chương trình mô phỏng/tqt

7/28/2019 chng trnh m phng/tqt

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GVHD: TS. L QUC CNG HVTH: CAO NHT BNH

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CHNG 4: M PHNG.

4.1 Mc ch ca vic m phng.Mng OBS c nhiu u im ng c quan tm tuy nhin mng OBS cha

tht sc trin khai trong thc t do cn thc hin vic m phng nh gi

nhng cht lng ca mng OBS. Mc tiu ca ti ny l tm hiu cht lng

dch v (QoS) da trn nhng thng sc ginh trc. M phng trong lun

vn cng so snh v nh gi cht lng dch v v xc sut mt gi trong iu kin

ti a vo mng khc nhau.

Phn m phng s thc hin vic m phng mt mng chuyn mch quang

chm OBS vi cc trng hp c cp trong chng III vi cc vn chnh

nh sau: QoS da trn vic ng khi burst, QoS da trn vic xp lch knh

truyn, QoS da trn vic bo hiu, QoS da trn vic gii quyt xung t.

M phng c thc hin bng phn mm m phng OBS4NS chy trn nn

ca phn mm m phng mng NS-2. M phng c thc hin tnh ton xc

sut mt gi v tr vi cc ti lu lng khc nhau. Kt qu m phng sc

a ra di dng th.

4.2 M hnh mng v cc thng s.

M hnh mng m phng c da theo m hnh mng NSFNET (National

Science Foundation Network) ca Hoa K vi 14 node mng. Vic s dng m

hnh ny do mng OBS cha thc sc trin khai trong thc t, hn na mng

NSFNET c s dng kh ph bin trong cc bi nghin cu v mng OBS ca

cc tc gi. Vic la chn mt mng chun c cc nh nghin cu xut so

snh kt qu l cn thit.


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Hnh 4.1 M hnh mng NSFNETSau y l cc thng s chnh trong trong m phng:

- Cc node mng u l cc node kt hp.- Lin kt l song hng vi mi hng c hai knh iu khin v hai

knh d liu. Do mt lin kt c 8 bc sng quang.

- Cc gi n c kch thc cnh l 1250 byte.- Tc truyn dn ca lin kt l 10Gbps.-

Thi gian chuyn mch l 10s

. Cng ngh chuyn mch ton quangc th da trn hai cng ngh l cng ngh chuyn mch gng vi thi

gian chuyn mch hng ms v cng ngh chuyn mch bn dn vi thi

gian chuyn mch vi s . Trng hp m phng ny tc gi gi s rng

chuyn mch ton quang u l cc chuyn mch bn dn.

- Kch thc gi iu khin l cnh v bng 64byte.- Thi gian x l gi iu khin l 2.5 s

4.3 Phn mm m phng mng ns-2

4.3.1 Gii thiu

[17,18,5] Phn mm NS-2 l phn mm m phng mng iu khin s kin

ring r hng i tng c pht trin ti UC Berkely, vit bng ngn ng C++


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v Otcl. Ns-2 l phn mm m phng m ngun mhu ch cho vic nghin cu

mng din rng (WAN) v mng local (LAN). Bn li ch ln nht ca Ns-2 l:

Kh nng kim tra tnh n nh ca cc giao thc mng ang tn ti

Kh nng nh gi cc giao thc mng mi trc khi a vo s dng

Kh nng thc thi nhng m hnh mng ln m gn nh ta khng th thc thi

c trong thc t

Kh nng m phng nhiu loi mng khc nhau

4.3.2 Kin trc ca NS-2

NS thc thi cc giao thc mng nh Giao thc iu khin truyn ti (TCP)

v Giao thc gi ngi dng (UDP); cc dch v ngun lu lng nh Giao thc

truyn tp tin (FTP), Telnet, Web, Tc bit cnh (CBR) v Tc bit thay i

(VBR) ; cc k thut qun l hng i nh Vo trc Ra trc (Drop Tail), D sm

ngu nhin (RED) v CBQ; cc thut ton nh tuyn nh Dijkstra NS cng thc

thi multicasting v vi giao thc lp iu khin truy cp ng truyn (MAC) i

vi m phng LAN.

Hnh 4.2 Tng quan vNS di gc ngi dng

OTcl Script Kch bn OTcl

Simulation Program Chng trnh M phngOTcl B bin dch Tcl mrng hng i tng

NS Simulation Library Th vin M phng NS

Event Scheduler Objects Cc i tng B lp lch S kin

Network Component Objects Cc i tng Thnh phn Mng


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Network Setup Helping Modules Cc m un Trgip Thit lp Mng

Plumbling Modules Cc m un Plumbling

Simulation Results Cc kt qu M phng

Analysis Phn tch

NAM Network Animator Minh ha Mng NAM

Trong hnh trn, NS l B bin dch Tcl mrng hng i tng; bao gm

cc i tng B lp lch S kin, cc i tng Thnh phn Mng v cc m un

Trgip Thit lp Mng (hay cc m un Plumbing).

s dng NS-2, user lp trnh bng ngn ng kch bn OTcl. User c th

thm cc m ngun Otcl vo NS-2 bng cch vit cc lp i tng mi trong

OTcl. Nhng lp ny khi sc bin dch cng vi m ngun gc. Kch bn

OTcl c th thc hin nhng vic sau:

Khi to B lp lch S kin Thit lp M hnh mng dng cc i tng thnh phn Mng Bo cho ngun lu lng khi no bt u truyn v ngng truyn gi

trong b lp lch s kin

Thut ng plumbing c dng ch vic thit lp mng, v thit lp mt

mng ngha l xy dng cc ng d liu gia cc i tng mng bng cch thit

lp con tr neighbour cho mt i tng chn a ch ca i tng tng

ng. Module plumbing OTcl trong thc t thc hin vic trn rt n gin.

Plumbing lm nn sc mnh ca NS.

Thnh phn ln khc ca NS bn cnh cc i tng Thnh phn Mng l

B lp lch S kin. B lp lch S kin trong NS-2 thc hin nhng vic sau:

T chc Bnh thi M phng Hu cc s kin trong hng i s kin Triu gi cc Thnh phn Mng trong m phng

Ph thuc vo mc ch ca user i vi kch bn m phng OTcl m kt

qu m phng c thc lu tr nh file trace. nh dng file trace sc ti

vo trong cc ng dng khc thc hin phn tch:


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File nam trace (file.nam) c dng cho cng c Minh ha mng NAM

File Trace (file.tr) c dng cho cng c Ln vt v Gim st M phng

XGRAPH hay TRACEGRAPH

Hnh 4.3Lung cc skin cho file Tcl chy trong NS

NAM Visual Simulation M phng o NAM

Tracing and Monitoring Simulation M phng Ln vt v Gim st

C++ v OTclHnh sau biu din kin trc chung ca NS. User c th tng tng mnh

ang ng gc tri di, thit k v chy cc m phng trong Tcl. Tcl dng cci tng m phng trong OTcl. Cc i tng B lp lch S kin v hu ht cc

i tng Thnh phn Mng thc thi bng C++ v sn c cho OTcl qua mt lin kt

OTcl. Lin kt OTcl ny c thc thi dng TclCL. Tt c lm nn NS, b bin

dch Tcl mrng hng i tng v cc th vin m phng mng.


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Hnh 4.4 Kin trc ca NS-2

NS s dng hai ngn ng lp trnh: Ngn ng kch bn (Tcl Tool

Command Language, c l tickle) v Ngn ng lp trnh h thng (C/C++)

NS l tng bin dch Tcl chy cc kch bn Tcl

Bng cch s dng C++/OTcl, b m phng mng phi hon ton l hng

i tng

Hnh sau ch ra cc i tng C++ c lin kt OTcl. Khi , nu chng to

nn mt phn cp th cc i tng OTcl cng c mt phn cp tng ng nh vy.


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Hnh 4.5 C++ v OTcl: Si ngu

TclCL l ngn ngc s dng cung cp lin kt gia C++ v OTcl.

Cc kch bn Tcl/OTcl c vit thit lp v cu hnh topology ca mng. TclCL

cung cp lin kt gia phn cp lp, khi to i tng, ni kt bin v gi lnh.

Hnh 4.6 TclCL hotng nhlin kt gia A v BVic s dng hai ngn ng v B m phng cn thc hin hai vic khc

nhau.

Mt mt l v cc m phng cho cc giao thc yu cu mt ngn ng lp

trnh h thng c th tnh ton mt cch hiu qu cc byte, cc tiu packet v cc


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thut ton thc thi ang chy trn mt tp d liu ln. Vi tc v ny, run-time

speed (tc thi gian chy thc) l quan trng trong khi turn-around time (thi

gian thay i) th t quan trng hn. Turn-around time bao gm thi gian chy m

phng, thi gian tm li, thi gian sa li, thi gian bin dch li v thi gian chy

li.

Mt khc, khi nghin cu mng th rt cn quan tm n cc tham s v cc

cu hnh c thay i nhng khng ng k, hay quan tm n cc scenario (tnh

hung) cn khm ph tht nhanh chng. Trong tc v ny th iteration time (thi

gian lp li, tc l thi gian hay i m hnh v chy li) l quan trng hn. V cu

hnh ch chy mt ln lc bt u m phng nn run-time trong tc v ny r rng

km quan trng hn.

Dng C++ :

M phng giao thc chi tit yu cu ngn ng lp trnh h thng Thao tc trn byte, x l gi, thc thi thut ton Tc thi gian thc l quan trng nht Thc hin bt k vic g m cn phi x l tng packet ca mt

lung.

Thay i hnh vi ca lp C++ ang tn ti theo nhng hng khng c lng trc.

V dng OTcl :

M phng nhng thng s hay cu hnh thay i Tham d nhanh mt s tnh hung Thi gian tng tc (thay i m hnh hay chy li) l quan trng Cu hnh, thit lp hay nhng g ch lm mt ln. Thc hin nhng ci ta mun bng cch thao tc trn cc i tng

C++ ang tn ti.

V d nh cc link l nhng i tng OTcl lin kt cc m un delay (tr

hon), queueing (hng i) v possibly loss (kh nng mt mt). Cn nu mun

thc hin nhng vic chuyn nghip hn th cn phi to ra i tng C++ mi.


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Hu ht nh tuyn c vit bng OTcl (d thut ton Dijkstra li vit bng

C++). M phng HTTP c tng lung bt u ti OTcl nhng vic x l tng gi

li c vit bng C++. Phng php ny chy tt cho n khi c n 100 lung bt

u thi gian m phng mi giy. Ni chung, nu phi triu gi Tcl nhiu ln mi

giy th c l nn chuyn sang C++.

V phng din m ngun, NS-2 c vit vi 100k dng m lnh C++, 70k

dng m Tcl v 20k dng ti liu.

4.3.3 Cc c tnh ca NS-2

NS-2 thc thi nhng tnh nng sau:

Cc k thut qun l hng i Router nh DropTail, RED, CBQ,

Multicasting

M phng mng khng dy

c pht trin bi Sun Microsystems + UC Berkeley (D n Daedalus)

Thuc mt t (di ng, adhoc, GPRS, WLAN, BLUETOOTH), v tinh Chun

IEEE 802.11 c thc m phng, cc giao thc Mobile-IP v adhoc nh DSR,

TORA, DSDV v AODV

Hnh vi ngun traffic www, CBR, VBR

Cc agent truyn ti UDP, TCPnh tuyn

Lung packet

M hnh mng

Cc ng dng Telnet, FTP, Ping

Cc packet tracing trn tt c cc link v trn cc link xc nh


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4.4 Phn mm m phng mng quang OBS4NS

4.4.1 Gii thiu.

Ns-2 kh y cho vic m phng mng thng thng, tuy nhin li t h

tr cho lp quang v m phng mng OBS v trong OBS cc burst d liu c

chuyn mch ton quang, khng b delay hay x l ti cc node mng. V l do ,

phn mm mrng OBS4NS chy trn nn NS-2 c xy dng gii quyt vn

m phng mng ton quang. Phn mm m phng mng OBS4NS c cc tc

gi trng i hc Vigo-Ty Ban Nha xy dng v pht trin phn ln cc chc

nng phc v tng i y cho m phng mt mng OBS hon chnh.

Phn mm OBS4NS c kh nng:

- To cc node bin, node li v node kt hp

- To cc lin kt WDM.

- Thc hin qu trnh ng khi.

- Thc hin nh tuyn.

- Thc hin vic gii quyt xung t bng bm, chuyn hng v phn

on burst.

- Thc hin vic lp lch knh truyn LAUC, LAUC-VF,..

4.4.2 Cc module trong OBS4NS.Phn mm OBS4NS c xy dng t cc module sau:

Module to node mng (ObsNode)Cc node trong mng OBS bao gm node bin v node li. Phn mm ny

cng xy dng mt module to cc node ny trong mng, cc node mng trong

phn mm ny l node unicast khng h trnode multicast.

- Node bin

Ng vo ca node bin l lu lng ly t module to lu lng. Cc thngs ca lu lng tu thuc vo lu lng a vo. Gi tr ng ra ca node bin l

cc burst d liu, gi iu khin, thng tin vng i ngn nht, bc sng cho

gi iu khin v burst d liu.


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Hnh di y m t kin trc ca node bin v node li trong OBS4NS.

Hnh v cho thy nhng phn ging nhau trong khi xy dng i tng m phng

l c node bin v node li u s dng chung thnh phn to kt ni

(Connector/ObsLink) v s dng bin entry_ xc nh li vo. Phn khc nhau

gia node bin v node li l node bin c phn giao din lp MAC cn node

li c chuyn mch quang khi (Classifier/ObsSwitch)

Hnh 4.7 Giao din lp MAC

Giao din n lp MAC l thnh phn c bn ca node bin c nhim v

nhn lu lng t khi to lu lng (lu lng c to ra bng mt s module

trong NS-2). N phn loi gi n theo ch n (Classifier/Addr) v theo lp dch

v (Classifier/CoS). Kn bng khi (Agent/Burstifier) c chc nng tp trung

cc gi tin lp cao vo bm ri to thnh burst d liu cng vi vic pht gi

iu khin. Cui cng l b lp lch knh truyn (ChannelScheduler) chn mt bc

sng thch hp cho burst d liu ng ra. Node bin ch c b gii ng khi

(Agent/Deburstifier) tch cc gi tin t burst d liu nhn c.


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Thnh phn quan trng nht ca giao din lp MAC l b ng khi

(Agent/Burstifier). Cc bin s cho bng khi quyt nh vic ng khi nh th

no:

MaxDBsize_ : ng khi theo tiu chun v dung lng ti a.

Max_packets_ : ng khi theo tiu chun v s lng gi ti a trong burst.

Time_out_ : ng khi theo tiu chun thi gian ti a.

Np_ : s lng gi trong mt burst thc tc pht i.

Size_ : dung lng thc tc pht i.

Hnh 4.8 Giao din lp MAC

Khi mt burst d liu c a vo mng, mt gi iu khin c to ra

cho burst ny. Gi iu khin ny c gi vo mng ngay tc khc cn burst d

liu phi i trong bm mt khong thi gian b mi c pht i. Thi gian b

c tnh nh sau:

extraiTxioffsetswitchBHPprocioffset TTTTnTT +++++= )()1)(max( 1,1,,


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Vi

n: s bc nhy t ngun n ch.

i: mc u tin dch v.

)max( BHPprocT : thi gian x l gi iu khin ti mi node. Nu chng ta gi

s rng thi gian x l gi iu khin cc i ti mi node l bng nhau k c node

ngun th tng thi gian x l gi iu khin l )max( BHPprocT (n+1)

switchT : thi gian chuyn mch ti mi node trung gian

1, ioffsetT : thi gian offset time ca burst c mc u tin cao hn.

1, iTxT

: thi gian truyn burst c mc u tin cao hn ti a. iu ny to ras cch ly 100% gia cc lp dch v.

- extraT : l thi gian pht sinh do cc tnh hung khc v c tnh nh say:

+++=randomBHPqueuedeflBHPprocextra

TTnTT )max(

defln : l s ln chuyn hng ti a ca mt burst theo mt phng thc

chng loop.

BHPqueueT : l thi gian gi iu khin cn phi cha trong hng i.

: l khong thi gian rt nh, l khong thi gian bo v, cho php chuyn

mch chuyn t trng thi hot ng sang trng thi cu hnh li.

randomT : l khong thi gian c to ngu nhin trong mt khong no

ng vai tr mt thng s ngu nhin no trong mng.

Max_bhp_queue_time_: bin ny cho php ci t BHPqueueT

Extra_random_time_: bin ny cho php ci t randomT

Extra_fixed_time_: bin ny gii hn s bin i randomT v 1, iTxT

Equal_offset_: cho php gi tr offset time ca cc lp dch v khc nhau

bng nhau.


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Bhp_struct_map_: cho php gi iu khin c th sa li khi thng tin v

burst trn ng truyn b thay i (v d nh burst b rt mt phn).

Bhp_size_: bin thit lp kch thc gi iu khin.

Segmentation_: cho php phn on burst trong min in.

Max_segmentation_: s lng on ln nht trong mt burst.

Min_segmentation_size_: kch thc ti thiu ca mi on.

Stats_ : cho php gi chc nng thng k.

Hnh 4.9 Thi gian offset

- Node li

Thnh phn ch yu ca node li l n viu khin chuyn mch SCU v

ma trn chuyn mch quang OXC.

Cc thnh phn ny thuc lp Classifier/ObsSwitch


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SCU

OXC

BHP

DB

Ng ra

(Classifier/ObsSwitch)

Hnh 4.10 Node li trong OBS4NS

Chng trnh xy dng SCU vi cc bin s sau:

Bhp_proc_time_: thi gian x l gi iu khin.

Channel_schedule_: chn la loi lp lch knh truyn.

Multipath_: cho php chn la nhiu ng i hay khng.

Deflection_ : cho php SCU cu hnh cho OXC chuyn hng burst trong

vic gii quyt xung t.

Segmentation_: cho php SCU cu hnh cho OXC phn on burst trong vic

gii quyt xung t.

Max_segmentation_size_: kch thc nh nht cho mi on.

Switch_time_: thi gian chuyn mch ca ma trn chuyn mch quang.


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- Node kt hp

Ngoi node bin v node li vi cc chc nng ring bit, phn mm cn xy

dng mt node kt hp bao gm c chc nng node bin ln chc nng node li.

Giao din ktni n lp

MAC

Node li OBS

Agent

Agent

Agent

Ng ra Ng ra

Ng

vo

Node kt hp

(Connector/ObsLink)

(Classifier/TypeSwitch)

Gii a hp(Classifier/Port)

IP

OBS

Hnh 4.11 Node kt hp

T hnh ta thy node kt hp c th x l hai loi lu lng IP v burst d

liu. Classifier/TypeSwitch c nhim v xt xem lu lng n l IP hay l burst, t

a ra quyt nh lu lng ny x l phn no (node li hay node bin).

Cc thng s lin quan khc c cu hnh ging nh cu hnh i vi node

bin v cu hnh i vi node li.

Module to lin kt trong mng (Connector/ObsLink)Do lin kt trong mng OBS l cc lin kt WDM nn trong xy dng

chng trnh cng c chc nng to lin kt WDM. Lin kt WDM trong chng

trnh to nn cc bin s sau:

ndc_: s knh d liu.

ncc_: s knh iu khin.


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dc_bandwidth_: bng thng knh d liu.

cc_bandwidth_: bng thng knh iu khin.

delay_: tr lan truyn trn mi lin kt.

Module n v truyn dn trong mng (ObsPacket)

Hai n v truyn dn trong mng l gi iu khin OBS_BHP v burst d

liu OBS_DB, burst d liu trong OBS4NS khng phi l mt gi c th nh trong

NS-2, chng trnh m phng ch xt hai gi tr vim bt u DB_START v kt

thc DB_END ca mi burst. C th trong chng trnh hai gi tr ny l hai bin

NULL, iu ny lm cho vic x l burst d liu nhanh hn v thch hp cho vic

x l ca my tnh.

OBS_BHP: chng trnh s to ra gi iu khin vi cc thng s sau:

Id_: bin s nhn din mi gi BHP.

Db_start_time_: thi im bt u ca burst.

Db_end_time_: thi im kt thc ca burst.

Channel_: gi BHP ny sa n knh no.

Ttl_: thi gian sng ca gi BHP.

Offset_obs_bhp_: thng s v thi gian b.

Stats_: bin gi module thng k.

Id_ Db_start_time_ Db_end_time_ Channel_ Ttl_ Offset_obs_bhp_ Stats_

OBS_DB: Chng trnh to ra burst d liu vi cc thng s sau:

Type_: cho bit l DB_START hay DB_END.

Id_: s nhn din burst, cng ch s vi OBS_BHP tng ng.

Src_: a ch node ngun.

Dst_: a ch node ch.Channel_: burst ny sc a ln knh no.

Stats_: bin gi module thng k.


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Phn Dbpayload i din cho phn d liu ca burst c pht i bao gm 3

bin s lin quan:

Np_: s gi tin thc t trong mt burst.

Size_: kch thc thc t ca burst

Number_DB_: s lng on trong mt burst d liu trong trng hp ng

khi kiu phn on.

Module lp lch knh truyn (ChannelScheduler)Khi mt burst d liu c to ra hoc khi n i qua cc node trung gian, n

cn c sp xp n mt bc sng no ng ra. Ba phng thc lp lch c

nhiu nh nghin cu quan tm nht c xy dng trong OBS4NS l: FFUC,

LAUC v LAUC-VF.

ChannelScheduler/FFUC: Thut gii lp lch knh l FFUC.ChannelScheduler/LAUC: Thut gii lp lch knh truyn l LAUC.

ChannelScheduler/LAU_VF: Thut gii lp lch knh truyn l LAUC-VF.

Module nh tuyn (ObsRoute)

OBS4NS tnh ton ng i da trn gii thut ng i ngn nht SPF. Mi

node mng cng vi cc lin kt to ra mt topo mng. Sau mi node mng s

lu tr mt bng cc node ln cn ca n. Vic tnh ton ng i ngn nht t

node ny n node kia ban u da vo s chng tm ng i ngn nht. Nunh vic tm ng i da vo s bc nhy tm c nhiu hn mt con ng

n ch th con ng ngn nht c chn chnh l con ng c tr lan

truyn nh nht.

Module thng k (stats)


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Trong phn mm OBS4NS burst d liu khng phi l mt gi c th nh

trong NS-2, chng trnh ch m phng hai gi tr thi im bt u v kt thc mi

burst, do khng tha ra kt qu bng file trace nh NS-2. Phn mm OBS4NS

h trvic theo di kt qu bng mt module thng k. Cc bin trong hm thng

k ny gm:

Get-global-stats-collector: Dng thng k tt c cc gi i vo h thng.

Get-flow-stats-collector:Dng thng k tt c cc gi i vo theo tng

lung ring r

4.5 Cc trng hp thc hin m phng.

TRNG HP 1: QoS da trn vic thay i cc thng sng gi. [20,1]:

Vic thc hin vic so snh cc thng sng gi khc nhau c thc hin di

tiu chun drop policy (DP) v phn mnh gii quyt xung t (SDP). Hai tiu

chun ny c cp n trong chng II.

Mt ngng vi hai mc u tin: Trong phn ny chng ta gi s mng

mang hai lp lu lng chy trn hai lp dch v vi hai mc u tin khc nhau:

lp 1 c mc u tin thp, lp 2 c mc u tin cao, tc gp i lp 1.

Vic thit lp mt thng s ngng cho tt c cc burst d liu trong mng ln lt

l:100, 150, 300 gi trong burst. Chng ta snh gi kh nng mt gi ca cc tia vo mng vi cc thng s ngng khc nhau.

TRNG HP 2: QoS da trn vic thay i cc tiu chun xp lch knh.

[10]: Vic thc hin m phng nh gi QoS da trn vic thay i cc tiu chun

xp lch knh vi s dng tiu chun drop policy v phn mnh gii quyt xung

t vi mt ngng ng gi cnh. Mng OBS m phng mang hai lp dch v.

- M phng mng OBS vi tiu chun xp lch knh LAUC.-

M phng mng OBS vi tiu chun xp lch knh FFUC.- M phng mng OBS vi tiu chun xp lch knh LAUCVF.

TRNG HP 3: QoS da trn vic gii quyt xung t.[1]: trng hp

ny s thc hin m phng mng OBS mang hai lp traffic vi hai mc u tin

khc nhau. Cc tiu chun gii quyt xung t c s dng l DP, SDP, DFSDP,


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DFDP, SFDP. Chng ta snh gi kt qu da trn kh nng mt gi ca lu

lng a vo mng vi mt ngng ng gi cnh.

TRNG HP 4: QoS da trn tn hiu u tin: Vic m phng s thc

hin trn mng OBS vi hai tn hiu c s dng l JET v JIT. Chng ta cng s

nh gi kt qu da trn kh nng mt gi vi cc mc lu lng khc nhau.

TRNG HP 5: Trng hp ny cp n tr do chuyn mch OBS

gy ra. Trng hp ny xt n 3 tnh hung:

- Tnh hung th nht: mng chuyn mch quang chm OBS chai lp dch v, lp dch v th nht c u tin thp hn lp th hai,

lp lch knh truyn LAUCVF, gii quyt xung t DP, ngng 100.

- Tnh hung th hai: mng chuyn mch quang chm OBS chai lp dch v, lp dch v th nht c u tin thp th hai, lp lch

knh truyn LAUCVF, gii quyt xung t SDP, ngng 100.

- Tnh hung th ba: mng chuyn mch quang chm OBS chai lp dch v, lp th nht c u tin thp hn lp th hai, s dng

giao thc bo hiu JET, lp lch knh truyn LAUCVF, ngng 100.

4.6 Xy dng kch bn m phng.

4.6.1 Lu xy dng kch bn m phng.


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Bt u

Ktthc

Ly ngun cho m phng

To m hnh mng NSFNET

Thit lp cc thng s mng

Khi to cc bin

Thit lp cc thng s SCU giiquyt xung t

a lu lng vo mng trnmi cp node

Thu thp kt qu

Kt thc lu lng

S gi gi


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4.6.2 Cc bc thc hin m phng.

Ly ngunPhn mm m phng OBS4NS xy dng tng i y cc th vin cn

thit cho vic m phng mt mng quang, chng ta gi li cc ngun cn thit cho

vic m phng bng cch trng dn n cc th vin nh sau:

Source {ng dn n th mc obs4ns-3.4}/tcl/lib/ns-obs-lib.tcl

Source {ng dn n th mc obs4ns-3.4}/tcl/lib/ns-obs-node.tcl

Source {ng dn n th mc obs4ns-3.4}/tcl/lib/ns-obs-link.tcl

Source {ng dn n th mc obs4ns-3.4}/tcl/lib/ns-obs-stats.tcl

Source {ng dn n th mc obs4ns-3.4}/tcl/lib/ns-obs-defaults.tcl

Khi to cc binKhai bo cc bin c nh ngha bn ngoi kch bn m phng a

ti vo mng. Bin load thay i t 0,1 (Erlang) n 1 (Erlang). i vi mi loi

lu lng thi im pht gi u tin ph thuc vo hm ngu nhin. Hm ngu

nhin ny to ra mt s ngu nhin da vo bin seed.

Set load [lindex $argv 0] //a ti vo mng

Set opt(seed) [lindex $argv] // Khi to cc s ngu nhin.

To i tng m phng mi.Set ns [new Simulator]

To cc node mng.Nh cp trong chng 2, mt mng OBS gm c cc node bin, node

li v node kt hp. Phn mm OBS4NS-3.4 h trvic xy dng cc node mng

nh sau:

Set c($i) [$ns ObsCoreNode $ncc $ndc ChannelScheduler/$stype CoS]

// Khi to cc node liSet e($i) [$ns ObsEdgeNode $ncc $ndc ChannelScheduler/$stype CoS]

// Khi to node bin.

Set h($i) [$ns ObsHybridNode $ncc $ndc ChannelScheduler/$stype CoS]

// Khi to cc node kt hp


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Trong :

ChannelScheduler/$stype: loi lp lch knh truyn.

Ndc: s lng knh d liu ng ra ca mi node.

Ncc: s knh iu khin ng ra ca mi node.

CoS: s mc dch v.

To cc lin kt trong mng.Sau khi to cc node mng bc tip theo chng ta s xy dng cc lin kt

trong mng to nn mt topology mng hon chnh. Cu lnh to lin kt song

hng gia hai node mng c dng nh sau:

$ns duplex-obs-link $c($i) $c($j) $ncc $ndc $d ChannelScheduler/$stype

Trong :

C($i): node th i

C($j): node th j

d: khong cch gia node th i v node th j, n v km.

duplex-obs-link: lin kt l song hng.

Dng lnh $ns compile-obs hon tt vic lin kt gia cc node mng.

Thit lp cc thng s mng. m phng hot ng ca mng OBS, chng ta s thit lp cc thng s

mng theo cc ginh ban u. Cc thng s cn thit lp l bng thng lin kt,

cc thng sng khi (burst assembly), cc thng s b kt ni quang cho OXC,

cc thng siu khin chuyn mch SCU.

Connector/ObsLink dc_bandwidth // thit lpbng thng knh d liu.

Connector/ObsLink cc_bandwidth // thit lp bng thng knh iu

khin.

Agent/Burstifier set max_db_size_ [expr 1250*$number] // ng khitheo kch thc ti a vi number l s lng gi tin trong mt burst.

Agent/Burstifer set timeout_ //ng khi theo tiu chun thi gian.

Agent/OXC switch_time // thit lp thi gian chuyn mch.

Agent/Burstifier set bhp_size_ // thit lp kch thc gi iu khin.


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Agent/SCU max_bhp_proc_time // thit lp thi gian x l gi iu khin.

Agent/Burstifier set max_segmentations_ // thit lp s lng on ti

a khi phn on mt burst.

Agent/Burstifier set min_segmentable_size_ // thit lp kch thc nh

nht ca mi on.

Agent/Burstifier set segmentation_ // thit lp cc thng s cho php

gii quyt xung t trong bng khi bng phn on burst.

Agent/SCU set signalling_ // thit lp k thut bo hiu.

y l phn quan trng nht trong vic m phng, vic xc lp cc thng s

ca b kt ni quang cho OXC v cc thng s iu khin chuyn mch SCU

quyt nh vic thay i cc thng s QoS trn mng.

a lu lng vo mng.Bc tip theo l a ti vo mng vi lu lng a vo mng theo phn

b Poisson:

Set rate [expr $load*$ndc*$n_link*[Connector/ObsLink

dc_bandwidth]/$n_app]

// Tc ca mi lung lu lng c tnh ra t ti a vo mng.

Set Poi($i$j) [new Application/Traffic/Poisson]// To lu lng theo phn b Poisson.

$Poi($i$j) set rate_ $rate

// Gn tc cho lu lng.

$Poi($i$j) set packetSize_

// Gn kch thc gi.

Set udp($i$j) [$c($i) set burstifier_([$c($j) id]:QoS)

// To udp gn lu lng vi QoS l th t lp dch v.$Poi($i$j) attach-agent $udp($i$j)

//t lu lng trn tt c cc cp node.

$udp($i$j) set-traffic-generator $Poi($i$j)

$ns at 0.0 $udp($i$j) start


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// cho php bt u chy lu lng khi mi bt u chy m phng.

Kt thc lu lng.M phng c gi s s kt thc khi s gi pht i vo mng t n con s

nh mong mun. Phn mm OBS4NS ch xc nh cc bin su vo v u ra

nn trong phn ny phi gi chc nng thng k thc hin vic m gi

set sc [$ns get-global-stats-collector k]

// khi to bin sc ghi nhn cc s kin, k l s th t ca lp dch v

$sc set-counter-convergence IP_IND 1000000

// m phng kt thc khi d liu c a vo mng t n mc 1 triu gi.

Stats stop-command stop

// gi hm stop kt thc m phng.

$ns at [RouteLogic/ObsRoute transit_time] $ns enable-stats

// cho php gi chc nng thng k trong thi gian thc hin m phng.

Hm stop c to ra nh sau:

Proc stop {} {

Global ns udp

$ns at-now $udp($i$j$k) stop

// Kt thc pht burstSet now [$ns now]

$ns at [expr $now +0.2] finish

// ch0.2s sau khi cc burst n ch ri mi kt thc m phng

Kt thc m phng v ly kt qu.Sau khi kt thc m phng, s thu thp kt qu v ghi kt qu ny vo mt

file text.

To hm finish nh sau:Proc finish {} {

Global ns sc

Set ip_snd [expr [$sc get-counter-value IP_SND]]

// ly s lng gi c pht i.


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Set ip_rcv [expr [$sc get-counter-value IP_RCV]]

// ly s lng gi nhn c.

Set ip_drop [expr $ip_snd - $ip_rcv]

// tnh s lng gi b rt.

Set ip_p [expr 1.0*$ip_p/$ip_snd]

// tnh xc sut mt gi.

Set file [open results.txt a]

// khi to mt file ghi kt qu.

Puts $file $ip_p

// ghi kt qu xc sut mt gi vo mt file

Exit 0

}

Bt u chy m phng.

Bt u chy m phng bng lnh:

$ns

4.7 Kt qu m phng.

Cc s liu t vic chy m phng c biu din di dng th. Nhng

th ny c v bng phn mm matlab 6.5.TRNG HP 1: QoS da trn cc thng s ngng ng khi (burst

assembly). Vic m phng ly 3 mc ngng l 100, 150, 300 trn hai lp dch v,

vi hai tc khac nhau. Lp dch v th nht c u tin thp, lp dch v th

hai c tc gp i lp th nht v c u tin cao. Tiu chun gii quyt xung

t l drop policy (DP) v Phn mnh gii quyt xung t (SDP), giao thc bo

hiu l JET.


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Hnh 4.13 Kt qu m phng da trn cc thng sng khi 100, 150, 300

v gii quy

t xung

t d

a trn tiu chu

n DP.


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Hnh 4.14 Kt qu m phng da trn cc thng sng khi 100, 150, 300

v gii quyt xung t da trn tiu chun SDP.Nhng kt qu trn cho thy rng trong c hai trng hp DP v SDP cho

nhng kt qu sau:

- Thng sng khi cng ln kh nng mt gi cng cao.- Lu lng a vo cng cao kh nng mt gi cng ln.- Burst c u tin cao t mt gi hn so vi burst c u tin thp.Trng hp ng khi vi tiu chun SDP cho mt gi thp hn trong

trng hp ng khi theo tiu chun DP.TRNG HP 2: QoS da trn cc thng s xp lch knh. Vic m phng

thc hin trn hai lp dch v vi hai mc u tin khc nhau da trn tiu chun

lp lch knh l FFUC, LAUC, LAUCVF vi ngng l 100 gi. Hai tiu chun

gii quyt xung t l SDP v DP, giao thc bo hiu l JET.


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Hnh 4.15 Kt qu m phng da trn cc thng sxp lch knh FFUC,

LAUC, LAUCVF v gii quyt xung t da trn tiu chun DP.


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Hnh 4.16 Kt qu m phng da trn cc thng sxp lch knh FFUC,

LAUC, LAUCVF v gii quyt xung t da trn tiu chun SDP.

Trong cc trng hp trn cho cc kt qu sau:

- Tiu chun lp lch knh LAUCVF cho mt gi thp nht.- Lu lng a vo cng ln kh nng mt gi cng ln.- Lp dch v c u tin cao cho mt gi thp hn rt nhiu sovi lp dch v c u tin thp.

- Tiu chun gii quyt xung t SDP cho mt gi t hn so vi DP.

TRNG HP 3: QoS da trn vic thay i cc tiu chun gii quyt xung

t. Cc tiu chun gii quyt xung t ln lt l: DP, SDP, DDP, SDDP, DSDP.

Ngng ng khi l 100, tiu chun lp lch knh l LAUCVF, giao thc bo hiu

l JET.


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Hnh 4.17 Kt qu m phng da trn cc tiu chun gii quyt xung t.

Cc m phng trn cho nhng kt qu sau:

- Hai tiu chun gii quyt xung t DSDP v SDDP cho khnng mt gi thp.

- Ti a vo mng cng cao kh nng mt gi cng cao.- Lp dch v c u tin cao kh nng mt gi thp hn lp

dch v c u tin thp.

TRNG HP 4: QoS da trn cc thng s bo hiu. M phng s dng

hai giao thc bo hiu l JET v JIT vi hai lp dch v khc c mc u tin

khc nhau, ngng ng khi l 100, tiu chun gii quyt xung t l DP v SDP.


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Hnh 4.18 Kt qu m phng da trn thng sbo hiu vi tiu chun gii

quyt xung t DP.


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Hnh 4.19 Kt qu m phng da trn cc thng sbo hiu vi tiu chun

gii quyt xung t SDP.Cc m phng trn cho cc kt qu:

- JET cho mt gi thp hn JIT.- Ti a vo mng cng ln kh nng mt gi cng thp.- Lp dch v c u tin cao t mt gi hn lp dch v c

u tin thp.

- Tiu chun SDP cho mt gi t hn so vi DP.


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TRNG HP 5: Xem xt tr trung bnh do chuyn mch quang chm

gy ra.

Hnh 4.20 : Delay trn mng OBS vi hai lp dch v, lp lch knh tryn LAUCVF,gii quyt xung t DP, ngng 100


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Hnh 4.21: Delay trn mng OBS vi hai lp dch v, lp lch knh tryn LAUCVF,gii quyt xung t SDP, ngng 100


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Hnh 4.22: Delay trn mng OBS vi hai lp dch v, lp lch knh tryn LAUCVF,ngng 100, giao thc bo hiu JET

Nhn xt: Trong c ba trng hp trn cho thy nhng lp c u tin cao

hn cho tr trung bnh t hn. Lu lng a vo mng cng cao tr trungbnh cng gim xung. K thut bo hiu JET v JIT c tr gn ging nhau

nhng JET c tr thp hn so vi JIT do phng php ng k tr hon, gii

phng bng thng tt hn. SDDP cho tr cao hn so vi DP v cn nhiu thi

gian x l hn.

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