Realize your full communications potential with SIP! Integrate SIP with existing systems and simplify your communications architecture! SIP is transforming instant messaging, voice, and video communications, by adding intelligence and reducing cost. The new world standard for facilitating communications, SIP makes it easier to communicate with the right people, at the right time, on the right device.
SIP Communications FOR DUMmIES ‰ AVAYA CUSTOM EDITION by Peter Gregory with Tom Doria, Chris Stegh, and Jim Su Foreword by Alan B.
SIP Communications For Dummies®, Avaya Custom Edition Published by Wiley Publishing, Inc. 111 River Street Hoboken, NJ 07030-5774 www.wiley.com Copyright © 2006 by Wiley Publishing, Inc.
Publisher’s Acknowledgments We’re proud of this book; please send us your comments through our online registration form located at www.dummies.com/register/. For details about how to create a For Dummies book for your company or organization, please contact dummiesrights& licenses@wiley.com.
Contents at a Glance Foreword ..........................................................v Introduction .....................................................1 Part 1: The Case for SIP....................................5 Part 2: SIP at a Glance...................................13 Part 3: How SIP Transforms User Communications .............................................23 Part 4: How SIP Transforms Enterprise Communications .............................................33 Part 5: SIP Interoperability.......
Foreword T hese days, in communications circles, Session Initiation Protocol, or SIP for short, is seemingly everywhere. SIP is supported by practically every manufacturer of IP Phone, Gateway, Call Manager, and IP PBX. It is part of the IP Multimedia Subsystem (IMS). It is powering the fastest growing VoIP residential and enterprise providers. It is a part of PC operating systems and has been enthusiastically adopted by the open source movement.
Not bad for a little protocol developed in academia back in the mid-1990s by such thinkers as Henning Schulzrinne and Jonathan Rosenberg. The authors have done an excellent job of explaining the what, why, and how of SIP in an understandable way. Enjoy your read of SIP Communications For Dummies, Avaya Custom Edition! Alan B.
Introduction I magine a communications environment where a central directory server not only knows how to reach an individual’s work phone, cell phone, and pager, but also her instant messaging (IM) program, e-mail, and PDA. Not only that, but also imagine that the central directory server also knows a party’s communication preferences and capabilities, and can intelligently alert a called party when someone is trying to reach her.
2 SIP Communications For Dummies, Avaya Custom Edition well as in other industry groups working to make sure that SIP works across enterprises that have a variety of architectures, standards, and products in use. About This Book This book describes SIP from both business and technical perspectives. You can read about SIP architecture and operations, as well as its impact on business.
Introduction Part III: How SIP Transforms User Communications describes how SIP “addressing” works with the concept of presence to make reaching users easier, regardless of which device they’re using or where they are. Part IV: How SIP Transforms Enterprise Communications explains how SIP drives down the cost and complexity of intra-enterprise and inter-enterprise communications by permitting their consolidation with IP data communications.
4 SIP Communications For Dummies, Avaya Custom Edition Icons Used in This Book Throughout this book, I occasionally use icons to call attention to material worth noting in a special way. Here is a list of the icons along with a description of each: Some points bear repeating, and others bear remembering. When you see this icon, take special note of what you’re about to read. This icon indicates technical information that is probably most interesting to IT professionals.
Part 1 The Case for SIP In This Part 䊳 Defining SIP 䊳 Connecting people anywhere, anytime, on any device 䊳 Facilitating interoperability 䊳 Streamlining communications with or without servers 䊳 Preparing for the future of SIP D o you increasingly feel like your communication devices are holding you hostage? Just as you finish checking your multiple voice mailboxes you get an instant message from someone that you just left a message for, saying, “I’m off the phone now, can you call me back?” Or have you le
6 SIP Communications For Dummies, Avaya Custom Edition With people more widely available and more connected than ever before, an unintended and unexpected communications paradox has emerged. Users need to manage multiple identities for each of the devices and networks that they want to use. Determining the best way to reach a person and managing a contact list for these multiple identities can be staggering. Simply put, communications today has become device-centric, not user-centric.
Part 1: The Case for SIP A brief history of SIP SIP traces its origins to the mid 1990s in the Internet’s experimental multicast backbone, or “Mbone.” This network was used to facilitate the distribution of streaming multimedia content including seminars, broadcasts of space shuttle launches, and IETF meetings. The original draft of the SIP specification was published in the IETF in 1996, and eventually standardized in 1999.
8 SIP Communications For Dummies, Avaya Custom Edition Do we need fold-out business cards? You probably don’t consider yourself a communications geek, but like most modern business people, you probably have many ways to communicate with others.
Part 1: The Case for SIP Encouraging Interoperability SIP uses a text-based language. That doesn’t mean that SIP supports only text; it means that SIP’s messages are easy to program and interpret, making it easier to achieve interoperability between different vendor implementations. SIP is also very modular and extensible, allowing for the integration of existing legacy protocols. These properties make SIP an ideal protocol for implementing a standards-based converged communications network.
10 SIP Communications For Dummies, Avaya Custom Edition transformation in communications between an enterprise and its ecosystem of partners, suppliers, and customers. SIP may eventually become the unifying protocol for all communications. You can find more information about SIP trunks, connectivity to PSTN networks, and connecting enterprise “islands” in Part 4. Simplifying Communications Architecture Communications networks today are complex and costly to operate.
Part 1: The Case for SIP 11 Building a Foundation for Standardized, Intelligent Communications SIP, defined in IETF standards, is a structured, text-based protocol that is modeled after HTTP, or HyperText Transport Protocol, the language that powers the World Wide Web. Because SIP is text-based and similar to HTTP, application developers and system engineers will have an easier time developing and integrating applications with communications systems.
12 SIP Communications For Dummies, Avaya Custom Edition We’re predicting that the multiple addresses associated with various modes of communication (IM, text messaging, e-mail, phone) will collapse into a single SIP user id. This single user id, coupled with SIP presence servers, will put communications (with the right people and in the right medium) at your fingertips, no matter what kind of communications device you or they are currently connected to.
Part 2 SIP at a Glance In This Part 䊳 Working with existing protocols 䊳 Extending SIP to multimedia sessions 䊳 Getting to know SIP presence 䊳 Examining SIP components 䊳 Following an example of basic operations S IP is an application layer Internet protocol for establishing, manipulating, and tearing down communication sessions. You can do a lot more with SIP than set up telephone calls.
14 SIP Communications For Dummies, Avaya Custom Edition Based on Existing Internet Standards Although SIP may seem new, it’s actually based on many protocols that are widely used today across the Internet and in many enterprise applications. The IETF community took Internet standards as a model, and used a text-based request/response model at the heart of the SIP protocol.
Part 2: SIP at a Glance 15 can reach Eileen’s multiple communication devices (known as user agents or UAs to techno-types) without having to know each of Eileen’s unique device addresses or phone numbers. To complement the AOR, SIP provides a mechanism called the Uniform Resource Identifier (URI) that establishes a common addressing scheme for all of an individual’s user agents. The format of a URI address follows the same basic format as a Web or e-mail address: contact-address@domain.
16 SIP Communications For Dummies, Avaya Custom Edition Because a SIP URI supports both numeric (phone numbers) and alphanumeric (Internet-style addresses) formatted contact addressing, the public switched telephone network (PSTN) and the Internet can be seamlessly linked together. With SIP, users can potentially contact any user, whether they are on the PSTN or on the Internet.
Part 2: SIP at a Glance 17 A SIMPLE Presence Solution One of the key SIP extensions defined by the IETF is SIP for Instant Messaging and Presence Leveraging Extensions (or even more simply, SIMPLE). SIMPLE defines functions for presence and instant messaging. In an advanced communications network, users can specify their communications preferences and availability.
18 SIP Communications For Dummies, Avaya Custom Edition Agents and Servers. These components can take the form of an additional software program (on a laptop computer, for example), or as an inherent part of a mobile device such as a PDA or cell phone. Using user agents User agents (UAs) are applications in SIP endpoints (such as a SIP phone, cell phone, PDA, or workstation, as shown in Figure 2-1) that interface between the user and the SIP network. A user agent can act as either a client or a server.
Part 2: SIP at a Glance 19 SIP devices can communicate directly if they know each other’s URI or IP address, but in practice SIP servers are often used in the network to provide an infrastructure for routing, registration, and authentication/authorization services. IP-based devices can identify and communicate with one another using IP addressing alone. However, in most cases, your network uses the Domain Name Service (DNS) to establish sessions with device names, which DNS translates into IP addresses.
20 SIP Communications For Dummies, Avaya Custom Edition ⻬ Redirect Server. If users are not in their home domains, sessions bound for them needs to be redirected to them. The redirect server maps a SIP request destined for a user to the URL of the device “closest” to the user. For example, if a call is destined for eileendover@ company.
Part 2: SIP at a Glance 21 Basic SIP Operations This section walks you through a basic communication session — how it works, and how SIP supports it. Figure 2-2 illustrates the path of a typical session. Dashboard Profile: Default Username: slp_user@avaya.
22 SIP Communications For Dummies, Avaya Custom Edition An INVITE request is generated and sent to John. The INVITE message contains Session Description Protocol (SDP) parameters that define the types of media the caller can accept and where it wishes the media to be sent. 2. A DNS SRV record lookup for SIP services resolves to John’s proxy server, proxy.bigcompany.com. The INVITE request is sent to the proxy server. 3.
Part 3 How SIP Transforms User Communications In This Part 䊳 Getting familiar with presence-enabled communications 䊳 Routing communications with presence 䊳 Choosing your modes of communication freely 䊳 Recognizing benefits for the mobile user T his part describes in detail how SIP, presence, and user preference can enhance the productivity and quality of communications and explains the concept of user-centric communications. To Be Available or Not to Be Available . . .
24 SIP Communications For Dummies, Avaya Custom Edition Probably the earliest manifestation of presence is the telephone network’s “busy signal”, signaling to a caller that the party is unable to communicate right now because he or she is already communicating with someone else. Instant messaging has taken presence a step further, with states that include Available, Away, On the Phone, and Busy, plus customizable preferences that include any message that the user wants to share (see Figure 3-1).
Part 3: How SIP Transforms User Communications 25 Presence means “being there” for your customers Every company wants to retain customer loyalty through superior customer service, but how can your agents keep all of the info they need for accurate responses? A credit card company is especially under pressure to perform 24/7 for helping customers keep accurate tabs on transactions.
26 SIP Communications For Dummies, Avaya Custom Edition Presence can span a number of different communication channels. The aggregated view of a user’s presence (that is, the availability across all of an individual’s SIP-enabled devices) is called Multiple Points of Presence, or MPOP. MPOP becomes powerful when presence is inferred from observation of a user’s actions.
Part 3: How SIP Transforms User Communications 27 The Internet Engineering Task Force (IETF) has a work group that is working to standardize the SIMPLE protocol. SIMPLE is based on RFC 3428, 3265, and 3856 but is being enhanced. SIMPLE is increasingly used to interconnect with previously closed public IM networks. Another protocol called XMPP, or Extensible Messaging and Presence Protocol, was designed and is currently maintained by the Jabber Software Foundation.
28 SIP Communications For Dummies, Avaya Custom Edition Because SIP can determine through the Session Description Protocol (SDP) what type of media stream the answering UA can support, SIP can make intelligent choices on what type of modality to use. (Part 2 explains more about SIP and SDP.) However, IM is just the beginning. SIP has the unique and natural ability to support multiple media types within a single communication session.
Part 3: How SIP Transforms User Communications 29 • Virtual Business Card with every voice call so that the user can have the caller’s contact information available. • Playback, skip, rewind, pause, slowdown, and speedup buttons using a Graphical User Interface in a screen phone, as opposed to using the telephone keypad to control the presentation of the voice messages.
30 SIP Communications For Dummies, Avaya Custom Edition By linking multiple modes of communication with user preference, SIP provides a unifying solution that helps to reduce user and operating costs by making even advanced communications more intuitive and more consistent to the user. Instead of requiring the user to interpret and interact with multiple applications, interfaces, and addresses, the communication system adapts to the need of the user.
Part 3: How SIP Transforms User Communications 31 a company can certainly gain cost savings and other efficiencies, the real benefit is that these efforts also serve as a steppingstone towards next-generation communications applications powered by SIP. Consider a business communications solution where SIP is the common interface providing integration between enterprise networks and service provider networks.
32 SIP Communications For Dummies, Avaya Custom Edition What about the user’s highly personalized services such as address lists, buddy lists, and speed dials? SIP preference tools features can make these personal services mobile.
Part 4 How SIP Transforms Enterprise Communications In This Part 䊳 Understanding how SIP and the PSTN work together 䊳 Getting familiar with SIP trunks 䊳 Federating SIP “islands” 䊳 Matching up phone numbers to URIs S IP will fundamentally improve the efficiency of communications between enterprises and their partners, suppliers, and customers. The initial wave of VoIP benefits has been primarily limited to intra-enterprise communications.
34 SIP Communications For Dummies, Avaya Custom Edition Working Together: SIP and the PSTN Clearly the telco world with its country codes, area codes, city codes, and telephone numbers will continue to serve many people for some time to come. So, how do you call SIP users with URIs from old push-button phones, and how do you call landline users from SIP-enabled devices? Fortunately, the mapping between SIP and telephony protocols has been defined.
Part 4: How SIP Transforms Enterprise Communications 35 Marveling at what a SIP trunk can carry SIP technology can alter the way that a retail business services its customers. Suppose a retailer with a number of store locations wants to offload the task of handling phone calls from its store employees so they can focus on in-store customers, but the retailer has no direct connectivity between its call center and each store.
36 SIP Communications For Dummies, Avaya Custom Edition appropriate federations and security protections established between them. The IP circuit continues to carry e-mail, Internet, and other corporate traffic as it does today, and voice is simply layered on top of the circuit as another IP application. SIP sets up and tears down voice calls to and from the enterprise over this IP circuit.
Part 4: How SIP Transforms Enterprise Communications 37 automatically rerouted over the service provider SIP network to another enterprise location. For enterprises, this system offers great flexibility in providing a local presence in all their markets while routing calls to a centralized call center for more efficient service. ⻬ Cost savings: For enterprises, SIP networking means reducing the monthly recurring cost of separate PSTN and data circuits to the premises.
38 SIP Communications For Dummies, Avaya Custom Edition In a converged network, voice becomes an IP application, sharing the common network infrastructure and services. Connecting SIP Enterprises A common concern for companies contemplating the switch to SIP is how quickly all these nifty advances are going to come together in a truly comprehensive way.
Part 4: How SIP Transforms Enterprise Communications 39 ⻬ Enabling SIP islands to discover the existence of one another ⻬ Ensuring that the two islands interoperate ⻬ Managing and controlling this interconnection so that spam and abuse does not become rampant One answer to all of the above issues is federation. Federation is the mechanism by which you/your company can provide end-to-end SIP communications for end-users.
40 SIP Communications For Dummies, Avaya Custom Edition Federation allows these islands of SIP communications to grow and expand and interconnect. Businesses can maximize the services and features from their SIP products and systems and participate in the growing SIP communication ecosystem. Mapping Phone Numbers to URIs When interconnecting islands of SIP, your network needs a method of discovering a SIP URI from a telephone number. The ENUM protocol has been developed to fulfill this purpose.
Part 4: How SIP Transforms Enterprise Communications 41 ENUM alternatives Until ENUM (or a similar standard) is widely adopted by service providers, enterprises using SIP can leverage existing solutions such as LDAP (Lightweight Directory Access Protocol) to store both a user’s URI and all associated phone numbers (E.164 addresses). SIP applications can then reference entries stored in LDAP structures to resolve and translate phone numbers to URIs.
42 SIP Communications For Dummies, Avaya Custom Edition SIP guide
Part 5 SIP Interoperability In This Part 䊳 Getting greater interoperability within a company 䊳 Examining interoperability between companies 䊳 Looking at industry interoperability efforts 䊳 Integrating multiple vendors S IP is successful and widespread because it is open, extensible, and driven by the IETF. Great strides have already been made to make SIP interoperable among the growing community of SIP-enabled hardware and software products.
44 SIP Communications For Dummies, Avaya Custom Edition Generally, SIP-adopting companies can expect a greater likelihood of interoperability among proxies, phones, and gateways. This integration is quicker and easier because these devices are modeled after traditional telephony devices with more predictable features and logic.
Part 5: SIP Interoperability 45 communications. Like TCP/IP in the 1980s and the World Wide Web in the 1990s, communications hardware and software product vendors are adding SIP capability to their products.
46 SIP Communications For Dummies, Avaya Custom Edition ⻬ SIP Foundry promotes interoperability of SIP products. More information can be found at http://sip foundry.org. ⻬ SIPit (SIP Interoperability Tests) test events at locations around the world. More information is available at http://www.sipit.net. ⻬ SPEERMINT is a new Operations Area working group in the IETF that is working on peering and operational issues of SIP. Find out more at http://www.ietf.org/ html.charters/speermint-charter.
Part 5: SIP Interoperability 47 ⻬ Interoperability among IVRs. ⻬ Firewalls. ⻬ Conferencing bridges. ⻬ Instant messaging platforms. In essence, these systems must rely on much more than standard SIP to make them work together. Nevertheless, SIP offers new options for multi-vendor integration within an IP telephony environment based on open standards. First, when needed, a specific user agent (a client device such as a PDA phone) can be connected to the PBX through SIP.
48 SIP Communications For Dummies, Avaya Custom Edition SIP guide
Part 6 SIP and Server-Free Communications In This Part 䊳 Implementing SIP communications for small offices 䊳 Getting the big picture on peer-to-peer communications 䊳 Using peer-to-peer SIP for maximum benefits D eploying SIP in the smallest business settings presents unique challenges. Models for deploying and operating SIP in larger enterprises (distributed or not) may not be optimal for smaller businesses.
50 SIP Communications For Dummies, Avaya Custom Edition ⻬ Deployment and Administrative Costs: Communications solutions often require on-site technical installation services. Additional costs are incurred when local support is required to fix problems, add capacity, or perform basic administrative tasks. ⻬ Speed: For many small offices, competitive advantage is all about speed — time to deployment drives time to market.
Part 6: SIP and Server-Free Communications 51 The peer-to-peer layer effectively replaces the registration, location, and lookup steps of SIP.
52 SIP Communications For Dummies, Avaya Custom Edition Reaping the Benefits of Peer-to-Peer SIP Communications With peer-to-peer SIP technology, you can dramatically simplify telephone system setup and installation. Plug the IP telephones into the local area network, and the system configures itself. In minutes, all users have access to the most commonly used set of features, including voice mail, conferencing, auto-attendant, and call management.
Part 6: SIP and Server-Free Communications 53 Peer-to-peer technology also enables sophisticated backup of phones and voice mail. Remarkably, you can achieve all this with no significant additional performance burden on the network. The peer-to-peer solution can easily grows with the needs of your business. As you add employees, simply add additional telephones — it’s that simple.
54 SIP Communications For Dummies, Avaya Custom Edition SIP guide
Part 7 SIP and the Future of Intelligent Communications In This Part 䊳 Increasing business applications’ productivity with presence 䊳 Improving the ease and speed of multimodal communications 䊳 Becoming smarter about prioritizing messages 䊳 Roaming around with location-aware services 䊳 Maintaining privacy 䊳 Enabling new services T o write this part, we got out our crystal ball and polished it up a bit, waved a cell phone over it, and chanted, “Presence, Presence, Presence, PRESENCE!!” Then we just typed
56 SIP Communications For Dummies, Avaya Custom Edition Applications will not need to be customized to account for new SIP capabilities. Rather, common libraries (such as dynamic linked libraries (DLLs) in Windows) will contain function calls that know how to query presence servers and return rich and meaningful results. Here’s an example: A factory assembly line worker is viewing the parts needed for an upcoming order in an inventory program, and notes that there is a shortage.
Part 7: SIP and the Future of Intelligent Communications 57 Seamless Use of Multiple Devices SIP presence will improve the productivity of businesspeople by enabling them to seamlessly use multiple communication devices. Today, most users view the presence status of a buddy only as it pertains to their IM/desktop status, resulting in inefficiencies in the way they communicate.
58 SIP Communications For Dummies, Avaya Custom Edition Combining presence from multiple SIP devices will inform the caller that the user is present or not, but the caller will not need to know on which number to call his buddy. He simply launches a message to sip:buddy@company.com, and the SIP server will start the session with the correct device (cell phone, desk phone, IM) at the correct time using the correct mode of communication (voice, text, video, and so on).
Part 7: SIP and the Future of Intelligent Communications 59 night) will improve accordingly. It is likely that tools that manage and aggregate presence will emerge in the coming years to manage and aggregate presence from multiple sources. As presence management tools evolve, they may take on “learning” characteristics (that is, catching on to user habits from heuristics or patterns of usage).
60 SIP Communications For Dummies, Avaya Custom Edition location, the device they’re currently using, and other factors. Such control will help to address big-brother type privacy concerns. Personal profile managers will need to be aware of privacy requirements in various parts of the world, and alter their behavior accordingly.
Part 8 Top Ten Reasons for SIPEnhanced Communications In This Part 䊳 Simplifying communications 䊳 Gaining more control 䊳 Working with divergent systems 䊳 Making mobility easier 䊳 Saving money S IP is a key enabling technology that can advance communications to an unrealized level of flexibility and usefulness. Even though SIP may end up being invisible to end-users, SIP is the glue that will help peer-to-peer communications work better than most people can imagine today.
62 SIP Communications For Dummies, Avaya Custom Edition the right medium (voice, video, IM), on the right device, and at the right time. Turn to Part 3 for more information on SIP forking. Preference-Based Communications Like SIP presence, SIP adds intelligence to communications through giving users control over the parameters of their communications (such as time of day, preferred medium, preferred callers, and so on).
Part 8: Top Ten Reasons for SIP-Enhanced Communications 63 Unified Addressing A single SIP AOR (address of record) provides a unifying identifier that can be used for routing all communication to a user. Simply put, an AOR allows for a single user identity to be mapped across multiple devices so that people connect with people, without needing to know which devices they have and are presently using.
64 SIP Communications For Dummies, Avaya Custom Edition Creation of New Services SIP is a structured, text-based protocol that is modeled after HTTP, or HyperText Transport Protocol, the language that powers the World Wide Web. SIP opens the door to a much larger developer community than traditional CTI, and so offers your company the potential to create competitive advantages with intelligent communications.
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Realize your full communications potential with SIP! Integrate SIP with existing systems and simplify your communications architecture! SIP is transforming instant messaging, voice, and video communications, by adding intelligence and reducing cost. The new world standard for facilitating communications, SIP makes it easier to communicate with the right people, at the right time, on the right device.
