why sip makes sense

7/30/2019 Why SIP Makes Sense

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White Paper

xo.com

Why SIP Makes SenseEnabling the Evolution to

Unifed CommunicationsWritten by Steven Shepard, President, Shepard Communications Group, LLC


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Why SIP Makes Sense

Contents

Abst ract 3

Introduct ion: The Evolution to Unifed Communications 3

Setting the Stage 3

Enabling the Evolution 4

Signaling the Future 4

Overview o the SIP Signaling Protocol 5

SIP Advantages and Applications 6

1. Intelligence at the Edge 6

2. SIP Is Part o the Overall IP Suite 6

3. Supports Any Network Transport Medium 6

4. Mobility and Presence Support 7

5. Virtual Numbers 8

6. Business Continuity and Disaster Recovery 8

7. Supply Chain Support 9

8. Unied Communications and Conerencing Applications 9

SIP Trunking and Cost Benefts 10

SIP Trunks 10

Reduced Network Service Costs 11

Eliminating PRI Trunks and IP Conversion Devices 12

Evolutionary Migration Path 12

Considerations or Implementation 12

Interoperability 12

Security 12

E911 Requirements 13

Conclusion: Making the SIP Decision 13

The XO Advantage 14

About Steve Shepard 14Appendices 14

About XO Communications 16

2 Solutions you want. Support you need


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XO Communications

Abstract

Written specically or IT decision makers in medium to large-sized businesses, this white

paper presents an overview o the Session Initiation Protocol (SIP) standard, its drivers,

benets, and barriers to implementation. The paper presents several business applica-

tions or SIP trunking and discusses the advantages o SIP as an enabler or Unied

Communications. Because SIP has become the de acto industry standard or IP telephony

development, the paper concludes that businesses and enterprises o all sizes will be well

served i they consider SIP as part o their evolving network strategy.

Introduction: The Evolution toUnifed Communications

Setting the Stage

Remember the rst mobile phones? You could always tell when someone had one: they

walked hunched over like Quasimodo because o the heavy battery inside. We all coveted

them everybody wanted one. They were so desirous that in the mid-80s the Sharper

Image Company actually sold a ake cell phone that had a suction cup on the end o the

handset cord that could be axed under the dashboard, allowing the owner to drive down

the street looking cool.

Remember the rst laptops? They were equally cool; we all wanted one o those as well.

But Id be willing to bet that very ew people reading this paper today carry a laptop

because its cool. My suspicion is that they carry a laptop because it has theirstuon it.

All the Microsot Word documents, spreadsheets, presentations, images, PDF documents,

sound les, music, movie clips, and other digital paraphernalia that our work and personal

lives require are typically resident on our computers and must, thereore, accompany us

wherever we go.

However, what i the need to have the physical computer were to go away? What i there

was a way to have access to work-related content atanytime, anywhere in the world, on

any network, using any access device over any access technology? Would that not sim-

pliy lie dramatically and make use o the network more ecient and relevant? Well, that is

more than a possibility it is becoming a reality today.

Te growing prolieration

o Unied Communications

(UC) technology in the

workplace is enabling anytime,

anywhere communications.


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Why SIP Makes Sense Enabling the Evolution to

Enabling the Evolution

Three phenomena are making this evolution possible:

Inexorable, steady migration o contentrom the hard drive on the users device (PC or lap-

top) to storage arrays located within the network and managed by the network provider

or hosted by the enterprise.

The growing prolieration o Unied Communications (UC) technology in the workplace,

which is enabling anytime, anywhere communications. UC applications include IP tele-

phony, unied messaging (i.e., voicemail, email, ax), instant messaging, presence, web/

rich media conerencing, document sharing, and the support or Internet Protocol (IP)

applications supported across dierent device types, including smart phones, and sot-

phones, such as laptops. Driving the adoption o UC is the growth o IP telephony, which

has already overtaken TDM in the enterprise. According to industry analysts, 74.2% o

telephony ports shipped worldwide in 2009 were or IP systems, expected to reach over

90% by 2016.1

The extension o the Internet Protocolas an application layer signaling protocol in the

telecommunications network inrastructure, or both wireline and wireless networks. SIP

enables the suite o IP-based Unied Communications applications to be extended rom

PBX systems and/or an IP network across dierent network transport services and end

user devices to support remote sites and mobile workers. In essence, it allows any user on

any network to have access to any content on-demand, regardless o their physical loca-

tion, the device theyre using, or the access modality theyre employing. How important is

SIP in enabling Unied Communications? According to Frost & Sullivan, End-to-end IP

communications that do not require protocol conversion anywhere between the customer

endpoints and the service provider data center will eventually deliver better quality and

greater eciencies to businesses deploying unied communications. SIP trunking, there-

ore, becomes a driver o IP telephony and UC adoption.2

This three-part migration acilitates a number o advantages, including increased enterprise

productivity through improved support or distributed workorces, timelier and higher qual-

ity responsiveness to customers, and reduced capital expenses (CAPEX) and operating

expenses (OPEX) or telecommunications inrastructures. And it gets even better. Using SIP

helps reduce the cost o networking, plus SIP trunks ree the customer rom being locked

into a specic system vendor or network provider now and in the uture.

Signaling the Future

Signaling the process o establishing a call, invoking enhanced services required or the

call (many based on the Caller ID unction), maintaining the call, and tearing it down at the

end is perormed by protocols that are part o the Signaling System 7 (SS7) network,

Driving the adoption o UC

is the growth o IP telephony,

which has already overtaken

DM in the enterprise.

According to industry analysts,

74.2% o telephony ports

shipped worldwide in 2009were or IP systems, expected to

reach over 90% 2016.

1 IP Systems numbers include converged and native IP. Frost & Sullivan, Worldwide Enterpr ise Telephony

Platorm and Endpoint Markets, June 2010.

2 Frost & Sullivan, World Unied Communications Markets: Business Models Evolve as Technologies Mature,

February 2010.


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XO Communications

a unctional adjunct to the Public Switched Telephone Network (PSTN). However, as the

migration to Internet Protocol (IP) continues, SS7 protocols are being replaced with IP pro-

tocols, most notably the Session Initiation Protocol, or SIP.

Service providers have upgraded their network platorms to provide value-added ea-

tures and applications that dierentiate their oerings and complement the SIP standard.

One such eature is virtual numbers, a signicant benet or companies with a distributed

workorce and customer base. Business continuity and network disaster recovery can also

be elements in a SIP environment, aecting not only customer service, but also providing

network managers with additional ways to improve network availability.

This paper presents an overview o the ongoing SIP migration, including an explanation o

what it is, how it works, and why it is important to businesses today.

Overview o the SIP Signaling Protocol

SIP is an application layer protocol that is used to establish, maintain, modiy, and end

communications sessions between two or more parties. As such, it can establish and

manage:

Two-party, multiparty, or multicast sessions

Internet telephony

Distribution o multimedia content

Management o multimedia conerences

SIP is designed to be completely independent o the transport layer and can operate over

the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), or the Stream

Control Transmission Protocol (SCTP). SIP-based clients (devices) use TCP or UDP proto-

cols to connect to SIP servers.

The primary driving orce behind SIPs development and deployment was the perceived

need to develop a signaling protocol or IP-based networks that can support the standard

call processing unctions ound in the PSTN. The SIP protocol itsel does not dene these

eatures, but enables their creation in network elements, such as proxy servers and user

agents. These eatures include digit collection, call ring, ring back, busy tone, and ast busy

or reorder. And while the manner in which these unctions are delivered in an IP-based SIP

environment is somewhat dierent rom the PSTN, the overall result is identical.

SIP is exible and

extraordinarily dynamic. Its

unctionality can be extended

to any number o applications,

including enhanced signaling

or valueadded services, VoIP,

and XMLtagged applications.

Copyright 2012. XO Communications, LLC. All rights reserved. 5

XO, the XO design logo, and all re lated marks are registered trademarks o XO Communications, LLC.


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SIP Advantages and Applications

When deployed in a network, SIP o ers distinct advantages that can be used to develop

powerul and compelling end-user applications. For example:

1. Intelligence at the Edge

SIP-enabled telephony systems oer most o the call processing and eature invoca-

tion procedures oered through traditional voice networks but in a dierent way.

Traditional voice networks use a hierarchical, centralized, core-based protocol designed

around the limited requirements o telephone sets which have no innate intelligence.

SIP, on the other hand, is apeer-to-peer protocol, which requires a dierent type o

network core inrastructure (preerably MPLS built on an IP platorm) with a blend o

intelligence located at the edge (i.e., sotware or end-user device hardware or PBX),

complimented by more scalable, granular, and rapidly deployed services oered by

service providers.

2. SIP Is Part o the Overall IP Suite

As part o the overall IP suite, SIP is fexible and extraordinarily dynamic. Its unctional-

ity can be extended to any number o applications, including enhanced signaling or

value-added services, VoIP, and XML-tagged applications. Because XML is used to

structure, store, and send inormation across the network, it works well with SIP in

environments where data needs to be retrieved and used, as in a call center environ-

ment where customer records must be accessed, or in a healthcare environment where

access to customer data is critical. As a lightweight, text-based protocol, SIP relies on

a text-based command structure that uses the now universally amiliar HTTP syntax and

URL addressing, both ideal or delivering telephony over an IP network where the logica

integration o applications (e.g., voice, messaging, conerencing, and Web access) cancreate an enhanced user experience.

3. Supports Any Network Transport Medium

Because SIP is anapplication layer protocol, it can ride seamlessly across any transpor

scheme and be transported across any access modality cable, DSL, private line,

Ethernet, and wireless. Thus, SIP can enable a broad range o applications and remote

session capabilities (such as mobile application delivery and supply chain management)

without the need to provision additional transport services. From an enterprise point-o-

view, this is critical because SIP oers seamless connectivity options or service deliv-

ery or branch locations, remote workers, or trading partners. Since U. S. enterprises

with 500 or more employees have an average o 62 branch oce locations, with anaverage o 53.5 employees per location,3 this is a signicant benet or the enterprise.

3 Frost & Sullivan, Trends in Communication Services and Solutions or Small Businesses and Branch

Oce, 10 Sep 2008.


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4. Mobility and Presence Support

SIP is now incorporated into a range o user devices, including mobile wireless devices

and desktop clients. Using SIP, session establishment requests are not sent to a device

they are sent to the network, which locates the users presence and establishes a

session based on the users current location and usage prole. Because SIP unshack-

les users physical location rom their logical address, they can have ully integrated

corporate communications regardless o location. They can also integrate instant

messaging and desktop collaboration applications.

Presence is a relatively new concept in the networking arena. The users client pub-

lishes his or her availability within the presence application, and all users then have

access to that persons availability via all services oce wireline voice, mobile,

e-mail, chat, etc. Users can customize their availability prole and publish it or the

world to see, thus making communications much more ecient. In short, SIP is the

protocol that supports the universal availability o presence inormation.

Example: An inbound call center might use presence to ensure that a customer has the

ability to get back in touch with a call center agent who was helping them with a techni-

cal support problem. With presence, the agent would not have to be in the call center,

but could be located by the network and have the call routed to them, regardless o

where they actually are, thus making it possible to ulll and exceed customer service

requirements without reliance on a physical call center presence (see Figure 1).

Because SIP unshackles users

physical location rom their

logical address, they can have

ully integrated corporate

communications regardless

o location. Tey can also

integrate instant messaging

and desktop collaboration

applications.

Figure 1. The caller places a call to a specic agent in call center (yellow arrow, lower right), but

because the agent is out o the oce, SIP routes the call to their remote location (blue arrow, lower

let), thus avoiding a service disconnect with the customer.


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5. Virtual Numbers

A th advantage is the ability to utilize virtual numbers, an assignable telephone num-

ber that has no physical phone line associated with it. In most cases, virtual numbers

are orwarded to either a VoIP account or to an alternate xed or mobile number. For

example, virtual numbers are perect or sales orces, business travelers, small busi-

nesses, and eld service personnel. With virtual numbers, businesses can also create a

local identity in markets that the company serves.

Example: Imagine a business serving customers in multiple, ar-fung locations, such as

Dallas, Los Angeles, and New York City. The company seeks to create a local identity

in these markets by publishing phone numbers with local area codes instead o toll ree

numbers. They would also like to route the call to specic individuals supporting each

market. The company, which is headquartered in Chicago, might purchase virtual Direct

Inward Dialing (DID) numbers rom their service provider with area codes in Dallas, Los

Angeles, and New York City, giving customers the impression that the company has

a local presence in those locations a major element o a customer-riendly contact

strategy (seeAppendix A).

6. Business Continuity and Disaster Recovery

SIP trunks, in concer t with VoIP, can play a major role inbusiness continuity and

disaster recovery. With a SIP-supported IP PBX, many businesses are now able to

design disaster recovery plans using plug and play phones, sotphones, and IP PBX

programmability capabilities. Whats more, automatic reroute in IP environments is

possible, thus reducing the headache o planning or every contingency. For businesses

o any size, SIP trunks provide connections to the PSTN so that outbound calls can

be rerouted and delivered over an Internet connection when the normal connection (or

location o the connection) is unavailable.

Example: Workers can setup their laptop rom home or a remote location as a vir tual

oce, using the sotphone capability that can support presence to detect online sta-

tus o company employees, customers, and trading partners. Additionally, IP PBXs can

be programmed to redirect calls in seconds to dierent phones or locations in the event

o an outage at key company locations.

In addition, business-class service providers build multiple layers o redundancy into

their networks to provide or business continuity. A carrier should provision network

session capacity to support ailover o trac between designated sites. Service provid-

ers also should track session usage or each o their customers sites and implement a

primary/backup arrangement to manage overfow trac. When sessions in one site areully used, the network automatically routes inbound trac, normally delivered to the

rst site, to the second site.

Because as many as 91%

o employees work outside

o headquarters oces,

collaborative applications that

overcome the challenges o

distance are key.


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7. Supply Chain Support

The overall supply chain is enhanced when executed in a SIP environment. By con-

verging its voice, data, and expanding video/rich media applications, businessescan

enhance the end-to-end supply chain, thus measurably improving their eectiveness

and eciency.

Example: Mobile inventory tracking devices not only speed up the overall execution o

supply chain management, but also reduce the errors associated with the logistics o

tracking constantly changing inventory. Supply chains are also early adopters o Unied

Communications applications.

8. Unifed Communications and Conerencing Applications

Because as many as 91% o employees work outside o headquarters oces,4 collabor-

ative applications that overcome the challenges o distance are key. Videoconerencing

has slowly become a part o this equation, but the cost and diculties traditionally

associated with setting it up and the need to go to a specic location to use it have

been showstoppers. Thus, videoconerencing and SIP have combined orces. Not only

do they oer anywhere, anytime video, but they also make it possible to incorporate

presence, screen sharing, Web sharing, and instant messaging.

Example: Customers and suppliers located thousands o miles apart can use vid-

eoconerencing and collaboration tools to review and modiy design specications.

Moreover, training events can be held more requently and e ectively by leveraging rich

media application that can be delivered on-demand or in real-time.

Accelerating the growth o Unied Communications will be the adoption o

Microsots Oce Communications Server (OCS), launched in 2007. OCS is a Unied

Communications client that helps people be more productive by enabling them to com-

municate easily with others, using a range o communication options. Among its key

eatures are support or enhanced presence and enterprise voice capabilities, enabling

users to place computer-to-computer calls and to place outbound calls to (and accept

incoming calls rom) traditional PBX / PSTN phone users.

Whats the Unied Communications orecast? Growth in UC and UC-capable clients is

expected grow rom 15.4 million vendor shipments in 2009 to 25 to 30 million in 2015.

The installed base o ully integrated UC solutions is orecasted to grow rom 2.1 million

users in 2009 to approximately 50 million users by 2015.5

4 Irwin Lazar, Nemertes Research, Leveraging Convergence or Collaboration: Meeting the Challenges O The

Virtual Workplace, 2007.

5 Frost & Sullivan, World Unied Communications Markets: Business Models Evolve as Technologies Mature,

February 2010.

Te installed base o ully

integrated UC solutions is

orecasted to grow rom 2.1

million users in 2009 to

approximately 50 million users

by 2015.5


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SIP Trunking and Cost Benefts

With these advantages in mind, lets now take a closer look at SIP trunking and the cost

benets that SIP trunks make possible.

SIP Trunks

SIP trunks are one o the more remarkable oshoots o the SIP amily o capabilities and

one o the more important enablers o SIP-dependent applications. SIP trunks are nothing

more than virtual circuits congured and delivered over an Internet connection, typically via

the private IP backbone o a VoIP-enabled carrier, as shown in Figure 2.

SIP trunks are oten used in conjunction with an IP PBX as replacements or evolutionary

next stages rom traditional ISDN PRI or analog circuits. In act, many analysts believe

that SIP trunks will ultimately replace T1 acilities in business networks. SIP trunks not only

make network deployment more fexible, but also make possible the seamless assurance

o operational continuity in the event o a network ailure. Their popularity, which is growing

rapidly, is largely due to a collection o actors, including cost savings and overall reliability.

Some o the more relevant cost benets are as ollows.

Figure 2. SIP trunks enable convergence to one IP connection over a standards-based con-

nection, eliminating the need or TDM-IP gateways.


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Companies that are not

ready to replace their legacy

DM PBXs but wish to

deploy SIP trunks can deploy

media gateways at branch

oces to convert DM voice

communication into IP voice

trac (and vice versa), instead

o installing a brand new IP

system.

Reduced Network Service Costs

Convergence implies that a single connection can serve multiple access requirements.

With SIP trunks:

Voice and data applications ride over one IP connection, instead o separate voice and

data services. According to Gartner, their clients report that savings o more than 40%

can be realized by replacing the Primary Rate Interace (PRI)/T1 and other TDM trans-

ports with SIP trunks. This typically amounts to a savings o more than $4,500 annually

or every PRI/T1 replaced with equivalent SIP trunks throughput, based on gener-

ally available commercial rates in North America, and more savings in other regions.

Furthermore, enabling trunk aggregation at the centralized site can achieve economies

o scale and improve utilization eciency. 6

The connection is highly ecient because unallocated SIP bandwidth is automatically

and dynamically made available or other uses and applications as required (see Figure

3). Added voice compression is available rom some service providers, such as XO

Communications, enabling higher throughput and eciency as well.

On-net dialing plans can be established amongst a companys locations and connected

via SIP trunks, resulting in lower toll costs as well (see Appendix B).

6 Gartner, User Exper iences Reveal Best Practices or Deploying Unied Communications, 21 June 2011.

Figure 3. Real-time IP dynamic bandwidth allocation gives priority to voice trac butmakes additional data bandwidth capacity available when phone lines are not in use.


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Eliminating PRI Trunks and IP Conversion Devices

SIP trunks eliminate the need or PRI PBX cards and IP conversion devices on the customer

premises, typically reerred to as TDM-IP gateways. This device supports the conversion rom IP

packets to PSTN trac, which is normally transmitted over an ISDN PRI. In addition to hardware

savings, better throughput is also achieved by minimizing a protocol conversion step.

Evolutionary Migration Path

Companies that are not ready to replace their legacy TDM PBXs but wish to deploy SIP trunks

can deploy media gateways at branch oces to convert TDM voice communication into IP voice

trac (and vice versa), instead o installing a brand new IP system. Thus, legacy TDM PBXs

placed in multiple sites are being interconnected via IP networks with the help o gateways that

transorm the PSTN trac into VoIP packets.

Considerations or Implementation

Interoperability

As IP PBXs have come booming into the market, problems o interoperabil ity have arisen with

regard to SIP. Almost all o the rst-generation IP PBXs on the market were designed around pro-

prietary IP signaling stacks because universal agreement on a single protocol had not yet been

achieved. Ultimately, SIP was chosen as that universal protocol, and PBX manuacturers wrote

proprietary interaces or their legacy TDM interaces. This created problems or developers

looking to write interaces or VoIP environments built on media server platorms, as well as com-

plications that required system-by-system interoperability testing or, in some cases, the creationo sotware interaces to perorm a protocol conversion that ensures interoperability beyond very

basic connect-and-disconnect capabilities.

Security

Thanks to new encryption capabilities such as SIP Transport Layer Security (TLS) and Secure Real-

Time Transport Protocol (SRTP), security vulnerabilities are no longer a major issue or SIP imple-

mentations. Just as most enterprise organizations encrypt the data that transverses their network,

they are requesting that VoIP providers encrypt voice and data packets transmitted over their VoIP

networks. Encryption provides customers with an added layer o protection to maintain privacy o

VoIP communications and helps prevent unauthorized access to voice conversations.

Business-grade service providers oer enterprise SIP customers a choice o either or both o the

industry signaling standards or encryption: SIP TLS and SRTP. TLS is based on the earlier Secure

Sockets Layer (SSL) method o encryption and uses cryptography to provide endpoint authentica-

tion and communications privacy over the internet. SRTP was developed by a small team rom

Cisco and Ericsson and denes a prole o RTP, intended to provide encryption, message authen-

tication and integrity, and replay protection to the RTP data.


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E911 Requirements

SIP and Unied Communications extend the mobile nature o VoIP by enabling

communications on a range o wireline and wireless devices that are not tethered to a

physical location address. Todays VoIP-enabled, Internet-based phones oer multiple

eatures or convenience o use that allow callers to use phones rom virtually any Internetconnection. While this technology has many benets or end users, it has created many

challenges or emergency communications call centers that were designed to receive

calls rom landline phone services associated with a xed address. So, how does a

carrier provide E911 services to remote locations; and what are the legal requirements or

providing back up and E911?

Interconnected VoIP service providers are required to comply with enhanced 911 rules

adopted by the FCC that are designed to integrate nomadic interconnected VoIP services

with the existing PSTN emergency 911 system. Careul planning and proper service

provisioning help to ensure phone users in all locations have accurately set up

E911 capabilities.

To provide E911 service to distributed users on a centralized, shared SIP trunk, the callers

telephone number must be provisioned so that the E911 service is programmed to ring

to the caller assigned local emergency dispatch call center, rather than to a center miles

away, across the region or across the country. Nomadic, or wireless 911 users require

a dierent solution rom a xed-IP E911 solution because the VoIP service provider

normally delivers the service to a stationary location. Providers that oer enterprises a

nomadic E911 capability enable employees to move their phones and still get the proper

address inormation transmitted to the Public Saety Answering Point (PSAP), as long as

the nomadic VoIP user keeps their inormation up to date. Updated inormation must be

provided by the user via location update unctionality provisioned by the service provider.

Conclusion: Making the SIP Decision

Like any large-scale technology shit, the move to SIP should be undertaken only ater con-

sidering all options and determining that a SIP migration strategy is the right move or the

enterprise. In most cases it will be but it makes sense to ask the questions. Furthermore, it

is criticalto seek the advice o SIP-seasoned proessionals beore undertaking the migra-

tion. The move to SIP is a relatively straightorward process. However, there is a level o

complexity associated with it that demands the help o a service provider already amiliar

with the overall process. This is what they do use them to your advantage.

SIP is a undamentally important technology in the evolving converged network and will

play an increasingly important role in enterprise and SMB networks in the very near uture.

The advantages listed above and the applications described in this paper are clear indica-

tors o its relevance as a protocol and as an enabler o service provider relevance in the

uture. SIP, like VoIP, is a when rather than aniquestion in todays enterprise. Its time

has come, and businesses o all sizes will be well served i they consider it as part o their

evolving network strategy.

Interconnected VoIP service

providers are required tocomply with enhanced 911

rules adopted by the FCC

that are designed to integrate

nomadic interconnected VoIP

services with the existing

PSN emergency 911 system.


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XO

SIP

Regional Office

Pittsburgh

XOSIP

NYC212 Nxx-xxxx

Virtual Number

L.A.213 Nxx-xxxx

Virtual Number

Dallas214 Nxx-xxxx

Virtual Number

PSTN

XOSIP

Servers

XOCertified

IP PBX

Data

Phone

CE Router

HQ

Chicago

Servers

XOManaged

IP PBX

Data

Phone

CE Router

Internet

WLAN

WLAN

XO SIP

Network

The XO Advantage

Investigate your SIP trunking options and savings potential. XO Communications o ers

a ull line o IP telephony oerings, including SIP trunks, Managed IP PBX, Cloud

Communications, and VoIP solutions that integrate MPLS IP-VPN and on-net dialing plans.

XO SIP and ESIP provide direct IP access to the XO private, OC-192 IP network, so you

get the most rom your centralized or decentralized IP PBX Solution. Need to serve many

markets rom a single location? XO SIP Service oers vir tual inbound Direct Inward Dial

numbers that allow customers outside your calling area to make local calls to reach you,

giving you a local presence in markets where you want to be one o many reasons why

SIP makes sense in todays evolution to Unied Communications.

About Steve Shepard

Dr. Steven Shepard, Ph.D. is president o the Shepard Communications Group. A proes-

sional writer, educator and industry analyst with more than 25 years o experience in the

technology industry, Dr. Shepard specializes in international telecommunications issues,

the social implications o technological incursion and the analysis o nancial issues

related to technology-dependent businesses. He is the author o 45 books on a wide

variety o topics and regularly speaks to audiences throughout the world, and has clients in

more than 50 countries. Mr. Shepard can be reached at: [email protected].

Appendices

XO SIP Service virtual DID numbers enable a company to establish a local identity in

several markets they serve. Additionall y, calls can be routed to the appropriate individual

assigned to each number.

XO Communications ofers

a ull line o IP telephony

oferings, including SIP

trunks, Managed IP

PBX, Enterprise Cloud

Communications and VoIP

solutions that integrate MPLS

IP-VPN and on-net

dialing plans.

Appendix A:


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MPLS IP-VPN Network

Headquarters

Regional Office

Failover

Branch 1

Branch 2

Branch 3

Branch 4

Branch 5

Branch 6Branch 8Branch 7

XO Communications

+

+

+

DIA #1

ILEC#1

PRI

DIA #2

ILEC

#2

PRI

Headquarters

Regional Office

Branch 1

+

+++

Provider

1

Provider

3

Provider

5

Provider

6

Provider8

Provider

4

+

Provider2

Provider

7

+

+

Branch 8Branch 7

Branch 6

Branch 5

Branch 2

Branch 3Branch 4

Appendix B:

Beore Enterprise SIP

Ater Enterprise SIP

BEFORE: Enterprises had to work with more than one local carrier to provide separate Primary Rate

Interace (PRI) lines or IP connections to each location.

AFTER: XO Enterpr ise SIP provides high-capacity SIP trunk ing to one or more pr imary locations,

thereby eliminating lines and equipment, gaining business continuity options and sharing capacity or

sessions across the entire enterprise.


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XO911WP-0412

Copyright 2012. XO Communications, LLC. All rights reserved.

XO, the XO design logo, and all re lated marks are trademarks o XO Communications, LLC.

About XO Communications

XO Communications is a leading nationwide provider of advanced broadband communications

services and solutions for businesses, enterprises, government, carriers and service providers.Its customers include more than half of the Fortune 500, in addition to leading cable companies,

carriers, content providers and mobile network operators. Utilizing its unique combination of high-

capacity nationwide and metro networks and broadband wireless capabilities, XO Communications

offers customers a broad range of managed voice, data and IP services with proven performance,

scalability and value in more than 85 metropolitan markets across the United States. For more

information, visit www.xo.com.

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