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網際網路服務與應用

網際網路服務與應用. 和春 技術學院 資訊管理 系 蘇溢芳. Broadband Network Technologies (1/2).

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網際網路服務與應用

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  1. 網際網路服務與應用 和春技術學院 資訊管理系 蘇溢芳

  2. Broadband Network Technologies (1/2) • Integrated Services Digital Network (ISDN) isan international communications standard for sending voice, video, and data over digital telephone lines or normal telephone wires. ISDN supports data transfer rates of 64 Kbps. • Asymmetric Digital Subscriber Line (ADSL) is a new technology that allows more data to be sent over existing copper telephone lines (POTS). ADSL supports data rates of from 1.5 to 9 Mbps when receiving data and from 16 to 640 Kbps when sending data. • Symmetric Digital Subscriber Line (SDSL) is a technology that allows more data to be sent over existing copper telephone lines (POTS). SDSL supports data rates up to 3 Mbps.

  3. Broadband Network Technologies (2/2) • High-bit rate Digital Subscriber Line (HDSL) is the earliest variation of DSL. It is used for wideband digital transmission within a business and between the telephone company and a customer. HDSL is symmetrical meaning an equal amount of bandwidth is available in both directions. • Very High Speed Digital Subscriber Line (VDSL) transmits data in the 13 Mbps - 55 Mbps range over short distances, usually between 1000 and 4500 feet (300 - 1500 meters), of twisted pair copper wire. The shorter the distance, the faster the connection rate.

  4. 廣域網路連接服務 • SLIP (Serial Line Internet Protocol) • 只支援 TCP/IP 通訊協定 • PPP (Point-to-Point Protocol; PPP) • 也適用於 IPX/SPX, NetBEUI 等協定

  5. ADSL(Asymmetrical Digital Subscriber Line)是DSL家族中應用最廣泛、最成熟的技術。 ADSL是什麼?

  6. xDSL

  7. Cable Modem是什麼?

  8. Cable Modem的分類 （1）從數據傳輸方向上有單向和雙向Cable Modem之分。 （2）從傳輸方式上可分為雙向對稱式傳輸和非對稱式傳輸。 （3）從網路通信角度上有同步（共享）和 非同步（交換）兩種方式。

  9. Cable Modem之架構

  10. Voice over IP (VoIP) • VoIP網路電話，是將語音訊號壓縮成數據資料封包後，在IP網路基礎上傳送的語音服務，也就是說，透過開放性的網際網路，傳送語音的電信應用服務。利用Internet不僅做到了可即時提供語音服務，更可連接至世界各地，讓使用者可以不需再透過傳統的公眾電話網路(PSTN)進行遠距離電話交談。

  11. Protocol Stack

  12. H.323 • H.323規範是在1996年經國際電信聯盟認定，可以解決多媒體傳輸所要求的即時性與連續性問題。其主要內容是在定義分封交換網路上終端機之間的壓縮和解壓縮標準、通話程序及媒體傳輸等協定，同時也定義了在分封交換網路上的終端如何與傳統的電話網路互相通話的機制。

  13. H.323 • H.323界定語音及視訊的壓縮／解壓縮設備，雙方溝通的設定與控制。在語音方面，它支援多種標準，其中以G.711為主；至於視訊方面，H.323則支援H.261與H.263兩種主要的視訊壓縮／解壓縮標準。

  14. Review - basic issues • Telephony Issues (PSTN v.s. VoIP) • Bearer • Transport • PSTN - TDM (Time Division Modulation) Trunk • VoIP - RTP over UDP/IP • Delay and Jitter • PSTN - circuitswitching / propagation delay • VoIP - packet switching / unbounded delay and jitter

  15. Review - basic issues • Telephony Issues (PSTN v.s. VoIP) • Signaling • Addressing / Control • PSTN - SS7 (ITU E.164) • VoIP - H.323、SIP、MGCP、Megaco/H.248 • Capability exchange • PSTN - Analog voice • VoIP - Digital voice / G.711(速率64kbps)、G.723.1(速率5.3kbps或者6.3kbps)、G.729(速率8kbps)

  16. Review - basic issues • H.323定義了一個綜合性的規範，使網路上的終端設備遵循這些規範，得以順利進行溝通，包括語音壓縮格式(G.711、G.729、G.723.1)、影像壓縮格式( H.261、H.263 )、呼叫信令(H.225)、控制信令(H.245) • H.323 架構由4個元件所組成，包括終端設備(Terminal)、閘道器(Gateway)、閘道管理員(Gatekeeper)、多點控制單元(MCU：Multipoint Control Unit)，

  17. Voice Quality of Service • Interactive Voice QoS factors • Packet lost • Delay • Jitter

  18. Introduction SIP • Session Initiation Protocol (SIP) • IETF standard • Internet Engineering Task Force • Application layer control protocol for creating, modifying and terminating sessions • Text-encoded protocol • SIP URL • Sip: bob@ntut.edu.tw • Sip: 11025919@ntut.edu.tw • Supporting Protocol • Session Description Protocol (SDP) • Session Announcement Protocol (SAP)

  19. Components of SIP Phone • SIP Clients • Proxy Server • acts as both a server and a client for the purpose of making requests on behalf of other clients • forwards client requests to another SIP server or to the final destination • may “fork” requests to multiple servers (“search tree”) • Registrar Server • A server that receives registrations from clients and regarding current locations • Redirect (Location) Server • redirects users to try other SIP server as the next-hop towards destination, and client has to contact it directly

  20. (3) tsengii@140.124.181.206 (2) tsengii (4) INVITEtsengii@140.124.181.206 (1) INVITE tsengii (5) 200 OK (6) 200 OK (8) ACK tsengii@140.124.181.206 (7) ACK tsengii@140.124.181.206 Invitation Location(Redirect) server key@140.124.181.217 tsengii Proxy key tsengii@140.124.181.206

  21. Comparison of PSTN and VoIP

  22. VOIP加密 • AES (最適合VOIP) • DES • MD5

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