White Paper: Advantages of SIP for VoIP


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White Paper: Advantages of SIP for VoIP

  1. 1. White Paper: Advantages of SIP for VoIP ______________________________________________________________ October 2003
  2. 2. White Paper: Advantages of SIP for VoIP October 2003 Definition Voice over Internet Protocol (VoIP) defines a way to carry voice calls over an Internet Protocol (IP) network including the digitisation and packetization of the voice streams. The VoIP standards enable the creation of a telephony system where higher-level features such as advanced call routing, voice mail, contact centres, etc., can be utilised. How does it work? Historically, telecommunications companies have relied on what is commonly referred to as circuit- switched technology to transport telephone calls. This technology establishes a 'permanent' connection between the calling and the called parties for the entire duration of the call. The problem with circuit-switched technology is that it requires a significant amount of bandwidth dedicated to each call, and it can only support certain types of calls (i.e. telephone to telephone). Moreover, the hardware needed to run circuit-switched networks is very expensive, due in large part to the fact that voice and data services must be carried on different wires and thus need separate hardware to accommodate the two types of traffic. Naturally, the traditional telephone companies pass along the costs of building and maintaining a circuit-switched network to the consumer in the form of higher rates for their telephone services. As the name implies, VoIP refers to calls that traverse networks using Internet Protocol. The voice stream is broken down into packets, compressed, and sent toward their final destination by various routes (as opposed to establishing a 'permanent' connection for the duration of the call), depending on the most efficient paths given network congestion, etc. At the other end, the packets are reassembled, decompressed, and converted back into a voice stream by various hardware and software elements, depending on the nature of the call and its final destination. Nokia 1
  3. 3. White Paper: Advantages of SIP for VoIP October 2003 Advantages of VoIP • New Integrated applications: Because VoIP is digital, it may offer features and services that are not available with a traditional phone. (See section ‘Examples of additional functionality made possible by using SIP for VoIP’ below) • Cost Reduction: No call tolls as it uses your Internet connection. With VoIP you can talk for as long as you want with anyone that has an Internet connection. You can also talk with many people at the same time without any additional cost. – Low-cost conferencing. • Single unified network: As voice is converted into data, it is transported on the data network and negates the need for a voice network at all. • Open standards: VoIP embraces an open architecture (see below) and provides the flexibility to integrate with backend systems • User attributes move with you: As soon as you log on to any VoIP-capable device such as PC, Mobile Phone, any IP Phone, Satellite Office system, or Home Office adapter. Cost Reductions VoIP systems increasingly demonstrate greater cost-effectiveness than traditional voice networks. As VoIP technology evolves, the cost/benefit ratio, alongside efficiency and flexibility in implementation, will continue to increase. The following chart compares the cost of two deployment scenarios for an enterprise of 10,000 phone users, where 50 percent of employees are divided between two large locations and the remainder among 12 branch offices. Analysis shows that replacing the current PBX with another PBX increases the cost by approximately 48 percent. However, replacing the existing PBX with an IP PBX saves approximately 11 percent of the overall replacement cost. Savings apply not only to enterprises but also to consumers, because service providers can pass the savings resulting from lower network deployment and maintenance costs on to subscribers. Nokia 2
  4. 4. White Paper: Advantages of SIP for VoIP October 2003 Nokia 3
  5. 5. White Paper: Advantages of SIP for VoIP October 2003 What Nokia mobile devices will it work on? • Symbian 7.0 supports SIP • Nokia phones that run Symbian 7.0 • Nokia 6600 • Nokia 6620 • Nokia 9300 • Nokia 9500 • Future devices that will support VoIP and VoWLAN • Zeus – 6830 (Public Announcement: 2nd Nov 04) • All IP 3G networks will also run VoIP to handset Nokia Project: Sophia Issues with VoIP • Network Latencies / Quality of Service support in the Internet • Session handovers • Reachablility through firewalls and VPN connections • Convergence confusion • Fixed/Mobile • Wireless • Call routing between IP, PSTN & GSM networks • Regulatory issues, - currently unregulated Open Architecture Standards bodies • IETF (Internet Engineering Task Force) The community of engineers that standardizes the protocols that define how the Internet and Internet protocols work. http://www.ietf.org/ • ITU (International Telecommunications Union) an international organization within the United Nations System where governments and the private sector coordinate global telecom networks and services. http://www.itu.int/home/index.html Nokia 4
  6. 6. White Paper: Advantages of SIP for VoIP October 2003 Protocols • H.323 - An ITU Recommendation that defines “Packet-based multimedia communications systems”. H.323 defines a distributed architecture for creating multimedia applications, including VoIP • SIP - Defined as IETF RFC 2543. SIP defines a distributed architecture for creating multimedia applications, including VoIP • MGCP - Defined as IETF RFC 2705. MGCP defines a centralized architecture for creating multimedia applications, including VoIP • H.248 - An ITU Recommendation that defines “Gateway Control Protocol”. H.248 is the result of a joint-collaborate with the IETF. H.248 defines a centralized architecture, and is also known as “Megaco” H.323 vs. SIP H.323 is actually a suite of protocols, and incorporates many individual protocols that have been developed for specific applications. H.323 Protocol Suite Video Audio Data Transport H.261 G.711 T.122 H.225 H.263 G.722 T.124 H.235 G.723.1 T.125 H.245 G.728 T.126 H.450.1 G.729 T.127 H.450.2 H.450.3 RTP X.224.0 Full implementation of H.323 requires a lot of overhead. SIP is a much more streamlined protocol, developed specifically for IP telephony. Smaller and more efficient than H.323, SIP takes advantage of existing protocols to handle certain parts of the process. For example, Media Gateway Control Protocol (MGCP) is used by SIP to establish a gateway connecting to the PSTN system. SIP allows two or more participants to establish a session consisting of multiple media streams using text-based request and response messages. A user, termed a SIP endpoint, is addressed by a SIP URL in the form of an e-mail address, such as sip:alice@vocal.com or sip:alice@ The application used for communication is called the user agent (UA). Call initiation and modification is done through INVITE messages of SIP. Two endpoints can communicate with each other directly, or they can make use of a SIP entity called the redirect server. The user first sends the request for call initiation to this server, which queries a location service to retrieve the IP address and port of the other user. The location service keeps track of the current location of the users. Since the underlying elements of SIP are so much like HTTP, creating network-based services such as time-dependent call forwarding is quick and straightforward. Developers can design and Nokia 5
  7. 7. White Paper: Advantages of SIP for VoIP October 2003 implement new SIP-based voice services just as quickly and easily as they develop web pages; and by not requiring major hardware upgrades to application servers, but rather enabling new software-based services using SIP, service providers can reduce the time associated with deploying new features from months to days. For subscribers, this means ever-improving communications service, plus lower initial and recurring telephone service costs. Examples of additional functionality made possible by using SIP for VoIP • Ringing tone and caller image is delivered within signaling (SIP transports MIME payload xxx) • URLs can be passed within signaling, seamless email/media-on-demand integration (e.g. call may be forwarded into rtsp URL: video mail answering service) • Receive voicemail messages via email • Possibility to create richer profiles "If caller is Bob, send soccer_results.html file to him (in SIP payload or by mail)" • Simple scripts: "If the time is past 4 p.m. and caller is boss, forward to voice mail." • Another form of SIP extension work is to define the usage of SIP in new context. For example, there is on-going work in IETF to use SIP to control networked appliances (e.g. “turn the lamp on”). New method (DO) has been proposed for this idea. Similar ideas (using SIP for new kind of services) will probably follow. SIP is generic protocol for every IP capable access networks. There lies the opportunity for Nokia to win more business in fast growing industry. SIP and HTTP form a powerful architecture for application development community. The snowball effect grows the market as already existing developer community finds it easy to implement compelling services for terminal users. Cisco Support Cisco has broad support for SIP across its entire product line: • IOS Gateways: 1751, 7200, 2600, 36x0, AS5300, AS5350, AS5400 Series, AS5850 • Call Agents/Soft switches: BTS 10200, PGW2200 • Endpoints: ATA 186, 7940, 7960 • Infrastructure: Cisco SIP Proxy Server, PIX Firewall, IOS NAT Cisco-driven solutions are being deployed today with Cisco SIP Global Long Distance having been deployed by several carriers including some with integrated H.323 gateways. Nokia 6
  8. 8. White Paper: Advantages of SIP for VoIP October 2003 Cisco-backed SIP IP Business Solutions are starting to emerge. SIP voice application solutions have been deployed by 5+ carriers (including Windows Messenger PC-to-Phone support) Microsoft Live Communication Server 2003 For years Microsoft has had computer telephony features embedded in its operating systems in products such as NetMeeting, an H.323-videoconferencing application, and Exchange Conferencing Server, for managing data, voice and videoconferencing. Windows XP brought along Microsoft Windows Messenger, which turned some heads in the telecom community for its use of SIP. Speculation about what Microsoft will do in telephony grew when company representatives began showing up at industry events such as Voice on the Net (VON), and later when it announced development of its Real Time Communication (RTC) Server, code-named Greenwich. RTC is renamed Live Communication Server 2003. The server acts as a control node for managing conferences among SIP clients. Windows CE 5.0 includes a greater VoIP focus so that IP phone and other device makers, as well as service providers, can expand their VoIP applications. The Windows CE 5.0 SIP stack is interoperable with Microsoft Windows XP and Microsoft Live Communications Server, enabling collaboration and communication through instant messaging and providing status information (presence) between desktop computers and Windows CE–based IP phones. In addition, Microsoft Visual Studio .NET for native Microsoft Win32–based applications, or for managed applications built on the Microsoft .NET Compact Framework, provides an easy-to- use tool to efficiently develop feature-rich IP phones and VoIP devices. Beyond the new feature, over the past 12 months Microsoft has focused on expanding its VoIP partners for Windows CE. At VON, it announced 13 new VoIP manufacturer partners focused on embedding Windows CE into IP phones and other devices as well as a host of new system integrators. Further reading See the following resources for more information: • RFC 3261: SIP: Session Initiation Protocol: http://www.ietf.org/rfc/rfc3261.txt • SIP Extensions for Presence: http://search.ietf.org/internet-drafts/draft-rosenberg-impp-presence-00.txt Nokia 7
  9. 9. White Paper: Advantages of SIP for VoIP October 2003 • Nokia Sofia IP Telephony Software suite: http://iptel.research.nokia.com/sofia/ • Microsoft Real-Time Communications: Protocols and Technologies: http://www.microsoft.com/technet/prodtechnol/winxppro/plan/rtcprot.mspx • Cisco SIP: http://www.cisco.com/warp/public/cc/techno/tyvdve/sip/ Nokia 8
  10. 10. White Paper: Advantages of SIP for VoIP October 2003 About Nokia Nokia is the world leader in mobile communications, driving the growth and sustainability of the broader mobility industry. Nokia is dedicated to enhancing people's lives and productivity by providing easy-to-use and secure products like mobile phones, and solutions for imaging, games, media, mobile network operators and businesses. Nokia is a broadly held company with listings on five major exchanges. For more information, please visit http://www.nokia.com/forbusiness. Americas Nokia 313 Fairchild Drive, Mountain View, CA 94043 Tel: 1 877 997 9199 Email: mobile.business.americas@nokia.com Europe, Middle East and Africa Nokia Nokia House, Summit Avenue Southwood, Hampshire, GU14 ONG, UK Tel UK: +44 161 601 8908 Tel France: +33 170 708 166 Email: mobile.business.emea@nokia.com Asia Pacific Nokia 438B Alexandra Road #07-00 Alexandra Technopark, Singapore 119968 Tel: +65 6588 3364 Email: mobile.business.apac@nokia.com www.nokia.com Copyright© 2004 Nokia. All rights reserved. Nokia and Nokia Connecting People are registered trademarks of Nokia Corporation. Other trademarks mentioned are the property of their respective owners. Nokia operates a policy of continuous development. Therefore we reserve the right to make changes and improvements to any of the products described in this document without prior notice. Under no circumstances shall Nokia be responsible for any loss of data or income or any direct, special, incidental, consequential or indirect damages howsoever caused. . __________________________________________________________________________ Nokia 9