Avia Avaya Custom Edition User Manual

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SIP guide

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SIP

Communications

Avaya Custom Edition

A Reference

for the

Rest of Us!

FREE eTips at dummies.com

Peter Gregory

with Tom Doria, Chris Stegh, Jim Su

Foreword by Alan B. Johnston

Enhance the way you communicate with SIP

SIP

SIP guide

Communications

FOR

‰

DUMmIES

AVAYA CUSTOM EDITION

by Peter Gregory

with Tom Doria, Chris Stegh, and Jim Su

Foreword by Alan B. Johnston

SIP Communications For Dummies®, Avaya Custom Edition

SIP guide

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Contents at a Glance

SIP guide

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.............................43

Part 6: SIP and Server-Free Communications....49

Part 7: SIP and the Future

of Intelligent Communications.........................55

Part 8: Top Ten Reasons for SIP-Enhanced

Communications.............................................61

Foreword

SIP guide

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.

Years ago, someone proposed a usage of SIP that was dubbed “SIP for Light Bulbs”! Don’t laugh, it may happen yet.

So what is SIP and why is the industry buzzing about it? This book will tell you. What can you use SIP for? This book will tell you that too. Why is SIP so important? You’ll find that here, too.

Before I leave you in the competent hands of the authors, I will add a few of my own answers here. SIP can be called a “rendezvous” protocol. That is, it allows endpoints on the Internet to discover, locate, negotiate, and establish sessions. What kind of sessions? Any kind of sessions. SIP is used to establish VoIP (of course), video, gaming, text, call control, and others I’m sure I’ve left out. Recent extensions to SIP add in instant messaging and presence capability. What is presence? This book will tell you, but presence stands ready to revolutionize enterprise communications the same way public Instant Messenger networks have revolutionized consumer communications.

Besides all these applications and uses, SIP is also generating its own ecosystem. In the same way that the Internet opened up networking by displacing closed, proprietary networking protocols, SIP has opened up communications and displaced closed and proprietary signaling protocols. It has created an entire ecosystem of interoperable and configurable devices and services that is revolutionizing the way communications is done.

Not bad for a little protocol developed in academia back in

SIP guide

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. Johnston February 2006

Introduction

SIP guide

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. Finally, imagine that phone calls to an unavailable person can be intelligently rerouted to another person or group depending upon a number of interrelated factors such as time of day, whether the called person is scheduled to be in a meeting, or whether one or more of her modes of communication is unreachable.

These capabilities aren’t some dream of a far-off utopian future, but are available today thanks to a remarkable advance in communications: Session Initiation Protocol (SIP). SIP is the glue — and the intelligence — that makes these advanced communications capabilities possible.

Vendors are rushing to incorporate SIP into their products, including those that work with Voice over Internet Protocol (VoIP). Here’s a short list of the kinds of products you can expect to become SIP-enabled:

⻬ VoIP phones, gateways, proxies, and servers ⻬ VoIP softphones — phone software programs that run on

PCs, PDAs, and other devices

⻬ VoIP PBXs ⻬ Instant messaging (IM) programs ⻬ Videoconferencing systems

SIP is an open standard, with an active working group on the Internet Engineering Task Force (IETF) that has given SIP tremendous legitimacy and momentum. Avaya and other major companies are active in the IETF SIP working group, as

SIP Communications For Dummies, Avaya Custom Edition

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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. You can discover how SIP can improve internal and external communications as well as the basics of how SIP technology works, and how to build a SIP environment.

Foolish Assumptions

We assume that you have a keen interest in ensuring that your company’s networking and telecommunications systems are up to the challenges of intelligent communications today and tomorrow. Regardless of your role in your organization, this book can help you quickly get up to speed on how SIP promises to revolutionize electronic communications.

How This Book Is Organized

Each part of this book considers a different aspect of SIP environments. You may want to read the book cover to cover to gain a fuller understanding of SIP, or you may prefer to skip around to find out what you need when you need it.

Part I: The Case for SIP gives you the high-level view of what SIP is and what it can do for your company’s communications. If you’re unfamiliar with SIP’s benefits, this is a great place to begin.

Part II: SIP at a Glance explains how being based in current standards makes SIP compatible with existing systems. It also introduces presence, the SIP feature that adds intelligence to communications at many levels, and it describes the components in a SIP network that make intelligent communications possible.

Introduction

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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. This part delves into the details of basic SIP calls, including proxy-mediated voice calls, presence-enabled calls, instant messaging, and videoconferencing. Here we explain the concept of trunking — that is, connecting enterprises’ IP-based communications systems together over long distances. We also discuss ENUM, the protocol that bridges the new SIPbased URI system with the old TDM phone number system.

Part V: SIP Interoperability discusses the principles needed to support an enterprise migration to SIP. No two enterprises are alike, so it would be difficult to come up with a single works-for-all recipe for migrating to SIP. Instead, this part explains what vendors are doing to make multi-vendor integration with SIP as straightforward as possible.

Part VI: SIP and Server-Free Communications discusses how small businesses and distributed offices can take advantage of SIP features, even without dedicated servers.

Part VII: SIP and the Future of Intelligent Communications

looks into the future of SIP and how it will continue to evolve and improve, embracing more communication technologies and supporting more enhanced communications capabilities.

Part VIII: Top Ten Reasons for SIP-Enhanced Communications offers a condensed list of the most impor-

tant reasons to put your communications on steroids. SIP will make your communications more intelligent than anything else available today. This intelligence pays off in more effective communications that result in happier customers and more productive employees. If you’re still sitting on the fence about SIP, start here.

SIP Communications For Dummies, Avaya Custom Edition

SIP guide

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.

If you see a tip icon, perk up — you’re about to find out how to save some aggravation.

Where to Go from Here

No matter where you are in your SIP project, always keep your eye on the big picture. Avaya has keen vision and leadership in the communications industry. You can learn a lot from this book, but a lot more from Avaya professionals. Turn the page and discover for yourself why Avaya is one of the leaders in converged voice and data environments powered by SIP.

Part 1

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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

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 left a greeting on your work voice mail saying, “If you’ve missed me, you can call me on my cell phone, or better yet, send me an e-mail if this is after hours.” You may be rapidly reaching the conclusion that everyone has too many devices, too many numbers, and too little time. Sometimes modern communications technology seems to have forgotten the main reason for using it: to communicate with another person more conveniently.

People have more options available to them today for communicating with each other than ever, yet they often have a harder time getting through. The selection of choices spans a dizzying array of technologies and devices that can deliver voice, e-mail, instant messages, and even video. Simply picking up the phone still works, but now users have more choices for deciding how to reach somebody — and, ironically, that is the problem.

SIP Communications For Dummies, Avaya Custom Edition

SIP guide

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.

This part outlines how SIP is one innovative technology that actually helps improve communications without complicating these issues.

What Is SIP?

Session Initiation Protocol (SIP, pronounced just like sip, as in sipping from a fire hose on a hot day) is an open signaling protocol for establishing any kind of real-time communication session. The communication session can involve voice, video, or instant messaging, and can take place on one of many devices that people use for communicating: laptop computer, PDA, cell phone, IM client, IP phone, and so on. SIP has been developed in the Internet Engineering Task Force (IETF) by common participation from various vendors, including Avaya.

SIP builds on a number of existing communications protocols. Developers and system administrators can easily work with SIP, customize it, and program with it. It is rapidly becoming a standard for service integration (how new services and applications are created and combined) within a variety of wireless and carrier networks, and is gaining momentum within enterprises. This growing acceptance in both enterprise and service provider networks offers the promise of a single unifying protocol that will transform not only communications within an enterprise, but communications between the enterprise and its ecosystem of partners, suppliers, and customers. Is SIP a refreshing solution to simplifying communications? For companies who need to sort out and reconnect the current tangle of disparate communications protocols and programs: Yes!

To understand the power behind this protocol, you need to examine some of the key factors that are driving SIP’s momentum across all aspects of enterprise communications.

Part 1: The Case for SIP

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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. Today, the most up-to-date core SIP specification can be found in RFC (Request for Comment) 3261.

Presenting Presence Services

SIP introduces a new model for communications through its support of presence. Presence enables you to locate a user and determine his willingness and ability to participate in a session, even before you initiate communications. This information, reflected across multiple devices such as IP phones, cell phones, and instant messaging clients, makes communication simple and efficient by helping you to reach the right person at the right time, on the right device.

Presence and preference features enabled by SIP are discussed in more detail in Part 3.

Celebrating User-Centric Communications

Communications today are device-centric. Every device has its own phone number, address, or alias. The more devices you use, the more addresses others need to remember in order to reach you. And without presence, as described in the previous section, communication becomes a guessing game when trying to connect with people, wherever they may be and whatever they’re doing.

SIP Communications For Dummies, Avaya Custom Edition

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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. For example, a typical salesperson may have:

⻬ Three phone numbers (home,

work, cell)

⻬ Text messaging and e-mail on

a PDA

⻬ IM identities on Yahoo!, Google,

MSN, and AOL

With SIP, communications become user-centric once again. A SIP address of record (AOR) provides one unifying identifier that can be mapped across multiple devices and media types. You can think of an AOR as the user’s “public address.” Part 2 explains more about AORs.

Simply put, SIP-based communications are between people, connected together without needing to know which device they happen to be using. No more tracking of multiple phone numbers, e-mail addresses, and IM contact names.

⻬ IM capabilities on a laptop and on

a cell phone

⻬ Four e-mail addresses

All of these identities operate in silos — none is aware of any other. The salesperson’s communications capabilities have not become easier, but more difficult, because of the lack of integration between all of these media types. SIP promises to bring all of these capabilities (and more) back together.

SIP is particularly suited to facilitating communications with mobile devices such as laptop computers, cell phones, and PDAs. Part 3 describes how SIP enables mobile communications.

Nevertheless, SIP still supports the legacy public switched telephone network (PSTN) with its numeric dialing because it’s going to be around for quite a long time. An effort to map PSTN telephone numbers with SIP’s newer user-centric identifiers is discussed in Part 4.

Part 1: The Case for SIP

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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.

The SIP standard is defined in RFC 3261 by the Internet Engineering Task Force (IETF). The IETF is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and its operation. Several neutral consortiums, including SIPit, SIP Foundry, and SIP Forum, arrange meetings and events where companies with SIP-based hardware and software products can test interoperability with other SIP-based products. This testing helps to promote smoother integration of SIP-based products in carrier and enterprise networks. We tackle this subject in depth in Part 5.

Some vendors have gone beyond these efforts with active SIP interoperability and ecosystem programs. In a well-run SIP ecosystem, devices and services obviously need to work together seamlessly, and the only way to ensure that they do is for many kinds of vendors to test their SIP-based products together. For example, Avaya has made a commitment to establishing openness and interoperability for SIP through its Developer Connection program, which support software developers, systems integrators, and service providers in testing interoperability and developing SIP-based solutions with Avaya products and services. You can find more information about interoperability efforts in Part 5.

The impact of SIP goes beyond internal communications within an enterprise. SIP has become a signaling standard for carrier networks. Service providers have started to provide SIP-based trunk services that can reduce costs and extend an enterprise’s SIP environment into the public network. The adoption of SIP for external connectivity will lead to a

SIP Communications For Dummies, Avaya Custom Edition

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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. When you begin investigating ways to transition to SIP telephony, you may feel rather bewildered by the array of protocols, gateways, security constraints, and quality of service issues. A considerable effort is required to plan, build, and operate these multiple media streams that often coexist on shared physical networks. Rush-hour traffic gridlock, by comparison, is an easy problem to solve.

SIP offers the promise of a single unifying protocol for all communications. With SIP being widely deployed in both service provider and enterprise networks, the need for gateways that translate one protocol to another (for example, IP to Time Division Multiplexing, or TDM) is eliminated. Proprietary signaling protocols give way to a single standard interface for all connectivity, whether for adding endpoints, deploying contact center adjunct services, or even connecting to trunk services for external communications. See Part 4 for more details on trunking with SIP.

An equally important foundation of SIP is the concept of distributed intelligence. This concept, evident in exciting new peer-to-peer (P2P) architectures such as Avaya one-X Quick Edition, creates a new paradigm in communications, requiring no PBX or communication server, only intelligent phones and other endpoint devices as the mechanism for establishing a working communications system. We discuss Quick Edition in more detail in Part 6.

SIP scales well for the smallest businesses, where SIP-enabled endpoints can be established in the absence of centralized proxies and registrars. We discuss how SIP can power small offices in Part 6.

Part 1: The Case for SIP

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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.

SIP’s architecture consists primarily of SIP endpoints and SIP servers. Endpoints are also called user agents — the programs and devices that actually perform the communications between end-users. In small organizations, the user agents can be smart enough to communicate to one another without the need for servers. In large enterprises, centralized SIP servers such as proxies, registrars, and presence servers, facilitate user agent communications. SIP components, and even an example call scenario, are found in Part 2.

SIMPLE (SIP for Instant Messaging and Presence Leveraging Extensions) is an important standard that facilitates instant messaging communication. SIMPLE is essentially a standardization of SIP’s presence features. We describe SIMPLE in more detail in Part 2.

Where Will SIP Take Communications in the Future?

SIP, extensible and versatile as it is, continues to grow and evolve. In the near future, you’ll likely see SIP become integrated into business applications with several types of functionality — far beyond simple click-to-call hyperlinks. Applications will be able to make communications routing and other decisions based upon interaction with users.

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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.

SIP may also follow the lead of E911 emergency location services in cellular networks by using a user’s known physical location to make even better decisions about the initiation of communication sessions.

We don’t want to give away all of our predictions here. Turn to Part 7 for more prognostications about SIP.

Part 2

SIP guide

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

IP is an application layer Internet protocol for establishing,

manipulating, and tearing down communication ses-

sions. You can do a lot more with SIP than set up telephone calls. The protocol is designed to be extensible — meaning SIP can be easily extended to accommodate video, instant messaging (IM), and yet-to-be-invented communications media and features. (XML is an example of another extensible language.) Aside from supporting communication call setup and tear down, SIP also currently supports extensions for instant messaging as well as advertising and tracking user availability (both familiar today in Yahoo! and AOL Instant Messenger).

SIP is used to identify, locate, and enjoin parties who wish to communicate using any peer-to-peer media type. However, SIP does not transport the media itself: that is handled by codecs within the communications programs or devices.

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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.

If you use Web browsers (and who doesn’t?), then you already depend on a protocol very similar to SIP, called HTTP (HyperText Transport Protocol) — yep, that bit before a standard Web address that you usually take for granted. SIP is modeled after HTTP, and in fact uses much of HTTP’s syntax and semantics. Both are text-encoded protocols, which means that they are easy to read and debug. This readability promotes integration across a decentralized architecture (such as the Internet) and interoperability across a distributed network. In effect, SIP is to converged communications what HTTP is to information exchange for the World Wide Web (WWW) — it makes the communications infrastructure transparent to end-users and enables ready access to many modes of communication. Just as pointing your browser to an HTTP site enables you to play video, download pictures, or upload files, SIP too has been designed to support multimedia communications.

SIP goes beyond HTTP by embedding in communications the intelligence to sense the media capabilities of the end device as well as the availability of a user to communicate.

Getting Down to One Address for Everything

One key feature of SIP is its ability to use an end-user’s address of record (AOR) as a single unifying public address for all

communications. So, in the world of SIP-enhanced communications, a user’s AOR becomes her single address that links the user to all of the communication devices or services that she uses. For example, user Eileen Dover’s AOR would look like SIP:eileendover@company.com. Using this AOR, a caller

Part 2: SIP at a Glance

SIP guide

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. By applying this style of addressing, SIP can map the unique addresses of a user’s multiple devices and services to a communication domain, and then link all the user agents to a user’s single AOR for that domain. Following are some examples of how this URI might be applied:

⻬ A phone: sip:408-555-1212@company.com;user=

phone

⻬ A fax: sip: 408-555-1214@company.com;user=fax ⻬ An IM user: sip:eileendover@company.com

A user typically has just one SIP AOR, such as eileendover@ domain. Then, each of the user’s devices has its own URI, such as sip:408-555-1214@company.com; user=fax.

SIP “business cards”

One nifty benefit of SIP is how easy it makes the transition for end-users who are still using traditional communications devices, like, um, telephones. For example, imagine professors at a university who want to make it easier for their colleagues, including researchers at other universities, to contact them. To do so, they are replacing multiple contact numbers on their business cards with a single easy-to-remember SIP address. The problem? The university has started to deploy SIP, but most of the professors are still using traditional (analog) phones, and a complete

update to SIP is still years away. As a solution, Avaya Handle-Based Dialing works with the university’s

Directory Access Protocol (LDAP)

directory server to reach any non-SIP phones by translating the SIP AOR in real time to a standard telephone number. Now, the professors can hand out their business cards and be reached at their existing phone through one simple address, such as: SIP: CoolestProf@oncampus.edu. (Part 3 explains how you can also still dial this number on a traditional phone.)

Lightweight

SIP guide

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.

Enabling Voice, Video, and IM, Oh My!

In keeping with the IETF philosophy of defining simple protocols with powerful functionality, SIP follows a peer-to-peer architecture containing a small set of different methods (types of messages). At the same time, SIP is also very modular and extensible, enabling you to integrate SIP into your existing legacy communications environment. As a result, SIP can interoperate with many traditional telephony protocols and scenarios, as well as with emerging communications services. These properties make SIP an ideal protocol for any company implementing a standards-based converged communications network.

SIP is not designed simply to replace the PSTN. Rather, SIP goes well beyond traditional telephony by facilitating any type of peer-to-peer communication session, instant messaging, video gaming, conferencing, and collaboration.

SIP is also not designed to be a one-stop shop for protocol needs. You essentially use SIP to set up and tear down media sessions (for example, IM, text, voice, or video communication sessions). SIP combines with other network protocols as well as application-layer technologies to provide complete end-to-end functionality. One such protocol is the Session Description Protocol (SDP), which carries within it information about the session that you’re setting up (namely, the type of media, the codec to use, and the protocol for actually transporting the media).

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