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Phần 1 cuốn sách Công nghệ VoIP và các giải pháp nâng cao chất lượng dịch vụ do ThS. Ngô Xuân Thành biên soạn cung cấp cho người đọc các kiến thức: Giới thiệu chung, tổng quan về giao thức TCP/IP, công nghệ VoIP. Mời các bạn cùng tham khảo nội dung chi tiết.
ThS N G O XU A N THA N H CONG NGHE VoIP ■ VA CAC Glfll PHAP NANG CAO CHAT LUONG DICH VU ■ UYEN LIEU N H A X U A T B A N B J U O IE N ■ ■ CONG NGHE VoIP VACAC GIAI PHAP NANG CAO CHAT LU0NG DjCH VU THS NGO XUAN THANH CONG NGHE VoIP V A C A C G lfll P H A P N A N G C A O C H A T L lO T N G D IC H V U ■ NHA XUAT BAN Bl/U DIEN Ha Noi, thang - 2005 ■ ■ LOfI N O I D A U Trong nhicng nam gan day cong nghe truyen thoai da co nhieu thay doi vicot bdc Thoai gio day da co the truyen tren m ang goi vd mot cdc cong nghe thoai goi nhieu him hen Id thoai IP Cong nghe truyen thoai qua mang sic dung giao thicc Internet doi vdi nhieu iru diem vd mang lai nhieu lai ich cho cd nguai sir dung vd nhd khai thac vien thong Thoai qua giao thicc IP co the Id VoIP hodc thoai Internet dang cdng dicoc sic dung rong rdi Nhin chung, cdc cuoc dien thoai qua giao thicc IP co chat hccxng thdp hem so voi cdc cuoc dien thoai truyen thong Doi khi, sic khde biet ve chat liromg Id nhd vd ngicai sic dung khong nhan thay dicac Tuy nhien thicc hien cdc cuoc goi qua Internet thi ngicai dung se thay chat luang thoai giam mot cach ro ret De thoai qua giao thicc IP thicc sic dap icng dicac mong doi ciia ngicai sic dung thi van de chat Iicong dich vu can giai quyet tot hem nica Nhdm cung cap cho doc gid cong nghe VoIP den ban doc, Nhd xudt ban Bicu dien xuat ban cuon sach “ Cong nghe VoIP va cdc giai pit dp nang cao chat luang dich v u ” Cuon sdeh gom chicong: Chiccmg I: Gioi thieu chung, trinh bay ve xu hiccmg vd icng dung ciia thoai IP ciing n/nc cdc ddc diem ciia tin hieu thoai Chicang II: Tong quan giao thicc TCP/IP La bo giao thicc chcac sic dung cho cdc mang IP, mang sic dung de truyen thoai IP tren Chxcang III: Cong nghe VoIP Chicang tr'inh bay can tr ie mot he thong VoIP vd cdc ky thudt md hoa, truyen tai sic dung thoai IP Chicang IV: Cdc giao thicc dieu khien, Id cdc bo giao thicc dieu khien sic dung cho thoai IP Chicang V: QoS vd cdc yen to chinh dnh hicdmg den chat licang thoai Chicang VI: Gidi phap ndng cao chat licang thoai Chicang tr'inh bay mot so gidi phdip co the sic dung de ndng cao chat licang thoai Hi vong cuon sdeh se la tai lieu tham khao him ich cho cdc can bo dang hoat dong ngdnh Buru dien, cdc ky su, cdc kv thudt vien dang hoat dong linh vicc vien thong, cdc sinh vien vd ban doc quan tam den van de r r % / Y kien dong gop ciia quy vi vd ban doc xin gici ve Nhd xuat ban Bicu dien - 18 Nguyen Du, Hd Noi Tran cam an./ Hd Noi, thang nam 2005 NHA XUAT BAN BlTU DIEN Chi/dng I g i6 i th ieu ch un g 1.1 LICH SU* VA XU Hl/ONG PHAT TRIEN CUA THOAI IP Cong nghe vien thong gan day co nhieu thay doi Ion, cac mang vien thong chu dao hoat dong tren nen chuyen mach kenh sc co \ u hirang chuyen sang hoat dong tren nen chuyen mach goi Dieu co nghTa la phan Ion luu lirong thoai se dugc truyen qua mang chuyen mach goi Dien thoai IP doi da gay dugc su chu y manh me va co kha nang tro nen tang cho m ang thoai dung cong nghe chuyen mach goi Nlumg lieu dien thoai II’ co the thay the hoan toan dien thoai truyen thong sir dung cong nghe chuyen mach kenh khong? Hay lieu co cho cho chuyen mach kenh hien tren the gioi cong nghe chuyen mach goi dang phat trien manh me? Thai gian se tra loi dieu Dieu ma chung ta dang nhan thay la mang the he mai sir dung cong nghe chuyen mach goi dang cang lan lucrt va thu hep dan pham vi cua mang PSTN sir dung cong nghe chuyen mach kenh truyen thong va cac mang truyen du lieu tnroc day Khai niem tru \e n tin hieu thoai qua mang chuyen mach goi khong phai la mot khai niem mai No da dugc nghien ciru kha nhieu vao nhung nam cuoi thap ky 1970 va nhung nam dau thap ky 1980 Cuoi thap ky 1970 da co nhung nghien ciru va thir nghiem vai thoai goi hoa truyen qua mang APPANET (ti£n than Cong nghe l olP va cac giai phap cua mang Internet nay) cho thay dieu co the thuc hien dugc Dau nam 1995, cong ty VocalTec dua san pham phan mem thoai qua Internet (ket noi diem - diem) dau tien tren the giai Sau do, nhieu cong ty da dau tu nghien ciru va dua san pham thuong mai Thang nam 1996, VocalTec ket hgp vai Dialogic da dua san pham cong ket noi PSTN va Internet (gateway) dau tien tren the giai Hiep hoi cac nha san xuat thoai qua may ti'nh (ECTF) da doi nham dua cac tieu chuan cho thoai qua giao thuc Internet Hiep hoi bao gom 36 cong ty may ti'nh va vien thong hang dau the giai nhu AT&T, IBM Sun Microsystem, Digital, Ericsson N don nhan cua cac phan xa hoi doi vai thoai goi co khac nhung deu co xu h u ang tich cuc thuc day no phat trien - Doi vai nguai su dung Internet la ho gia dinh thi xem thoai goi nhu mot p h u a n g tien de thuc hien cac cuoc goi tur bat ky noi nao tren the giai - Cac nha quan ly cong ty vien thong xem thoai goi nhu la p h uang tien de tich hgp thoai va du lieu mot mang nhat va nho ma tiet kiem gia dau tu va quan ly - Cac nha cung cap djch vu Internet (ISP) co the xem thoai n h u m ot dich vu va co the hy vong tao lgi nhuan tu dich vu m - Cac cong ty cung cap duong truyen co the sir dung hieu qua h an dutm g truyen va co the chia se tai nguyen d uang tru\ en giua cac mang thoai va Internet ( hiarng I: Giai thieu chung - Cac nha san xuat thiet bi co the ban them nhieu san p ham m - Cac cong ty thoai co co hoi giam gia va tang ti'nh canh tranh Hinh 1.1 duai day la lich su phat trien ciia thoai qua giao thuc IP Cac nghien cuu va thuc nghiem ve sir hoi tu cua cac cong nghe tir nhung nam cua thap ky 1980 Tuy nhien, sir hoi tu m ang chuyen mach goi va thoai dien cham, cho mai den giua thap ky 1990 cac thuc nghiem mai cong Va tir do, thoai truyen qua giao thuc IP dugc phat trien manh me Mang chuyen mach kenh 1970 Mang chuyen mach goi Cac thi nghiem ve thoai goi PCM APAPnet Giao thifc TCP/IP 1980 Ma hoa thoai Ma hoa dang song 1990 Ma lai ghep H.323 Hoi nghi qua Internet (RTP, SIP, H.323) IP Multicast WWW Internet toan cau Dich vu tich hdp Dich vu khac biet 2000 Thoai qua IP Hlnh 1.1: Lich sir phat trien cua VoIP Vai lgi the gia cu ac thap, djch vu thoai qua mang IP thuc sir da lam nhieu nha kinh doanh tren the giai quan tarn Tuy mai dirge trien khai, song luu lugng thoai qua mang Internet da tang 10 C o n g nghe I o l P va ciic g ia i p h ap dang ke Viec dira VoIP vao mang co the coi la mot cuoc cach mang thuc su nganh vien thong Thoai IP la cong nghe truyen thoai qua mang su dung giao thuc IP no co the goi la VoIP hoac thoai Internet Mang IP da phat trien nhanh chong va cang tra nen bien nhung nam gan day Thoai truyen mang IP co nhieu uu diem hon thoai qua mang chuyen mach kenh nhu: de dang tich hop cac loai dich vu, thong tin da p h u an g tien: su dung hieu qua bang thong Dong lire chinh de phat trien truyen thoai trC-n nen IP la tiet kiem bang thong, giam dugc gia mang Nguyen ly cua cong nghe la tin hieu thoai dirge so hoa, sau dcS phan doan (vi du phan cac doan vai chieu dai la 10 ms) va dong vao cac goi tin sau giri chung qua mang IP Tai dau thu, du lieu dugc lay tir cac goi, dugc giai m a va bien doi lai tin hieu thoai ban dau M ang IP co the la mang cue bo (LAN) nhu Intranet, mang dien rong (W AN), mang pha tron giura mang Internet cong cong va cac m ang Extranet logic ca nhan nhu mang rieng ao (VPN) dugc quan ly bang IP va Ian nhat la mang Internet Day chinh la mot nhung moi truang hap dan ciia IP cho nha cung cap dich vu mang Hoan toan khong co su giai han ve loai m ang m a IP chay tren IP co the chay tren nhieu loai mang ma khong can nhung thay doi lan ve cau true goi tin IP va cac c a che hoat dong IP la mot giao thuc mang chung no co the phii hgp vai rat nhieu loai loai mang ma khong doi hoi cac phien ban dac biet de thuc hien chuc nang chuven doi cho phii hgp tir m ang LAN sang mang WAN va ngugc lai ( 'h in nig I: (7/7/ / 1hieu chung 11 Chi phi cho dich vu dien thoai khong phai la re so sanh vai cac chi phi sinh hoat thong thirang gia dinh va chi phi kinh doanh T ruac day dien thoai la mot dich vu rat xa xi va chi phi cho no la kha Ion Cuac phi cho cuoc goi noi hat da cao, nhung cho cuoc goi d uang dai cao lion va dac biet la cuoc goi quoc te Khai dau dien thoai chu yeu phuc vu cho viec kinh doanh, nhicn sau no xam nhap vao thj truang la cac gia dinh Nlur vay, van de cuoc phi dugc quan tarn hang dau Bon uu dieni tlurong dugc de cap den cua VoIP la: - Giam cuoc phi dich vu thoai duang dai - Ho trg nhieu cuoc ggi vai bang tan nho han - Kha nang ho trg nhieu dich vu mai vai chat lugng tot han - Sir dung co hieu qua giao thirc IP Sau day chiing ta phan tich tirng uu diem ciia VoIP 1.1.1 Giam cirac phi djch vu thoai dircmg dai Cac doi tugng nh u doanh nghiep thucmg hay goi cac cuoc ggi d u an g dai nhieu han so vai ho gia dinh Vi vay, giam cuoc phi dich vu thoai d u an g dai bao g ia cung la muc tieu xuyen suot Chi phi ggi d u an g dai sir dung VoIP cung chi bang khoang 30% chi phi ciia cuoc ggi qua mang dien thoai chuyen mach cong cong (PSTN) Do dac thii ciia kinh doanh, cac doanh nghiep thuc hien rAt nhieu cac cuoc ggi duang dai Chiing ta de dang nhan M y lgi ich lan nhat ciia VoIP doi vai cac doanh nghiep la giam cuac phi dich vu thoai Trong thuc te tinh phan tan tu nhien ciia cac doanh Chuang III: Cung nghe VoIP 123 - Lira chgn viing: cho phep thue bao ciia mang chuyen mach kenh giCr nguyen so theo khuyen nghj E.164 hg di chuyen tir viing sang viing khac - Lira chgn nha cung cap dich vu: cho phep thue bao ciia mang chuyen mach kenh giur nguyen so theo khuyen nghj E 164 nguai chuyen tir sir dung djch vu ciia nha cung cap dich vu sang nha cung cap dich vu khac - So lira chgn djch vu: cho phep thue bao ciia mang chuyen mach kenh giu nguyen so theo khuyen nghi E.164 ngudi chuyen tir sir dung djch vu sang dich vu khac Trong cac khuyen nghi ciia ITU-T, cac sd lira chgn dugc gia sir la co the thuc hien dugc giua cac so theo khuyen nghi E.164 ciing mot quoc gia Mac dii viec nghien ciru ve cac so lira chon chii vcu dugc img dung mang chuyen mach kenh, nhien khai niem ve so lira chgn co the dugc ap dung cac dich vu vien thong khac bao gom ca djch vu dien thoai IP IETE va ETSI da dua cac khuyen nghj rieng biet ve khai niem danh dia chi linh hoat dich vu dien thoai IP 3.5.2 Phirong phap danh so thue bao 3.5.2.1 Yeu cau doi v&i quy tac danh so Quy tdc danh sd mang VoIP dugc trinh bay khuyen nghi TS 101 324 Ver.2.1.1 va TR 101 327 Ver 1.1.1 ciia ETSI phai dap ung cac veu cdu toi thieu sau day: - Cac s6 co the chi bao gom cac sd thap phan; - Do dai ciia sd thue bao co the dugc sir dung mang toan cau hoac viec phoi hgp giua cac mang noi bo; 124 Cong nghe VoIP va cdc gidi phap - So thuc bao phai la nhat pham vi toan cau doi voi mang cong cong; - Cac so thue bao phai cho phep ngudi sir dung quay so mpt cap; - Cac so phai ho tro viec di dong mot viing va lien viing theo khuyen nghi TR 101 338; - Cac so phai ho trg lira chon nha cung cap dich vu van giu nguyen so r r ? w » 3.5.2.2 Quy tdc danh so de ho tra tai giao dien doi vai mang PSTN r r Quy tac sau dugc ap dung doi vdi moi trudng hgp cuoc goi a) Doi vai mang VoIP cong cong Trong mang VoIP cong cong, cac so dja chi trao doi voi mang PSTN phai tuan theo khuyen nghi E.164 ciia ITU-T Chu y: khuyen nghi E.164 ciia ITU-T dua nhieu cach lira chon danh so khac Co the ciing mot luc lira chon mot hay nhieu khuon dang danh so Doi vdi mang VoIP khong can •X « • * * thiet phai danh so tuong img m dt-m ot giua mot so E.164 doi vai mot dau cuoi mang VoIP vi co the co nhieu ngudi sir dung ciing sir dung mot dau cuoi VoIP b) Doi vai mang VoIP noi bo Trong mang VoIP noi bo, cac dia chi trao doi vdi mach chuyen mach kenh noi bo phai tuan theo khuyen nghj ETS 300 189 hoac ISO/IEC 11571 Trong mang VoIP noi bo, cac dja chi trao doi vcri mang PSTN phai tuan theo khuyen nghj E.164 ciia ITU-T C huang III: Cong nghe VoIP 125 3.5.2.3 Phuang phap danh so thue bao a) Quy tac cua IETF Theo IETF, he thong danh so cho dien thoai IP dira tren nguyen tac moi sd E 164 duoc dang ki cho moi ngudi sir dung de co the truy nhap Internet thong qua bat cu mot dau cuoi nao cua mang Nam 1998 Lee va Orsis da dua hai uu diem cua viec an dinh so E.164 doi vdi ngudi su dung may tinh truy cap Internet Viec an dinh so E 164 cho phep ngudi sir dung de dang hon viec sir dung cong dien thoai de goi cho ngudi khac sir dung may tinh Ben canh do, nhung chirc nang san co tren mang Internet co the duoc sir dung de cung cap cho djch vu dien thoai IP Khi viec dinh tuyen tren Internet dua tren so E.164 da dang ky ung vdi thue bao bi goi, thi so E.164 can phai chuyen doi dia chi IP tuong img Viec chuyen doi duoc thuc hien thong qua co sd du lieu ciia mang duoc dat phan tan tai moi cong ket noi ciia nha cung cap dich vu Co phuang an doi vdi cau true hinh cay co uu tien cua c a sd d u lieu de chuyen doi giua so E.164 va dia chi IP * S u dung he thong ten theo vimg cho dien thoai IP Nam 1998 Faltstrom da dua nguyen tac sir dung he thong ten viing (DNS) cho dich vu dien thoai IP DNS cung cap chuyen doi giua ten viing va dia chi IP Khi so E.164 dugc ghi theo dang ten viing thi DNS co the thuc hien chuyen doi tir s6 E.164 va dia chi IP cho dich vu dien thoai IP Nguyen tdc: tao mot mien phu el6 4.in t va ghi lai sd E.164 dudi dang ten viing Trong cau true so E.164, dau tien la ma Cong nghe VoIP vd cdc gidi phap 126 quoc gia (CC), sau la ma nude cua thue bao bi ggi (NDC) rdi den so cua thue bao bi goi (SN) Mat khac, cau true cua ten viing la: dau tien la viing mire thap, sau la viing mire cao Chinh vi vay ten viing ciia so E.164 co cau true doi lap vdi so E.164 ban dau va viet theo thir tu ngugc lai Vi du: Sd E.164 la: “+ 555 123 ’ So ten viing ciia no la : “7.6.5.4.3.2.1.5.5.5.1.el64.int” Ung dung nguyen tac tren bang cach sir dung phuang thirc viing phu tcp.int cho dich vu dien thoai IP Nam 1998, Brown da de xuat cau true co so d u lieu ciia so E.164 cho phep anh xa cau true hinh cay Trong cau true hinh cay ciia mot co so du lieu, moi chu so ciia so E.164 dong vai tro nhu mot diem nut C o so du lieu dem lai nhieu lgi the viec trien khai cac dich vu tu an g lai b) Khuyen nghi cua ETSI ETSI da nghien ciru ve ung dung ciia dien thoai IP va ten dir an cua no la TIPHO N N yeu cau doi vai loai hinh ket noi PC - dien thoai: - Thue bao bi goi sir dung dien thoai da phai dang ki so E 164 mang chuyen mach kenh - Thue bao chii ggi sir dung may tinh thong qua Internet co the quay so E.164 de xac dinh thue bao bi goi So E 164 se dugc lam ro phan nao la dia chi cong, phan nao la dia chi ciia dau cuoi hoac ngudi sir dung - Viec chuyen doi tir so E.164 dang dia chi IP can phai dugc san sang, sd E.164 dugc sir dung de nhan dugc thue bao bi goi va thiet lap dudng noi tir PC den dien thoai ( hta/ng HI: Cong nghe VoIP 127 Vi the so E.164 dugc quy djnh la thong tin dja chi dugc chuyen thong qua mang chuyen mach kenh va Internet Ben canh djch vu dien thoai IP cung yeu cau nhan dang dugc thue bao chu goi, nhan dang dugc loai cuoc ggi nhu nhung cuoc ggi cap ciru khan cap v.v Vi vay, mang chuyen mach kenh cung yeu cau thue bao chu ggi phai dang ki so E.164 vi chi co so E.164 moi co the dugc sir dung de nhan dang thue bao chii goi mang ETSI da dua kieu cau true ciia so E.164 nen sir dung djch vu dien thoai IP Do la: so dinh vj theo viing dia ly quoc gia, so cho cac quoc gia khong chia viing dja ly va so djnh vj toan cau 3.5.3 Phirong phap chuyen doi so E.164 va dja chi IP 3.5.3.1 Khuyen nghi cua IETF Nam 1998, Rosenberg va Schulzrinne da dira co che chuyen doi giua so E.164 va dia chi IP trudng hgp ket noi dien thoai - dien thoai va PC - dien thoai Ho da dua cac dac tinh co ban ciia cong ket noi cho dich vu dien thoai IP va de xuat cac may chii djnh vj Moi cong ket noi dugc xac dinh bdi thong so: - Viing so E 164 m a no co the cung cap dich vu - So luong dich vu ma no co the cung cap dugc - Kieu dich vu m a no co the cung cap Nhung dac diem nav dugc sir dung de may chu lira chon cong ket noi va thiet lap dudng truyen cho cuoc goi Nam 1998, Agapi va mot so ngudi khac da dua co cdu chuyen doi dja chi vdi loai hinh ket noi may tinh - dien thoai va Cong nghe Voll* va cdc giai plidp 128 may tinh - may tinh va dira mo hinh kinh doanh sir dung phoi hop hoat dong vdi may chii dinh vi nhu sau: - ITSP (nha cung cap dich vu thoai Internet) trien khai va tri hoat dong ciia tat ca cac cong ket noi va may chii dinh vi May chii dinh vj ciia ITSP chiu trach nhiem chuyen doi so E.164 dia chi IP ciia cong ket noi thich hop de thiet lap cuoc thoai - Cac ITSP phoi hop voi chia se cac cong ket noi va thong tin dia chi ciia cac cong ket noi voi May chii dinh vi ciia cac ITSP trao doi thong tin ket noi vdi Cac may chii dinh vi thuc hien chirc nang chuyen doi dia chi E.164 ciia thue bao bi goi dia chi IP ciia cong ket noi diing chung mang, xac dinh cong ket noi thich hop nhat de thiet lap cuoc thoai - Tat ca cac ITSP co the chia se cong ket noi va thong tin dia chi cong ket noi mang cong cong Tat ca cac may chii dinh vi trao doi thong tin ciia chiing vdi va chia se cac thong tin chuyen doi giua so E.164 ciia thue bao bi goi va dia chi IP cua cong ket noi - Nam 1998 Lee va Orsic da dua phuang thirc chuyen doi dia chi loai hinh ket noi dien thoai - may tinh may tinh may tinh hai trudng hop nay, thue bao bi goi la may tinh tren Internet Gia sir rang moi khach hang sir dung PC ket noi Internet co mot so E.164 va moi ket noi Internet nav co mot dia chi IP M o hinh chuyen doi gan giong vdi m d hinh Rosenberg va Schulzrinne dua 3.5.3.2 Md hinh phoi hop hoat dong chuyen doi dia chi Cac khuyen nghi cua Agapi va cac nha nghien ciru khac viec chuyen doi dia chi co the duoc m d rong va ap dung C huang HI: Cong nghe VulP 129 cho tat ca cac loai ket ndi dien thoai IP Sau day la mo hinh tong quat: mang rieng, mang quan he mat thiet va mang lien ket md Sau phan se dua phuang thuc dinh tuyen tren ba mo hinh * Mu hinh mcing rieng Moi ITSP tu trien khai va tri hoat dong cua tat ca cac cong ket noi can thiet va cac may chu de cung cap dich vu dien thoai IP ITSP luu tru cac thong tin dja chi cong ket noi cua ho cac may chu cua ho N eu cac ITSP khac thiet lap cuoc thoai IP thi no cung luu giu cac thong tin dia chi vao o nhd may chu ung vdi thue bao cua ho tham gia cuoc thoai de phuc vu cho cac lan ket noi sau * Mu hinh nhom quan he mat thiet Mot vai ITSP chia se cong ket noi lien ket Moi ITSP lien ket luu tru thong tin dia chi cong ket noi may chu cua no Ngoai ta no co the cung cap thong tin dia chi cua thue bao thiet lap dich vu Chinh vi the cac ITSP co the chia se thong tin dia chi va do can phai co mot chuan chung cho du lieu dja chi cac lien ket * Md hinh lien ket m a Tdt ca cac ITSP chia se cong ket noi lien ket Mdi ITSP lien ket luu tru thong tin dia chi cong may chu cua no Ngoai ta no co the cung cap thong tin dia chi cua thue bao th ilt lap dich vu Cau true he thong du lieu m d duoc yeu chu d6 chia se cac thong tin dja chi Cong nghe VoIP vd cdc giai phap 130 ITSP cung cap dich vu chuyen tiep theo cac thong tin dia chi cliia se Khi mot thue bao cua mang chuyen mach kenh bi goi thi may chu cua ITSP se chuyen doi so E.164 dia chi IP cua cong ket noi phu hop nhat Khi mot thue bao may tinh ket noi Internet bi goi thi may chu se chuyen doi so E.164 dia IP cua thue bao Moi ITSP co the lira chon mo hinh thich hop cho muc dich kinh doanh cua minh Tuy nhien moi ITSP chi co the chon mpt ba mo hinh khong the chon mo hinh hoac nhieu hem tai cung mot thai diem Viec chuyen doi thong tin dia chi giua cac ITSP can phai ho trg lan mo hinh lien ket mang rieng tat ca cac hoat dong doi hoi chuyen doi dia chi deu IT SP tu thuc hien nen ITSP co the sir dung nhimg giao thirc rieng cho viec chuyen doi Tuy nhien mo hinh lien ket mang rieng co nhung han che ve cung cap dich vu su giai han ciia cac cong ket noi Ben canh do, no khong cung cap dugc cac dich vu chuyen tiep thue bao bi goi la may tinh sir dung Internet dang ky dich vu vai mot ITSP khac mo hinh nhom quan he mat thiet, ITSP can sir dung giao thirc thong th uang cho viec chuyen doi Giao thirc co the doc lap vai cac lien ket Do cac cong ket noi dugc chia se voi cac ITSP khac lien ket nen mo hinh nhom quan he mat thiet se co it han che hon viec cung cap dich vu so voi mo hinh lien ket mang rieng Tuy nhien giong mo hinh lien ket mang rieng no khong cung cap dugc cac dich vu chuyen tiep thue bao bi goi la may tinh sir dung Internet dang ky djch vu vai cac ITSP khong nam lien ket C hutrng ///.• Cong nghe VoIP 131 Ben canh do, doi voi he thong lien ket ma, viec lien ket giua cac cong ket n6i co the khong giai han cac dich vu ma ITSP cung cap Tuy nhien, ITSP can sir dung giao thirc chuan cho viec chuyen doi * Dinh tuyen cho cac loai hinh dich vu - Dinh tuyen ket noi dien thoai - dien thoai Trong loai hinh lien ket nay, thue bao chii goi lua chgn ITSP co the cung cap djch vu chuyen giao cho ho ITSP duoc chon se lira chon mot cong rieng de thiet lap ducmg dan toi thue bao bj goi Neu ITSP dugc lira chon theo mot hinh lien ket mang rieng no can lira chon cong Neu so lugng cong co the chia se cang nhieu thi kha nang lua chon cang cao Khi quang d uang truy nhap vao mang chuyen mach kenh se ngan hon hoac ta se co mot viing cung cap djch vu lan han Vai loai hinh lien ket theo he thong m d co the se mang lai cho ITSP mot kha nang lua chon Ion nhdt cho cong rieng biet va mot khoang truy nhap ngan nhat mang chuyen mach kenh - Dinh tuyen ket noi dien thoai - may tinh Trong loai hinh lien ket nay, ITSP cung cap viec thiet lap djch vu cho thue bao bj goi Thue bao chii goi sir dung dien thoai mang ch u y ln mach kenh co the khong biet thue bao bi goi sir dung may tinh tren Internet Thue bao chii goi khong co y dinh sir dung dich vu chuyen giao loai hinh dich vu dien thoai IP Khi do, thue bao chii goi chi bam so E.164 ciia thue bao bi goi Do vay, cau true cua so E.164 ciia thue bao bj ggi can Cong nghe VoIP vd cdc gidi phap 132 phai co mot phan dac biet de bo phan dinh tuyen mang chuyen mach kenh co the nhan thue bao bj goi sir dung may tinh tren Internet va truy cap vao cong cua ITSP Ma nhan dang (IC) hoac mot vai chu so ciia ma nuoc bi goi (NDC) co the su dung nhu la mot phan ciia so E.164 cho viec thong bao dich vu dien thoai IP Dieu se gay them su phirc tap he thong dinh tuyen mang chuyen mach kenh - Dinh tuyen ket noi tir may tinh - dien thoai Trong loai hinh ket noi tir may tinh den dien thoai, ngudi goi lua chon ITSP co kha nang cung cap dich vu chuyen giao cho ho ITSP cung cap djch vu chuyen giao cho thue bao chii goi can lua chon cong thich hop de thiet lap duang dan den thue bao bj goi thong qua no Cac ph uang thirc khac dua cac d u an g dan khac Neu ITSP duoc lira chon theo mot hinh lien ket mang rieng * ■> r f no can lira chon cong Neu so lugng cong co the chia se cang nhieu thi kha nang lira chgn cang cao Khi quang duong truy nhap vao mang chuyen mach kenh se ngan hem hoac ta se co mot viing cung cap djch vu lan han Vai loai hinh lien ket theo he thong m o co the se mang lai cho ITSP mot kha nang lua chon lan nhat cho cong rieng biet va mot khoang truy nhap ngan nhat mang chuyen mach kenh - Djnh tuyen ket noi may tinh - may tinh Trong loai hinh ket noi may tinh - may tinh thue bao chii goi lira chon ITSP co kha nang cung cap djch vu chuy en giao cho ho Ben canh do, ITSP cung cap djch vu dau cuoi cho thue C huem g III: Cong nghe VoIP 133 bao bj goi ITSP duoc lua chon bdi thue bao chu goi can tim dja chi IP cua thue bao bj goi thong qua so E.164 duoc bam bdi thuc bao chu goi Can phai luu y rang ITSP duoc lua chon bdi thuc bao chu goi can phai khac vdi ITSP cung cap djch vu dau cuoi cho thuc bao bj goi Vi the nhung gi xay vdi viec djnh tuyen loai hinh ket noi giua may tinh vdi may tinh cung giong nhu loai hinh dien thoai vdi may tinh thue bao chu goi co y djnh sir dung djch vu chuyen giao cua djch vu dien thoai IP Neu ITSP duoc lira chon bdi thue bao chu goi cung cap nhung djch vu dau cuoi cho thue bao bj goi, ITSP co the khoi phuc lai duoc dja chi IP ciia thue bao bj goi tir co sd du lieu ciia no bat ke mo hinh lien ket ciia ITSP Vi the ITSP co the thiet lap dudng dan tir thue bao chii goi den thue bao bj goi Mat khac ITSP dugc lira chgn tir thue bao chii ggi khac vdi ITSP cung cap thiet djch vu dau cuoi cho thue bao bj ggi Vdi ITSP hoat dong theo md hinh lien ket mang rieng biet, ITSP co the cung cap dich vu chuyen giao cho thue bao chii goi lai khong the truy nhap co sd d u lieu theo thong tin dja chi ciia thue bao bj goi da dugc luu tru va do dudng dan khong dugc thiet lap Vdi ITSP hoat dong theo mo hinh lien ket dong goi va nhung ITSP khac khong co ciing mdi lien ket, ITSP khong the truy nhap co sd d u lieu theo thong tin dja chi ciia thue bao bj ggi da dugc luu tru va do dudng dan khong dugc thiet lap Neu ca hai ITSP hoat dong theo mo hinh lien k it dong goi ciing mot mdi lien ket hoac neu ca hai ITSP hoat dong theo 134 Cong nglie Vo/P vd cue giai phap mo hinh lien ket he thong md, ITSP co the khoi phuc lai duac dia chi IP cua thue bao bi goi tir co sd du lieu da chia se Giong nhu bieu hien ciia viec dinh tuyen ket noi dien thoai - may tinh, mot thue bao chii goi co y dinh su dung dich vu chuyen giao ciia dien thoai IP, mot phan dac biet so E.164 ciia thue bao chii goi thong bao djch vu dien thoai IP khong duoc sir dung cho viec dinh tuyen trudng 3.5.4 Phirong phap djnh tuyen giua PSTN va IP Khi thuc hien mot cuoc goi ma thue bao chu goi va thue bao bi goi nam rieng re mang chuyen mach kenh va Internet, thue bao chii goi phai dua thong tin dja chi cua thuc bao bi goi dc he thong dinh tuyen mang chuyen mach kenh va mang Internet can cir vao dinh tuyen cuoc goi Co cach khac de dinh tuyen cuoc thoai IP giua cac thue bao nam rieng re mang chuyen mach kenh va Internet 3.5.4.1 Cach thir nhat Them cac chirc nang mdi cho mang chuyen mach kenh de xir ly cac thong tin dinh tuyen sir dung mang Internet Cac thong tin dja chi duoc sir dung tren Internet co the la dia chi IP ten viing, dia chi e-mail v.v N ngudi sir dung djch vu dien thoai IP can duoc dang ki dia chi IP Thue bao chii goi se chi dinh thue bao bi goi thong qua cac thong tin dia chi ciia thue bao bj goi Cau true ciia no giong nhu cau true ten viing bang viec su dung cac chir so tir - va cac ki hieu U va * Do can phai dua cac quy udc sir dung nhung ki tu Tuy nhien dieu co the khong kha thi viec dua dia chi vao se rat phirc tap C hin m g III: Cung nghe VoIP 135 3.5.4.2 Cach thir hai Them cac chuc nang mdi cho mang chuyen mach kenh de giao tiep vdi so E.164 tren Internet Mdi thue bao su dung dich vu dien thoai IP duoc dang ki sd E.164 Moi chuc nang mdi ddi can dua phep chuyen doi tir so E.164 sang dia chi IP Khi ngudi sir dung chi dua vao sd E 164 va he thong coi nhu la thong tin dia chi ciia ngudi sir dung dich vu dien thoai IP Tuy nhien dich vu dien thoai IP sir dung chung so E.164 vdi cac djch vu khac nen dung luong ngudi sir dung dich vu dien thoai IP se bi gidi han 3.5.4.3 Cach thir ba Them cac cach thirc danh dja chi mdi doc lap vdi he thong dia chi IP va sd E.164 Mot he thong danh dia chi mdi can duoc sir dung cho dich vu dien thoai IP He thong can phai cai tien tir cac he thong danh dia chi cu va ap dung cho ca thuc bao chu goi va thue bao bi goi Tuy nhien cung giong nhu he thong danh dja chi IP dieu co the khong kha thi viec dua dia chi vao se rat phirc tap Vi vay tac gia quyet dinh lira chon phuang thirc thir hai la phuang thirc dang ki dia chi cho cac thue bao sir dung dich vu dien thoai IP 3.5.5 Khuyen nghj Giai phap phii hop nhat ddi vdi he thong danh sd mang dien thoai qua Internet bao gom ba yeu to sau day: - Danh so E.164 toan cau cho ngudi sir dung theo may tinh d5u cuoi tren Internet Cong nghe VoIP vd cdc giai phap 136 - Phuang phap he thong m o doi voi co che lap so giua so E.164 va cac dja chi 1P3 - Yeu cau doi voi tro giup cho quay so mot giai doan khong qua ma truy nhap nha cung cap dich vu Sir ket hop giua cac yeu to dem lai dung luong danh so ldn cho ngudi sir dung tren Internet, cho phep sap xcp de dang cac irng dung di chuvcn so va tranh trudng hap dudng dan khong the thiet lap C o quan co tham quyen nen quyet djnh cach thirc va mire ma dien thoai qua Internet duoc coi la djch vu dien thoai Co quan co tham quyen can phai xem xet cac a canh sau day dua chinh sach: - He thong phan so E.164 can phai thay doi de dong thai phan cho ngudi sir dung tren Internet - Can co quy tac phoi hop giua nha cung cap dich vu VoIP (ITSP) va nha cung cap djch vu tren mang chuyen mach kenh cho dien thoai qua Internet 'r* • ’ i - U ng dung di chuyen so cho dien thoai qua Internet co the ddi hoi viec ciing co cac ITSP va nha cung cap djch vu tren mang chuyen mach kenh C o sd du lieu cho djch vu dien thoai qua Internet duoc chia co sd du lieu hanh chinh gom thong tin phan dja chi va co sd du lieu sir dung thdi gian thuc de djnh tuyen 1'rong co sd du lieu hanh chinh can phai duoc quan ly dudi quyen phan thong tin dja chi, viec quan ly co sd du lieu sir dung thdi gian thuc co the khong can phu thuoc vao quyen I uy nhien, giao thirc C huang I I I C ong nghe VoIP 137 chuan m o la can thiC't dc trao ddi du lieu lap s a giua cac ca sa du lieu su dung thai gian thuc vai Viec phan so E.164 cho ngudi sir dung tren Internet dugc coi la ddi hoi tdi thieu ddi vdi mdi quan he qua lai giira mang chuyen mach kenh va Internet Nhung lie thong dia chi khac vdi he thong E.164 co the dugc sir dung ket ndi may tinh den may tinh He thong phan dia chi phu hgp khac cho ket ndi may tinh den may tinh can phai dugc nghien ciru them ... vu bo sung chu veu la cho cac dich vu so lieu 16 Cong nghe VoIP va cdc gidi phap Tong dai A Tong dai B Hinh 1. 3: Ket hap so lieu vd thoai VoIP 1. 1.3 Ho trff cac dich vu moi Noi chuyen tren dien... ven cua no 4000 3000 2000 10 00 - 10 00 - 2000 - 3000 Hinh 1. 6: D ang song cua mot doan thoai ChUdng II T O N G Q U A N G IA O T H l f C T C P /IP 2 .1 BO GIAO THUC TCP/IP VoIP hay thoai Internet... tot han - Sir dung co hieu qua giao thirc IP Sau day chiing ta phan tich tirng uu diem ciia VoIP 1. 1 .1 Giam cirac phi djch vu thoai dircmg dai Cac doi tugng nh u doanh nghiep thucmg hay goi cac