Acronyms and Abbreviations The Rise of IP-Based Voice and the Need for Global IP Telephony Reachability Introduction New Challenges on VoIP Service Offerings Why Global IP Telephony Reachability Is Needed The VoIP Protocols Jungle Overview SIP SDP RTP/RTCP SIP-I SIP-T BICC IAX DUNDi TRIP TGREP ENUM What Is This Book about? IP TELEPHONY: OVERVIEW Traffic Analysis VoIP versus PSTN /Mobile This Chapter at a Glance Fixed VoIP Focus on France Focus on Portugal Focus on Latin America Focus on South Korea Focus on the United States Mobile VoIP Peer-to-Peer (P2P) References IMS: IP Multimedia Subsystem What Is IMS? Transport Layer Control Layer Service Layer IMS Functional Elements Call Session Control Function (CSCF) Home Subscription Server (HSS) PSTN Gateways Application Servers (AS) IMS Flow Examples References Further Reading TISP AN Overview Overview Brief History Concerning NGN Standardization Basic Principles TISPAN Functional Architecture Brief Description of the Subsystems Service Level Transport Layer Protocols SIP Diameter H.248 Interface between NGN and Legacy Networks PSTN/ISDN Interconnection IP-Based External Network Interconnection Interoperator IP Backbone Network References Interconnection Practices in PSTN Overview Interconnection Services Access Interconnection Points Interconnection Circuits Interconnection Services Signaling Traffic Interconnection Circuits Interconnection through Circuits Provided by Other Operators Traffic Registration Interconnection Planning and Developing Interconnection Establishment Previous Information Services and New Services Security and Protection Numbering Technical Characteristics Interconnection Circuits Transmission Characteristics Signaling Interfaces between Exchanges Signaling Network Structure Synchronization between Networks Quality of Service (QoS) Operation, Management, and Maintenance Capacity Resale Prices Transit PSTN Interconnection: Economic Models CPNP (Calling Party Network Pays) BAK (Bill and Keep) Optimize Interconnection Costs References Further Reading Roaming Practices in Mobile Networks Overview Roaming Types of Roaming Roaming Agreements Roaming Data IMS Roaming References Interconnection Practices in GPRS Networks Interconnection Practices in GPRS Networks IMS Interconnection Requirements for Voice Calls SIP Profile Advanced Services References IP TELEPHONY INTERCONNECTION: REQUIREMENTS AND BUSINESS MODEL Terminology and Definitions VoIP Service Providers and Telephony Service Providers VoIP Service Providers Traditional Service Providers VoIP Service Providers a la Internet Definitions Address of Record Address of Contact Back-to-Back User Agent (B2BUA) Call Initiator, Calling Party, Caller Invitee, Invited User, Called Party, Callee Registrar End Point IP Network Provider and Service Provider IP Telephony Administrative Domain (ITAD) Proxy Server (PS) Location Server (LS) Interconnection Node (IN) Signaling Path Border Element (SBE) Data Path Border Element IP Telephony Administrative Domain and Autonomous Systems Frontiers between ITADs and ASs Adjacent Domains Balanced/Unbalanced Traffic Symmetric/Asymmetric Telephony Paths Interconnection and Peering Anonymization Assumptions References Business Actors and Relationships Panorama of Main VoIP Service Providers Incumbent Operators "Virtual" VoIP Operators Proprietary Third-Party VoIP Service Providers Cooperation Agreements between Different Types of VoIP Service Providers Business Actors Involved in VoIP Interconnection Customer End User Service Provider Network Provider Business Relationships SLA (Service Level Agreement) CPA (Connectivity Provisioning Agreement) NIA (Network Interconnection Agreement) SIA (Service Interconnection Agreement) Conclusion References IP Telephony Interconnection: Service Requirements Introduction Telephony Service Providers: Toward Global IP Telephony Services No Assumption on the Intraprovide Service Engineering Support of Various Interconnection Models IP Version Agnostic Global Coverage Support of numbering Schemes Other Than E.164 Discovery of Remote Voip Service Providers and Their Capabilities Service Interconnection Agreement Flexibility Interoperability Exchange of Homogenous IP Telephony Routing Data Avoid Signaling Loop Ability to Configure the Call Route Selection Process Support of Multiple Interprovider Telephony Routes Optimization of Signaling Paths and Media Paths Resilience and Availability of the VoIP Service at the Service and Control Layers Synchronize Service Layer and Control Layer Ability to Detect IP Network Provider Spirals Ability to Evaluate the QoS Treatment When Selecting a Given Inter-ITAD Path Operation and Maintenance (O&M) Charging and Billing Interprovider Interconnection Agreements Assurance and Monitoring Support of Import and Export Policies Security Protect against SPAM over Telephony (SPIT) Support of Privacy and Confidentiality No Assumption on the Negotiated Media Session Load Path-Coupled and Path-Decoupled Models Planned Maintenance Operations Customer Requirements Global Reachability Transparency of Interdomain Media Sessions Quality of Service (QoS) Cost Reliability and Robustness Ability to evaluate the QoS provided by the VoIP Service Service Mobility and Roaming Confidentiality and Privacy Anonymization and Customization Freedom of CODEC Usage Free to Subscribe to a Service Offering Service Not Bound to a Specific Interface Environmental Impact Support of Emergency Calls Ability to Support Heterogeneous Calls SLA Verification References Further Readings Telephony Interconnection: Regulatory Constraints European Commission Activities Analysis Constraints on Service Providers Following the Adoption of the Review Proposals Current Activities in Europe and the United States Ofcom OPTA BNetzA AGCOM ANACOM RTR FCC (Federal Communication Commission) References IP TELEPHONY INTERCONNECTION: STATE-OF-THE-ART AND INTERCONNECTION MODELS Related Ongoing Activities Introduction Current Number Portability Practices The Need for Number Portability Types of Number Portability Service Provider Number Portability Schemes All Call Query (ACQ) Query on Release (QoR) Scheme Call Dropback Scheme Onward Routing (OR) Scheme Comparisons of the Various Schemes Database Queries and Call Routing Potential Implications for VoIP ENUM Overview and Use Cases ENUM Deployment Models Source-Based ENUM Query/Answer Mechanism ISN i3 Forum SIP Profile Media Dimensioning SPEERMINT IETF Working Group Overview The SPEERMINT Reference Architecture Interconnection Relationships VIPR Voice Peering Fabric Cable Operators PacketCable Overview PacketCable Architecture Interconnect Functional Component ENUM Server Provisioning Protocol (ESPP) References Further Readings VoIP Interconnection Models Introduction Interconnection Models Star Model Centralized Model Hybrid Model Cascaded Model Analysis of Interconnection Models Reference Interconnection Nodes: Usage of Session Border Controllers Deployment Context Technical Features Topology Hiding Media Traffic Shaping Fixing Capability Mismatches NAT Traversal Access Control Protocol Repair Media Encryption Focus on Interconnection Segment Interconnection Scenarios SBCs at the Border of Each ITAD Shared Interconnection SBC Telephony Exchange Point References Implementation Models for IP Telephony Interconnection at Large Introduction DNS-Based Mode Flooding Approach Signaling Media Layer Interactions References IP: TELEPHONY INTERCONNECTION ENGINEERING ISSUES AND SOLUTION SPACE Service Engineering Issues Content of Agreements Content of Service Level Agreements (SLA) Content of Service Interconnection Agreement (SIA) Advertisement and Discovery End-to-End Signaling Path Optimization End-to-End Media Path Optimization Dynamic and Flexible Interprovider IP Telephony Routing IP Network Provider Spiraling Synchronization between the Service and Network Layer Interprovider Congestion Interprovider Load Balancing Optimize Interconnection Costs Optimize Interconnection Agreements Bidirectionality Issue Legal Intercept Issues Topology Hiding Correlating between Signaling and Media Streams Shaping and Policing Frozen Interconnection Architecture Interprovider Monitoring General Overview What Is Good Quality? Probes Signaling Interprovider Monitoring Issues Service Interconnection Assurance and Fulfilment Security Issues References Solution Space Overview TRIP (Telephony Routing IP Protocol) Why a Dynamic Protocol Is Needed TRIP at a Glance ITAD Numbers Transport Considerations TRIP Messages TRIP Attributes Extend TRIP to Advertise Diverse URI Schemes Needs Proposal Advertise AS Path in the Telephony Signaling Protocol INP Spiral Issues Prevent INP Spiral Optimize Inter-ITAD Quality of Service (QoS) Service Need Solution Proposal QoS Route Capability Modified TRIP Route Attribute On the Utilization of QoS Information Illustration Example Interprovider Multiple Paths Path Diversity Enhance TRIP to Support Multiple Paths Procedure Example Avoid Inter-ITAD Congestion Phenomenon Avoid Congested Links and ITADs TRIP-Based Procedure to Prevent Congestion Summary References VoIP Interconnection Perspectives
Mohamed Boucadair is a Senior IP Architect with France Telecom. He has worked for France Telecom R&D and has been part of the team working on VoIP services. He is now working at the France Telecom corporate division responsible for making recommendations on the evolution of IP/MPLS core networks. He has been involved in IST research projects, working on dynamic provisioning and inter-domain traffic engineering. He has also worked as an R&D engineer in charge of dynamic provisioning, QoS, multicast and intra/inter-domain traffic engineering. He has published many journal articles and written extensively on these subject areas. Mr. Boucadair holds several patents on VoIP, IPv4 service continuity, IPv6, etc. Maria Isabel Borges received a degree in Electronics and Telecommunications engineering from Aveiro University, Portugal, in 1989 and the MSc from the same University in 1998. From October 1989 to September 1990 she accomplished a post-graduation degree at the same University, and was involved in training students at the laboratory of propagation. From October 1990 to February 1991 she worked at TEKA Portuguesa on a Television Receiver Only system. She joined the PT Inovacao, S.A. (PTIN), formerly Centro de Estudos de Telecomunicacoes, in 1991, working on applied research on optical communications, until 1995. Since then, she has been involved in several national and international R&D programs, namely in the area of development and integration of broadband access networks technologies, ATM, IP networking and Services, and VoIP systems. She is involved in training actions and consulting services. She is author or co-author of several publications on the above-mentioned subjects and a reviewer of IEEE Communications Magazine. Pedro Neves received his B.S. and M.S. degrees in Electronics and Telecommunications Engineering from the University of Aveiro, Portugal, in 2003 and 2006 respectively. Since 2007 he has also been pursuing a Ph.D. in Computer Engineering and Telecommunications at the same University. After graduation, he became a research fellow of the Telecommunications Institute, where he worked on European funded projects on broadband wireless access networks. In June 2006 he joined PT Inovacao, working on heterogeneous wireless environments in the context of European and Eurescom funded projects. In 2010 he began his research activities in the area of cloud computing, with emphasis on the relationship of this paradigm with telecom operators. He participated in more than 10 international collaborative projects, is co-author of five international books, and has published more than 30 articles in journals and conference proceedings. Olafur Pall Einarsson received a BSc degree in Electical Engineering from the University of Iceland in Reykjavik in 2005. From there he moved to Copenhagen to continue his education in Telecommunication Engineering at the Technical University of Denmark (DTU) and received an MSc degree in 2007. Following his education he started to work for Icelandic Telecom (Siminn) in R&D where he participated in several national and international research projects. Some of the main areas of specialty are SIM development, mobile security, and integrating a national mobile PKI architecture in Iceland.