Tap chi Khoa hgc va Phat tridn 2009: Tap 7, sd 5: 657 - 666 TRU'CiNG DAI HOC NONG NGHIEP HA NQI
HUG DUNG CONG NGHE VOIP TAI TRUUNG DAI HOC NONG NGHIEP HA NOI
The Application of VoIP Technology in Hanoi University of Agriculture Nguyen Van Djnh
Khoa Cong nghe Thong tin, Tru&ng Dgi hoc Nong nghiep Hd Noi , ;;
Dia chi email tae gia lien l a c [email protected]
TOM TAT
Bai bao nay nghien ciru mot s6 v i n 6e v l cong nghe truyin thong sii' dung giao thiJc mang Internet (cong nghe VoIP). Tren co' so nhirng nghien ciru do, du'a ra giai phap d§ xay dirng mot he thdng truyin thong img dung cong nghe VoIP tai Trirong Dai hpc Nong nghiep Ha Npi. Bai bao cung gioi thieu nhu'ng k i t qua bu'oc d i u cua viec li'ng dung cong nghe VoIP va kha nang xay dirng mot mang truyin thong hap n h i t tai Trirang Dai hpc Nong nghiep Ha Npi.
Tir khoa: Asterisk, PSTN, SIP, softphone, VoIP, VoIP phone, Wifi.
SUMMARY
This paper studies some problems on communication technology using Internet protocol (VoIP technology). Based on this study, a solution to build a communication system that applies VoIP technology in Hanoi University of Agriculture is proposed. The paper also presents some initial results of the application of VoIP technology and the potential to build an Unified Communication Network in Hanoi University of Agriculture.
Key words: Asterisk, PSTN, SIP, softphone, VoIP, VoIP phone, Wifi.
l.DATVANDE
Tii nhieu nam nay, trUdng Dai hgc Ndng nghiep Ha Ndi da sd dung tdng dai PBX (Private Branch eXchange: Tong dai nhdnh analog) de cung cap dieh vu dien thoai ngi bg cho cac ddn vi trong trudng. Tuy nhien, vdi sU phat trien ciia nha trUdng, yeu cau ve thdng tin thoai la rat ldn, ma sd'lUdng dau so' ciia td'ng dai PBX khdng dap iing du. Tii nam 2007, viec xin ca'p them cae dau so'ndi bd eho eac bd mdn mdi thanh lap da khdng dUdc dap ling. Viee lien tuc md rong tdng dai PBX va phat trien mang dien thoai ndi bd la kha ton kem so vdi ngan sach eua trudng. Giai phap tam thdi la eae ddn vi mdi se duge lip them eae so thue bao eiia mang dien thoai edng cdng (PSTN: Public System Telephone Network) va viec lien lac giiia cae ddn vi se
phai thdng qua PSTN de ggi triic tie'p vdi nhau, hoac lai ggi vao tdng dai PBX ciia trudng de nd'i tdi mgt may ndi bd,... nhiing chi phi lien lac phat sinh la rat ldn, gay lang phf eho ngan sach nha trUdng, hoac ngan sach ciia cae ddn vi (Bang 1).
De giai quyet nhu eau thdng tin thoai eua ta't ea cae ddn vi trong trUdng, ehiing tdi da nghien eiiu xay diing mdt he thd'ng thdng tin thoai diia tren giao thiie truyen thdng Internet (Voice over IP - VoIP) va tfch hdp vdi mang LAN (Local Area Network: mang mdy tinh noi bg) ciia TrUdng Dai hgc Ndng nghiep Ha Ndi. Uu diem ciia he thd'ng nay la khdng phai dau tu gi them ve ha t i n g , ma kha nang md rdng la rat ldn va de dang. He thd'ng cd the dap iing tat ca cae yeu clu ve thdng tin thoai, giii va nhan FAX cho mgi
ddn vi va ca nhan trong toan trUdng thdng qua mang LAN s i n ed va ed the tfch hdp vdi he thddng dien thoai ndi bd analog cii eiia trUdng, neu ed yeu eau.
Bai bao nay trinh bay ed sd ly thuyet va eae giai phap edng nghe de xay dung mdt he thd'ng truyen thdng thoai diia tren edng nghe VoIP tai TrUdng Dai hgc Nong nghiep Ha Ndi. Bai bao ciing neu len nhiing ket qua budc d I u cua viec ilng dung cong nghe VoIP tai Trudng Dai hge Ndng nghiep Ha Ndi va trinh bay kha nang phat trien eiia he thdng thanh met mang truyen thdng hdp nhat da dich vu.
2. PHU{3NG
P H A PNGHIEN CUtr
PhUdng phap chuyen khao: Nghien ciiu eac yeu elu cua mgt he thd'ng VoIP, eae edng nghe VoIP, cac chUdng trinh dieu hanh he thd'ng va cac chUdng trinh iing dung, ke't ndi cac thiet bi dau - cud'i.
PhUdng phap phan tich, thie't ke he thd'ng: Nghien eiiu va phan tich he thd'ng thoai diia tren cdng nghe VoIP, cae ludng thdng tin, chat lUdng am thanh... va kha nang tich hdp edng nghe VoIP vao mang LAN ciia trUdng.
Md hinh hoa he thd'ng danh gia nhiing tinh hud'ng thuan ldi va khd khan de chinh siia he thd'ng. Diia tren md hinh, viia nghien ciiu viia chinh seta, thu thap y kien eiia ngUdi dung de hoan thien san pham trUdc khi dUa vao trien khai iing dung
3. KET QUA NGHIEN CUtJ VA THAO LUAN
2.1. T i n h h i n h n g h i e n cufu v a iJfng d u n g c u a c o n g n g h e V o I P
Voice over IP (VoIP) la md hinh truyen thoai sii dung giao thiic mang Internet hay cdn ggi la giao thiic IP. VoIP ed the thiie hien tat ca cac dich vu thong thudng nhu tren mang dien thoai cdng edng (PSTN) va nhieu
dich vu nang cao khae. Ngay nay, VoIP dang trd t h a n h mdt trong nhiing edng nghe vien thdng ha'p d i n nhat hien nay, no mang lai ldi ieh cho ea eae nha khai thac va ngUdi sU dung bdi sU tiet kiem ehi phi cho cd sd ha t i n g va chi phi lien lae, nhat la lien lae dudng dai va lien lae qud'c te. (Ted WalHngford, 2005).
O Viet Nam, cae dieh vu dien thoai cd iing dung edng nghe VoIP mang tinh thudng mai eiing phat trien r a t manh, nhu eac dich vu dien thoai dudng dai 171 ciia VNPT hay 178 eua Viettel, dien thoai qud'c te gia re 1719, eae dieh vu dien thoai Internet diing the...
Tinh bao mat eua eac he thd'ng VoIP eiing dUde nang eao ra't nhieu nhd cae edng eu ehd'ng xam nhap trong Asterisk (David Endler, Mark Collier; 2006 va Ben Jackson, Champ Clark; 2007). Neu VoIP chi trien khai tren mang LAN thi kha nang bi xam nhap la ra't tha'p.
2.2. C a c m o h i n h m a n g VoIP Mo hinh PC to PC
Trong md hinh nay, mdi may tfnh can cd mdt microphone, mdt speaker va dUde ket nd'i triie tie'p vdi mang LAN hoae Internet.
Mdi may tinh dUde cung ca'p mdt dia chi IP, va hai may tinh ed the trao ddi eae tfn hieu thoai vdi nhau thdng qua mang LAN hoac Internet. Ta't ea eac thao tac nhU la'y mau tin hieu am t h a n h , ma hoa va giai ma, nen va giai nen tin hieu deu dUde may tfnh thiic hien. Trong md hinh nay chi ed nhiing may tinh nd'i vdi eiing mdt mang mdi cd kha nang trao ddi thdng tin vdi nhau (Ted Wallingford, 2005).
Mo hinh PC to Phone
Md hinh PC to Phone la mgt md hinh dUdc cai tie'n hdn so vdi mo hinh PC to PC.
Md hinh nay cho phep ngudi sii dung may tfnh ed the thiie hien cugc ggi den mang dien thoai cdng cong thdng thudng (PSTN) va ngUdc lai (Ted Wallingford, 2005).
NguySn Van Bjnh
Hinh 1. Mo h i n h PC t o PC
H i n h 2. Mo h i n h PC t o P h o n e
Hinh 3. Mo h i n h P h o n e t o P h o n e Mo hinh Phone to Phone
Day la md hinh md rdng cua md hinh PC to Phone sii dung Internet lam phUdng tien lien lac giiia cac mang PSTN. Tat ea cac mang PSTN deu ke't nd'i vdi' mang Internet thdng qua cac gateway. Khi tie'n hanh cude ggi mang PSTN se ket nd'i de'n gateway gan nhat, tai day, sd' dien thoai se dUdc ehuyen ddi sang dia chi IP de cd the dinh tuye'n den mang dich. Ddng thdi
gateway ngudn cd nhiem vu chuyen ddi tin hieu thoai tUdng tu t h a n h dang sd sau dd ma hoa, nen, ddng gdi va g i i qua mang Internet. Mang dich ciing dUde ket nd'i vdi mgt gateway va tai dd dia ehi IP dUde chuyen dd'i trd lai t h a n h dia ehi PSTN va tin hieu dUde giai nen, giai ma ehuyen ddi ngUde lai t h a n h tfn hieu analog gui vao mang PSTN de'n may dich (Ted Wallingford, 2005).
Md hinh phone to phone cho phep ggi dien thoai dudng dai va qudc te thong qua Internet, vdi chi phi gan nhu bang khdng.
Tuy nhien, hien nay d Viet nam chi cd mdt sd' it cdng ty dien thoai Nha nUdc duge phep khai thac dieh vu nay. Cac mang VoIP ciia cae td chiic khae khdng dUdc phep khai thac md hinh nay, vi se gay that thu cudc vien thdng cua Nha nude. Trong de tai nay, chung tdi chl nghien ciiu md hinh nay, ma khdng trien khai iing dung.
2.3. He t h o n g ASTERISK Gidi thieu Asterisk
Asterisk la 1 phan mem ma ngudn md cd tinh nang tUdng dUdng nhu 1 tdng dai PBX.
Mdi trudng trien khai Asterick la mdi trUdng UNIX. Vdi Asterisk, mgt may ehii hoac mgt may tinh PC chay he dieu hanh Linux cd the trd thanh tdng dai cho mdt he thd'ng dien thoai ldn.
Kie'n true Asterisk
Asterisk co tjie dUdc eoi la mdt phan trung gian d giiia dung de ket nd'i Ineternet va dien thoai hay cac iing dung thoai. Cae ting dung ciia Asterisk ed the ket nd'i bat cii dien thoai, dudng day dien thoai hay gdi tin
thoai nao de'n mgt dich vu hay giao dien khac.
Asterisk c6 the triln khai de dang va tin cay tii quy mo nhd de'n rat ldn va hd trg eae iing dung day dae (David Gomillion, 2005).
Asterisk hd trd mgi kha nang ed the cd eiia edng nghe telephony. Asterisk ed the hdp tae hoat ddng vdi hau het eae thie't bi thoai tieu ehuan, eac phan eiing ket ndi vdi Asterisk deu ed gia thanh khdng eao.
Asterisk hd trd edng nghe dien thoai truyen thd'ng bao gdm ggi dien, hgi thao, voieemail, tra ldi tii ddng va nhieu iing dung khac.
Asterisk server ke't nd'i vdi mdt mang LAN ciing ed the ke't nd'i vdi mang PSTN thdng qua thiet bi ATA (Analog Telephone Adaptor: thie't bi ket nd'i dien thoai analog).
Dieu nay cho phep cae cude ggi cd the dUdc ggi va dUdc nhan tii mang PSTN va dUdc ket nd'i vdi thiet bi thoai VoIP trong mang LAN.
Cae cude ggi ed the duge ehuyen giiia Asterisk server nay vdi Asterisk server khac.
Mdt dien thoai dUde dieu khien bdi mdt Asterisk server ed the ehuyen sang Asterisk server khae va sau dd di vao mang PSTN.
(David Gomillion, 2005).
Hinh dudi day md ta md hinh cua mdt he thddng Asterisk:
IP Phones Analog Phones
TelcoorPBX
Medb Gateway f Voice Mall
Confefdncc Music on hold
Hinh 4. Mo hinh chung cua he thong Asterisk
NguySn Van Bjnh
Cdc tinh ndng cua Asterisk
Ngoai nhiing tinh nang tUdng tii nhU tdng dai PBX, Asterisk cdn cd them nhieu tinh nang khac ma chi cd the ed dUde d nhiing tdng dai rat d i t tien. Mdt sd'trong eae tinh nang dd la:
• Voieemail Services with Directory - cho phep nhan cae VoieeMail vdi dieh vu thu mue quan ly ngUdi dung, dam bao an toan thong tin.
• Conferencing Server - Server hgi thao truyen hinh
• Custom Interactive Voice Response (IVR) system - He thd'ng tra ldi tu ddng
• Soft switch — Chuyen mach mem
• Standalone Voieemail System - He thd'ng VoieeMail
• Call Forward - Chuyen hUdng eudc ggi Asterisk hd trd giao thiie SIP, la mdt giao thiie ehuan eiia IETF, dUde trinh bay dudi day. Chiing tdi ciing liia chgn giao thiic SIP eho he thd'ng VoIP tai Dai hge Ndng nghiep Ha Ndi.
2.4. Giao thifc SIP
Dinh nghia giao thdc SIP
SIP (Session Initiation Protocol: giao thiic thiet lap ket nd'i) la mdt giao thiie chuan eiia IETF (Internet Engineering Task Force) dUOc sii dung trong viec truyen thdng da phUdng tien thdng qua mang IP, de thiet lap eac ket nd'i VoIP.
Giao thiie SIP eung cap mdt khudn khd de thiet lap voice, video, hdi thao va thdng diep van ban truyen theo kieu point-to-point.
SIP la mdt giao thiic dieu khien ldp ilng dung de tao mdi, ehinh siia va ket thiic eae session. Ca'u triic eiia SIP gid'ng nhu HTTP (client-server protocol). Cae request dUdc tao ra bdi cae may client va giii tdi server.
Server xii ly cac request va giii mdt response lai cho client. Mdt request va response la hai thanh p h l n de tao ra 1 giao dieh. Giao thiic SIP cho phep thiic hien cae thao tae, tao cac thong so'cho mdt ke't nd'i VoIP nhu sau:
• User Location: Xae dinh thiet bi dau cud'i de sii dung cho viee truyen thong.
• Call Setup: Bao ehudng va thiet lap cac thdng so'eho ngudi ggi va bi ggi.
• User Availability: Xae dinh sU san sang eiia ngudi eii dung.
• User Capabilities: Xac dinh phUdng tien va cae thdng sd' dUde sii dung.
• Call handling: Chuyen giao va ket thiic cugc ggi.
Kie'n true cua SIP
Hai thanh phan chinh trong he thd'ng SIP bao gdm: SIP User Agents va SIP Network Servers.
• SIP UA (User Agent: dai ly ngudi dung -UA):
Muc dfch eiia SIP la iam eho cac session cd the thiet lap giiia eae UA. Mdt UA la mdt he thd'ng dau eud'i hoat ddng tren danh nghia eua ngUdi diing. Mdt UA phai cd kha nang thiet lap mdt session ciia phUdng tien nay vdi cac UA khac. Met UA phai duy tri trang thai tren eae eudc ggi ma nd khdi tao hoac tham gia vao. Mdt UA chiia mdt iing dung client va mgt iing dung server. Hai thanh phan tren la mdt user agent client (UAC: dai ly ngUdi diing khach trong quan he client-server ) va mdt user agent server(UAS: dai ly ngUdi dung chu trong quan he client-server). UAC b i t d i u eae request trong khi UAS thi tao ra eae response (Ted Wallingford, 2005 va David Gomillion, 2005).
• SIP Network Servers -. ,...
Proxy Server
Mgt SIP proxy server nhan mdt SIP request tii mdt User Agent hoae mdt proxy khae va hanh dgng tren nhan danh ciia User Agent trong forwarding hoae responding tdi request. Mdt Proxy server phai ed truy xuat de'n eac database hoae vi tri eae dieh vu de giiip dd nd trong qua trinh xii ly cac request.
Proxy ed the sii dung nhieu kieu database trong qua trinh xii ly eac request. Database cd the ehiia SIP registration, cac thong tin
hien hiiu, va nhieu kieu khac ciia thdng tin ve ndi ma user dUdc chi dinh. Mdt SIP server eung ca'p cae dich vu va chiic nang vdi UA.
(David Gomillion, 2005).
Registration Servers
Mdt registration server dUde biet nhu la mdt registrar, chap nhan cae request ciia SIP REGISTER. Thdng tin hen quan tii request iam cho eae SIP server cd san ben trong gid'ng Administrator Domain, chang han nhu proxies va redirect server.
Registration server thudng yeu elu cae user agent (UA) dang ky de xac thiic, vi vay cae eudc ggi di vao khdng bi chie'm doat bdi cac
user khdng dugc xae thiic. Mdt REGISTER request eo the dUde sii dung bdi mgt user agent de la'y lai mdt danh sach eiia eac registration hien thdi, lam sach tat ca registrations, hoac them vao mdt registration URL (David Gomillion, 2005).
4. K E T Q U A T R I E N K H A I L T N G D U N G 4 . 1 . Xay d i i n g k i e n t r u e he t h o n g
Diia tren nhiing nghien eiiu ve edng nghe VoIP da trinh bay d tren, ehiing tdi xay diing kie'n true cho he thd'ng mang VoIP tai TrUdng Dai hgc Ndng nghiep Ha Ngi nhu sau:
Hinh 5. Kie'n triic ciia he thong VoIP t a i TrUdng Dai hpc N o n g nghiep Ha Noi Cd sd ha tang eiia mang VoIP la ed sd ha
tang eua mang LAN san ed ciia Trudng Dai hgc Ndng nghiep Ha Ndi, eho nen khdng mat ehi phi cho viec xay diing mang.
Chung tdi liia chgn giao thiie SIP eho he thd'ng, vi day la mgt giao thiie chuan ciia IETF (Internet Engineering Task Force), hien dai va dUdc hd trd bdi Asterisk server.
May chii ciia he thd'ng VoIP dUdc diing chung vdi mgt may chu cd san cua Trung tam
tinh toan va Tfch hdp dii lieu, tren dd ed thiet lap mdt server ao ehay he dieu hanh Linux.
Phan mem dieu khien VoIP la phan mem ma ngudn md Asterisk ed tinh nang tUdng dUdng nhU 1 tdng dai PBX, eai dat tren server ao chay he dieu hanh Linux.
Nhu vay, mdt he thd'ng SIP Network Servers hoan chinh, dUdc tich hdp trong mdt server cd s i n cua Trung tam tinh toan va Tich hdp dii lieu.
NguySn Van Bjnh 4.2. Lap dat cac thie't bi dau cuoi VoIP
tai Khoa Cong n g h e t h o n g tin Do kinh phi cua de tai rat han che, eho nen chi cd the trang bi dUde mgt sd' it thiet bi phan Cling, chii ye'u la de thvi nghiem he thd'ng VoIP trong pham vi Khoa Cdng nghe thdng tin (CNTT).
VoIP phone
Day la thie't bi phan cting ket nd'i vdi mang VoIP gid'ng nhu may dien thoai de ban thdng thUdng nhUng danh cho VoIP, can phai thiic hien ca'u hinh trUde khi sU dung.
VoIP video phone
Chiing tdi da trang bi mgt so' may VoIP video phone tai Khoa CNTT de thii nghiem cho cac dich vu dam thoai. hgi nghi co hinh.
Vicleo phone GXV-3000 S P S l O l VoIP Teieohone
Hinh 7. May dien thoai Video phone GXV-3000 va VoIP phone SPSlOl Softphone
Softphone la phan mem mien phi X-Lite dUde eai tren may tfnh, ed the thiie hien ta't ca cac chUc nang gid'ng nhU thiet bi dien thoai VoIP. Khi sii dung softphone, may tinh
Hinh 8. Giao dien ciia SoftPhone
phai ed headphone va firewall khdng bi khda. Khi kich hoat, mdt giao dien nhU mdt dien thoai di ddng se xuat hien (hinh ben), cd the quay sd' ggi di, hoae nhan mdt eudc ggi den thdng qua he thd'ng VoIP. Neu may tinh cd webcam, softphone se hoat ddng nhU mdt video phone.
ATA (Analog telephone Adaptors) Thiet hi ATA gdm 2 loai port: RJ-11 de ket nd'i vdi may hoac mang dien thoai Analog thdng thudng, cdn RJ-45 de ket nd'i vdi mang VoIP. ATA ddng vai trd nhU mgt gateway, chuyen ddi tin hieu Analog sang tin hieu sd' sii dung eho mang VoIP, lam nhiem vu ke't nd'i giQa mang PSTN va mang VoIP. De tan dung may dien thoai Analog, ed the sii dung ATA nhu la mgt adapter ehuyen dd'i sang IP phone, thay vi phai trang bi dien thoai VoIP.
Nokia E66
La met trong so' eac dien thoai di ddng Nokia E-series, ed tich hdp cdng nghe WiFi va hd trd giao thiie SIP, ed the ket nd'i vao mang VoIP. Hai thiet hi Nokia E-series ed the dam thoai di ddng trong mang mien phi.
hoac cd the ggi/nhan cude ggi vdi mdt may VoIP trong mang cd phu sdng WiFi. Khi ggi trong he thd'ng VoIP, phai chgn "cugc ggi Internet".
4.3. Cac dich v u da trien khai tren he t h o n g VoIP tai Triidng Dai h o c N o n g n g h i e p Ha Noi
Hien nay, he thd'ng VoIP da dUde tieh hdp vao mang LAN cua Dai hgc Ndng nghiep Ha Ndi, tat ea cac may tfnh va thiet bi VoIP vdi dia ehi thude ldp mang 192.168.12.x deu cd the khai thac he thd'ng nay.
Da khdi tao 80 so' may VoIP ed' dinh va 20 sd' may di ddng de san sang hda mang cho cae bd mdn va ea nhan cd nhu cau. Da thii nghiem thanh cdng cac dieh vu dUdi day tren eac thiet hi VoIP va softphone dat tai Trung tam TT&THDL va mdt sd' bg mdn tai khoa CNTT.
Dich vu goi noi bo trong mqng VoIP Dieh vu nay eho phep eae may ndi bd trong mang ggi lan nhau, nhu la eae may trong mang ndi bd cii ciia trUdng. Khi cd yeu cau, cd the ket nd'i cac may ndi bd VoIP vdi cac may ndi bd cii eiia trUdng, thong qua mdt ATA. Khi dd, cd the tang dung lugng mang dien thoai ngi bd ciia trudng bang viec sii dung dong thdi he thd'ng VoIP va he thd'ng Analog, viec lien lae giiia hai he thd'ng khdng mat chi phi ke't nd'i va ehi phf dam thoai (David Gomillion, 2005). ,.• '. '
Dich vu goi tit mqng VoIP ra mqng PSTN vd GSM
Tai eac dia diem khdng ed may dien thoai ed' dinh eiia PSTN, ed the sii dung cac thiet bi thoai VoIP ggi ra ngoai PSTN, hoac vao cac mang di ddng GSM. Cudc phi nhU dd'i vdi cae may ndi bd eiia trUdng ggi vao PSTN, hoac ggi vao mang di ddng GSM.
(David Gomillion, 2005).
Dich vu nhdn cupc gpi tit mqng PSTN vd GSM vdo mqng VoIP
Cho phep n h a n cudc ggi tit mang dien thoai cdng cdng PSTN hoae GSM tdi may VoIP.
Ngudi ggi se ggi tdi sd' eiia tdng dai VoIP, sau dd dUde hudng d i n tii ddng de quay sd ndi bg VoIP eiia ngUdi dUde ggi (David Gomillion, 2005).
Dich vu Video conference
Cho phep nhieu ngUdi diing (set dung 3-4 video phone hoae softphone ed webcam) hdi thao vdi nhau ed kem theo hinh anh. Mdt Video phone hoac softphone (de ehe do AA - auto anser va AC- auto conference) ddng vai trd la phdng hgp, cho eae may khae ggi vao (David Gomillion, 2005 va Tien Pham Van 2005).
Dich vu audio conference
Cho phep nhieu ngUdi diing hdi thao vdi nhau tii eac thiet bi VoIP. Tuy khdng truyen dUde hinh anh nhUng ngUdi diing ed the tii nhieu thiet hi VoIP khae nhau nhU softphone, IP phone, videophone ed the hdi thao thoai vdi nhau (David Gomillion, 2005).
Dich vu voieemail
Cho phep nghe lai ldi nhan tii ngUdi ggi (trong mang VoIP hay tii ngoai ggi vao). Khi may duge ggi khdng tra ldi, ngUdi ggi cd the de lai ldi nhan, he thd'ng se ehuyen vao hdm thu ngUdi dUde ggi dUdi dang email. Chi cd ngUdi dUde ggi cd the nghe lai dUdc ldi nhan qua email, hoac nghe lai tii mdt may VoIP, vdi ten truy nhap va mat khau (David Gomillion, 2005).
5. DANH GIA HIEU QUA vA TINH KHA THI
Khdo sdt he thdng dien thoqi Analog hien tai cua trUdng
Hien tai, TrUdng Dai hgc Ndng nghiep Ha Ndi dang sii dung mdt he thd'ng dien thoai ndi bd vdi eae tfnh nang ky thuat va ehi phi nhu d bang 1.
NguySn Van Bjnh
B a n g 1. Khao sat h e tho'ng dien thoai Analog h i e n tai c u a triidrng
Thiet bi / Dich vg Tong dai analog PBX Panasonic 16SLC
- 8 du'ong trung l<e cua VNPT cho tong dai - 35 du'O'ng dign thoai tryc tiep cho BGH va cac phong ban
Tong cong
Tinh nang l<y thuat - 8 du'O'ng trung kk - 88 so noi bp
- KSt n6i vo'i tong dai de gpi ra ngoai va nhan goi vao.
- Goi trong mang PSTN, va gpi vao mang npi bp thong qua tong dai
Kha mo
nang rpng - Khong con kha nang mo rflng, phai thay tong dai moi.
Chi phi d4u tu' lin dSu
3.200 USD + VAT {57.000.000 d + VAT)
-15.000.000 vnd + V A T (trung binh 350.000d/1 du'O'ng dien thoai khong ke may)
71.000.000 vnd + VAT
Chi phi hang thang
-Khau hao 10%/nam/12 thang = 480.000 d + VAT
10.000.000-12.000.000 vnd + VAT
12.000.000 vnd+VAT
Bang 2. Dii trii cho he thong dien thoai VoIP tai Triidrng Dai hpc Nong nghiep Ha Noi
Thiet bi / Dich vg -Tong dai mem Asterisk Server - Analog FXO IP Gateway, GS- GXW4104 - ATA GS-HT486
- 1 du'ong trung ke cua VNPT ket n6l qua gateway
- 1 duong dien thoai noi bp ket noi voi ATA.
Tong cOng
Tinh nang ky thuat - 8 du'd'ng trung ke - 80 s6 noi bo bdn - 20 so npi bO di dpng.
Analog FXO IP Gateway, 4 FXO ports
Analog adapter SIP VoIP FXS ports - K6t n6i vol tong dai de gpi ra ngoai va nhan cupc gpi vap tif PSTN.
- Gpi trpng mang V P I P va gpi vap mang npi bp analpg cua tru'O'ng.
Kha nang mc rpng -BSn 16trk§
-BSn hdng ngan SP npi bp
Chi phi dau tu' lan dau - Phiin mem ma nguen ma, miin phi. Cong Coii dat 1.000.000 vnd 271 USD + VAT (-4.880.000 vnd) 63 USD + VAT (-1.134.000 vnd)
350.000d + VAT { 1 duong dipn thoai khong k^ may)
6.714.000 vnd + VAT
Chi phi hang thang - 300.000d + VAT cong bao tri. (CP t h e t y lam)
- 200.000d + VAT (chi phi thue bac va cuoc phi che 1 du-ong dien thoai ciJa VNPT.)
500.000 vnd + VAT
Hien nay tdng dai Analog PBX ndi bd khdng the md rdng them dau so', neu mud'n md rdng gap ddi dung lUdng sd' ndi bd hien nay (tii 88 so' len khoang 160 sd) ehi ed each mua tdng dai mdi, kha td'n kem so vdi ngan sach ciia trUdng. Giai phap tam thdi tii ma'y nam nay, da phai l i p dat them tren 30 sd dien thoai triic tie'p (PSTN) cho cae ddn vi ed
nhu eau, va viee lien lae giiia cac ddn vi se phai thdng qua PSTN de ggi triic tie'p vdi nhau, hcac lai ggi vao tdng dai PBX eua trUdng de nd'i tdi mdt may ngi hg. Neu tie'p tue md rdng mang dien thoai ciia trUdng theo hudng nay thi nhiing chi phi lien lae phat sinh la rat ldn, gay lang phi eho ngan sach nha trudng, hoac ngan sach eiia eac ddn vi.
Sd tien dau tu eho viee md rong va ehi phi hang thang se tang them mgt khoan tUdng tii nhu he thd'ng hien cd (Bang 2).
Du trii cho he thdng dien thoqi VoIP tqi Trudng Dqi hpc Nong nghiep Hd Npi
He thd'ng VoIP thii nghiem tai Khoa Cdng nghe thdng tin dUdc lap dat vdi cae thie't bi cd eae thdng so' ky thuat va gia ea nhu sau (khdng tinh de'n eac thiet bi dau cud'i)
Qua so sanh 2 bang tren, ta thay viee xay diing he thd'ng dien thoai VoIP la hoan toan kha thi va rat hieu qua. Hdn niia, ed the ket nd'i he thd'ng nay vdi he thd'ng dien thoai ngi bg eiia trudng de nang ga'p ddi dau so'ndi bd, ma ehi phi ehi b i n g khoang 10% so vdi viee lap dat them mdt tdng dai analog eung dung lUdng vdi tdng dai cii de tang ga'p ddi dau sd' ndi bd, vi tdng dai cii hien nay khdng the md rdng them dau so'.
6. K E T L U A N VA D E X U A T
Vdi mdt kinh phi kha han hep tii mdt p h l n eua de tai KHCN ca'p Bg va vdi thdi gian hdn 8 thang, chiing tdi da dat dUdc mdt sd' ket qua budc d i u trong viee nghien ciiu va trien khai iing dung cdng nghe VoIP tai TrUdng Dai hge Ndng nghiep Ha Ndi.
Chiing tdi xin de xuat dUde tie'p tuc nghien eiiu thii nghiem he thd'ng tai khoa CNTT va mdt sd' phdng ban, ket hdp vdi du an TRIG de trien khai he thd'ng tren mang
WiFi ciia du an, phat trien thanh he thd'ng mang truyen thdng hdp nhat da dich vu, mang lai mgt ha tang truyen thdng hien dai va hieu qua eho Trudng Dai hge Ndng nghiep Ha Ngi.
L d i c a m tfn
Trong qua trinh nghien eiiu va trien khai iing dung de tai,<-"<chung tdi xin cam dn sii giiip dd hieu qua ciia TS. Nguyen Chan Hiing va nhdm sinh vien K49, khoa Dien tii Vien thdng, Dai hge Bach khoa Ha Ndi.
Dae biet, ehiing tdi xin ehan thanh cam dn Bd Giao due va Dao tao da hd trd kinh phi de thiic hien nghien eiiu nay.
TAI LIEU THAM KHAO
Ben Jackson, Champ Clark (2007). Asterisk Hacking, Syngress Publishing, Inc.
Burlington, MA 01803, USA.
David Endler, Mark Collier (2006). Hacking Exposed VoIP Voice over IP Security Secrets
& Solutions, McGraw - Hill Osborne Media, Inc, Columbus, OH. USA. (2005). Building Telephony Systems with Asterisk, Packt PubHshing, Ine. Birmingham, UK. (2005).
Switching to VoIP, O'Reilly Media, Ine.Sebastopol, CA, USA.
Tien Pham Van (2005). "Real-time Video over Programmable Networked Devices".
Springier - Verlag LNCS 3779, pp. 409 - 416.
