voip - VoIP BASICS Handout 770 00905 0680 VHBE Ed. 02...

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770 00905 0680 VHBE Ed. 02 VoIP BASICS Handout
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770 00905 0680 VHBE Ed. 02 2 / 86 Status Released Change Note Short Title VoIP BASICS All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel.
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Contents 770 00905 0680 VHBE Ed. 02 3 / 86 Contents Preface 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Definitions 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 VoIP 'history' 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Why VoIP? 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Challenges for VoIP 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Circuit Switching versus Packet Switching 13 . . . . . . . . . 1.5.1 Circuit Switching network 14 . . . . . . . . . . . . . 1.5.2 IP network 15 . . . . . . . . . . . . . . . . . . . . . . . . . . 2 VoIP scenarios 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Overview of the VoIP protocol architecture 21 . . . . . . . . . . . 3.1 General architecture 21 . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 VoIP protocols 22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Introduction 22 . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Protocols used in the dataplane 23 . . . . . . . . 3.2.3 Protocols used in the control plane 23 . . . . . 3.2.4 Conclusion 27 . . . . . . . . . . . . . . . . . . . . . . . . . 4 Real-Time Transport Protocol 29 . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction 29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 RTP/UDP/IP 30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 RTP basics 30 . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 RTP concepts 31 . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 The RTP header 33 . . . . . . . . . . . . . . . . . . . . . 4.2.4 RTP/UDP/IP: a lot of overhead? 36 . . . . . . . . 4.2.5 How to minimize the overhead? 36 . . . . . . . 4.3 RTCP 39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Functions of RTCP 39 . . . . . . . . . . . . . . . . . . . 4.3.2 Bandwidth limitation 39 . . . . . . . . . . . . . . . . . 4.3.3 RTCP packet types 39 . . . . . . . . . . . . . . . . . . . 4.3.4 RTCP Packet formats 40 . . . . . . . . . . . . . . . . . 4.4 Conclusion 44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 H.323 45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Introduction 45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 H.323 environment 45 . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 H.323 Protocol architecture 48 . . . . . . . . . . . . . . . . . . . . . 5.3.1 The Standard 48 . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 H.225.0 RAS signalling 49 . . . . . . . . . . . . . . .
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Contents 770 00905 0680 VHBE Ed. 02 4 / 86 5.3.3 H.225.0 Call signalling 50 . . . . . . . . . . . . . . . 5.3.4 H.245 Call control 51 . . . . . . . . . . . . . . . . . . . 5.4 Setting up a H.323 call 52 . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Steps in a call set up 52 . . . . . . . . . . . . . . . . . 5.4.2 Call scenario 53 . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Drawbacks of H.323 54 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 SIP 55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Introduction 55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 SIP environment 55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 SIP protocol architecture 56 . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 SIP requests 58 . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 SIP responses 58 . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 SIP addressing 59 . . . . . . . . . . . . . . . . . . . . . . 6.3.4 SDP (Session Description Protocol) 59 . . . . . 6.4 Setting up a SIP call 60 . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 SIP call scenario 60 . . . . . . . . . . . . . . . . . . . . . 6.5 Advanced services with SIP 61 . . . . . . . . . . . . . . . . . . . . . 6.5.1 SIP registrar server 61 . . . . . . . . . . . . . . . . . . . 6.5.2 SIP proxy server 62 . . . . . . . . . . . . . . . . . . . . . 6.5.3 SIP redirect server 63 . . . . . . . . . . . . . . . . . . . . 6.6 H.323 versus SIP 66 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Media Gateway to Media Controller Protocols 67 . . . . . . . . 7.1 Introduction 67 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1 Why do we need Media Gateway to Media Controller Protocols? 67 . . . . . . . . . . . . . . . . . 7.1.2 Which protocol will be chosen? 68 . . . . . . . . 7.2 MEGACO environment 68 . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Main functions of MEGACO 69 . . . . . . . . . . . . . . . . . . . . 7.4 Setting up a MEGACO call 71 . . . . . . . . . . . . . . . . . . . . . 7.4.1 Scenario: Residential GW to Residential GW (RGW) 71 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Quality of Service in a VoIP network 75 . . . . . . . . . . . . . . . . . 8.1 Introduction to QoS 75 . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Parameters influencing the QoS for VoIP 76 . . . . . . . . . . 8.2.1 Audio quality 76 . . . . . . . . . . . . . . . . . . . . . . . . 8.2.2 End to end delay (mouth to ear delay) 78 . . 8.3 Two approaches to achieve an acceptable QoS 79 . . . 8.3.1 Differentiated Services (Diff-Serv) 79 . . . . . . 8.3.2 Integrated Services (Int-Serv) 80 . . . . . . . . . 9 Alcatel's VoIP solutions 81 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Contents 770 00905 0680 VHBE Ed. 02 5 / 86 Abbreviations 83 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Request for Your Comments 85 . . . . . . . . . . . . . . . . . . . . . . . . .
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Contents 770 00905 0680 VHBE Ed. 02 6 / 86 Figures Figure 1 VoIP 'history' 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 2 A circuit switched network 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 3 IP packet forwarding for VoIP 15 . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 4 IP packet forwarding for VoIP 16 . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 5 VoIP typical scenarios 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 6 Phone to phone scenarios 18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 7 PC to phone and phone to PC scenarios 18 . . . . . . . . . . . . . . . . Figure 8 PC-to-PC scenario 19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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This note was uploaded on 08/08/2011 for the course CS 310 taught by Professor Aartisingh during the Spring '11 term at National Institute of Technology, Calicut.

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voip - VoIP BASICS Handout 770 00905 0680 VHBE Ed. 02...

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