Chủ đề: VoIP_Part_I_3: Các ứng dụng của thoại IP

3.IP telephony application
Phan nay se trinh bay overview ve giao dien analog; digital; ethernet voice. Mo phong cac mo hinh voice trong campus; enterprise va service provider

Noi dung:
• Mo ta ba giao dien analog co ban va cac thiet bi telephony ma chung ket noi vao
• Mo ta ba giao dien so; kieu tin hieu ma moi giao dien ho tro
• Mo ta ba lua chon ket noi vat li cho ip phone va chuc nang cua cisco ip phone
• Nam thanh phan co ban cua integrated voice va data trong mang LAN campus
• Su khac nhau cua mo hinh voip phan tan va tap trung; liet ke thanh phan cua moi network type


3.1.Analog interface
de cap den ba loai giao dien analog:
• FXS (foreign exchange station)
• FXO (foreign exchange office)
• Ear and mouth (E&M)

FXS interface

FXS cung cap ket noi truc tiep toi mot analog phone; fax machine hoac cac thiet bi tuong tu. Tren quan diem cua telephone; FXS dong vai tro cua mot switch nen no can cung cap line power; ring voltage va dial tone

FXS int chua mot bo codec nham convert cac tin hieu thoai analog thanh dang so va se duoc xu li boi voice gw

FXO interface

FXO cho phep mot ket noi analog co the huong truc tiep toi CO cua pstn hoac mot station int cua mot pbx. Switch coi FXO int nhu mot telephone boi vi giao dien gan truc tiep vao line side cua switch. FXO int cung cap ca pulse hoac DTMF digit choo outbound dialing

Trong pstn; mot ket noi FXO-to-FXS con duoc goi la mot FX (foreign exchange) trunk. Mot FX trunk la mot CO trunk co truy cap toi mot CO o xa. Do ket noi nay la FXS tai mot dau va FXO tai dau con lai nen no dong vai tro nhu mot su mo rong ket noi local telephone line.

Vi du: local user co the nhac may va co dial tone tu mot thanh pho khac. User trong thanh pho khac co the dial so local number ca thuc hien cuoc goi toi user trong local city

E&M interface

E&M int: cung cap signaling cho analog trunking. Analog trunk noi giua PBX va CO.

3.2.Digital interface
ba loai giao dien co ban: E1; T1; BRI

T1 Interface
ket noi giua PSTN va toi PBX cua voice gw la ket noi so

mot giao dien T1 cho phep xay dung nen mot ket noi so co the mang dong thoi 24 cuoc thoai tren cap day. Khi T1 trong che do full-duplex mode: mot cap gui tin va mot cap nhan tin.

T1 int co the mang ca CAS hoac CCS. Khi T1 su dung CAS: van chuyen tin hieu in band. Khi T1 su dung CCS; Q931 signaling duoc su dung tren mot kenh khac.

E1 Interface

E1 co toi 32 kenh va co the truyen dong thoi 30 kenh thoai. Hai kenh con lai dung de framing va signaling.

Mac du E1 co the su dunng ca channel associated signaling hoac common channel signaling nhung thuong su dung common channel signaling hon. Khi e1 dung channel associated signaling; tin hieu se la out of band nhung co mot han che la phai lien he giua tin hieu trong kenh signal va kenh ma tin hieu duoc apply. Signaling channel la 16

Trong frame dau tien; kenh bao hieu mang 4 bit tin hieu cua kenh 1 va 4 bit cua kenh 17. frame thu 2: 4 bit kenh 2 va kenh 18….Qua trinh nay cho phep tao out-of-band channel associated signaling

Khi e1 su dung common channel signaling; giao thuc q931 duoc su dung tren mot kenh rieng; thuong la kenh 17.

BRI interface

thuong duoc su dung o chau au cho ket noi PBX; bri cung cap 16 kbps kenh D de signal cho hai kenh 64 k B cho voice.

3.3.IP phone
cac kieu ket noi giua IP phone va may tinh:

bao gom:
• Single cable: PC qua IP phone roi toi switch: tiet kiem
• Multiple cable: phan tach ro giua pc va switch: cho phep phan tach giua voice va data
• Multiple switch: noi ra hai switch khac nhau.
Multiple switch duoc su dung trong cac truong hop:
• Cung cap inline cho IP phone ma khong can nang cap ha tang data
• Han che so luong switch can UPS
• Han che cau hinh STP

Ket noi vat li cho mot IP phone can co cac tinh nang:
• Duplex va speed
• Inline power

Ket noi logic can co:
• IP add
• VLAN
• STP
• Cau hinh CoS va queuing

Cisco IP phone:

3.4.Campus LAN enviroment
Mo hinh trien khai IP phone trong mang LAN campus:

cac thanh phan chinh de co the trien khai IP telephony bao gom:
• IP phone: cung cap IP voice toi desktop
• Call manager cluster: dong vai tro nhu trung tam xu li cuoc goi cho moi thiet bi VoIP trong mang. Call manger cluster con duoc su dung cho cau hinh dien thoai; lap ke hoach dinh tuyen cho gw; quan li cac app server
• Gateway: ket noi IP voice toi mang voice ben ngoai nhu PSTN; voice device hoac he thong IVR hoac fax. Gw thuc hien cac tinh nang quan trong: codec tin hieu digital va analog; cung cap cac tai nguyen conferencing
• MCU: (multipoint control unit): cung cap kha nang hoi nghi
• Application server: cung cap cac dich vu them nhu voice mail hoac dich vu unified message

3.5.Enterprise enviroment
Mo hinh ket noi: lien quan toi cac ket noi WAN den tru so o xa
Co hai moi hinh co the trien khai: xu li cuoc goi tap trung hoac phan tan

Xu li cuoc goi tap trung:

mo hinh cung cap truy cap voice tren mang vi toan doanh nghiep trong do cac cuoc goi va cac dich vu voice khac duoc dieu khien tu mot trung tam. Trong moi truong nay, central site cung cap tat ca cac dich vu: call manager; voice mail; unified message. Ip phone tai remote site ket noi toi cisco manager thong qua IP WAN cho qua trinh xu li cuoc goi

Cac thanh phan cua mot mo hinh tap trung hoa bao gom:
• IP phone: cung cap IP voice cho dek
• Call manager cluster (chi cho central site)
• Gw (cho moi site): ket noi IP voice toi mang voice ngoai
• Multipoint control unit : central site
• App : central site
• Unity server: cung cap kho chua cho unified messaging nhu voice mail; e-mail hay fax
• Srst (survivable remote site telephony): dua vao cisco ios : chi dung cho remote site: cung cap kha nang xu li cuoc goi local tham chi khi ket noi wan khong con dung duoc nua (the thi co le no se chuyen sang dung duong pstn)
• IP WAN: dong voi tro la duong ket noi voice chinh giua cac site voi PSTN la duong backup

Xu li cuoc goi phan tan:

Mo hinh nay khac voi mo hinh quan li tap trung o cho: cac dich vu va trung tam dieu khien cuoc goi phan tan o khap noi. Khi do can co su lien ket lam viec giua cac trung tam nay thong qua ket noi chinh IP WAN

Cac ung dung mang duoc su dung chinh trong moi truong enterprise bao gom:
• E-business
• E-learning
• Customer care
• Unified messaging
• Videoconferencing
• Voice calls placed from web pages

3.6.Service provider enviroment
Mo hinh mang cung cap dich vu IP telephony cua mot SP co dang:

Cac yeu cau doi voi trien khai VoIP cho service provider:
-dung luong thue bao (voi so thue bao lon khoang 1 trieu thue bao tro len: nen dung softswitch)
-co kha nang interconnect bao hieu ss7 giua cac tong dai (ss7 intertrunking)