Technology influences business models � Technology decisions affect business models Economics of signaling � Business models influence technology decisions � Example 1: the end2end principle � TCP/IP, control at the edges of the network � Example 2: Voice over IP (VoIP) Signaling = application control!!! � H323: preserves vertically integrated control of carriers � SIP: allows control to the edges of the network � IMS: SIP-based architecture, provides control to network operators � We would like to understand the economic implications of technology decisions in the Internet C. Courcoubetis The end2end principle The paradox of the simple network � Provides a rationale for moving a function upward in a � The simple network core (Internet) provides commodity layered system, closer to the application that uses the services, cannot make money! function (J.H. Saltzer, D.P. Reed and D.D. Clark) � Simplicity: � Result: most of the functions are moved to the edges of the � key factor for success, low cost network, network does simple tasks (IP) � No bargaining position due to commoditization � Internet: provides IP functionality only. Edges provide � “The best network is the hardest one to make money intelligence (TCP and up) running!” � Can not control edge applications � How to build a sustainable Internet? -> NGN, IPsphere � Telephone network: assumes simple edge devices, has all � What should be the business of future NSPs? the intelligence � Controls services (creation, usage, pricing) � Analogy: freeway system vs railroad tracks � -> Technology influences business models! C. Courcoubetis C. Courcoubetis
Signaling and competition The role of signaling � The Internet evolves from being a research network � The network control layer influences business models � New requirements, new design principles � Controls operation of applications and access to content � Important reality: different stakeholders of network � Connects applications to network services infrastructure have interests that are adverse to each � Who controls the control?... other := “the tussle” (David Clark) ? � New network architecture must accommodate this tussle Offered by other parties � Application control = signaling protocols Applications, content � Example of “tussle-ready” signaling technologies: SIP, Network control Strategic role!! ENUM, IMS (signaling) � We examine such technologies to analyze their effects Network services Offered by network operator on competition: the range of tussle they allow ? C. Courcoubetis C. Courcoubetis Topics covered VoIP � VoIP (briefly) � SIP Voice over IP � ENUM � BT Fusion � IMS C. Courcoubetis
VoIP – Voice over IP The impact of VoIP � Voice becomes just another application on the Internet � VoIP: all forms of call setup & voice transmission using � VoIP means different things to different people Internet protocol (IP) technology � ILECs & Mobile operators: threat to their main source � over private, managed IP-based networks or the public of revenue as well as antidote (upfront CAPEX vs Internet reduced OPEX and advanced services) � PC-to-PC, PC-to-phone or phone-to-phone – IMS � CLECs: opportunity (lower barriers to entry) � Wholesalers: opportunity (more alternatives to destination � control) � ASPs: new niche markets � End-Users: more value, cost savings � Regulator: dilemma C. Courcoubetis C. Courcoubetis VoIP call phases � VoIP telephone call procedure is similar to PSTN SIP � call setup : getting a dial tone, dialing a phone number, getting a ring or a busy signal at the far end, and picking up the phone to answer the call Session Initiation Protocol � telephone conversation : voice samples digitized, compressed, packetized, transferred, reordered, buffered (causing extra delay), decompressed and converted back to analog � Call control: mute, call-waiting,… � End of call: tear down � …but, more complicated since the voice application is decoupled from network services � Call setup may involve many intermediaries; each one controls the next hop C. Courcoubetis
Introduction to SIP User’s registration with SIP SIP is an end-to-end session signaling protocol � � A session could be any transaction on the Internet; more suited for multimedia (calls, chat, video conferences, …) It defines how SIP devices will communicate � � SIP addresses are similar to email addresses and used for locating the session’s destination(s) – In the context of VoIP: identify callee and callee’s “home provider” � SIP messages describe the action to be performed – In the context of VoIP: call setup, call-state modifications, … SIP entities reside at � � End-users (User Agent Client, User Agent Server) � Providers (Proxy server, Location Server, Registrar Server) C. Courcoubetis C. Courcoubetis Invitation through one SIP Proxy server Invitation through one SIP server in redirect mode In this case, the two parties have registered to the same proxy SIP. In this case, the called party has roamed to another proxy SIP. C. Courcoubetis C. Courcoubetis
SIP and multimedia session control SIP is based on the request-response paradigm (client-server) but in � a distributed way (through proxying): different control structures ENUM The end-user grants control to a “home provider”, because only this � provider knows how other users (that learned a SIP address issued by this provider: mnemonic address) can reach her (even in case of tElephone NUmber Mapping roaming) � An end-user can acquire any number of SIP addresses (free SIP (or E.164 NUmber Mapping) addresses are also available, i.e. sip2sip.info), but she will have to “pay” a switching cost – ENUM can minimize this switching cost, although some users are restrained to use locked devices When a destination (i.e. PSTN end-user) can be reached by several � providers, an intermediate provider (i.e. a wholesaler) possessing this information can control the provider that will participate in the session. SIP does not transport data nor control media path (QoS can be � achieved with complementary protocols-systems) C. Courcoubetis Introduction to ENUM Registration into ENUM A user (“owner” of a E.164 number) informs an ENUM registrar � ENUM is a global directory of services where users have signed- � about the current services he is currently subscribed into and his up and can be reached from preference (he has control) Service examples: VoIP, voicemail, POTS � � In closed ENUM systems users’ preferences are absent, so Lookup is performed by E.164 numbers (usually in 2 phases) � providers have full control – Uses the DNS architecture for acquiring other mnemonic Registration is not obligatory (opt-in) � addresses '+12025332600‘ ↔ 'sip:user@sipservice.com‘ I.e. User ckalog enters the following identifiers (in descending � – Find the IP address of the user’s provider SIP proxy 'sip:user@sipservice.com‘ ↔ 192.251.255.250 preference) � 1. sip:ckalog@iptel.org Generally, enables the finding of alternative routing numbers � e.g. Alternative ways to make a phone call to the same person � 3. tel:302108203683 (PSTN or mobile or VoIP) � 4. mailto:ckalog@aueb.gr – Lower control to the Home Provider Due to bureaucracy ENUM is operating in only a few countries � (Switzerland, Austria, …) This has led to the emergence of “closed” ENUM systems (in � parallel to public ENUM) C. Courcoubetis C. Courcoubetis
Bypassing PSTN with ENUM (IP-IP calls) 2. Application client formats number into FQDN (e.g., BT Fusion 7.8.7.6.6.3.2.3.7.9.1.e164.arpa) and looks up name in DNS 3. DNS returns all NAPTR records DNS associated with FQDN 1. End user enters E.164 Number: 1-973-236-6787 (e.g., in to: field) IP-based 4. Application selects appropriate NAPTR record (e.g., mailto:sdlind@att.com) Network and completes processing C. Courcoubetis BT Fusion BT Fusion � The first commercially available service bringing Fixed- User owns a special access point and a dual-mode handset � Mobile Convergence (since fall 2005) User is assigned only one identifying number (from BT) � � BT decides the most appropriate access network for Calls routed to fixed-line network within range of Bluetooth access � delivering services, based on subscriber’s location point (WiFi in future) � VoIP if quality is acceptable, POTS otherwise � 3 choices in case of telephony services: POTS, VoIP, Out of range calls routed to cellular network Mobile � BT has full control (not the user)! � � Combines functionality of a mobile phone with reliability of fixed telephony and/or lower charges Cellular (especially for VoIP) Convergent network Handset PSTN � Vodafone is the associated mobile operator Cell site PSTN Link NTE Fusion Access Point Broadband VoIP Gateway OR Link Bluetooth ADSL NTE or WiFi C. Courcoubetis C. Courcoubetis
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