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IP TELEPHONY POCKET GUIDE BY BARRY CASTLE 2nd Edition September 2004 ShoreTel,

IP TELEPHONY POCKET GUIDE BY BARRY CASTLE 2nd Edition September 2004 ShoreTel, Inc. 960 Stewart Drive Sunnyvale, CA 94085 408.331.3300 1.800.425.9385 www.shoretel.com info@shoretel.com TABLE OF CONTENTS Executive Summary . . . . . . . . . . . . . . . . . . .4 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . .4 1.1 Expectations and Desired Outcome . . . . . . .6 2 Enterprise Voice Systems . . . . . . . . . . . . . . .8 2.1 Call Switching, Processing and Signaling . . .9 2.2 Line Interfaces . . . . . . . . . . . . . . . . . . . . . .11 2.2.1 Terminal Line Cards . . . . . . . . . . . . . . . . .11 2.2.2 Trunk Line Interfaces . . . . . . . . . . . . . . . . .11 2.2.3 Trunk Features . . . . . . . . . . . . . . . . . . . . .12 2.2.4 Trafﬁc Calculations . . . . . . . . . . . . . . . . . .13 2.3 Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . .14 2.4 Basic Features and Functions . . . . . . . . . . .15 2.5 Enhanced Features and Applications . . . . .16 2.6 Call Flows and Dial Plans . . . . . . . . . . . . .17 2.7 Automated Attendant . . . . . . . . . . . . . . . .18 2.8 Call Detail Records and Billing . . . . . . . . . .19 2.9 Next Steps . . . . . . . . . . . . . . . . . . . . . . . . .20 3 Data Networking . . . . . . . . . . . . . . . . . . . .20 3.1 LAN Infrastructure . . . . . . . . . . . . . . . . . .20 3.1.1 Ethernet Switching . . . . . . . . . . . . . . . . . .23 3.1.2 Power over Ethernet . . . . . . . . . . . . . . . . .25 3.1.3 Wireless LANs . . . . . . . . . . . . . . . . . . . . . .26 3.2 IP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 3.2.1 IP Addresses and Names . . . . . . . . . . . . . .29 3.2.2 Allocating and Managing Addresses . . . . . .30 3.2.3 WAN Infrastructure . . . . . . . . . . . . . . . . . .31 3.2.4 Routers and Routing . . . . . . . . . . . . . . . . .32 3.2.5 The Real Time Protocol (RTP) . . . . . . . . . .33 4 VoIP – Technologies and Standards . . . . . .35 4.1 How IP Voice Actually Works . . . . . . . . . .35 4.2 VoIP Components . . . . . . . . . . . . . . . . . . .36 4.3 VoIP Standards . . . . . . . . . . . . . . . . . . . . .41 4.3.1 Session Initiation Protocol (SIP) . . . . . . . . .42 4.3.2 MGCP/MEGACO/H.248 . . . . . . . . . . . . . .43 P.2 4.3.3 ITU H.323 . . . . . . . . . . . . . . . . . . . . . . . . .44 4.3.4 Codecs . . . . . . . . . . . . . . . . . . . . . . . . . . .46 4.3.5 Which Standard? . . . . . . . . . . . . . . . . . . . .48 5 Deployment Issues . . . . . . . . . . . . . . . . . .49 5.1 Legacy Integration . . . . . . . . . . . . . . . . . . .49 5.1.1 Basic Connectivity . . . . . . . . . . . . . . . . . . .49 5.1.2 Voicemail Integration . . . . . . . . . . . . . . . . .50 5.2 Supporting Voice Quality (QoS) in the Network . . . . . . . . . . . . . . . . . . . . .51 5.3 Reliability . . . . . . . . . . . . . . . . . . . . . . . . .55 5.4 Security . . . . . . . . . . . . . . . . . . . . . . . . . . .58 5.4.1 Telephony System Security Issues . . . . . . .59 5.4.2 Network and Computer Security . . . . . . . .59 6 Telephony Applications . . . . . . . . . . . . . . .63 6.1 Convergence: Computer Telephony Integration (CTI) . . . . . . . . . . .63 6.1.1 TAPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64 6.2 Personal Productivity . . . . . . . . . . . . . . . . .64 6.3 Collaboration . . . . . . . . . . . . . . . . . . . . . . .68 6.4 Voicemail and Uniﬁed Messaging . . . . . . .69 6.4.1 Uniﬁed Messaging . . . . . . . . . . . . . . . . . . .70 6.5 Supporting Teleworkers and Road Warriors . . . . . . . . . . . . . . . . . . .71 6.6 Multi-Site Connectivity . . . . . . . . . . . . . . .71 6.7 Call Centers and Customer Relationship Management . . . . . . . . . . . . .73 7 Options for Enterprise Voice Communications . . . . . . . . . . . . . . .75 7.1 Key Systems . . . . . . . . . . . . . . . . . . . . . . .75 7.2 PBX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75 7.3 IP-PBX . . . . . . . . . . . . . . . . . . . . . . . . . . . .77 7.4 Total Cost of Ownership (TCO) . . . . . . . . .79 8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . .80 9 Terms and Abbreviations . . . . . . . . . . . . . .82 P.3 EXECUTIVE SUMMARY IP telephony (IPT) offers a viable alternative to the legacy voice exchange, delivering improved application integra- tion, scalability , and multi-site management. It is precisely these features that make this rapidly-maturing technology so attractive to organizations seeking to reduce costs, increase productivity and improve customer relations. However, voice is critical to business, and a major change to emerging technologies like IPT requires an understand- ing of a broad range of technologies, careful planning and thoughtful implementation. This guide has been com- piled to help decision makers to understand the relevant technologies as they deﬁne their strategies. Following the introduction, we will review the typical components and features of an enterprise telephony sys- tem. We then introduce voice over IP (VoIP), the under- lying network infrastructure, and then we address the various issues one must take into account when design- ing the network to carry voice. We conclude uploads/Management/ voip-guide.pdf