boco 141008120923 conversion gate02

GVHD: Nguyn Minh Hi SVTH: Mai Thanh Sn

0 THIT LP TNG I VOIP

TRNG I HC CNG NGHIP TP.HCM

KHOA CNG NGH THNG TIN

----------

N CHUYN NGHNH

THIT LP TNG I VOIP

Gio vin hng dn: Sinh vin thc hin:

Nguyn Minh Hi Mai Thanh Sn - 10071091

TPHCM, Ngy 2 Thng 7 Nm 2014



NHN XT CA GIO VIN HNG DN

(TPHCM, NgyThngNm 2014)

K tn



NHN XT CA GIO VIN PHN BIN

(TPHCM, NgyThngNm 2014)

K tn



MC LC

CHNG I. TNG QUAN V VOIP ..6

I. TNG QUAN V VOIP ............................................................................................................ 6

1. GII THIU CHUNG V VOIP ....................................................................................................... 6

1.1. u im .................................................................................................................................. 6

1.2. Nhc im. ........................................................................................................................... 7

2. CC KIU KT NI .......................................................................................................................... 8

2.1. Computer to Computer .......................................................................................................... 8

2.2. Computer to Phone ................................................................................................................ 9

2.3. Phone to Phone ................................................................................................................ .10

3. CC THNH PHN TRONG MNG VOIP...11

II. CCH THC HOT NG CA VOIP ............................................................................................ 12

1. VOIP HOT NG NH TH NO?........................................................................................... 12

1.1. Qu trnh ly mu (Sampling) ............................................................................................... 14

1.2. Qu trnh lng t ha (Quantization) ................................................................................ 14

1.3. M ha (Encoding) ................................................................................................................ 14

1.4. Nn ging ni (Voice Compression).......14

2. CC NHN T NH HNG15

2.1. Tr (Delay)...15

2.2. S bin thin tr (Jitter ).15

2.3. Mt gi...15

III. CC GIAO THC TRONG VOIP16

1. GIAO THC H.323..16

1.1. Gii thiu.............................................................................................................................. 16

1.2. Cc giao thc ca H.323 ....................................................................................................... 16

1.3. Cc thnh phn c bn ca H.323 ....................................................................................... 16

1.4. Phng thc hot ng ca H.323 ...................................................................................... 17

2. GIAO THC SIP .......................................................................................................................... 21

2.1. Gii thiu .............................................................................................................................. 21

2.2. Cc thnh phn trong SIP...................................................................................................... 21

2.3. Cc bn tin trong SIP ............................................................................................................. 23

2.4. Phng thc hot ng........................................................................................................ 24



2.5. Tnh nng ca SIP .................................................................................................................. 27

2.6. Cc giao thc ca SIP......27

IV. TNH BO MT V HNG KHC PHC...28

1. TNH BO MT TRONG VOIP .............................................................................................. .28

2. HNG KHC PHC V BIN PHP GII QUYT ..................................................................... 29

CHNG II.....ASTERISK30

I. GII THIU V ASTERISK....30

II. CI T ASTERISKNOW 3.0 V CU HNH CC TNH NNG CN BN...31

1. CI T31

2. CU HNH..37

2.1. To s in thoi (user).38

2.2. ng k s dng v thc hin cuc gi..40

2.3. Chc nng nhc ch....44

2.4. Thit lp tng i IVR.....47

2.5. Kt ni hai tng i.....49

CHNG IIITNG KT.66



LI M U

Ra i t cch y rt lu nhng in thoi vn l phng tin lin lc hu

hiu trong mi lnh vc - t qun s, an ninh quc phng cho n sinh hot i sng

sinh hot hng ngy ca chng ta.

Ngy nay, vi s pht trin mnh m ca Internet, ra i nhiu loi hnh dch

v phc v cho vic lin lc ca con ngi. Trong VoIP l cng ngh mang tnh

cch mng lm thay i th gii in thoi vi cht lng dch v kh cao.

hiu r c bn cht v ng dng ca VoIP, chng ta cng tm hiu c th

qua tng phn ca cng ngh ny.

Ni dung ti gm 2 chng ln:

Chng 1: Tng quan v VoIP

Tm hiu v VoIP, cch thc hot ng, cc giao thc s

dng trong h thng VoIP.

Chng 2: Asterisk

Dng Asterisk ci t, cu hnh cc chc nng c bn

xy dng mt tng i VoIP n gin.



CHNG I: TNG QUAN V VOIP

I. TNG QUAN V VOIP

1. GII THIU CHUNG V VOIP

VoIP (Voice over Internet Protocol) l mt cng ngh cho php truyn thoi s

dng giao thc mng IP, trn c s h tng sn c ca mng internet. VoIP l mt

trong nhng cng ngh vin thng ang c quan tm nht hin nay khng ch i

vi nh khai thc, cc nh sn xut m cn c vi ngi s dng dch v.

VoIP cho php to cuc gi dng kt ni bng thng rng thay v dng ng

dy in thoi tng t (analog). Nhiu dch v VoIP c th ch cho php bn gi

ngi khc dng cng loi dch v, tuy nhin cng c nhng dch v cho php gi

nhng ngi khc dng s in thoi nh s ni b, ng di, di ng, quc t.

Trong khi cng c nhng dch v ch lm vic qua my tnh, cng c vi dch v dng

in thoi truyn thng qua mt b iu hp (adaptor).

Nguyn tc hot ng ca VoIP bao gm vic s ho tn hiu ting ni, thc

hin vic nn tn hiu s, chia nh cc gi nu cn v truyn gi tin ny qua mng, ti

ni nhn cc gi tin ny c rp li theo ng th t ca bn tin, gii m tn hiu

tng t phc hi li ting ni ban u.

1.1. u im

Mt u im u tin l gi min ph nu s dng cng dch v, cng

thit b VoIP hoc cng tng i IP ( hay cn gi l gi ni mng). Hoc

nu khng th gi thnh cng r ng k so vi s dng cch gi truyn

thng PSTN (Public Switched Telephone Network)

Gii php VoIP cng lm gim ng k chi ph cho vic qun l bo tr

h thng mng thoi v d liu.

Tch hp mng thoi, mng s liu v mng bo hiu: trong in thoi

IP, tn hiu thoi, s liu v ngay c bo hiu u c cng i trn mt

mng IP. iu ny s gip tit kim chi ph khi u t nhiu mng ring

l.

Kh nng m rng: Cc tng i in thoi thng l nhng h thng

kn, rt kh thm vo nhng tnh nng th cc thit b trong mng

internet thng c kh nng thm vo nhng tnh nng mi.

Trong mt cuc gi ngi s dng c th va ni chuyn va s dng

cc dch v khc nh truyn file, chia s d liu hay xem hnh nh ca

ngi ni chuyn bn kia.



Mt li ch na l, vic s dng ng thi c in thoi bn thng

thng v in thoi IP (c dy hoc khng dy) qua h thng mng

LAN (Local Area Network) s m bo thng tin lin lc ca doanh

nghip khng b gin on khi xy ra s c.

1.2 . Nhc im

K thut phc tp: c c mt dch v thoi chp nhn c, cn

thit phi c mt k thut nn tn hiu phi t c cc yu cu nh: t

s nn ln, c kh nng suy on v to li thng tin ca cc gi b tht

lc, tc x l ca cc b codec (Coder and Decoder) phi nhanh

Vn bo mt (Security): Mng internet l mt mng c tnh rng

khp v hn hp. Trong c rt nhiu loi my tnh khc nhau v cc

dch v khc nhau cng s dng chung mt c s h tng. Do vy khng

c g m bo rng nhng thng tin ca ngi s dng c bo mt an

ton.



2. CC KIU KT NI

2.1. Computer to Computer

Vi 1 knh truyn Internet c sn, l 1 dch v min ph c s dng

rng ri khp ni trn th gii. Ch cn ngi gi (caller) v ngi nhn

(receiver) s dng chung 1 VoIP service (Skype, Yahoo Messenger,),

2 headphone + microphone, sound card . Cuc hi thoi l khng gii

hn.

M hnh ny p dng cho cc cng ty, t chc, c nhn p ng nhu cu lin lc m khng cn tng i ni b

Hnh 1: Computer to conputer



2.2. Computer to Phone

L 1 dch v c ph. Bn phi tr tin c mt account v mt software

(VDC, Evoiz, Netnam,). Vi dch v ny mt my PC c kt ni ti

mt my in thoi thng thng bt c u ( tu thuc phm vi cho

php trong danh sch cc quc gia m nh cung cp cho php). Ngi

gi s b tnh ph trn lu lng cuc gi v khu tr vo ti khon hin

c.

Hnh 2: Computer to phone



2.3. Phone to Phone

L mt dch v c ph. Bn khng cn kt ni Internet m ch cn mt

VoIP adapter kt ni vi my in thoi. Lc ny my in thoi tr

thnh mt IP phone.

Hnh 3: Phone to phone



3. CC THNH PHN TRONG MNG VOIP

Cc thnh phn ct li ca 1 mng VoIP bao gm: Gateway, VoIP Server, IP

network, End User Equipments

Hnh 4: Cc thnh phn trong VoIP

Gateway: l thnh phn gip chuyn i tn hiu analog sang tn hiu s

(v ngc li).

VoIP gateway : l cc gateway c chc nng lm cu ni gia mng

in thoi thng ( PSTN ) v mng VoIP.

VoIP GSM Gateway: l cc gateway c chc nng lm cu ni cho cc

mng IP, GSM v c mng analog.

VoIP server : l cc my ch trung tm c chc nng nh tuyn v bo

mt cho cc cuc gi VoIP. Trong mng H.323 chng c gi l

gatekeeper. Trong mng SIP cc server c gi l SIP server.



Thit b u cui (End user equipments ): Softphone v my tnh c

nhn (PC): bao gm mt headphone, mt phn mm v mt kt ni

Internet. Cc phn mm min ph ph bin nh Skype, Ekiga,...

in thoi truyn thng vi IP adapter: s dng dch v VoIP th my

in thoi thng dng phi gn vi mt IP adapter c th kt ni vi

VoIP server. Adapter l mt thit b c t nht mt cng RJ11 ( gn

vi in thoi) , RJ45 ( gn vi ng truyn Internet hay PSTN) v

mt cng cm ngun.

IP phone : l cc in thoi dng ring cho mng VoIP. Cc IP phone

khng cn VoIP Adapter bi chng c tch hp sn bn trong

c th kt ni trc tipvi cc VoIP server

II. CCH THC HOT NG CA VOIP

1. VOIP HOT NG NH TH NO?

Trong VoIP khi ni vo ng nghe hay microphone, ging ni s to ra tn hiu

in t, l nhng tn hiu analog. Tn hiu analog c chuyn sang tn hiu s

dng thut ton c bit chuyn i. Nhng thit b khc nhau c cch chuyn

i khc nhau nh VoIP phone hay softphone, nu dng in thoi analog thng

thng th cn mt Telephony Adapter (TA). Sau ging ni c s ha s

c ng vo gi tin v gi trn mng IP.

Cc bc c bn thc hin mt cuc gi trong VoIP:

Xc nh a im cn gi n (m quc gia, m tnh,) v bm s cn

gi n.

Cc kt ni gia ngi gi v ngi nhn s c thit lp.

Khi ni vo ng nghe hay microphone, ging ni s to ra tn hiu in

t, l nhng tn hiu analog. Tn hiu analog c chuyn sang tn

hiu s dng thut ton c bit chuyn i. Sau ging ni c

s ha s c ng thnh gi tin v gi trn mng IP. Trong sut tin

trnh mt giao thc nh SIP hay H323 s c dng iu khin

(control) cuc gi nh l thit lp, quay s, ngt kt ni, v RTP th

c dng cho tnh nng m bo tin cy v duy tr cht lng dch

v trong qu trnh truyn.

D liu s c truyn ti qua kt ni c thit lp lc u.



D liu cha m thanh m bn ni s c chuyn ha tr li thnh m

thanh m ngi nghe hiu c.

Cui cng m thanh bn ni ra s c pht ra bn pha ngi nhn.

Qu trnh s ha tn hiu analog:

Biu din tn hiu analog thnh dng s (digital) l cng vic kh khn.

V bn thn dng m thanh nh ging ni con ngi dng analog do phi

cn mt s lng ln cc gi tr digital biu din bin (amplitude), tn s,

v pha (phase), chuyn i nhng gi tr thnh dng s nh phn (0 & 1) l

rt kh khn. V vy, thc hin s chuyn i ny chng ta cn phi dng

n thit b c gi l codec (coder-decoder) hay l thit b m ha v gii

m. Tn hiu analog c t vo u vo ca thit b ny v c chuyn

thnh cc chui s nh phn u ra. Sau qu trnh ny thc hin tr li

bng cch chuyn i chui s nh phn thnh dng analog u cui.

C 4 bc lin quan n qu trnh s ha mt tn hiu analog:

Ly mu (Sampling)

Lng t ha (Quantization)

M ha (Encoding)

Nn ging ni (Voice Compression)

Cc k thut s dng trong qu trnh s ha: Multiplexing: Ghp knh l qui trnh chuyn mt s tn hiu ng thi qua mt

phng tin truyn dn. TDM (Time Division Multiplexing): Ghp knh phn chia theo thi gian:Phn

phi khong thi gian xc nh vo mi knh, mi knh chim ng truyn cao tc trong sut mt khong thi gian theo nh k.

FDM (Frequency Division Multiplexing): Ghp knh phn chia theo tn s: Mi knh c phn phi theo mt bng tn xc nh, thng thng c b rng 4Khz cho dch v thoi.

PCM (Pulse Code Modulation): iu ch theo m: l phng php thng dng nht chuyn i cc tn hiu analog sang dng digital ( v ngc li) c th vn chuyn qua mt h thng truyn dn s hay cc qu trnh x l s.



1.1. Ly mu (Sampling)

Simpling l t l ly mu th - s mu mi giy dng m ha m thanh.

Tn hiu m thanh trn mng in thoi c ph nng lng t n 10KHz. Tuy

nhin, hu ht nng lng u tp trung phn thp hn trong di ny.

Trong VoIP, t l ly mu thng l 8 KHz, tn s khong 16 KHz. C th s

dng trong cc tnh hung khi m yu cu cht lng m thanh cao (bng thng

cao). Vic la chn tn s ly mu cho tng loi m thanh khng phi ngu nhin,

m c mt quy tc ring l: tn s ly mu phi ln hn hoc bng hai ln so vi

lu lng bng thng.

1.2. Lng t ha (Quantization)

Lng t ha l s bit c s dng biu th cho tng mu m thanh. Trong

thc t, mun lm vic vi ton b byte chng ta phi xem xt 8 bit hoc 16 bit.

Mu 8 bit, mi mu c th biu th cho 256 gi tr khc nhau, v vy chng ta

c th lm vic vi cc dy s trong dy t -128 n +127. V ton b l s nn

khng th trnh khi cc ting n ln vo trong tn hiu cng nh chuyn i n

thnh mu s. Ch vi 256 gi tr, vic chuyn i analog sang tn hiu s s to

qu nhiu ting n. ci thin chng ta chuyn qua cc mu 16 bit, n s cung

cp cho chng ta 65536 gi tr i din khc nhau (t -32768 n +32767).

1.3. M ha (Encoding)

Mi mc lng t c ch nh mt gi tr s 8 bit, kt hp 8 bit c 256 mc

hay gi tr. Quy c bit u tin dng nh du gi tr m hoc dng cho mu.,

by bt cn li biu din cho ln.

1.4. Nn ging ni (Voice Compression)

Phng php ny thc hin m ha ting ni vi tc nh hn tc ca

PCM, nh tn dng c kh nng ca h thng truyn dn s. Chc hn, cc

m ha tc thp ny s b hn ch v cht lng, t bit l nhiu v lch tn s.



2. CC NHN T NH HNG

Cht lng ca m thanh c khi phc qua mng in thoi l mc tiu c bn

ca dch v. C 3 nhn t c th nh hng n cht lng dch v thoi:

2.1. Tr (Delay)

Hai vn gy ra bi s tr u cui trong mt mng thoi l ting vang v

chng ting. y l mt vn cht lng ng k, nn cc h thng VoIP phi

kim sot v cung cp cc phng tin loi b ting vang. Hin tng chng ting

l ging ngi ny gi ln ging ngi kia.

2.2. S bin thin tr (Jitter)

Jitter l s bin thin thi gian tr gy nn bi s tr ng truyn khc nhau

trn mng. Loi b jitter i hi thu thp cc gi v gi chng lu ghp cc

gi chm nht n pht li ng th t, lm cho s tr tng ln.

2.3. Mt gi

Mng IP khng th cung cp mt s bo m rng cc gi tin s c chuyn

ti ch ht. Cc gi s b loi b khi qu ti v trong thi gian tc nghn. Truyn

thoi rt nhy cm vi vic mt gi. Tuy nhin, vic truyn li gi ca TCP thng

khng ph hp. Cc cch tip cn c s dng b li cc gi mt l thm vo

cuc ni chuyn bng cch pht (play) li gi cui cng, v gi i thng tin d.

Tuy th, s tn tht gi trn 10% ni chung l khng chp nhn c.



III. CC GIAO THC TRONG VOIP

1. GIAO THC H.323

1.1. Gii thiu

H thng giao tip da trn gi a phng tin, hay cn gi l H.323. L

mt chun quc t ca VoIP c pht trin bi Lin Minh Vin Thng Quc

T (ITU International Telecommunicatinons Union). y l cu trc cht

ch, phc tp v ph hp vi vic thc thi cc c tnh thoi truyn thng.

H.323 thit k cho vic truyn audio, video v data qua mng IP.

1.2. Cc giao thc ca H.323

Khi lm vic vi H.323, c th nhn ra rng n khng phi l mt giao thc

n m l tp hp ca mt nhm giao thc. Cc giao thc ring c s dng

trong mng H.323 bao gm:

H.255 - bo hiu cuc gi.

H.245 - iu khin a phng tin (thng s knh m thanh v

video).

H.235 - bo mt v chng thc.

Q.391 - s dng cho tn hiu cuc gi.

T.120 - chia s d liu.

RTP - truyn ti a phng tin (truyn dng m thnh v video).

1.3. Cc thnh phn c bn ca H.323

Cc thnh phn c bn trong h thng mng H.323 c quy nh nh sau:

cc u cui, cng kt ni, thit b iu khin cng kt ni (gatekeeper) v khi

iu khin a im MCU (Mutipoint Conference Unit).

Terminal th thng l phn mm hoc phn cng in thoi VoIP. Mt s

chng trnh c th xem nh cc thit b terminal trong vic trao i giao thc.

Gateway l mt thit b cho php mt thng tin giao tip hai chiu vi cc

thit b trong mng vin thng khc. Cc mng vin thng khc thng l

PSTN.



MCU l mt thit b c dng cho cuc hi thoi nhiu ngi. L ni chu

trch nhim cho vic trn cc knh m thanh video trong cc cuc hi thoi.

Terminal, gateway, cc MCU c gi chung l cc thit b u cui. Ngoi

cc thit b u cui trn, mng H.323 c thm mt thnh phn th 4 l

gatekeeper. Thit b gatekeeper ng vai tr nh mt b iu khin trung tm

trong mng. Nhim v chnh ca gatekeeper l ng k thit b u cui gi

vo. Tp hp cc thit b u cui c qun l cng mt gatekeeper gi l mt

khu (Zone).

Hnh 5: Cc thnh phn ca H.323

1.4. Phng thc hot ng ca H.323

Phn trn chng ta tm hiu v H.323, by gi chng ta s tm hiu v

phng thc hot ng ca H.323, xem H.323 hot ng nh th no?

Gi s, mt mng s dng gatekeeper v cc dng dch chuyn tn hiu i

thng qua gatekeeper (m hnh c nh tuyn). Chng ta c hai thit b

u cui (in thoi IP) v mt gatekeeper, cc s in thoi c gn cho cc

thit b tng ng l 100 v 200. Mt ngi vi s in thoi l 100 quay s

200. Nhng vic c din ra nh sau:

Thit b u cui m thit lp cuc gi bit c s gi l 200 nhng

n khng bit a ch IP lin quan n s . Cng thi im, t khi

n c ng k vi gatekeeper, n phi yu cu gatekeeper cp

quyn t cuc gi bng cch gi thng ip ARQ (Admission

Request - thng ip yu cu cp IP) cho gatekeeper. ARQ s ch s

Internet



c gi (200) bo co cho gatekeeper rng thit b u cui cn c

s c phn gii thnh a ch IP.

Gatekeeper s kim tra d liu ca cc thit b u cui ng k

d n cha s 200. Vy th gatekeeper s kim tra nu 100 c gi

n 200 th gatekeeper s gi li mt cu tr li thng ip ACF

(Admiss Confirm thng ip chng thc) cha a ch IP ca 200

v gi ACF n thit b cui ang gi.

Hnh 6: M t hai bc u

Thit b u cui 100 by gi s m mt knh tn hiu cuc gi

(knh TCP) n a ch c cung cp bi gatekeeper trong thng

ip ACF. Thng ip tn hiu cuc gi c gi qua TCP vi giao

thc H.255, c nhng vo Q.931 (k hiu l Q.931/H.255).

Thit b u cui s m mt knh TCP ti gatekeeper v gi thng

ip Setup (ci t) Q.931/H.255, gatekeeper s m mt knh TCP

th hai n thit b u cui 200 v chuyn tip thng ip ci t.

Hnh 7: Gi thng ip Setup



Thit b u cui 200 u tin s tr li Q.931/H.255 bng thng

ip Call Proceeding (cch tin hnh gi) cho bit n bt u

lm vic trn thit lp cuc gi v gatekeeper s chuyn tip thng

ip n thit b u cui ang gi (100). Sau 200 s yu cu

gatekeeper quyn gi (ARQ) v gatekeeper s tr li bng thng ip

ACF.

Hnh 8: Gi thng ip call proceeding

Cc in thoi c gi (200) bt u chung v gi li tn hiu

cho bn kia vi thng ip cnh bo (Alerting).

Bn c gi (200) bt my v thit b u cui c th bo hiu cuc

gi c chp nhn. Vic ny kt thc bng cch gi thng ip

Connect. Ti thi im ny, cc bn s phi iu chnh gi tr cho

cc knh m thanh v ty chn video. Giao thc H.245, s c s

dng cho vic iu chnh ny.

Hnh 9: Gi thng ip Alerting v Connect



Thit b u cui gi i m mt knh TCP ti a ch H.245 nhn

c trong thng ip Connect v gatekeeper s to mt na knh

bo hiu H.245 th hai.

Cui cng, hai thit b u cui c th bt u gi cc dng RTP v

hai bn s nghe ln nhau.

Hnh 10: Trao i thng ip ca H.245



2. GIAO THC SIP

Trc y khi cp n VoIP, tiu chun quc t thng cp n l H.323.

Nhng nhng nm gn y th giao thc SIP li chim u th v dn s thay th

hn H.323, v VoIP l mt trong nhng dch v s rt pht trin trong tng lai.

By gi chng ta s i tm hiu c th v giao thc ny:

2.1. Gii thiu

SIP (Session Initiation Protocol) l giao thc bo hiu iu khin lp ng dng

c dng thit lp, duy tr, kt thc cc phin truyn thng a phng tin

(multimedia). Cc phin multimedia bao gm thoi Internet, hi ngh v cc ng

dng tng t c lin quan n cc phng tin truyn t (media) nh m thanh,

hnh nh v d liu.

SIP s dng cc bn tin mi (INVITE) thit lp cc phin v mang cc

thng tin m t mang phin truyn dn. SIP h tr cc phin n b (unicast) v

qung b (mutilcast) tng ng cc cuc gi im ti im v cc cuc gi a

im.

SIP l mt giao thc dng vn bn, rt cng khai v linh hot. c thit k

tng thch tng thch vi cc giao thc khc nh TCP, UDP, IP,. cung cp

mt lnh vc rng hn cho dch v VoIP.

2.2. Cc thnh phn trong SIP

SIP gm hai thnh phn ln l SIP client (l thit b h tr giao thc SIP) v

SIP server (l thit b trong mng x l cc bn tin SIP). Trong SIP c 5 thnh

phn quan trng l:

User Agents (UA): l cc u cui trong mng SIP, n i din cho

pha ngi s dng khi to mt yu cu ti SIP server hoc User

Agent server.

Proxy server: lm nhim v chuyn tip cc SIP request ti cc ni

khc trong mng. Chc nng chnh ca n l nh tuyn cho cc bn

tin n ch.



Hnh 11: Proxy server

Redirect server: l user agent server nhn cc bn tin request t cc

user agent client v tr v bn tin return thng bo thit b l

chuyn hng bn tin ti a ch khc t lin lc thng qua a ch

tr v.

Hnh 12: Redirect Server

Registrar server: l server nhn bn tin SIP Register yu cu cp nht

thng tin m user agent cung cp t bn tin Register.

Location Server: lu lng thng tin, trng thi hin ti ca ngi

dng trong mng SIP.



2.3. Cc bn tin trong SIP

INVITE: bt u thit lp cuc gi bng cch gi bn tin mi u

cui khc tham gia

ACK: bn tin ny khng nh my trm nhn c cc bn tin tr

li bn tin INVITE

BYE: bt u kt thc cui gi

CANCEL: hy yu cu nm trong hng i

REGISTER: thit b u cui ca SIP s dng bn tin ny ng

k vi my ch ng k

OPTION: s dng xc nh nng lc ca my ch

INFO: s dng ti cc thng tin nh m bo

REQUEST: cho php user agent v proxy c th xc nh ngi

dng, khi to, sa i, hy mt phin.

RETURN: c gi bi user agent server hoc SIP server tr li

cho mt bn tin request trc .



2.4. Phng thc hot ng

Hot ng ca my ch y quyn (Proxy Server)

Hnh 13: M hnh hot ng ca Proxy server

Hot ng ca Proxy server c trnh by nh trong hnh: SIP Client

[email protected] gi bn tin INVITE cho [email protected] mi

tham gia cuc gi.

Cc bc c thc hin nh sau:

Bc 1: [email protected] gi bn tin INVITE cho user B

min hotmail.com, bn tin ny n Proxy server SIP ca min

hotmail.com (bn tin INVITE c th i t Proxy server SIP

ca min yahoo.com v c Proxy ny chuyn n Proxy

server ca min hotmail.com)

Bc 2: Proxy ca min hotmail.com s tham kho server

nh v (Location server) quyt nh v tr hin ti ca user

B. T Proxy server ca min hotmail n s n Location

server nh v tr hin ti ca user B.



Bc 3: Server nh v tr li v tr hin ti ca user B (gi s

l [email protected] ).

Bc 4: Proxy server gi bn tin INVITE ti

[email protected]. Proxy server thm a ch ca n trong

mt trng ca bn tin INVITE.

Bc 5: User B p ng cho server Proxy vi bn tin 200 OK.

Bc 6: Proxy server gi p ng 200 OK tr v

[email protected] .

Bc 7: [email protected] gi bn tin ACK cho user B

thng qua Proxy server.

Bc 8: Proxy server chuyn bn tin ACK cho

[email protected]

Bc 9: sau khi c hai bn ng tham d cuc gi, mt

knh RTP/RTCP c m gia hai im cui truyn tn

hiu thoi.

Bc 10: Sau khi qu trnh truyn dn hon tt, phin lm

vic b xa bng cch s dng bn tin BYE v ACK gia hai

im cui.



Hot ng ca my ch chuyn i a ch (Redirect Server)

Hnh 14: M hnh hot ng ca Redirect server

Hot ng ca Redirect Server c trnh by nh trong hnh:

Cc bc c thc hin nh sau:

Bc 1: Redirect server nhn c yu cu INTIVE t user A

(Yu cu ny c th i t mt Proxy server khc).

Bc 2: Redirect server truy vn server nh v a ch ca user

B.

Bc 3: Server nh v tr li a ch ca user B cho Redirect

server.

Bc 4: Redirect server tr li a ch ca user B cho user A. N

khng pht yu cu INTIVE nh Proxy server.

Bc 5: User Agent bn user A gi li bn tin ACK n Redirect

server xc nhn s trao i thnh cng.

Bc 6: user A gi yu cu INVITE trc tip n a ch c

tr li bi Redirect server. User B p ng vi ch th thnh cng

(200 - OK), v user A p tr bn tin ACK xc nhn. Cuc gi

c thit lp.



2.5. Tnh nng ca SIP

Thit lp mt phin: SIP s dng bn tin INVITE yu cu thit

lp mt phin truyn thng.

n gin v c kh nng m rng: SIP c rt t bn tin, khng c

chc nng tha nhng SIP c th s dng thit lp nhng phin

kt ni phc tp nh hi ngh Cc phn mm ca my ch y

quyn, my ch ng k, my ch chuyn i a ch,c th chy

trn cc my ch khc nhau v vic ci t thm my ch hon ton

khng nh hng n my ch c.

H tr ti a s di ng ca u cui: do my ch y quyn, my

ch ng k v my ch chuyn i a ch h thng lun nm c

a im chnh xc ca thu bao. V d thu bao vi a ch

[email protected] c th nhn c cuc gi thoi hay thng ip

bt c a im no qua bt c u cui no nh my tnh bn,

my xch tay, in thoi SIP Vi SIP rt nhiu dch v di ng

mi c h tr.

nh v ngi s dng: nhng ngi s dng u cui s lun di

ng v a ch IP ca h l khng c nh, cc u cui c th ng

k vi mt SIP server thng qua bn tin REGISTER, SIP server s

lu li a ch IP ca u cui ng k. Khi c mt yu cu thit lp

cuc gi ti SIP server, SIP server s tm a ch ca ngi c gi

v forward bn tin INVITE ti ngi c gi.

2.6. Cc giao thc ca SIP

UDP (User Datagram Protocol): l giao thc tng vn chuyn khng

c iu khin tc nghn. N c dng vn chuyn bn tin SIP v

n gin v thch hp vi cc ng dng thi gian thc.

TCP (Transmission Control Protocol): l giao thc tng vn

chuyn do c iu khin tc nghn, hn na c th vn chuyn nhiu

gi tin c kch thc bt k.

SDP (Session Description Protocol): c s dng m t cc

thng s media cho mt cuc gi, cc thng s ny l cc thng tin

v bng thng, cc chun ha audio, video v mt s thng tin khc.



IV. TNH BO MT V HNG KHC PHC

1. TNH BO MT TRONG VOIP

Chnh v VoIP da trn kt ni Internet nn n c th c im yu i vi bt

k mi e da v cc vn m my tnh phi i mt. VoIP c th cng b tn

cng bi virus v m nguy him khc. Nhng k tn cng c th chn vic truyn

thng, nghe trm v thc hin cc tn cng gi mo bng vic thao tng ID m

lm hng dch c ca bn.

Gy gin on v quy ri dch v: k tn cng c gng ph dch v

VoIP cc mc: h thng qun tr, h thng d phng, h thng truy

nhp v iu khin. Phng thc tn cng c th t xa, thng qua vic

li dng cc l hng ca giao thc dng trong VoIP.

S gin on dch v: c th l do tn cong t chi dch v Dos. Tn

cng Dos c hai loi chnh l Dos thng thng v DDos DDos phn

tn, khi b tn cng ny th rt t h thng c kh nng chng c.

Cc tn cng lin quan n dch v thoi: m bo thng sut trong

h thng VoIP th cc h thng in thoi kt ni vo phi hot ng

mt cch thng sut. Cc dch v lin quan ny gm c:

Voicemail

Caller ID (thng tin c nhn)

Location

Call waiting

V d: Voicemail tn cng mt cch n gin c th l on mt khu nu

mt khu khng mnh. Chng s xa tin nhn, i thng tin c nhn,

Nghe trm: y l hnh thc tn cng t ra hiu qu khi d liu trn ng truyn khng c m ha. Ngi tn cng c th da vo cc

li bt cc gi tin ti cc im trung gian nh gateway, proxy,

Gi mo: v nguyn l phng php tn cng ny rt n gin l gi mo ci gi l thc. Phng thc ny xut pht t chnh i sng x hi.

Truy cp tri php: l kh nng xm nhp vo dch v, h thng chc nng, thnh phn mng mt cch khng chnh thng. Ngi tn cng c



th xm nhp qua cc l hng nh trn b m, cu hnh mc nh, mc

bo v km c th b b gy.

2. HNG KHC PHC

Trc khi i vo tm hiu nhng cng ngh m bo cho mng VoIP. u

tin cn phi hiu nhng vn v nhu cu bo mt tiu biu.

IP Sec: l giao thc bo mt c chng t v trin khai rng ri, n

s gip cho dch v trnh b nghe ln.

Ch k s: s dng nh trong th gii thc xc nhn mt thng ip

hay mt d liu no .

Share key (kha dng chung): trong mt h thng, ngi gi v ngi

nhn chia s vi nhau mt mt khu m bn th ba khng th bit c.

Ngi gi s dng mt khu dng chung m ha ni dung thng ip

v truyn d liu m ha ti ngi nhn. Ngi nhn m ha vi mt

khu dng chung v ta li vn bn gc.



CHNG II: ASTERISK

I. GII THIU V ASTERISK

Asterisk l phn mm m ngun m, c vit bng ngn ng C v ban u c

to ra bi Mark Spencer (nay l Gim c cng ngh ca Digium - cng ty ti tr cho

hu ht cc pht trin ca Asterisk).

Asterisk c th c ci t trn bt k phn phi Linux, v vy chng ta c th s

dng Debian, Ubuntu, Mint, CentOS, RedHat, OpenSuse,. N cng c th c ci

t trong FreeBSD, h iu hnh MacOS v c mt s cng cho Windows, nhng

Linux l ni h tr y thc hin.

Asterisk em n cho ngi s dng cc tnh nng v ng dng ca h thng tng

i PBX v cung cp nhiu tnh nng m tng i PBX khng c, nh s kt hp

chuyn mch VoIP v chuyn mch TDM, l kh nng m rng p ng nhu cu

cho tng ng dng.

V mun cu hnh c asterick ta phi da trn tng i FreePBX. FreePBX l

phn mm m ngun m vit trn Web, nh chng ta bit asterisk khng cung cp cho

ngi s dng cu hnh h thng qua giao din ha, mun cu hnh asterisk khng

cch no khc l thc hin cc dialplan qua cc tp tin cu hnh do asterisk cung cp

ti th mc etc/asterisk. V d: mun cuc gi i theo lung iu khin nht nh no

th phi khai bo cc cu lnh bn trong tp tin extensions.conf. Ni chung vic cu

hnh asterisk v cng kh khn vi nhng ngi khng chuyn su v asterisk.

FreePBX ra i nh l mt cng c h tr cu hnh cho asterisk, FreeBBX c

thit k thn thin vi ngi s dng, cu hnh asterisk mt cch d dng qua giao

din ha trn nn web mt cch trc quan d hiu. Ngi s dng khng chuyn

cng c th cu hnh c asterisk.



II. CI T ASTERISKNOW 3.0 V CU HNH CC

TNH NNG CN BN

1. CI T

c c mt my o asterick, u tin cn chun b file ISO ca

AsteriskNOW 3.0, chng ta c th ti v a ch:

http://www.asterisk.org/downloads/asterisknow

y chng ta s xy dng mt i bng my o trn VMWare nn ch cn

mt my o RAM t nht l 1GB, a o mount file ISO vo, cng khong

15GB. Nu ci trc tip trn my tht th cn chp file ISO vo a DVD hoc

USB ci t, cc bc tin hnh ging nh ci trn my o.

Tin hnh ci t:

Sau khi khi ng my o c gn file ISO, my s chy vo mn hnh

la chn cch thc ci. Chn phm 1 ci asterisk v FreePBX, phm 2

ci asterisk v khng c FreePBX. y chng ta xy dng mt tng

i asterisk da trn FreePBX nn ta chn phm 1 ci asterisk v

FreePBX.

Hnh 1: Giao din ci FreePBX



Chn v tr ni gn nht ca bn:

Hnh 2: Chn v tr

Lp mt khu cho my ch: ti khon y l s dng ti khon qun

tr cho h thng Linux ROOT, mt khu l: 123456

Hnh 3: To mt khu cho my ch



Chn cng: do l cng mi nn ta s chn Use All Space dng

ht cng.

Hnh 4: Chn cng cho my

Qu trnh ci t bt u

Hnh 5: Qu trnh ci t



Su khi ci t hon tt, chon Reboot khi ng li my

Hnh 6: Reboot my o

Sau khi Reboot li h thng, n s cp cho chng ta mt a ch IP

Hnh 7: Mn hnh chnh ca Asterisk

Ta s dng a ch IP c cp trn truy cp vo asterisk thng qua

giao din Web. Chn FreePBX Administration bt u cu hnh cho

tng i



Hnh 8: Mn hnh tng i FreePBX

Nhp user name v password mc nh l admin/admin ng nhp:

Hnh 9: ng nhp vo FreePBX



Mn hnh chnh sau khi ng nhp: v y cng l giao din chng ta s

lm vic, cu hnh trn giao din FreePBX

Hnh 10: Giao din chnh ca FreePBX



2. CU HNH

Hnh 11: M hnh tng i VoIP



2.1. To s in thoi (user)

to s in thoi, ta vo mc Extensions:

Hnh 12: Ca s Extensions

Trong qun l s (extensions), do tng i mi ci t nn cha c s.

to s, ta chn loi thit b ti mc Device - y chn thit b SIP, sau

chn Submit



Hnh 13: Device

Cn bn to mt s in thoi ta ch cn in thng tin nh sau: User 1

s in thoi l 1001, Display Name l 1001 (tn hin th) v mt khu l

abc123, sau chon Submit

Hnh 14: To user



2.2. ng k s dng v thc hin cuc gi

Ta s dng mt phn mm SIP phone ng k s dng s in thoi

c ng k trn tng i. dy chng ta dng phn mm Express Talk

cu hnh ng k user 1 vi s in thoi l 1001: Vo mc Option Line

(phn mm ny h tr 6 Line), ta s chn Default Line Settings ng k

mu cho cc Line khc. Display Name l tn hin th cho ti khon, phn

server y ta s nhp a ch IP ca tng i PreePBX cung cp cho

chng ta, SIP number l s in thoi mun ng k, Password ta nhp mt

m ca s in thoi khi chng ta ng k trong phn Extensions:

Hnh 15: ng k cho Line 1



Giao din chnh ca phn mm vi ti khon c ng k l 1001, n

hin th hp thoi cui cng:

Hnh 16: ng k thnh cng cho cc user

Ngoi ra, chng ta cn to thm cc s in thoi khc nh: 1002, 1003,

1004, ng k cng ging nh user 1.

Ta s ly user 4 c s in thoi l 1004 v ng k trn Express Talk

tin hnh gi 2 user (gi ni b). Dng my tnh th 2 ci t Express

Talk v tin hnh ng k Line nh my 1:



Hnh 17: ng k user cho my 2

Kt qu cuc gi :

User 1 gi user 4:

Hnh 18: user 1 gi user 4



User 4 gi tr li user 1:

Hnh 19: user 4 gi user 1

l phn chng ta gi ni b trong mt tng i, v mun gi ra mng

in thoi thng thng PSTN, ta cn phi mua mt ti khon gi l ti

khon Trunk, th chng ta mi c th gi c ra mng ngoi. V t mng

ngoi gi tr li vo trong l cng vic rt kh v khi chng ta mua mt ti

khon Trunk nh cung cp cho chng ta mt u s gi ra ngoi, v u

s khng c c nh nn chng ta khng th thc hin c cng vic

gi li vo trong tng i.



2.3. Chc nng nhc ch

s dng chc nng nhc ch, ta vo mc Music On Hold:

Hnh 20: Music onHold

To mt th mc cha nhc ch, ta chn Add Music Category v nhp tn

th mc sau bm Submit Changes:

Hnh 21: To th mc nhc ch



Ti ca s Music On Hold, vo th mc Nhacchodienthoai va to:

Hnh 22: On Hold Music

Chn tp tin (nh dang WAV) ri bm upload a bn nhc ch vo h

thng, sau khi upload xong bm Apply Config thao tc c hiu lc:

Hnh 23: Upload file m thanh

xa mt bi nhc ch upload ln, ta chn du tr (-) sau mi bi ht.

Mc nh nhc ch s pht bi ht u tin trong danh sch, ta chn Enable

Random Play nhc ch c pht ngu nhin. Tip theo, chon sang Tab

Applycations vo mc Fllow Me gn nhc ch cho cc user ty .



Tip theo ta chn Flow Me gn nhc ch cho cc user:

Hnh 24: Flow Me

Trong Flow Me ta chn user cn gn nhc ch, y ta dng user 2 (1002)

gn cc bn nhc ch ti ln:

Hnh 25: Gn nhc ch cho user



2.4. Thit lp tng i IVR

u tin ta v phn System Recordings a file m thanh c pht khi

gi vo tng i:

Hnh 26: System Recordings

Sau khi upload file nhc chng ta s save li, ta vo phn IVR v chn Add

New IVR, ti trang ny ta nhp tn IVR vo IVR Name, mc

Announment chn file m thanh va upload ln. Phn IVR Entries ta s cu

hnh cho cc phm khi gi vo tng i:

Phm 1: Nghe gii thiu v n

Phm 2: Gi n user 2 (s in thoi l: 1002)

Phm 3: Gi n user 3 (s in thoi l: 1003)

Phm 4: thc hin chc nng gi nhm (Ring Group)

Phm 0: Tt my



Hnh 27: Cu hnh IVR

Tip theo , tao vo phn Extensions v to s my l 1900, s my ny s

khng ng k nh cc user to trn nn ta s ty chnh ti phn Optional

Destinations Not Reachable v chn IVR l IVR s c pht khi gi

vo s 1900, y ta chn tongdaiIVR va to, sau chon Submit



Hnh 28: To s tng i

2.5. Kt ni hai tng i (Trunk)

Khi chng ta c sn mt tng i v chng ta mun st nhp thm mt

tng i khc vo. Mt tng i khc cng c c s h tng, th chng

ta khng th xa b ht c, lm nh vy s mt rt nhiu thi gian. Thay

vo chng ta s thc hin mt phng l Trunk 2 tng i vi nhau

bng SIP Trunk.

Trunk l mt ng mng o, gip kt ni cc h thng tng i vi nhau

cng nh cc dch v vin thng khc.

y mun kt ni hai tng i vi nhau, ta phi dng hai my o Asterisk

ring bit, hai my l:

Server 1: a ch IP l 192.168.43.206

Hnh 29: Server 1



Server 2: a ch IP l 192.168.43.2

Hnh 30: Server 2

trn hai server chng ta to khong 3 user (Extensions), dng kt ni

v gi cho nhau. (cch to user xem phn to s in thoi).

Sau trn mi Server chng ta chn 1 user dng Trunk sang tng

i bn kia, user ny c gi l mt user ni b (hay cn gi l user lm

mu) dng lin lc vi tt c cc user khc c trong tng i. V khi to

mt user chng ta cng nn t chng mt cch nht thng v khng c

t ba bi, lm vy s rt kh qun l v sau.

server 1 , a ch IP l 192.168.43.206, cc user c t theo th t

l 1001, 1002, 1003 (1xxx).

Hnh 31: Extensions ca server 1

server 2 , a ch IP l 192.168.43.2, cc user c t theo th t l

101, 102, 103 (1xx).



Hnh 32: Extensions ca server 2

By g chng ta s bt u cu hnh trn Server 1:

y mnh chn user 1 (1001) lm user ni b

Hnh 33: Tab Trunk



Sau chn Add SIP Trunk:

Hnh 34: Add SIP Trunk

phn ny chng ta s cu hnh Trunk sang Server 2 (192.168.43.2), tab Trunk Name

ta s t tn l trunk-sv2:

Hnh 35: trunk server2



Outgoing Settings l phn cu hnh rt quan trng chng ta Trunk sang Server 2

Hnh 36: Cu hnh Trunk Outgoing server 1

phn cu hnh trn chng ta thy c rt nhiu phn, nhng chng ta ch cn

cu hnh cc phn : host, user name, v secret (mt khu ca user). y chnh l phn

cu hnh chng ta gi sang server 2.

Ci a ch host chnh l a ch IP ca server 2 192.168.43.2. V chng ta

cng chn mt user bn server 2 lm user ni b, y chng ta chn user 101 lm

user ni b cho server 2. User 101 vi s in thoi l 101 v mt khu l abc123.

l phn Outgoing, khi m c cuc gi t server 1 (192.168.43.206) theo lut

i ra, th n s tm trong ci Trunk m chng ta to trn (trunk-sv2) sau n s

tm n ci a ch m chng ta cu hnh Trunk sang server 2 theo a ch host l

192.168.43.2 v trong ci host n s ly ci user 101 ca server 2 kt ni.

Khi m server 1 c user bn server 2 gi vo chng ta s cu hnh trong phn

Incoming Settings:



Hnh 37: Cu hnh Incoming Settings server 1

Chng ta s ly user 1001 lm user ni b, th phn USER Context chnh l

ci user dng lm user ni b cho server1, mt khu l abc123. Cui cng ta chn

Submit Changes hon thnh cng vic cu hnh.

phn trn chng ta cu hnh cho server 1, bn server 2 chng ta cng

s cu hnh tng t nh server 1:

Chng ta cng to cc user cho server 2, sau chng ta cng to mt

ng Trunk nh server 1, nhng cch t tn th chng ta t l trunk-

sv1:



Hnh 38: Add SIP Trunk

phn Outgoing Settings, chng ta s cu hnh Trunk sang server 1. a ch IP

ca server 1 l 192.168.43.206, bn server 1 chng ta chn trn, user 1001 l user

ni b, nn phn username chng ta s chon l 1001 vi mt khu l abc123.

Hnh 39: Cu hnh Trunk Outgoing server 2



phn Incoming Settings, l phn gi vo cho server 2. Chng ta chon user

101 lm user ni b cho server 2, nn phn USER Context s l user 101, mt khu

ca 101 l abc123

Hnh 40: Cu hnh Incoming Settings server

V cui cng chng ta chn Submit hon thnh cu hnh cho server 2.

Nh vy l chng ta cu hnh xong cng vic l Trunk 2 tng i vi

nhau, nhng chng ta vn cha th gi 2 tng i vi nhau c v n ang

cn thit mt ci lut gi. By gi chng ta s to mt ci lut gi cho 2

tng i, vo phn Outbound Routes:

Hnh 41: Outboand Routes



Sau chn phn Add Route

Hnh 42: Add Route

server 1 chng ta t tn l goi-sv2:

Hnh 43: Route Settings

Trong phn Dial Patterns that will use this Route l ci phn cu hnh gi sang

server 2, do server 2 chng ta t cc user l 101, 102, 103 nn chng ta s g l cc

k t sao cho n gn gng cc s in thoi trong user, y chng ta g 1xx.

Trong phn Trunk Sequence for Matched Routes chng ta tr n trunk-sv2

cu hnh trunk m chng ta va to trn. Cui cng chon Submit Changes hon

tt cng vc



Hnh 44: Thao tc lut gi

bn server 2, chng ta lm tng t nh trn, ch cch t tn l khc vi bn

server1, phn Route Name chng ta t tn l trunk-sv1

Hnh 45: Route Settings server 2

Trong phn Dial Patterns that will use this Route ta g l 1xxx v bn server 1

cch t cc user l 1001, 1002, 1003.



Hnh 46: Thao tc lut gi server 2

Trong phn Trunk Sequence for Matched Routes chng ta tr n trunk-sv1

cu hnh trunk m chng ta va to server 2. Cui cng chn Submit Changes

hon thnh.

Nh vy l chng ta hon thnh cng vic cu hnh Trunk hai tng i

vi nhau. V by gi chng ta s tin hnh thc hin cuc gi cho hai tng

i. y chng ta cng dng phn mm Express Talk ng k s in

thoi ca hai server gi vi nhau.

server 1 cc user l 1001, 1002, 1003. Chng ta c th ng k 1 hoc

nhiu user. Nhng khi tng i bn kia gi sang, ch c mt user hin th

l user dng lm user ni b: server 1 l 1001



ng k cho 1001

Hnh 47: ng k cho 1001

ng k cho 1002:




ng k cho 1003:


Cc user c ng k:

Hnh 50: ng k hon tt

bn server 2 chng ta lm tng t vi 3 user 101, 102, 103



ng k cho 101:


ng k cho 102:




ng k cho 103:


Cc user c ng k cho server2:

Hnh 54: ng k hon tt

By gi chng ta s tin hnh gi hai tng i

Bn server 2 chng ta chn mt user bt k ca server 1 gi sang server 1:



y ta chn user 1002

Kt qu: do user 1001 l user ni b nn khi gi tt c cc user trong server 1 th user

1001 s hin th trong cuc gi:

Hnh 55: Server 2 gi server 1



Server 1 gi server 2: ta chn 102

Kt qu: bn server 2 101 l user ni b

Hnh 56: Server 1 gi server 2

Nh vy l chng ta hon thnh cc tnh nng quan trng trong Asterisk.



CHNG III: TNG KT

Qua vic nghin c v VoIP, ti nhn thy c c hi v hng pht trin ca

n trong tng lai. VoIP gip cho cch doanh nghip gim chi ph cuc gi, gp phn

pht trin nn kinh t, to iu kin Vit Nam c nhng sn phm c ch nu c

u t v pht trin ng hng.

AsteriskNow l mt h thng gip chng ta xy dng mt tng i rt tt. Vic

cu hnh Asterisk cng kh n gin do s dng giao din Web FreePBX gip cho

ngi s dng c th d dng thit lp nhng kt ni in thoi analog bnh thng

vi in thoi IP. Asterisk l gii php hp l cho cc cng ty, doanh nghip mun

xy dng mt h thng in thoi ni b cng nh gim chi ph gi in ng di.

i vi bn thn, lm mt n chuyn nghnh ny em cng tm hiu rt

nhiu v cng ngh VoIP ny, do kin thc v kinh nghim nghin cu cn t nn em

cha th tm hiu su sc tt c c cc tnh nng cao cp khc ca VoIP cng nh cc

tng i h tr cho VoIP (FreePBX, Asterisk, Trixbox, Elastix,.). Vi vn kin thc

tm hiu c em ch dng li vic xy dng mt m hnh VoIP nh vi cc tnh

nng cn bn nh: gi ni b, gi ra mng ngoi (PSTN), thit lp tng i tr li t

ng, nhc ch,.

Nu c thi gian, cng vi nim am m v c s vt cht, hy vng trong thoi

gian ti em c th xy dng mt m hnh tng i VoIP ln hn v chuyn su hn

ca cng ngh ang rt pht trin hin nay.



Bng k hiu cc t ting anh trong n

K HIU TN Y

VOIP Voice over Internet Protocol

UAC User Agent Client

UAS User Agent Server

SIP Session Initiation Protocol

IVR Interactive Voice Response

UDP User Datagram Protocol

PSTN Public Swiched Telephone Network

RTP Real Time Protocol

RTCP Real Time Control Protocol

TDM Time Division Multiplexing

FDU Frequency Division Multiplexing

PCM Pulse Code Modulation

TCP Transmission Control Protocol

SDP Session Description Protocol

MCU Mutilpoint Conference Unit

PBX Private Branch Exchange

UA User Agent

ARQ Admission Request

ACF Admission Confirm

boco 141008120923 conversion gate02

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