Overview of Voice over IP February 2001 – University of Pennsylvania Technical Report MS-CIS-01-31* Princy C. Mehta Professor Sanjay Udani [email protected] [email protected] * This paper was written for an Independent Study course. Princy Mehta Overview of Voice over IP Professor Udani Table of Contents ACRONYMS AND DEFINITIONS...............................................................................................................3 INTRODUCTION...........................................................................................................................................5 IMPLEMENTATION OF VOICE OVER IP...............................................................................................6 OVERVIEW OF TCP/IP ...................................................................................................................................6 PACKETIZATION.............................................................................................................................................7 COMPONENTS OF VOIP..................................................................................................................................8 SIGNALING ....................................................................................................................................................8 H.323 .............................................................................................................................................................8 Logical Entities..........................................................................................................................................9 H.323 Stack................................................................................................................................................9 SIP ...............................................................................................................................................................11 SIP Functionality.....................................................................................................................................11 Initiating a SIP Call.................................................................................................................................11 H.323 VS. SIP ..............................................................................................................................................12 SIGNALING SYSTEM 7..................................................................................................................................13 SS7 Network Topology ............................................................................................................................13 Integrating SS7 and IP ............................................................................................................................14 VOICE CODERS ..........................................................................................................................................14 CRITERIA FOR VOCODER .............................................................................................................................15 ITU-T SPECIFICATIONS ...............................................................................................................................16 G.711 .......................................................................................................................................................16 G.723.1 ....................................................................................................................................................16 G.729A.....................................................................................................................................................16 FUTURE CODERS..........................................................................................................................................17 TRANSPORT ................................................................................................................................................17 RTP..............................................................................................................................................................18 RTCP...........................................................................................................................................................18 GATEWAY CONTROL...............................................................................................................................19 MEDIA GATEWAY CONTROL PROTOCOL.....................................................................................................19 MEGACO ......................................................................................................................................................20 WIRELESS NETWORKS............................................................................................................................20 IEEE 802.11X ..............................................................................................................................................21 Overview of 802.11..................................................................................................................................21 Enhancements via 802.11b......................................................................................................................22 Enhancements via 802.11a......................................................................................................................22 Support for Time-Sensitive Data .............................................................................................................22 802.11x Security ......................................................................................................................................23 BLUETOOTH .................................................................................................................................................23 Bluetooth Security ...................................................................................................................................24 Interference with 802.11b........................................................................................................................24 SUMMARY OF WIRELESS TECHNOLOGIES ...................................................................................................24 February 2001 1 Princy Mehta Overview of Voice over IP Professor Udani IP Security ...............................................................................................................................................24 IMPACT OF WIRELESS VOIP ........................................................................................................................25 VoIP via Wireless LAN............................................................................................................................25 QUALITY OF VOIP.....................................................................................................................................26 QUALITY OF SERVICE ..................................................................................................................................26 IPv6 QoS Support....................................................................................................................................27 PACKET LOSS...............................................................................................................................................27 JITTER ..........................................................................................................................................................27 LATENCY .....................................................................................................................................................27 Consequential Issues ...............................................................................................................................28 VOIP EXPERIMENTS.................................................................................................................................28 CISCO IP PHONE ..........................................................................................................................................28 DIALPAD VOIP.............................................................................................................................................30 SUMMARY....................................................................................................................................................31 BIT-RATE VS. VOICE QUALITY ....................................................................................................................31 REVISITING WIRELESS VOIP .......................................................................................................................32 IMPACT OF VOIP..........................................................................................................................................32 REFERENCES ..............................................................................................................................................34 Table of Figures Figure 1: VoIP Applications............................................................................................................................6 Figure 2: OSI and TCP/IP Reference Models .................................................................................................7