c dng trong cc min multicast khc nhau, ging nh dy a ch dnh ring trong

RFC1918. a ch ny khng c s dng gia cc min multicast nn n

c th c dng li nhiu ln.

28 bit

nh x sang a ch MAC Multicast

MAC Address 0 0 0 0 0 0 0 1 0 0000000010111010

1110

5 bit

Khng s dng

01 00 5E X Y Z

X Y Z

IP Multicast

224 - 239

tim hieu cong nghe ip muliticast 4291

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