[Laptrinh.vn]-Chuyển mạch nhãn đa giao thức tổng quát GMPLS_RWA_MPLS

8/4/2019 [Laptrinh.vn]-Chuyn mch nhn a giao thc tng qut GMPLS_RWA_MPLS

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Chuyn mch nhn a giao thc tng qut GMPLS

LI CM N

C th ni y l mt ti rt mi v cng rt kh. Nhng vi s n

lc ca bn thn v trn ht l s ch bo v tn tnh hng dn ca PGS,

TS Nguyn Kim Giao em hon thnh lun n ny. V vy li u tin em

xin chn thnh cm n s quan tm gip ch bo v hng dn ca

thy.

Ngoi ra em cng xin chn thnh cm n cc thy c gio trong

Khoa in T Vin Thng - trng i hc Cng Ngh - i hc quc gia

Ha Ni ging dy v to mi trng tt cho em nghin cu v hc tp.

Cui cng ti xin chn thnh cm n cc bn hc cng kho K49

nhng ngi lun st cnh bn ti trong sut qu trnh hc tp cng nh

trong thi gian lm kho lun tt nghip.

H Ni, thng 5 nm 2008

Sinh vin

inh Mnh Hi

inh Mnh Hi - Lp K49B 1


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TM TT NI DUNG

Vn RWA hin nay rt c quan tm nghin cu vi mt s

lng cng trnh ng k c cng b. Vi cng mt cu trc vt l,

bng cc phng php nh tuyn v gn bc sng hp l trong cu trc

mng quang cho ta truyn c lu lng cao v mang li hiu qu s

dng bng tn cng nh cht lng dch v

Lun vn trnh by tng quan v chuyn mch nhn a giao thc

MPLS v chuyn mch nhn a giao thc tng qutGMPLS.

Trn c s mt s gii php in hnh cho bi ton RWA, lun vn

xy dng c m hnh m phng cc bi ton xut bng OMNET++

cho mng quang thng minh ION.



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MC LC

Li cm n .....................................................................................................

Mc lc.............................................................................................................

Thut ng vit tt.............................................................................................

Li m u..........................................................................................................................

1

Chng 1:Tng quan v cng ngh chuyn mch nhn a giao thc

MPLS v GMPLS..........................................................................................................................

3

11. Gii thiu..........................................................................................................................

3

1.2. Cng ngh IP..........................................................................................................................

4

1.3. Cng ngh ATM..........................................................................................................................

4

1.4. Cng ngh MPLS..........................................................................................................................

6

1.4.1. Cc khi nim c bn MPLS..........................................................................................................................

9

1.4.2. Thnh phn c bn ca MPLS..........................................................................................................................

11

1.4.3. Cc giao thc s dng trong MPLS



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..........................................................................................................................

11

A. Giao thc phn phi nhn (LDP)..........................................................................................................................

12

B. Giao thc RSVP..........................................................................................................................

24

C. Giao thc CR LDP..........................................................................................................................

29

D. Giao thc MPLS BGP..........................................................................................................................

30

1.5.Cng ngh GMPLS..........................................................................................................................

30

1.5.1.Nhn tng quan ca GMPLS

..........................................................................................................................31

1.5.2.B giao thc GMPLS..........................................................................................................................

32

Chng 2: Gii thiu bi ton nh tuyn v gn bc sng trong

mng quang....................................................................................................

..........................................................................................................................33

2.1. Gii thiu..........................................................................................................................

33

2.2.Cc loi bi ton RWA..........................................................................................................................

34

2.2.1. Thit lp lung quang tnh (SLE)



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..........................................................................................................................

34

2.2.2. Thip lp lung quang ng (DLE)..........................................................................................................................

34

2.3.Cc phng php gii quyt bi ton..........................................................................................................................

34

2.4.C s l thuyt..........................................................................................................................

35

2.4.1. Gii thiu l thuyt th..........................................................................................................................

35

2.4.2. Gii thut Dijkstra..........................................................................................................................

35

2.5. Bi ton RWA trong thit lp lung quang tnh (SLE)..........................................................................................................................

36

2.6. Bi ton RWA trong thit lp lung quang ng (DLE)..........................................................................................................................

37

2.6.1. Bi ton nh tuyn..........................................................................................................................

38

A. nh tuyn c nh..........................................................................................................................

38

B. nh tuyn thay th c nh..........................................................................................................................

38

C. nh tuyn thch nghi da trn thng tin tng th..........................................................................................................................

39



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D. nh tuyn thch nghi da trn thng tin cc b..........................................................................................................................

43

2.6.2. Bi ton gn bc sng..........................................................................................................................47

A. Thut ton gn bc sng theo th t bc sng..........................................................................................................................

47

B. Thut ton gn bc sng ngu nhin..........................................................................................................................

47C. Thut ton gn bc sng da trn bc sng s dng nhiu nht t

nht..........................................................................................................................

48

2.6.3. Bo hiu v t trc ti nguyn..........................................................................................................................

48

A. t trc sng sng..........................................................................................................................

48

B. t trc theo chng..........................................................................................................................

49

Chng 3:Phng php nh tuyn v gn bc sng trong mng

quang da.. trn k thut GMPLS..........................................................................................................................

50

3.1 MPLS v mng quang thng minh..........................................................................................................................

50

3.1.1. Tm bao qut rng ln ca MPLs..........................................................................................................................

50



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3.1.2. Cc giao thc nh tuyn v phn phi nhn trong nn MPLS..........................................................................................................................

51

3.1.3. Hng ti ngn xp giao thc n gin hn: IP/MPLS qua DWDM..........................................................................................................................51

3.1.4. Tng quan gia MPLS v mng quang..........................................................................................................................

51

3.1.5. Lin kt v qun l ba mt phng iu khin..........................................................................................................................

523.2 Bi ton nh tuyn v gn bc sng trong mng quang t chc trn

k thut GMPLS..........................................................................................................................

53

3.2.1. Tng quan v k thut GMPLS..........................................................................................................................

53

3.2.2.Thit lp v khi phc lung quang..........................................................................................................................

54

3.3. Cc iu kin rng buc trong nh tuyn quang..........................................................................................................................

54

3.3.1. iu kin rng buc trong lp vt l

..........................................................................................................................55

3.3.2. Cc rng buc bc sng..........................................................................................................................

55

3.3 Kin trc GMPLS..........................................................................................................................

55

3.4. B nh tuyn GMPLS thc t: B nh tuyn Hikari



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..........................................................................................................................

56

3.5 Kt lun chng..........................................................................................................................

58

Chng 4: Xy dng m hnh bi ton nh tuyn v gn bc sng

trong mng quang s dng k thut GMPLs..........................................................................................................................

59

4.1. Tng quan v OMNET++..........................................................................................................................

594.1.1. Gii thiu chung..........................................................................................................................

59

4.1.2. Cc thnh phn chnh ca OMNET++..........................................................................................................................

59

4.1.3. ng dng..........................................................................................................................

60

4.1.4. M hnh thut ton trong OMNET++..........................................................................................................................

60

4.1.5. Lp trnh thut ton..........................................................................................................................

61

4.1.6. S dng OMNET++..........................................................................................................................

61

4.1.7. H thng file..........................................................................................................................

63

4.2. Phng php thc lun nghim



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..........................................................................................................................

65

4.2.1. Cc gi thuyt..........................................................................................................................

65......................................................................................................................

A. nh ngha bi ton..........................................................................................................................

65

B. Xem xt thi gian thit lp yu cu..........................................................................................................................

65

C. Yu cu n..........................................................................................................................

66

D. Xem xt kin trc ca mng quang thng minh ION..........................................................................................................................

67

E. Cc iu kin rng buc vt l

..........................................................................................................................67

4.2.2. Xy dng hm mc tiu..........................................................................................................................

69

4.2.3. M t bi ton RWA..........................................................................................................................

70

A. Gii thut nh tuyn..........................................................................................................................

70

B. M t bi ton nh tuyn..........................................................................................................................

72

4.3. Xy dng m hnh

..........................................................................................................................76



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4.3.1 ng li thc thi..........................................................................................................................

76

A. M hnh mng..........................................................................................................................76

B. Cc tham s h thng..........................................................................................................................

78

4.4. Kt qu v so snh..........................................................................................................................

784.4.1. So snh cc bi ton gn bc sng..........................................................................................................................

78

4.4.2. Tc nghn v trung bnh tuyn lin kt s dng..........................................................................................................................

79

4.4.3. Nhn xt chung v tc nghn trong mng ION..........................................................................................................................

80

4.4.4. So snh gia cc thc o TAW n gin v nng cao..........................................................................................................................

81

Kt lun..........................................................................................................................

82



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THUT NG VIT TT

ADM Add-Drop Multiplexer B ghp knh xen r

ARIS Aggregate Route-Based IP Chuyn mch IP theo

phng php tp hp tuyn

ASE Amplified Spontaneous Emission Pht x t pht c

khuych tn

ATM Asynchronous Tranfer Mode Phng thc truyn ti khng

ng b

BGP Boder Gateway Protocol Giao thc nh tuyn cng minCLNP Connectionless Network Protocol Giao thc mng phi kt

ni

CPU Central Processor Unit B x l trung tm

CR-LDP Constraint-Based routing Labed Giao thc phn b nhn

c xc

Distribution protocol nh tuyn da trn rng buc

CSR Cell Switching Router B nh tuyn chuyn mch t bo

DLCI Data Link Connection Identifier Nhn dng kt ni lp lien kt

d

liu

DLE Dynamic Lightpath Establishment Thit lp lung quang

ng

DWDM Dense Wavelength Division Ghp knh phn chia theo bc

Muntiplexing sngmt cao (40 hoc

80 knh

quang trn m si)

FEC Forwarding Equivalence Class Lp chuyn tip tng ng

FIB Forwarding Information Base C s d liu chuyn tip trong

b nh tuyn



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GMPLS Generalized Multi Protocol Label Chuyn mch nhn a

giao thc

Switching tng qut

IETF International Engineering Task T chc tiu chun k thutQuc

Force t cho Internet

IGP Interior Gateway Protocol Giao thc nh tuyn

trong min

ILP Integer Linear Program Quy hoch tuyn tnh

nguyn

IP Internet Protocol Giao thc Internet

ISCD Interface Switching Capability B m t kh nng chuyn

mch

Descriptor giao din

IS-IS Intermediate System to Giao thc nh tuyn IS-IS

Intermediate System

IS-IS-TE Intermediate System to Giao thc nh tuyn IS-IS c k

Intermediate System Traffic thut lu lng

Engineering

LDP Label Distribution Protocol Giao thc phn b nhn

LMP Link Management Protocol Giao thc qun l knh

LSA Link State Advertisement Bn tin qung b trng

thi lin kt

LSP Label Switching Path ng chuyn mch nhn

LSR Label Switching Router B nh tuyn chuyn mch

nhn

MPLS Multi Protocol Label Switching Chuyn mch nhn a giao

thc

NGN Next Generation Network Mng th h sau



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NP Subset op class NP problems Tp hp con ca lp cc bi

ton

Complete NP m n c xem rt kh

giiOSPF Open Shortest Path First Giao thc nh tuyn

OSPF

OSPF-TE Open Shortest Path First-Traffic Giao thc nh tuyn

OSPF

Engineering c k thut lu lng

OXC Optical Cross-Connect u ni cho quang

PMD Polarization Mode Dispersion Tn sc mt phn cc

PPP Point to Point Protocol Giao thc im - im

RIP Realtime Internet Protocol Giao thc bo hiu IP thi gian

thc

RSVP Wavelength Resvation Protocol Giao thc t trc ti

nguyn

RSVP-TE Wavelength Resvation Protocol- Giao thc t trc ti

nguyn c

Traffic Engineering k thut lu lng

RWA Routing and Wavelength nh tuyn v gn bc sng

Assignment

SDH Synchronous Digital Hierarchy Phn cp truyn dn s ngb

SLE Static Lightpath Establishment Thit lp lung quang tnh

Sonet Synchronous Optical Network Mng quang ng b

TCP Transport Control Protocol Giao thc iu khin

truyn ti

TE Traffic Engineering K thut lu lng



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TED Traffic Engineering Database C s d l iu c k thut lu

lng

TLV Type Length Value Gi tr chiu di tuyn (s

nt)TWA Total Wavelength and Available Tng s bc sng v

bc sng

C th s dng

UDP User Data Protocol Giao thc d liu ngi

s dng

UNI User Network Interface Giao din mng- ngi s dng

VCI Virtual Circuit Identifier Trng nhn dng knh o

VPI Virtual Path Identifier Trng nhn dng ng o

WCC Wavelegth Continuity Rng buc bc sng lin tc

Constraint

WRN Wavelength Routed Network Mng inh tuyn bc sng



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LI M U

Trong nhng nm gn y,cng vi vic bng n Internet trn ton cuko theo l cc dch v mi nh truyn hnh s a phng tin, video,

x l nh i hi bng thng ngy cng cao ln ti c gigabyte vi khong

cch xa, mt cao ri ro thp. Nhng cc giao thc hin nay khng th

p ng c nhu cu . Do xu th tt yu l cn phi c mt giao

thc mi ra i nhm tho mn cc yu cu trn.Theo nghin cu th cc

si quang vi thun li v bng thng (tn s sng mang c 200 THz),

trong lng v kch thc nh; hon ton cch bit v in, khng c giao

thoa cng nh suy ho v ng truyn thp. V nhng u im

c pht trin cho cc ng dng rng ri trong mng truyn dn hin nay.

tn dng c nhng u im trn th vic phn lung v gn bc

sng ph hp cho tn hiu n v i cho cc tuyn trn si quang l cng

vic rt c ngha nhm pht huy nng lc tim tng ca si trong vic

tng dung lng ng truyn

Trn th gii mng ghp knh theo bc sng WDM (Wavelength

Division Multiplexing) c thng mi ho t nm 1996. Xu th phttrin mng hin nay Vit Nam l mc tiu xy dng mng truyn ti ton

quang cho mng th h sau NGN (Next Generation Network) da trn cng

ngh WDM. Nhng l lc phi thng v cng ngh truyn dn quang trong

tp trung vo nghin cu vn cng ngh mng WDM trn th gii

hin nay ang dn dn p ng c nhu cu tt yu ca mng. C nhiu

vn cn phi c gii quyt trong mng WDM nhm ngy cng hon

thin c tnh mng. Trong cc vn th nh tuyn v gn bc

sng trong mng quang ni chung v mng WDM ni ring c coi l mt

trong nhng k thut quan trng nht v c tnh sng cn. Mt mt k thut

ny cho php xy dng c mng truyn dn quang linh hot v m bo

thng sut cc lu lng tn hiu ln. Mt khc n cho php tn dng bng

tn ca si quang trong khi vn n gin ho c rt nhiu cu trc

mng. iu c tc ng ln ti vic xy dng v bo dng mng rt c

hiu qu sau ny.



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Trong nhng nm gn y ngnh cng nghip vin thng v ang

tm mt phng php chuyn mch c th kt hp u im ca IP (nh c

cu nh tuyn) v ca ATM (nh thng lng chuyn mch). Cng ngh

chuyn mch nhn a giao thc MPLS (Multi Protocol Label Switching) l

kt qu pht trin ca nhiu cng ngh chuyn mch Ip s dng c ch

hon i nhn nh ca ATM tng tc truyn gi tin m khng cn

thay i cc giao thc nh tuyn ca IP. Nhng gn y nn cng nghip

vin thng li b ht v chuyn mch nhn a giao thc tng qut GMPLS

(Generalized MPLS) do gii php v mt phng iu khin cho mng quang

th h sau.GMPLS h tr khng ch cc thit b thc hin chuyn mch gi

m cn thc hin chuyn mch theo min thi gian, theo bc sng v

theo khng gian. GMPLS nhm hin i ho vic nh tuyn qua mngthng tin quang bng vic to ra mt mt phng chung gia cc lp qun l

dch v IP v cc lp thng tin quang, c bit cho php chng phn ng

rt linh hot vi cc yu cu thay i bng thng, cho php thit lp cc

dch v thng tin quang nng ng hn.

Vi ngha cng vic nghin cu tm hiu v nh gi cc thut

ton nh tuyn v gn bc sng trong mng quang da trn GMPLS

c tin hnh trong lun vn ny l rt cn thit, c bit khi xu th mng

NGN yu cu vic cp pht ti nguyn.Vi ton b ni dung trnh by trong

lun vn ny, ti mong mun c tip tc nghin cu v vn ny

nhm tham gia v trao i mt vn hc thut trong mt lnh vc mng

thng tin quang cn rt rng ln v hp dn.

Mc ch ca ti lun vn l nghin cu cc k thut nh tuyn v

gn bc sng trong mng quang da trn GMPLS. Vi mc tiu ni

dung ca lun vn bao gm cc vn sau:

Chong 1: Gii thiu tng quan v cng ngh chuyn mch nhn a

giao thc (MPLS) v chuyn mch nhn a giao thc tng qut (GMPLS)

Chng 2: Gii thiu v vn nh tuyn v gn bc sng trong

mng quang (RWA) v cch thc chung gii quyt bi ton ny

Chng 3: Tp trung trnh by v phng php nh tuyn v gn

bc sng trong mng quang da trn k thut chuyn mch nhn a giao

thc tng qut GMPLS



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Chng 4: Tp trung vo vic xy dng m hnh bi ton nh tuyn

v gn bc sng trong mng quang da trn k thut chuyn mch nhn

a giao thc tng qut GMPLS

CHNG 1TNG QUAN V CNG NGH CHUYN MCH

NHN A GIAO THC MPLS V GMPLS

1.1 GII THIU

Trong nhng nm gn y cng vi s bng n ca Internet trn

ton cu th cc dch v thoi v a phng tin cng ngy cng pht trin

vi tc chng mt. Ko theo l vn v tc v di thng ca ccdch v ny vt qu ti nguyn h tng ca Internet hin nay.

Nh chng ta bit giao thc nh tuyn TCP/IP c u im l kh

nng nh tuyn v truyn gi tin mt cch ht sc mm do v linh hot.

Tuy nhin nhc im ca n l khng m bo c cht lng dch v,

tc truyn tin theo yu cu. Trong khi cng ngh ATM c th mnh

u vit v tc truyn tin cao, m bo thi gian thc v cht lng dch

v theo yu cu nh trc nhng n li khng c c kh nng nh

tuyn mm do nh ca TCP/IP. Gii php c t ra i vi cc nh

khoa hc l tm ra mt phng thc chuyn mch c th kt hp ng thi

u im ca TCP/IP v ATM. S kt hp c th l gii php k vng cho

mng vin thng tng lai- mng th h sau NGN.

Chuyn mch nhn l gii php p ng c nhu cu . C l yu

t thc y quan trng nht ng sau chuyn mch nhn l nhu cu pht

trin chc nng nh tuyn ca Internet v IP. V cng l iu tt yu do

i hi ca s pht trin nhanh chng ca Internet.



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S ra i ca chuyn mch nhn a giao thc MPLS gp phn

gii quyt cc vn m cc mng ngy nay ang phi i mt nh tc ,

lu lng truyn kh nng m rng cp mng, qun l cht lng dch

v (QoS). MPLS xut hin p ng cc yu cu dch v v qun l

bng thng cho giao thc Internet (IP) th h sau da trn mng ng

trc.

Ni tm li, s ra i ca MPLS ng mt vai tr quan trng trong

vic nh tuyn, chuyn mch v chuyn tip cc gi qua mng th h sau

cng nh gii quyt cc vn lin quan ti kh nng m rng mng. N

c th hot ng vi cc mng Frame Relay v ch truyn ti khng

ng b ATM hin nay p ng cc nhu cu dch v ca ngi s dng.

1.2. CNG NGH IP

Nh nhc trn MPLS l s kt hp ca hai cng ngh IP v

ATM. Nn chng ta s gii thiu khi qut v hai cng ngh ny.

S pht trin t bin ca IP, s tng trng theo cp s nhn ca

thu bao Internet l mt thc t khng ai c th ph nhn. Hin nay,

lng dch v ln nht trn cc mng ng trc trn thc t u l t IP.Trong cng tc tiu chun ho cc loi k thut, vic m bo tt hn cho IP

tr thnh trng im ca cng tc nghin cu.

IP l giao thc lin mng phi kt ni. Vic chuyn gi tin thc hin

theo c ch phi kt ni. IP nh ngha c cu nh s, c cu chuyn tin,

c cu nh tuyn v cc chc nng iu khin mc thp (ICMP). Gi tin

IP gm a ch ca bn nhn a ch l s duy nht trong ton mng v

mang y thng tin cn cho vic chuyn gi ti ch. T khi giao thc

ny ra i, n nhanh chng tr thnh giao thc lin mng thng dng nht.

Ngy nay gn nh cc lin mng cng cng s dng giao thc IP. Mng IP

c mt khp mi ni, mng Internet ton cu chng ta hin nay cng

ang s dng giao thc IP.

Bn cnh nhng u im tuyt vi ca giao thc IP (nh kh nng

nh tuyn), n cng c khng t nhng nhc im (nh kh nng qun l

cht lng dch v), cc nh cung cp mng trong qu trnh pht trin lin

tc b sung cc giao thc, thut ton mi (chng hn cc giao thc QoS



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nh: RSVP, IntServ, DiffServ; giao thc IPSec, RTP/RTCP hay cc thut

ton tng tc tm kim a ch trong bng nh tuyn) c th khc phc

cc nhc im ca mng IP. Nhng ci g cng c gii hn ca n, khi nhu

cu s dng dch v ca ngi s dng tng ln c v loi hnh ln cht

lng dch v th mi s b sung l khng v cn c nhng cng ngh

mng mi c bn cht khc (khng l gii php phi kt ni) p ng yu cu

QoS tt hn. V th l nhiu cng ngh mng ra i, in hnh l FR v

ATM.

Tm li, IP l mt giao thc chuyn mch gi c tin cy v kh

nng m rng cao. Tuy nhin, vic iu khin lu lng rt kh thc hin

do phng thc nh tuyn theo tng chng. Mt khc, IP cng khng h

tr cht lng dch v.

1.3. CNG NGH ATM

Cng vi s pht trin ca Internet v tng tc x l ca b nh

tuyn l s pht trin mnh trong lnh vc chuyn mch. Mng s dch v

tch hp bng rng (B-ISDN) l mt k thut cho php truyn thng thi

gian thc gia cc thit b truyn thng u cui, s dng k thut ATM.

ATM c th mang mi lung thng tin nh thoi, d liu, video, phn mnh

n thnh cc gi c kch thc c nh (gi l cell), v sau truyn ti cccell trn ng dn c thit lp trc, gi l kt ni o.

Cng ngh ATM da trn c s phng php chuyn mch gi,

thng tin c nhm vo cc gi tin c chiu di c nh, trong v tr ca

gi khng ph thuc vo ng h ng b, v da trn nhu cu bt k ca

knh trc. Cc chuyn mch ATM cho php hot ng vi nhiu tc v

dch v khc nhau.

ATM c hai c im quan trng:

- Th nht ATM s dng cc gi c kch thc nh v c nh gi l

cc t bo ATM, cc t bo nh vi tc truyn ln s lm cho tr truyn

lan v bin ng tr gim nh i vi cc dch v thi gian thc, cng s

to iu kin cho vic kt hp knh tc cao c d dng hn.

- Th hai ATM c kh nng nhm mt vi knh o thnh mt ng

o nhm gip cho vic nh tuyn c d dng.



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ATM khc vi nh tuyn IP mt s im. N l cng ngh chuyn

mch hng kt ni. Kt ni t im u n im cui phi c thit lp

trc khi thng tin c gi i. ATM yu cu kt ni phi c thit lp

bng nhn cng hoc thit lp mt cch t ng thng qua bo hiu. Mt

khc, ATM khng thc hin nh tuyn ti cc nt trung gian. Tuyn kt ni

xuyn sut c xc nh trc khi trao i d liu v c gi c nh

trong sut thi gian kt ni. Trong qu trnh thit lp kt ni, cc tng i

ATM trung gian cung cp cho kt ni mt nhn. Vic ny nhm thc hin

hai iu: dnh cho kt ni mt s ti nguyn v xy dng bng chuyn t

bo ti mi tng i. Bng chuyn t bo c tnh cc b v ch cha thng

tin v cc kt ni ang hot ng i qua tng i. iu ny khc vi thng

tin v ton mng cha trong bng chuyn tin ca router dng IP.Qu trnh chuyn tip t bo qua tng i ATM cng tng t vic

chuyn gi tin qua router. Tuy nhin, ATM c th chuyn mch nhanh hn

v nhn gn trn cell c kch thc c nh (nh hn ca IP), kch thc

bng chuyn tin nh hn nhiu so vi ca IP router, v vic ny c thc

hin trn cc thit b phn cng chuyn dng. Do vy, thng lng ca

tng i ATM thng ln hn thng lng ca IP router truyn thng.

Do c kh nng h tr truyn d liu, thoi, v video vi cht lngcao trn mt s cc cng ngh bng tn cao khc nhau, ATM tng c

xem nh l cng ngh chuyn mch ha hn v thu ht nhiu s quan tm.

Tuy nhin, hin nay cng nh trong tng lai h thng ton ATM s khng

phi l s la chn ph hp nht.

i vi cc ng dng c thi gian kt ni ngn, th mi trng hng

kt ni dng nh li khng thch hp do thi gian thit lp kt ni cng

nh t l phn thng tin mo u li qu ln. Vi cc loi lu lng nh

vy th mi trung phi kt ni vi phng thc nh tuyn n gin, trnh

phi s dng cc giao thc bo hiu phc tp s ph hp hn.

1.4. CNG NGH MPLS

Chuyn mch nhn a giao thc (MPLS) l kt qu ca qu trnh

pht trin nhiu gii php chuyn mch IP, c chun ho bi IETF. Tn

gi ca n bt ngun t thc t l hon i nhn c s dng nh l

k thut chuyn tip nm bn di. S dng t a giao thc trong tn

ca n c ngha l n c th h tr nhiu giao thc lp mng, khng ch



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ring IP. Ngoi ra cc nh cung cp mng c th cu hnh v chy MPLS

trn cc cng ngh lp 2 khc nhau nh Fram Relay khng ch ring

ATM. V mt kin trc iu ny l ng, nhng trong thc t MPLS thng

tp trung vo vic vn chuyn cc dch v IP trn nn ATM.

MPLS l gii php nhm lin kt nh tuyn lp mng v c ch hon

i nhn thnh mt gii php n nht t c cc mc tiu sau:

Ci thin hiu nng nh tuyn

Ci thin tnh mm do ca nh tuyn trn cc m hnh xp chng

truyn thng.

Tng tnh mm do trong qu trnh a v pht trin cc loi hnh

dch v mi.

Mng MPLS c kh nng chuyn cc gi tin ti lp 3 bng vic s

dng x l tng gi v chuyn tip gi tin ti lp 2 s dng c ch hon i

nhn. MPLS da trn m hnh ngang cp, v vy mi mt thit b MPLS

chy mt giao thc nh tuyn IP, trao i thng tin nh tuyn vi cc thit

b ln cn, v ch duy tr mt khng gian cu hnh mng v mt khng gian

a ch.

MPLS chia b nh tuyn lm hai phn ring bit: chc nng chuyngi tin v chc nng iu khin. Phn chc nng chuyn gi tin vi nhim

v gi gi tin gia cc b nh tuyn IP, s dng c ch hon i nhn

tng t nh ca ATM.Trong MPLS nhn l mt thc th c di c nh

v khng ph thuc vo lp mng. K thut hon i nhn v bn cht l

vic tm chng k tip ca gi tin trong mt bng chuyn tip nhn, sau

thay th gi tr nhn ca gi ri chuyn ra cng ra ca b nh tuyn. Vic

ny n gin hn nhiu so vi vic x l gi tin thng thng v do vy ci

tin kh nng ca thit b. Cc b nh tuyn s dng thit b ny gi l b

nh tuyn chuyn mch nhn LSR (Label switching Router). Phn chc

nng iu khin ca MPLS bao gm cc giao thc nh tuyn lp mng vi

nhim v phn phi thng tin nh tuyn gia cc LSR, v th tc gn nhn

chuyn thng tin nh tuyn thnh bng nh tuyn chuyn mch nhn.

MPLS c th hot ng c vi cc giao thc nh tuyn Internet nh

OSPF (Open Shortest Path First) v BGP (Boder Gateway Protocol) hay

PNNI ca ATM. Do MPLS h tr iu khin lu lng v cho php thit lp



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tuyn c nh nn vic m bo dch v ca cc tuyn l hon ton kh thi.

Ngoi ra, MPLS cn c c ch nh tuyn li nhanh (fast rerouting).

Bn cnh tin cy, cng ngh MPLS cng h tr vic qun l mng

c d dng hn. Do MPLS qun l vic chuyn tin theo cc lung thngtin, cc gi tin thuc mt FEC (Forwarding Equivalence Class - lp chuyn

tip tng ng) c th c xc nh bi gi tr ca nhn. Do vy, trong

min MPLS, cc thit b o lu lng mng c th da trn nhn phn

loi cc gi tin. Bng cch gim st lu lng ti cc b nh tuyn chuyn

mch nhn LSR, nghn lu lng nhanh chng c pht hin v v tr xy

ra nghn lu lng c th xc nh. Tuy nhin, gim st lu lng theo

phng thc ny khng a ra c ton b thng tin v cht lng dch

v (v d nh tr xuyn xut ca min MPLS). Vic o tr c th c thchin bi giao thc lp hai. gim st tc ca mi lung v m bo

cc lung lu lng tun th tnh cht lu lng c nh trc, h

thng gim st c th dng mt thit b nh dng lu lng. Thit b ny s

cho php gim st v m bo tun th c tnh lu lng m khng cn

thay i cc giao thc hin c.

Khi mt gi tin vo mng MPLS, cc b nh tuyn chuyn mch

nhn khng thc hin chuyn tip theo tng gi m thc hin phn loi gitin vo trong cc lp tng ng chuyn tip FEC, sau cc nhn c

nh x vo trong cc FEC. Mt giao thc phn b nhn LDP c xc nh

v chc nng ca n l n nh v phn b cc rng buc FEC/nhn

cho cc b nh tuyn chuyn mch nhn LSR. Khi LDP hon thnh nhim

v ca n, mt ng dn chuyn mch nhn LSP c xy dng t li

vo ti li ra. Khi cc gi vo mng, LSR li vo kim tra nhiu trng trong

tiu gi xc nh xem gi thuc v FEC no. Nu c mt rng

buc nhn/FEC th LSR li vo gn nhn cho gi v nh hng n ti giaodin u ra tng ng. Sau gi c hon i nhn qua mng cho n

khi n n LSR li ra, lc nhn b loi b v gi c x l ti lp 3.

Hiu nng t c y l nh vic a qu trnh x l lp 3 ti bin ca

mng v ch thc hin mt ln ti thay cho vic x l ti tng node trung

gian nh ca IP. Ti cc node trung gian vic x l ch l tm s ph hp

gia nhn trong gi v thc th tng ng trong bng kt ni LSR v sau

hon i nhn- qu trnh ny thc hin bng phn cng.



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Mc d hiu nng v hiu qu l 2 kt qu quan trng, song chng

khng phi l cc li ch duy nht m MPLS cung cp. Trong mt ca

nhng nh cung cp cc mng ln, th kh nng thc hin k thut lu

lng tin tin m khng phi tr gi v hiu nng ca MPLS c quan

tm c bit.

MPLS thc hin cc chc nng sau:

+ Xc nh c cu qun l cc tnh ht khc nhau ca cc lung lu

lng, nh cc lung gia cc my, phn cng khc nhau hoc thm ch

cc lung gia nhng ng dng khc nhau.

+ Duy tr s c lp ca cc giao thc lp 2 v 3

+ Cung cp phng php nh x a ch IP vi cc nhn n gin,c di c nh c s dng bi cc cng ngh chuyn tip gi v

chuyn mch gi khc nhau

+ Giao din vi cc giao thc nh tuyn hin c nh giao thc t

trc ti nguyn RSVP (Resource Reservation Protocol) v giao thc m

ng ngn nht u tin (OSPF)

+ H tr IP, ATM v giao thc lp 2 Frame Relay

Trong MPLS vic truyn d liu xy ra trn cc ng chuyn mch nhn

LSPs (Label Switch Path) to ra t u vo n u ra ca mng MPLS

dng chuyn tip gi ca FEC no s dng c ch chuyn i nhn.

LSPs c thit lp trc khi truyn d liu (kch thch iu khin). Cc

nhn (tn nhn dng chnh xc giao thc) c phn b bng vic s dng

giao thc phn b nhn LDP (Label Ditribution Protocol) hoc RSVP hoc

c i ln (piggybacked) cc giao thc nh tuyn nh giao thc nh

tuyn cng min (BGP) v OSPF. Mi gi d liu bc v mang cc nhntrong sut hnh trnh ca chng t ngun ti ch. Bi v cc nhn c

di c nh c chn u gi hoc t bo nn c th chuyn mch gi

nhanh gia cc tuyn lin kt bng phn cng.

1.4.1. CC KHI NIM C BN MPLS

Nhn

Nhn l mt thc th c di ngn, c nh v khng c cu trc

bn trong. Nhn xc nh ng m gi s i qua. Nhn khng trc tip mho thng tin ca mo u lp mng, nh a ch lp mng. Nhn c



24/106


25/106


L thit b (Router hay Switch) s dng trong mng MPLS chuyn

cc gi tin bng th tc phn phi nhn. C mt s loi LSR c bn nh

sau: LSR, LSR bin, ATM-LSR, ATM-LSR bin

Cc lp chuyn tip tng ng FEC (Forwarding EquivalenceClasses)

Cc lp chuyn tip tng ng (FEC) l khi nim c dng

ch mt lp cc gi c u tin nh sau (chng u gi ti chng tip

theo nh nhau) qua mng MPLS ngay c khi c s khc bit gia cc gi

tin ny th hin trong mo u lp mng.

+ Bng chuyn tip chuyn mch nhn

L bng chuyn tip nhn c cha thng tin v nhn vo, nhn ra,giao din vo, giao din ra.

ng chuyn mch nhn LSP (Label Switching Path)

L tuyn to ra t u vo n u ra ca mng MPLS dng

chuyn tip gi ca mt FEC no s dng c ch hon i nhn. LSP

c thit lp trc khi truyn d liu. MPLS cung cp hai la chn cho

vic thit lp LSP.

nh tuyn theo chng - Mi LSR la chn chng tip theo mt cch

c lp cho mt FEC nht nh. Phng php ny ging vi hin nay

c s dng trong mng IP. LSR s dng giao thc nh tuyn c sn

no nh OSPF, giao din mng - mng ring ATM (PNNI)

nh tuyn r rng (explicit) nh tuyn r rng ging nh nh tuyn

ngun. LSR li vo (tc l LSR m d liu bt u truyn) xc nh danh

sch cc nt m ER-LSP truyn qua. ng dn xc nh c th khng

ti u cng c. Dc ng i ti nguyn c th c t trc mbo QoS cho lu lng d liu. iu ny lm gim nh k thut lu lng

khp mng, v cc dch v phn bit c cung cp bng vic s dng cc

lung da trn cc chnh sch hoc phng thc qun l mng.

C s d liu nhn.

L bng kt ni trong LSR. C cha gi tr nhn FEC c gn vo

cng ra cng nh thng tin v ng gi phng tin truyn.

Gi tin dn nhn



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Gi tin dn nhn l gi tin m nhn c m ho trong . Trong mt

vi trng hp, nhn nm trong mo u ca gi tin dnh ring cho mc

ch dn nhn. Trong cc trng hp khc, nhn c th c t chungvo trong mo u lp mng v lp lin kt d liu min l y c trng

c th dng cho mc ch dn nhn. Cng ngh m ho c s dng phi

ph hp vi c thc th m ho v thc th gii m.

n nh v phn phi nhn.

Trong mng MPLS, quyt nh kt hp nhn L c th vi mt FEC

M c th l do LSR pha trc thc hin. LSR pha trc sau khi kt hp s

thng bo vi LSR pha sau v kt hp . Do vy, cc nhn c LSRpha trc n nh v cc kt hp nhn c phn phi theo hng t

LSR pha trc ti LSR pha sau.

1.4.2. THNH PHN C BN CA MPLS

LSR: L thnh phn quan trng c bn ca mng MPLS. LSR l thit

b nh tuyn chuyn mch nhn (Label Switching Router). Thit b ny thc

hin chc nng chuyn tip gi thng tin trong phm vi mng MPLS bng

th tc phn phi nhn.LSR bin: L thit b nm bin ca mng MPLS. LSRs bin gi hay

nhn cc gi thng tin t hay n mng khc nhau (Frame Relay,ATM.)

v chuyn tip lu lng ca cc mng ny ln mng MPLS sau khi thit

lp LSPs bng vic s dng giao thc bo hiu nhn li vo v phn b

lu lng tr li mng truy nhp li ra. LSR bin gn hay loi b nhn

cho cc gi thng tin n hoc i ra khi mng MPLS. Cc LSR bin c th

l Igress Router (router li vo) hay Egress Router (router li ra).

ATM- LSR: S dng giao thc MPLS trong bng iu khin thit lp

knh o ATM. Chuyn tip t bo n nt ATM-LSR tip theo.

ATM-LSR bin: Nhn gi c nhn hoc khng c nhn, phn vo cc

t bo ATM v gi cc t bo n nt ATM-LSR tip theo. Nhn cc t bo

ATM t

ATM-LSR cn k, ti to cc gi t cc t bo ATM v chuyn tip

gi c nhn hoc khng nhn.1.4.3. CC GIAO THC S DNG MPLS



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Tham gia vo qu trnh truyn thng tin trong mng MPLS c mt s

giao thc nh LDP, RSVP, CR-LDP, MPLS-BGP. Cc giao thc nh RIP,

OSPF s dng trong mng router nh tuyn cc gi IP s khng c

cp n phn ny.

A. Giao thc phn phi nhn LDP

Giao thc phn phi nhn c nhm nghin cu MPLS ca IETF

xy dng v ban hnh di tn RFC 3036. Phin bn mi nht c cng

b nm 2001 a ra nhng nh ngha v nguyn tc hot ng ca giao

thc LDP.

Giao thc phn phi nhn c s dng trong qu trnh gn nhn

cho cc gi thng tin. V tr ca giao thc LDP v cc mi lin kt chcnng c bn ca LDP vi cc giao thc khc th hin trn hnh 2.6. Giao

thc LDP l giao thc iu khin tch bit c cc LSR s dng trao

i v iu phi qu trnh gn nhn/FEC. Giao thc ny l mt tp hp cc

th tc trao i cc bn tin cho php cc LSR s dng gi tr nhn thuc

FEC nht nh truyn cc gi thng tin.

Mt kt ni TCP c thit lp gia cc LSR ng cp m bo

cc bn tin LDP c truyn mt cch trung thc theo ng th t. Cc

bn tin LDP c th xut pht t bt c mt LSR (iu khin ng chuyn

mch nhn LSR c lp) hay t LSR bin li ra (iu khin LSP theo lnh)

v chuyn t LSR pha trc n LSR pha sau cn k. Vic trao i cc

bn tin LDP c th c khi pht bi s pht hin ca lung s liu c

bit, bn tin lp d tr RSVP hay cp nhp thng tin nh tuyn. Khi mt

cp LSR trao i bn tin LDP cho mt FEC nht nh th mt ng

chuyn mch LSP t u vo n u ra c thit lp sau khi mi LSR

ghp nhn u vo vi nhn u ra tng ng trong LIB ca n. LDP cth hot ng gia cc LSR kt ni trc tip hay khng trc tip.



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Thnhphngiaoth cMPLS

Thnhphngiaothckhngphi MPLS

Csthngtinnhn

Mgr Dscy Sess Adtv Notf

OSPF UDP TCP

IP

MPLSFwd ARP

MAC

PHY

Mgr QunlLDPDscy BntinthmdSess BntinqunlphinAdvt Pht hnhLDPNotf Bntinxcnhn

Giaothcphnbnhn

Hnh 1.2. V tr giao thc LDP trong b giao thc MPLSCc loi bn tin LDP

LDP nh ngha 4 loi bn tin: Bn tin thm d, Bn tin phin, Bn tin

pht hnh, Bn tin thng bo. Bn loi bn tin ny cng ni ln chc nng

m n thc hin.

Bn tin thm d (Discovery): Dng thng bo v duy tr s c

mt ca 1 LSR trong mng. Theo nh k, LSR gi bn tin Hello

qua cng UDP vi a ch multicast ca tt c cc router trnmng con.

Bn tin phin (Session): thit lp, duy tr, v xo cc phin

gia cc LSR. Hot ng ny yu cu gi cc bn tin Initialization

trn TCP. Sau khi hot ng ny hon thnh cc LSR tr thnh

cc i tng ngang cp LDP

Bn tin pht hnh (Advertisement): Dng to, thay i v

xo cc rng buc nhn vi cc FEC. Nhng bn tin ny cngmang trn TCP. Mt LSR c th yu cu 1 nh x nhn t LSR

ln cn bt k khi no n cn. N cng pht hnh cc nh x nhn

bt c khi no n mun mt i tng ngang cp LDP no s

dng rng buc nhn.

Bn tin thng bo (Notification): Dng cung cp cc thng bo

li, thng tin chn on, v thng tin trng thi. Nhng bn tin ny

cng mang trn TCP.



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a s cc bn tin LDP chy trn giao thc TCP m bo tin

cy ca cc bn tin (ngoi tr bn tin thm d).

LDP c thit k d dng m rng, s dng kiu bn tin c bit

thu thp cc i tng m ho TVL (kiu, di, gi tr).Th tc thm d LSR ln cn

Th tc pht hin LSR ln cn ca LDP chy trn UDP thc hin nh

sau (hnh 1.3):

Mt LSR nh k gi bn tin Hello ti cc cng UDP bit trong

tt c cc b nh tuyn trong mng con ca nhm multicast.

Tt c cc LSR tip nhn bn tin Hello ny trn cng UDP. Nh vy,

ti mt thi im no LSR s bit c tt c cc LSR khc m n

c kt ni trc tip.

Khi LSR nhn bit c a ch ca LSR khc bng c ch ny th

n s thit lp kt ni TCP n LSR .

Khi phin LDP c thit lp gia 2 LSR. Phin LDP l phin hai

chiu c ngha l mi LSR hai u kt ni u c th yu cu v gi

rng buc nhn.

Trong trng hp cc LSR khng kt ni trc tip trong mt mng

con, ngi ta s dng mt c ch b sung nh sau:

LSR nh k gi bn tin Hello n cng UDP bit ti a ch IP xc

nh c khai bo khi lp cu hnh. u nhn bn tin ny c th tr li li

bng bn tin HELLO khc truyn mt chiu ngc li n LSR gi v vic

thit lp cc phin LDP c thc hin nh trn.

Thng thng trng hp ny hay c p dng khi gia 2 LSR cmt ng LSP cho iu khin lu lng v n yu cu phi gi cc gi c

nhn qua ng LSP .



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UD P Hel lo

UD P Hel lo

TCP Open

Initialization

Label Request

Label Mapping

IP

Hnh 1.3. Th tc pht hin LSR ln cn

Tiu bn tin LDP

Mi mt bn tin LDP c gi l n v d liu giao thc PDU, c

bt u bng tiu bn tin v sau l cc bn tin LDP nh c

trnh by trn. Hnh 2.8 ch ra cc trng chc nng ca tiu LDP v

cc trng ny thc hin cc chc nng sau:

Phin bn: Ch s phin bn ca giao thc, phin bn ang s

dng hin ti l phin bn 1.

di PDU: Tng di ca PDU tnh theo octet, ngoi tr

trng phin bn v trng di.

Nhn dng LDP: Nhn dng khng gian nhn ca LSR gi bn

tin ny. Bn octet u tin cha a ch IP c gn cho LSR

(nhn dng b nh tuyn). Hai octet cui nhn dng khng giannhn bn trong LSR.Vi LSR c khng

gian nhn ln, trng chc nng ny t v gi tr 0.

.

0 1 5 3 1

P h i n b n d i P D U

N h n d n g L D P

N h n d n g L D P



31/106


Hnh 1.4. Tiu LDP

M ho TLV

LDP s dng lc m ho kiu- di-gi tr m ho cc thng

tin mang trong bn tin LDP. Nh ch ra trn hnh 2.9, TVL c m hothnh mt trng 2 octet trong s dng 14 bt c trng cho kiu, v

2 bit (U, F) cho trng hp LSR khng nhn ra c kiu, 2 octet tip theo

l trng di v trng gi tr c di thay i.

Trng kiu qui nh cc trng m gi tr c dch.

Trng di xc nh di ca trng gi tr.

Trng gi tr c th cha cc TLV khc.

0 1 5 3 1

K i u d i

G i t r

U F

Hnh 1.5. M ho TLV

Da trn bn tin nhn c, khi bit U c gi tr 0, LSR s gi thngbo ngc li ti ni pht v ton b bn tin s c b qua. Nu U c gi

tr 1 th mc d khng nhn ra kiu LSR khng cn gi thng bo v vn x

l phn cn li ca bn tin nh th l bn tin cha bit kiu ny khng tn

ti.

Bit F ch c s dng khi bit U = 1 v bn tin LDP cha bn tin

cha bit kiu ny c truyn i. Nu bt F bng 0 th bn tin cha bit

kiu s khng chuyn i cng bn tin LDP cha n v nu bit F=1 th bn

tin cha bit kiu s chuyn i cng bn tin LDP cha n.

Cc khun dng v chc nng ca cc TLV(vt khi phm vi

n ny nn xin php khng ni n).

Khun dng bn tin LDP


ID bn tin

U Kiu bn tin di bn tin


32/106


Hnh 1.6. Khun dng cc bn tin LDP

Bit U: bit bn tin cha bit. Nu bit ny bng 1 th n khng th

c thng dch bi pha nhn, lc bn tin b b qua m khng

c phn hi.

Kiu bn tin: Ch ra kiu bn tin l g?

di bn tin: Ch ra chiu di ca cc phn nhn dng bn tin,

cc thng s bt buc, v cc thng s tu chn.

Nhn dng bn tin: l mt s nhn dng duy nht bn tin.

Trng ny c th c s dng kt hp cc bn tin thng

bo vi mt bn tin khc.

Thng s bt buc, v Thng s tu chn tu thuc vo tng

bn tin LDP.

V mt nguyn l, mi th xut hin trong bn tin LDP c th c

m ho theo TLV, nhng cc c t LDP khng phi lun lun s dnglc TLV. N khng c s dng khi n khng cn thit v s s dng

n khi s gy lng ph khng gian. Chng hn khng cn thit phi s

dng khun dng TLV nu chiu di ca gi tr l c nh hay kiu ca gi

tr c bit v khng phi ch nh mt nhn dng kiu.

Khun dng v chc nng cc bn tin LDP

Phn ny cung cp thng tin v khun dng v chc nng ca cc

bn tin LDP bao gm: Bn tin Notification - Bn tin Thng bo

Bn tin Hello Bn tin Cho hi

Bn tin Initialization - Bn tin khi to

Bn tin Keepalive - Bn tin gi ng

Bn tin Address - Bn tin a ch

Bn tin Address Withdraw Bn tin Thu hi a ch


Thng s bt buc

Thng s tu chn


33/106


Bn tin Label Mapping - Bn tin Rng buc nhn

Bn tin Label Request Bn tin Yu cu nhn

Bn tin Label Withdraw - Bn tin Thu hi nhn

Bn tin Label Release Bn tin Gii phng nhn

Bn tin Label Abort Request - Bn tin Yu cu hu b nhn

Bn tin Notification:

Bn tin thng bo cho bit mt li khng th trnh khi, l kt qu ca

qu trnh x l bn tin hay trng thi ca phin LDP.

Nu mt LSR bt gp mt iu kin m cn thng bo ti LSR

ngang cp cng vi thng tin t vn hay li, n gi LSR mt thng bo

cha TLV trng thi m m ha thng tin v cc TLV ty chn thm. Nu

iu kin l khng th trnh khi, sau khi gi bn tin thng bo, LSR chm

dt phin LDP bng cch ng kt ni TCP v loi b tt c cc trng thi

lin kt cng vi phin ny.

Bn tin Initialization:.

Cc bn tin thuc loi ny c gi khi bt u mt phin LDP gia

2 LSR trao i cc tham s, cc i lng tu chn cho phin. Cc tham

s ny bao gm:

Ch phn b nhn

Cc gi tr nh thi

Phm vi cc nhn s dng trong knh gia 2 LSR .

C 2 LSR u c th gi cc bn tin Initialization v LSR nhn s tr

li bng KeepAlive nu cc tham s c chp nhn. Nu c mt tham sno khng c chp nhn th LSR tr li thng bo c li v phin kt

thc.

Bn tin KeepAlive:

Cc bn tin KeeepAlive c gi nh k khi khng c bn tin no

c gi m bo cho mi thnh phn LDP bit rng thnh phn LDP

khc ang hot ng tt. Trong trng hp khng xut hin bn tin

KeepAlive hay mt s bn tin khc ca LDP trong khong thi gian nht



34/106


nh th LSR s xc nh i phng hoc kt ni b hng v phin LDP b

dng.

Bn tin Address:

Mt LSR gi mt bn tin a ch n LSR ngang cp thng bocc a ch giao din ca n. Mt LSR nhn mt thng ip bn tin a ch

s dng cc a ch n bit duy tr c s d liu cho nh x gia cc b

nhn dng LDP ngang cp v cc a ch chng tip theo. Khi mt phin

LDP mi c khi to v trc khi gi bn tin yu cu v gn nhn, mt

LSR thng bo cc a ch giao din ca n vi mt hay nhiu a ch giao

din. Bt c khi no mt LSR kch hot mt a ch giao din mi, n cn

thng bo a ch mi cng vi bn tin a ch. Khi n mun hy kch

hot a ch no , n cn thu hi a ch cng vi bn tin thu hi a ch.

Bn tin Label Mapping:

Cc bn tin Label Mapping c s dng qung b lin kt gia

FEC (tin t i ch) v nhn. Bn tin Label Withdrawal thc hin qu trnh

ngc li: n c s dng xo b lin kt va thc hin. Bn tin ny

c s dng khi c s thay i trong bng nh tuyn (thay i tin t a

ch) hay thay i trong cu hnh LSR lm tm dng vic chuyn nhn cc

gi trong FEC .

Bn tin Lable Realease:

Bn tin ny c LSR s dng khi nhn c chuyn i nhn m

n khng cn thit na. iu thng xy ra khi LSR gii phng nhn

thy nt tip theo cho FEC khng phi l LSR qung b lin kt

nhn/FEC .

ch hot ng gn nhn theo yu cu t pha trc, LSR syu cu gn nhn t LSR ln cn pha trc s dng bn tin Label

Request. Nu bn tin Label Request cn phi hu b trc khi c chp

nhn (do nt k tip trong FEC yu cu thay i), th LSR yu cu s

loi b yu cu nh bn tin Label Request Abort.

Pht hnh v s dng nhn

C mt vi cng c c s dng pht hnh v phn b nhn.

Cc c t kin trc MPLS thit lp cc th tc y cho nhng hotng ny. Nhng th tc ny c t chc nh sau.



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Cc LSR ng xung nh ngha 5 th tc, trong c 4 th tc

phn b v 1 th tc thu hi. Cc th tc phn b l: (a) y khng iu

kin; (b) y c iu kin; (c) Ko khng iu kin; (d) Ko c iu kin.

Cc LSR ng ln nh ngha 9 th tc gm 4 loi l: Cc th tc Yu cu gm: (a) th tc Khng bao gi yu cu, (b)

th tc Yu cu khi cn, (c) th tc Yu cu theo yu cu.

Cc th tc Khng kh dng gm: (a) th tc Yu cu c th li,

th tc Yu cu khng th li.

Cc th tc Gii phng gm: (a) th tc Gii phng khi thay i,

(b) th tc Gii phng khi khng thay i.

Cc th tc S dng nhn gm: (a) th tc S dng ngay, (b) th

tc S dng nu lp vng khng c pht hin.

Cc th tc LSR ng xung (Rd)

Hnh 1.7 minh ho cc th tc ca LSR ng xung.

Th tc y khng iu kin

y khng iu kin l trng hp phn b nhn ng xung

khng theo yu cutrong ch iu khin LSP c lp.

Gi s X l tin t a ch trong bng nh tuyn ca LSR-Rd v LSR-

Ru l thc th ngang cp phn b ca Rd. Nu iu kin ny tho mn,

LSR-Rd phi rng buc 1 nhn vi X v gi rng buc ny ti LSR-Ru.

Trch nhim ca Ru l phi lun cp nht rng buc ny v phi thng bo

cho Rd bit mi s thay i.



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LSR - Ru LSR - Rd

Rngbucnhnvi tintach X

(a) ykhngiu kin

LSR - Ru LSR - Rd

(b) yciukin

LSR - Ru LSR - Rd

(c) Kokhngiu kin

LSR - Rn

(d) Kociukin

Yucurngbucnhnvi tintach X

1.Rngbuc nhnvitinta ch X

2.Yucurngbucnhnvitinta ch X

Bngnhtuyn

Tinta ch X

Bngnhtuyn

Tinta ch X

Rngbucnhnvi tintach X

Bngnhtuyn

Tintach X

LSR - Ru LSR - Rd LSR - Rn

1.Rngbuc nhnvitintach X

2.Yucurngbucnhnvitintach X

3.Rngbucnhnvi tinta ch X

Bngnhtuyn

Tinta ch X

3.Rngbuc nhnvi tinta ch X

Hnh 1.7. Cc th tc LSR ng xung

Th tc y c iu kin

y c iu kin l trng hp phn b nhn ng xung khngtheo yu cu trong ch iu khin theo lnh.

Gi s X l tin t a ch trong bng nh tuyn ca LSR-Rd; LSR-Ru

l li ra ca LSP; chng tip theo ca Rd l Rn. Hn na, Rn rng buc

1 nhn vi X v phn b rng buc ti Rd. Trong tnh hung ny, Rd

nn rng buc 1 nhn vi X v gi n ti Ru.

S khc nhau gia y khng c iu kin v y c iu kin l

ch: y khng c iu kin thc hin phn b cc rng buc nhn cho ttc cc tin t a ch trong bng nh tuyn, cn y c iu kin ch thc

hin phn b rng buc nhn cho cc tin t a ch m Rd nhn cc

rng buc t chng k tip ca LSP.

Th tc Ko khng iu kin

Ko khng iu kin l trng hp phn b nhn ng xung theo

yu cu, bng vic s dng ch iu khin LSP c lp.

Gi s X l tin t a ch trong bng nh tuyn ca LSR-Rd. LSR-Ruyu cu LSR-Rd rng buc nhn vi X, v phn b rng buc nhn ny cho



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ti n. Rd phi tn trng yu cu rng buc ny, v nu n khng th

(chng hn, n khng l i tng ngang cp phn b nhn vi Ru), th n

cng phi thng bo cho Ru bit. Nu Rd gi mt rng buc, th n phi

gi mt rng buc mi. Rng buc c vn gi nguyn tc dng. Kt qu

cui cng l 2 nhn c kt hp vi cng 1 tin t a ch. Ti sao nh

iu hnh mng mun lm iu ny? MPLS hiu r iu ny. Chng cn

nh: Nu cc kha cnh khc ca FEC bn cnh tin t a ch c xem

xt, n s cho php rng buc cc nhn khc nhau vi cc FEC khc nhau

c cng tin t a ch.

Th tc Ko c iu kin

Ko c iu kin l trng hp phn b nhn ng xung theo yu

cu, bng vic s dng ch iu khin LSP theo lnh.

Gi s X l tin t a ch trong bng nh tuyn ca LSR-Rd. Ru yu

cu Rd rng buc 1 nhn vi X v phn b rng buc ny ti Ru. Rn l li

ra ca LSP, hay chng k tip lp 3 ca Rd ca X l Rn v Rn rng

buc 1 nhn vi X v phn b rng buc ti Rd. Nu nhng iu kin

ny tho mn, Rd phi rng buc 1 nhn vi X v phn b rng buc ti

Ru.

Th tc Thu hi nhn

Nu mt LSR quyt nh ph v rng buc nhn v tin t a ch,

bn tin hu rng buc nhn LDP phi c phn b ti tt c cc LSR m

rng buc nhn ny i qua lc u.

Cc th tc LSR ng ln (Ru)

Cc hot ng LSR ng ln l n gin hn nhng hot ng

LSR ng xung nh ni trn. Nhng hot dng ny c tm ttngn gn da vo phn 5.1.2 ca RFC 3031.

Cc th tc Yu cu

Th tc Khng bao gi yu cu

LSR khng bao gi yu cu 1 rng buc nhn. Chng hn, trong hnh

2.11a v 2.11b, LSR ng xung thc hin cc hnh ng cn thit

rng buc cc nhn vi cc tin t a ch. LSR ng ln khng cn thit

phi thc hin nhng nhim v ny. Th tc ny c th p dng khi 1 LSRs dng phn b nhn ng xung khng theo yu cu v trong ch



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duy tr nhn y , nhng khng nn c s dng nu Rd s dng cc

th tc Ko khng c iu kin hay Ko c iu kin.

Th tc Yu cu khi cn

Khi mt router tm mt tin t a ch mi hay khi 1 tin t mi ccp nht, th th tc ny c thc hin - nu 1 rng buc nhn khng tn

ti. Th tc ny c thc hin bi 1 LSR nu ch duy tr nhn hn ch

c s dng.

Th tc Yu cu khi c yu cu

Hot ng ny sinh ra mt yu cu bt c khi no nhn c mt

yu cu, iu ny l khc vi sinh ra yu cu khi cn. Nu Ru l khng c

kh nng nh mt LSR li vo, n c th sinh ra mt yu cu ch khi n

nhn c 1 yu cu t router ng ln. Nu Rd nhn c 1 yu cu

nh vy t Ru v tin t a ch m Rd phn b nhn ti Ru, lc Rd

n nh mt nhn mi, rng buc n vi X, v phn b rng buc .

Cc th tc khng kh dng

Th tc khng kh dng xc nh Rd phn ng nh th no vi tnh

hung sau:

1. Ru v Rd tng ng l cc thc th ng cp phn b nhn vi

tin t a ch X.

2. Rd l chng k tip lp 3 ca Ru vi tin t a ch X.

3. Ru yu cu 1 rng buc vi X t Rd.

4. Rd tr li rng n khng th cung cp 1 rng buc ti thi im

ny bi v n khng c chng k tip ca X.

C 2 th tc iu khin hnh vi ca Ru l: Th tc Yu cu c th

li v Th tc Yu cu khng th li.

Th tc Yu cu c th li

Ru phn tn li yu cu ti mt thi im. Sau th tc ny nn

c s dng khi phn b nhn theo yu cu ng xung c s dng.

Th tc Yu cu khng th li

Ru khng bao gi phn tn li yu cu, thay vo n tha nhn

rng Rd s cung cp rng buc mt cch t ng khi n c th. iu ny l

c ch nu Rd s dng th tc y khng c iu kin, ngha l nu phn

b nhn ng xung khng theo yu cu c s dng.



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Cc th tc gii phng nhn

Cc th tc gii phng nhn c ngha n gin ch l rng buc nhn

vi FEC b xo ti LSR. Kch bn cho qu trnh gii phng l nh sau. Rd l

mt LSR rng buc 1 nhn vi tin t a ch X; n phn b rngbuc ti LSR Ru. Nu Rd khng l chng k tip ca Ru vi tin t a

ch X hay n khng s dng chng k tip ca Ru vi tin t a ch X,

lc Ru ang khng s dng nhn, v n khng c l do g m duy tr

nhn tr khi c kh nng l s rng buc ny xy ra sau . C 2 th tc

iu khin hnh vi ca Ru: Th tc Gii phng khi thay i v th tc

Khng gii phng khi thay i.

Th tc Gii phng khi thay i

Ru gii phng rng buc v thng bo vi Rd rng n gii phng.

Th tc ny c s dng thc hin ch duy tr nhn hn ch.

Th tc Khng gii phng khi thay i

Ru duy tr rng buc nhn n c th s dng li nu sau Rd tr

thnh chng k tip ca Ru vi tin t a ch X. Th tc ny c s dng

thc hin ch duy tr nhn y .

Cc th tc s dng nhnChng ta hy tha nhn rng Ru nhn c 1 rng buc nhn L

vi tin t a ch X t LSR Rd, v Ru l router ng ln ca Rd tng

ng vi tin t a ch X, v Rd l chng k tip ca Ru. Ru s s dng

rng buc nu Rd l chng k tip ca Ru. Nu ti thi im rng buc

nhn, Ru bit c rng Rd khng l chng k tip ca Ru, th Ru khng

s dng mi rng buc nhn ti thi im . Tuy nhin, Ru c th bt u

s dng rng buc nhn ny ti thi im sau nu Rd tr thnh chngk tip ca Ru. Ru c th s dng 2 th tc: S dng ngay lp tc v S

dng nu lp vng khng c pht hin.

Th tc S dng ngay lp tc

Ru c th s dng rng buc nhn ngay lp tc. Ti mi thi im

khi Ru c rng buc nhn vi X t Rd v Rd l chng kt tip ca Ru, th

Rd cng s l chng k tip LSP ca Ru. Th tc ny c s dng khi

pht hin lp vng khng c s dng.Th tc S dng nu lp vng khng c pht hin



40/106


Th tc ny l ging nh th tc S dng ngay lp tc, tr khi Ru

pht hin 1 vng lp trong LSP. Nu 1 vng lp c pht hin, Ru s

khng tip tc s dng nhn L chuyn tip gi ti Rd. Th tc ny c

s dng khi pht hin lp vng c s dng

v s tip tc cho n khi chng k tip ca X thay i hay cho n khi lp

vng khng cn c pht hin.

b. Giao thc RSVP

Nh tn gi ca n, giao thc dnh trc ti nguyn (RSVP) dng

dnh trc cc ti nguyn cho mt phin lm vic (dng lu lng) trong

mng Internet. Kha cnh ny ca Internet l mt iu kh c bit v hikhc nhng g chng ta c bit Internet cung cp cc dch v n lc

cao nht, khng lin quan n nhng yu cu xc nh trc cho ng dng

ngi dng.

RSVP cung cp s m bo hiu nng bng cch phc v cc ti

nguyn cn thit ti mi thit b nm trn ng kt ni h tr cho lung

lu lng (chng hn nh hi ngh video hay audio). Cn nh rng IP l

giao thc khng hng kt ni, n khng thit lp trc ng i cho ccdng lu lng, trong khi RSVP thit lp trc nhng ng i ny v

m bo cung cp bng tn cho ng i .

RSVP khng cung cp cc hot ng nh tuyn nhng n ng dng

IPv4 hoc IPv6 nh mt k thut truyn ti theo cng mt cch ging nh

cch m giao thc bn tin iu khin Internet (ICMP) v giao thc bn tin

nhm Internet (IGMP) hot ng.

L S R b i nL S R l i L S R l iP A T H

R E S VM y g i M y n

Hnh 1.8. Th tc bo hiu trong RSVP.

RSVP l giao thc cho php cc ng dng thng bo cc yu cu v

QoS vi mng v mng s p ng bng nhng thng bo thnh cng

hoc tht bi, sau khi phn tch cc yu cu RSVP gi ti tt c cc node



41/106


trn tuyn cn truyn cc thng tin v thc t ca lung, bn tin RSVP

cha cc thng tin sau:

Thng tin phn loi, nh n m cc lung lu lng vi cc

yu cu QoS c th c th c nhn bit trong mng. Thng tinny bao gm a ch IP pha gi v pha nhn, s cng UDP.

Ch tiu k thut ca lung lu lng v cc yu cu QoS, theo

khun dng Tspec v Rspec, bao gm cc dch v yu cu (c

bo m hoc ti iu khin).

R rng l RSVP phi mang nhng thng tin ny t cc my ch ti

tt c cc tng i chuyn mch v cc b nh tuyn dc theo ng

truyn t b gi n b nhn. V vy tt c cc thnh phn mng phi thamgia vo vic m bo cc yu cu QoS ca ng dng.

RSVP mang cc thng tin trong hai loi bn tin c bn l: PATH v

RESV. Cc bn tin PATH truyn t b gi ti mt hoc nhiu b nhn c

cha TSpec v cc thng tin phn loi do b gi cung cp. Mt l do cho

php c nhiu b nhn l RSVP c thit k h tr a hng. Mt bn

tin PATH bao gi cng c gi ti mt a ch c gi l a ch phin,

n c th l a ch unicast hoc multicast. Chng ta thng xem phin i

din cho mt ng dng n, n c xc nhn bng mt a ch ch v s

cng ch s dng ring cho ng dng.

Khi my nhn nhn c bn tin PATH, n c th gi bn tin RESV

tr li cho my gi. Bn tin RESV xc nhn phin c cha thng tin v s

cng dnh ring v RSpec xc nhn mc QoS m b nhn yu cu. N

cng bao gm mt s thng tin xem xt nhng b gi no c php s

dng ti nguyn ang c cp pht. Hnh 2.12 biu din trnh t bn tin

trao i gia b gi v b nhn. y chng ta lu rng cc cng dnhring l n cng. Nu cn s dng cc cng dnh ring sng cng (v d

nh phc v cho thoi truyn thng) th phi c cc bn tin b sung theo

chiu ngc li. Cng ch rng cc bn tin c nhn v chuyn tip bi

tt c cc b nh tuyn dc theo ng truyn thng tin, nn vic cp pht

ti nguyn c th c thc hin ti tt c cc nt mng cn thit.

Khi cc cng dnh ring c thit lp, cc b nh tuyn nm gia

b gi v b nhn s xc nh cc gi tin thuc cng dnh ring no nhkim tra 5 trng trong phn mo u ca IP v giao thc truyn ti l:



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a ch ch, s cng ch, s giao thc (v d UDP), a ch ngun v cng

ngun. Chng ta gi tp cc gi tin c nhn dng theo cch ny gi l

lung dnh ring. Cc gi tin trong lung dnh ring thng b khng ch

(m bo cho lung khng pht sinh lu lng vt qu so vi thng bo

trong Tspec) v xp vo hng i ph hp vi yu cu v QoS. V d mt

cch c dch v bo m l s dng cc hng i c trng s (WFQ),

y mi cng dnh ring khc nhau c xem nh mt lung i vi cc

hng i, v trng s c n nh cho mi lung ph hp vi tc dch

v yu cu trong Rspec ca n.

i vi cc lung n hng th RSVP kh n gin. N phc tp

hn trong mi trng a hng, bi v c th c rt nhiu b nhn dnh

ring cng cho mt phin n v cc b phn khc nhau c th yu cucc mc QoS khc nhau. Hin nay MPLS ch yu tp trung vo cc ng

dng n hng ca RSVP, chng ta s khng i su vo kha cnh a

hng ca RSVP.

Cc bn tin PATH v RESV in y cc thng tin nhn dng lung

v cc yu cu cht lng dch v ca lung, cc yu cu ny ch th cc

dch v m bo nh l tc nh ca lung tin, kch thc ln nht khi

bng n lu lng, tc go dvv. Thay v mt dch v m bo, mtiu hnh ti iu khin c th c thc hin. Vi tip cn ny, mng c

gng duy tr iu chnh tng lung lu lng m khng nh hng ti

cht lng dch v ca cc dng lu lng khc.

im cui cng phi ch v RSVP v y l giao thc trng thi

mm. c tnh phn bit giao thc trng thi mm vi cc giao thc

loi khc l trng thi s t ng ht hiu lc sau mt thi gian tr khi n

c lm ti lin tc theo chu k. iu c ngha l RSVP s nh k

gi i cc bn tin PATH v RESV lm ti cc cng dnh ring. Nu

chng khng c gi trong mt khong thi gian xc nh th cc cng

dnh ring t ng b hu b.

MPLS h tr RSVP

Mc tiu u tin ca vic b xung h tr RSVP vo MPLS l cho

php cc LSR da vo vic phn loi gi tin theo nhn ch khng phi theo

mo u IP nhn bit cc gi tin thuc cc lung ca cng dnh ring. Ni

cch khc, cn phi to v kt hp phn phi gia cc lung v cc nhn



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cho cc lung c cc cng dnh ring RSVP. Chng ta c th xem mt tp

hp cc gi tin to ra bi cng dnh ring RSVP nh l mt trng hp

ring khc ca FEC.

iu ny tr nn kh d dng kt hp cc nhn vi cc lungdnh ring trong RSVP, t nht l vi unicast (n hng). Chng ta nh

ngha mt i tng RSVP mi l i tng LABEL c mang trong bn

tin RSVP RESV. Khi mt LSR mun gi bn tin RESV cho mt lung RSVP

mi, LSR cp pht mt nhn t trong tp nhn ri, ti mt li vo trong LFIB

ca n vi nhn li vo c t cho nhn cp pht, v gi i bn tin

RESV c cha nhn ny. Ch l cc bn tin RESV truyn t b nhn ti

b gi l di dng cp pht nhn xui.

Khi nhn c bn tin RESV cha i tng LABEL, mt LSR thit

lp LFIB ca n vi nhn ny l nhn li ra. Sau n cp pht mt nhn

s dng nh l nhn li vo v chn n vo bn tin RESV trc khi gi

n i. R rng l, khi cc bn tin RESV truyn n LSR ngc th LSP

c thit lp dc theo tuyn ng. Cng ch l, khi cc nhn c

cung cp trong cc bn tin RESV, mi LSR c th d dng kt hp cc ti

nguyn QoS ph hp vi LSP. Hnh 2.13 minh ho qu trnh trao i ny.

Trong trng hp ny chng ta gi s cc my ch khng tham d vovic phn phi nhn. LSR-R3 cp pht nhn L cho cng dnh ring ny v

thng bo n vi LSR-R2. LSR-R2 cp pht nhn M cng cho cng dnh

ring ny v thng bo n ti LSR-R1. By gi c mt LSP cho lung

dnh ring t LSR-R1 ti LSR-R3. Khi cc gi tin tng ng vi cng dnh

ring ny (v d gi tin gi t H1 ti H2 vi s cng ngun, ch thch hp

v s giao thc giao vn thch hp) ti R1, R1 phn bit n bng cc thng

tin mo u IP v lp truyn ti to ra QoS thch hp cho cng dnh

ring v d nh c im v hng i cc gi tin trong hng i li ra. Nicch khc, n thc hin cc chc nng ca mt b nh tuyn tch hp dch

v s dng RSVP. Hn na, LSR-R1 a mo u nhn vo cc gi tin v

chn gi tr nhn li ra l M trc khi gi chuyn tip gi tin ti LSR-R2.

Khi LSR-R2 nhn gi tin mang nhn M, n tm kim nhn trong

LFIB v tm tt c cc trng thi lin quan n QoS xem kim sot

lung, xp hng i gi tin, v.v.. nh th no. iu ny tt nhin khng cn

kim tra tiu lp IP hay lp truyn ti. Sau R2 thay th nhn trn gitin vi mt nhn li ra t LFIB ca n (mang gi tr L) v gi gi tin i.



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L S R - R 3L S R - R 1 L S R - R 2P A T H

R E S VM y g i M y nN h n = M N

H 1 H 2

Hnh 1.9. Nhn phn phi trong bng tin RESV

Lu rng, do vic to ra nhn kt hp c iu khin bi cc bn

tin RSVP v vy vic kt hp c iu khin nh trong cc mi trng

khc ca MPLS. y cng l mt v d chng t vic mang thng tin kt

hp nhn trn mt giao thc c sn khng cn mt giao thc ring nh

LDP.

Mt kt qu quan trng ca vic thit lp mt LSP cho mt lung vi

cng dnh ring RSVP l ch c b nh tuyn u tin trong LSP m trong

v d trn l LSR-R1 lin quan ti vic xem xt cc gi tin thuc lung dnh

ring no. iu ny cho php RSVP c p dng trong mi trng MPLS

theo cch m n khng th thc hin c trong mng IP truyn thng.

Theo qui c, cc cng dnh ring RSVP c th ch to cho nhng lung

ng dng ring l, tc l nhng lung c xc nh nh cc trng mo

u. Tuy nhin, c th t cu hnh LSR-R1 la chn cc gi tin datrn mt s cc tiu chun. V d, LSR-R1 c th ly tt c cc gi tin c

cng mt tin t ng vi mt ch v y chng vo LSP. V vy thay v c

mt LSP cho mi lung ng dng ring, mt LSP c th cung cp QoS cho

nhiu lung lu lng. Mt ng dng ca kh nng ny l c th cung cp

ng ng vi bng thng m bo t mt im ny ti mt im khc.

Kh nng ny cng hu ch cho mc ch iu khin lu lng, y mt

lu lng ln cn c gi dc theo cc LSP vi bng thng ti lu

lng.

h tr mt s cch s dng tng cng RSVP, MPLS nh ngha

mt i tng RSVP mi c th mang trong bn tin PATH l: i tng

LABEL_REQUEST. i tng ny thc hin hai chc nng. Th nht, n

c s dng thng bo cho mt LSR ti pha cui ca LSP gi RESV

tr v thit lp LSP. iu ny hu ch cho vic thit lp cc LSP Site-to-

Site. Th hai, khi LSP c thit lp cho mt tp cc gi tin, khng ch l

mt lung ng dng ring, i tng cha mt trng xc nh giaothc lp cao hn s s dng LSP. Trng ny c s dng tng t



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nh m phn knh xc nh giao thc lp cao hn (IPv4, IPX, v.v..), v

vy s khng c trng phn knh trong mo u MPLS na. Do vy, mt

LSP c th cn c thit lp cho mi giao thc lp cao hn nhng y

khng gii hn nhng giao thc no c h tr. c bit, khng yu cu

cc gi tin mang trong LSP c thit lp s dng RSVP phi l cc gi tin

IP.

RSVP v kh nng m rng

Mt trong nhng iu chc chn v RSVP l n c th chu tn tht

v kh nng m rng mt mc no y. Trong thc t, c tnh ny

khng chnh xc hon ton. RSVP khi u c thit k h tr d tr

ti nguyn cho cc lung ng dng ring v y l nhim v vi nhng

thch thc v kh nng m rng vn c.Ni chung thut ng ny c s

dng ch gii hn s dng ti nguyn tng nhanh nh th no khi mng

tng trng. V d, trong mng IP quy m ln nh mng xng sng nh

cung cp dch v Internet, chng ta c th quan tm n vic liu mt bng

nh tuyn s chim b nh ca b nh tuyn ln n mc no, kh nng

b x l v bng thng lin kt. V th, bng nh tuyn tng chm hn

nhiu so vi s ngi s dng kt ni vo mng.

D tr ti nguyn cho cc lung ng dng ring r rng l nhhng xu n kh nng m rng. Chng ta c th cho rng mi ngi s

dng s d tr ti nguyn ti mt vi tc trung bnh, v th s ti nguyn

d tr c to ra qua mng ln c kh nng tng nhanh bng s ngi

s dng ca mng. iu ny s dn n chi ph ln nu mi b nh tuyn

phi lu tr trng thi v tin trnh mt vi bn tin cho mi ti nguyn d tr

cho lung ng dng ring.

Ni tm li, s chnh xc hn nu ni rng mc d tr ti nguyn chocc lung ng dng l km hn so vi RSVP. S khc nhau ny c bit

quan trng khi chng ta xem xt rng RSVP khng nhng i hi cho vic

d tr ti nguyn cho cc lung ng dng ring m cn d tr ti nguyn

cho lu lng tng hp.

C. Giao thc CR-LDP

Giao thc CR-LDP c s dng iu khin cng bc LDP.

Giao thc ny l phn m rng ca LDP cho qu trnh nh tuyn cng



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bc ca LSP. Cng ging nh LDP, n s dng cc phin TCP gia cc

LSR ng cp gi cc bn tin phn phi nhn.

Mt h thng h tr nh tuyn cng bc cn m bo cc yu cu

sau: th nht, nt ngun cn bit cu hnh mng. Th hai, ngun cn bitcc thuc tnh ca lin kt trong mng. Th ba, h thng c h tr nh

tuyn hin. Th t, ging nh tuyn c thit lp gia nt ngun v nt

ch, s dnh ring ti nguyn c th xy ra v trng thi thuc tnh ca

ng lin kt phi c cp nht lin tc. Nh vy, h tr nh tuyn

cng bc ngoi mt s iu kin khng ch v bng thng, khong cch

qun l cn cn c kh nng nh tuyn hin (hoc nh tuyn ngun).

xc nhn thng tin ti nguyn dnh ring theo LSR, CR-LDP to

thm i tng mi tham s iu khin lu lng gm 7 tham s: Tc

s liu nh, kch thc s liu bng pht, tc s liu ngu nhin, kch

thc ln qu hn, tn s v trng s. Hai tham s u nh ngha v s

lng ln nht ca lu lng trong LSP. Hai tham s sau nh ngha v s

lng lu lng. Tn s ch ra khong thi gian LSP t c cung cp

rng bng ca LDR v trng s c dng xc nh rng bng trn

CDR, phn chia theo LSP.

C hai l do s dng MPLS. Trc ht MPLS cho php tch ccthng tin s dng chuyn tip (nhn) t cc thng tin c trong mo u

ca gi IP. Th hai l vic chuyn i gia FEC v LSP ch c gii hn

trong LSR ti mt u ca LSP. Ni mt cch khc, vic quyt nh gi IP

no s nh tuyn hin nh th no hon ton do LSR tnh ton xc nh

tuyn. V nh trnh by trn, y chnh l chc nng cn thit h

tr nh tuyn cng bc.

Cng nh cc chc nng khc ca MPLS, chc nng nh tuyn hinca MPLS cng c chia lm hai phn: iu khin v chuyn tip. Phn

t iu khin chu trch nhim thit lp trng thi chuyn tip nhn dc theo

tuyn hin. Phn t chuyn tip s dng trng thi chuyn tip c thit

lp bi phn t iu khin cng nh cc thng tin c trong cc gi tin

truyn cc gi tin dc theo tuyn hin.

D. Giao thc MPLS-BGP

MPLS m rng chc nng cho BGP mang cc nhn trong giaothc cng bin gii BGP, MPLS-BGP cho php b nh tuyn chy BGP



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phn phi nhn ti cc b nh tuyn bin khc mt cch trc tip thng

qua bn tin cp nht ca BGP. Tip cn ny m bo cho qu trnh phn

phi nhn v cc thng tin nh tuyn n nh v gim bt tiu ca bn

tin iu khin x l.Trong mng s dng cc b nh tuyn BGP nh l mt

b nh tuyn bin kt ni vi cc mng khc, n c th cho php cc b

nh tuyn khng c chc nng trao i trc tip bn tin BGP hot ng

ng thi vi cc b nh tuyn bin ny. Khi hai b nh tuyn bin khng

kt ni trc tip, cn phi thit lp mt ng dn chuyn mch nhn gia

hai b nh tuyn ny thng qua mt vi k thut phn phi nhn khc.

MPLS-BGP cng c th c s dng thit lp cc dch v mng

ring o VPN da trn nh tuyn BGP (RFC 2547), trong RFC 2547 nh

ngha cho kiu mng khng phn cp v cc yu cu v kh nng ca ccb nh tuyn bin trong mng cung cp dch v:

Kh nng duy tr cc bng nh tuyn tch bit (theo tng

mng ring o) ti cc thit b g mng.

H tr cc kiu a ch thc hin trong cc VPN ti cc b nh

tuyn BGP cung cp dch v.

1.5. CNG NGH GMPLS

T chc tiu chun k thut quc t cho Internet IETF (International

Engineering Task Force) m rng b giao thc MPLS gi l MPLS tng

qut (GMPLS) cung cp mt phng (bo hiu v nh tuyn) cho cc

thit b m chuyn mch theo min gi, theo thi gian, theo bc sng (v

d DWDM Dense Wavelenght Division Multiplexing), theo si quang v

theo khng gian (v d OXC) qua GMPLS. Mt phng chung ny n gin

ho s hot ng v qun l mng bng vic cung cp cc kt ni im -

im, qun l ti nguyn mng mt cch t ng, cung cp mc QoS miv cc ng dng phc tp hn. iu ny cho php mng da trn GMPLS

tm v cung cp ng i ti u da trn nhng yu cu lu lng ngi

s dng cho lung khi to trn mng IP, sau c truyn ti bi mng

quang ng b SONET v tip theo c chuyn mch sang mt bc

sng c th trn mt si vt l c th.

Thch thc c bn vi giao thc iu khin chung l vic thit lp,

bo tr, v qun l cc ng k thut lu lng cho php mt phng dliu truyn ti d liu ngi s dng mt cch hiu qu t ngun ti ch.



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Lung ngi s dng c th truyn qua mt s nhp mng, v d nh mt

mng li vo hoc mng bin tp hp cc lung t nhiu ngi s dng (v

d nh cc ng dng doanh nghip) a vo mng trung tm m da

trn SONET hoc ATM. Cc mng ny li c kt hp nhiu lung t cc

mng bin khc nhau a vo mng c ly di. ng i t trc c

s dng a d liu ti ch ca n.

Cc mng ny v cc thit b in hnh c th hin trn hnh 1.10.

Database

Database

1.5.1. NHN TNG QUAN CA GMPLS

c th h tr cc thit b chuyn mch trong cc min khc nhau,

GMPLS a vo nhng b sung mi cho khun dng ca cc nhn. Khun

dng nhn mi gi l nhn tng qut , n cha thng tin cho php cc

thit b thu lp chng trnh chuyn mch v chuyn tip d liu bt k cutrc ca n (gi, TDM, Lambda ..). Nhn tng qut c th biu din cho

mt bc sng n, mt si quang hoc mt khe thi gian. N cng th

hin cc nhn MPLS truyn thng, v d nh ATM, VCC hoc shim IP.

Thng tin c gn vo nhn tng qut gm:

1. Kiu m ho LSP m th hin loi nhn ang c mang (gi,

bc sng SONET).

2. Loi chuyn mch th hin nt c kh nng chuyn mch hocgi, khe thi gian, bc sng hoc si quang.

3. B nhn dng ti trng chung th hin loi ti ang c mang

bi LSP (v d nh nhnh o VT, DS-3, ATM, Ethernet, ..)

Ging nh MPLS, s phn b nhn bt u t LSR pha trc yu

cu mt nhn t LSR pha sau. GMPLS thc hin iu ny tt hn bng



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vic cho php LSR pha trc ngh nhn cho LSP m c th c u

tin bi LSR pha sau.

1.5.2. B GIAO THC GMPLS

Cuc cch mng ca MPLS sang GMPLS m rng cc giao thcbo hiu (RSVP- TE, CR LDP) v cc giao thc nh tuyn (OSPF-TE, IS-

IS-TE). Cc m rng thch nghi vi nhng c tnh ca TDM/SONET v cc

mng quang.

Mt giao thc mi, giao thc qun l lin kt LMP (Link Management

Protocol) c a vo p dng qun l v bo tr hot ng mt

phng v d liu, iu khin gia hai nt ln cn. Giao thc qun l lin kt

LMP l giao thc da trn IP, bao gm RSVP m rng v CR-LDP mrng.

Ngn xp giao thc nh tuyn IS-IS-TE ging vi OSPF-TE ngoi tr

thay v IP, mt giao thc mng phi kt ni (CLNP Connectionless Network

Protocol) c s dng mang thng tin IS-IS-TE.

text

LMP

IP

UDP OSPF-TE TCP

ATM FRAME-RELAY

PPP/Adaption LAYER

SONET

FIBER

Wavelengthswitching

RSVP-TE CR-LDP BGP

MAC/GE

Hnh 1.10 : Ngn xp giao thc GMPLS



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CHNG 2:

GII THIU BI TON NH TUYN V GN BC SNG

TRONG MNG QUANG

2.1. GII THIU

Qua mt vi nm gn y, DDWM (Dense Wavelenght Division

Multiplexing) tr thnh mt cng ngh ch o cho mng quang th h su.

Vic s dng DWDM a knh c phn bit bi cc bc sng khc

nhau c th c truyn trn mt si quang, vi mi knh hot ng tc

nh ca n. Mi bc sng ca mi si ca mt tuyn lin kt l mt

knh con hon ton c lp vi cc bc sng khc trn cng mt si. Mtkhi nim nh vy thng c gi l mng quang v mng quang thng

minh ION, l ni lp quang vt l tr nn nhn bit c cc kt ni

bng vic xc nh cc bc sng ca chng. Mt cng ngh in hnh ca

mng DWDM v cc knh lin kt khc ca n c bit n nh cc bc

sng c cho trn hnh 2.1.

text

text

text

text

texttext

text

textH thng u

cui

Chuyn mch quang

Lung quang vi bcsng 1

Lung quang vi bcsng 2

Hnh 2.1. Mng DWDM nh tuyn bc sng

Trong mng nh tuyn, ngi s dng ny thng tin vi ngi s dng

khc qua knh ton quang, cc knh ny c xem nh l cc lung

quang. Mt lung quang c s dng h tr mt kt ni trong mng

inh tuyn bc sng v c th lin kt cc si quang. Trong trng hp



51/106


khng s dng b chuyn i, mt lung quang chim cng bc sng

trn tt c cc lin kt si m n i qua. c tnh ny gi l iu kin rng

buc bc sng lin tc. Gi s rng mi chuyn mch quang c ni ti

mt nt truy nhp nh l mt nt. Khi a ra mt tp kt ni, bi ton thit

lp cc lung quang bng nh tuyn v gn bc sng mi kt ni c

gi l bi ton nh tuyn v gn bc sng (RWA- Routing and

Wavelength Assignment).

2.2.CC LOI BI TON RWA

Thng thng, c hai loi lu lng mng l tnh hoc ng. Do vy bi

ton RWA gm hai loi tnh v ng. iu ny dn n hai kiu thit lp

lung quang: Bi ton thit lp lung quang tnh v thit lp lung quang

ng.

2.2.1 THIT LP LUNG QUANG TNH (SLE)

Trong bi ton ny tt c cc yu cu kt ni c bit trc v

khng thay i. l yu cu cho vic thit lp mt tp hp cc ng

quang c a ra u tin. Cc ng quang ny khng b gii phng

ngay khi chng c thit lp. Cc ng quang c gi s l cc lung

quang, l rng buc bc sng lin tc. Bi ton ti u l ti thiu s

bc sng cho mt cu hnh mng nht nh, s si quang, v tp hp cc

ng quang yu cu.

2.2.2. THIT LP LUNG QUANG NG (DLE)

Trong bi ton ny tt c cc yu cu kt ni n mt cch ng v

lung quang c gii phng sau mt thi gian hn nh. Bi ton ti u l

ti thiu xc sut tc nghn yu cu cho mt s bc sng nht nh v

hoc ti thiu gi thnh mng.

Bi ton thit lp lung quang tnh c th t c nhiu hn vi

cng ngh hin nay v s l gii php tng lai gn trong mng quang

thng minh ION. Nhng khi lu lng trong mng li s tr nn ng hn

th thit lp lung quang ng s phi c thc hin trong mng ION. Do

vy lun vn ny s tp trung ch yu vo vic gii quyt bi ton DLE.

2.3. CC PHNG PHP GII BI TON

Bi ton RWA lin quan n cc phn khc nhau, thng c giiquyt ring bit n gin ho bi ton. Vi bi ton nh tuyn th c ba



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phng php nh tuyn c bn: nh tuyn c nh, nh tuyn thay th c

nh v nh tuyn thch nghi.

Trong nh tuyn c nh, ch c mt tuyn c nh (v d nh ng

ngn nht) gia cp nt ngun v ch.Trong nh tuyn thay th c nh, mi nt duy tr mt bng nh tuyn

m cha mt danh sch cc tuyn c nh c yu cu ti mi nt ch.

V d nh, cc tuyn ny c th bao gm tuyn ngn nht u tin, tuyn

ngn nht th hai, tuyn ngn nht th ba vv.. Tuyn thc t cho mt yu

cu kt ni ch c th c chn la t tp cc tuyn ny.

Trong nh tuyn thch nghi, nh tuyn da trn bc sng c th s

dng hin c trn mi tuyn lin kt. Bt k tuyn kh thi no t nt ngunti nt ch c th ng c nh tuyn thc t cho mt yu cu kt ni. Vic

la chn tuyn ph thuc vo chnh sch mng c s dng nh ng

u tin chi ph ngn nht hoc ng u tin tc nghn t nht.

Ni chung, nh tuyn c nh l n gin nht trong khi nh tuyn

thch nghi mang li c tnh tt nht. nh tuyn thay th c nh em li s

tho hip gia s phc tp v c tnh mng.

Bi ton gn bc sng l mt phn khc ca bi ton RWA. Nichung, n d dng hn nhiu so vi bi ton nh tuyn, nhng cng ph

thuc vo kt qu ca gii php nh tuyn. Tuy nhin n thng nh

hng ti kt qu hiu sut ca gii thut RWA.

2.4. C S L THUYT

2.4.1. GII THIU L THUYT TH

Trong l thuyt th, cu hnh mng c th c biu din nh

th G (V, E), V biu th tp cc nh (cc nt mng) v E l tp hp ccbin (Cc tuyn lin kt mng). V th hin s nt trong th v thng

c gi l bin ca th. Mi tuyn lin kt (i, j) E c th c kt

hp vi mt hm trng W ji, m biu din bng mt phng php no

xc nh chi ph s dng tuyn lin kt (i, j). Bc ca nt iV l s nt

ln cn ca nt i.

Ta ch xt bi ton ng i ngn nht trong th. Cho th G(V,

E) bi ton t ra l tm ng i trong th m ti thiu tng trng lngca tt c cc tuyn lin kt din ra gia hai nh. L thuyt th cung cp



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nhiu cch gii quyt bi ton . Gii thut ph bin nht l gii thut

Dijkstra v Bellman- Ford. Di y ch gii thiu v gii thut Dijkstra.

2.4.2. GII THUT DIJKSTRA

Gii thut Dijkstra c gii thiu vo nm 1959 cung cp mt giithut hiu qu nht cho vic gii quyt bi ton ng i ngn nht. N tm

ng i ngn nht t mt nh ngun s cho ti mi nh d trong V bng

vic trin khai cc ng i theo th t di ng i tng dn. Mi nt

c dn nhn bng khong cch ca n t nt ngun dc theo ng

c xem l tt nht. u tin khng ng i no c bit n do vy

tt c cc nt c dn nhn l . Khi gii thut tin hnh v cc ng i

c tm ra th cc nhn c th thay i tng ng vi cc ng i tt

hn. Nhn c th l thm d hoc c nh. Ban u tt c cc nhn l thm

d. Khi n c khm ph ra m nhn th hin ng i ngn nht c th

t ngun ti nt th n oc to c nh v khng bao gi oc

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