Sip Trunking for the Enterprise whitepaper Authored by: Steve Shepard, President Shepard Communications Group, LLC Commissioned by XO Communications

1. SIP For Enterprise:
White Paper
and What It Can Do For You
Written by Steven Shepard, President, Shepard Communications Group, LLC
xo.com

2. SIP for the Enterprise
And What Can it Do For You
Authored by: Table of Contents
Steve Shepard, President
Shepard Communications Group, LLC SIP for the Enterprise — How Did We Get Here? 1
Commissioned by XO Communications
What Exactly is SIP? 1
The Combination for Success — The New Age is Here 2
What is Enterprise SIP (ESIP)? 2
Key Advantages and Business Benefits of Enterprise SIP 5
Advantages 5
Key
Business Benefits 5
Options When You Have a Private Network Already in Place 6
Added Business Continuity 6
Is an Enterprise SIP Solution Right for You? 6
Summary 7
2 Solutions you want. Support you need.

3. XO Communications
SIP for the Enterprise — How Did We Get Here?
Over the last ten years, telephony as a service has evolved. How it works, what it does, and
how it is used by both consumers and businesses has changed. The telephone network
was originally designed to transport voice calls, something it did well. Over time, the mar-
ket demanded much more. In response, and thanks to the signaling network known as SS7,
the Public Switched Telephone Network (PSTN) was enhanced to deliver a broader array of
supplementary services.
Enter the debut of the Private Branch Exchange (PBX) which put more control into the hands
of the enterprise’s technical support personnel. The Internet and Internet Protocol (IP) became
accepted and pervasive. With the introduction of Voice over IP (VoIP), the cost and complexity
of operating the network declined (a boon to the service provider) and the range and richness
“When SIP is deployed in the of services available to the customer increased.
network, telephony becomes a The diversity of the telecommunications services demand profile forced a redefinition of the
Web application. It integrates network architecture by which services are delivered. Instead of delivering services from deep
seamlessly with other Internet within the core of the network, it became more efficient to move the point of delivery out to
the edge, particularly for enterprise companies. But because SS7 was designed as a core-
services, and the convergence
based protocol, it could not meet the new demands being placed on the network. A new solu-
of voice and data including tion was required; that solution is the Session Initiation Protocol, commonly known as SIP.
video, audio and image transfer
becomes real.”
What Exactly is SIP?
Like SS7, SIP is a signaling protocol designed to set up communication sessions in a net-
work, but this time, in an IP network. These sessions include everything from a simple phone
call to a multi-location, multimedia conference.
Because SIP was designed to support a wide array of service types, new and innovative
capabilities become possible such as Web page click-to-call, Instant Messaging with incor-
porated buddy list access, and IP PBX support.
SIP is a simple, command-response protocol that is operationally similar to the protocol that
governs the functionality of the Web: HTTP. When SIP is deployed in the network, telephony
becomes a Web application. It integrates seamlessly with other Internet services, and the
convergence of voice and data including video, audio and image transfer becomes real.
SIP has become the basis for the next-generation network. It undoubtedly will be deployed by
all service providers, from traditional wireline players, to mobile providers, to cable compa-
nies offering VoIP, to ISPs.
SIP facilitates the delivery of everything from traditional voice services to a host
of capabilities such as convergence, IMS, femtocell deployment, online gaming, voice and
video conferencing, among many others. And SIP is an internationally recognized standard (a
subset of the IP protocol suite), meaning that interoperability is a non-issue.
3

4. SIP for the Enterprise
The Combination for Success — The New Age is Here
The flexibility and richness of IP is combined with the highly customizable nature
of the PBX, creating the IP-PBX. The result is extraordinary.
Now we have technology emerging with the power to redefine the way businesses
communicate. The flexibility and richness of IP, the power and control of the
PBX, and the breadth that SIP brings to the table shine a bright light for Enterprise
businesses. Enterprise SIP is the optimal result.
What is Enterprise SIP (ESIP)?
Network gurus for multi-location businesses know the process of interconnecting the
“In addition to hosted unified branches to facilitate effective site-to-site communications is complicated, expensive and
communications, SIP trunking time-consuming.
and its offspring like XO
In many cases companies rely on several service providers to provide full connectivity across
Enterprise SIP will be the their entire enterprise geography. As service demands change, when
transport with which unified more bandwidth is required to a particular site, for example – the modifications required to
communications is carried.” make that happen can be costly in terms of both money and time.
To further complicate matters, many multi-location businesses have grown through acquisi-
tions and mergers, resulting in an inherited mix of on-premise equipment types and local
~ Rebecca Swensen, IDC
services. This collage of premise configurations makes seamless site to site communications
and a unified customer experience next to impossible.
The solution? Enterprise SIP.
Enterprise SIP is a powerful new solution designed for multi-location businesses that enables
the business to serve its distributed branches with telephone service through one or a hand-
ful of centralized PBXs. It can provide centralized trunking and eliminate the need for PRIs or
business lines at each location.
Enterprise SIP also enables the business to carry all voice and data over its private Wide
Area Network (WAN), resulting in more efficient use of the network. It does all of this with
built-in load-sharing capabilities to provide bandwidth where and when it’s needed to fully
satisfy demand. Some SIP for the Enterprise services also provide bursting capabilities to
accommodate seasonal demands or catastrophic network events.
4 Solutions you want. Support you need.

5. XO Communications
Before Enterprise SIP, it has been common for a multi-location business to have a telecom
infrastructure similar to the network illustrated in Figure 1.
Because of the company’s many locations, it was often necessary to engage multiple
service providers to ensure connectivity between each location’s PBX and the Public
Switched Telephone Network (PSTN). In most cases, these connections were either ISDN PRI
connections or IP trunks.
Figure 1: Typical SIP
Configuration before an
Enterprise SIP deployment.
Branch 2
Provider
2 Branch 4
Branch 1 Branch 3
Provider
ILEC Provider
1
Provider
3 4
#1
PRI DIA #1
+
+ +
+
+
Provider
Headquarters 5
Provider Provider
8
7
DIA #2 Provider
6
ILEC
#2
+
PRI + +
+
+ Branch 5
Regional Office
Branch 6
Branch 8
Branch 7
5

6. SIP for the Enterprise
With the arrival of Enterprise SIP, things change.
Instead of connections to each branch and through multiple carriers, it is now possible to
provide an increased level of connectivity, with added redundancy – by consolidating those
connections through a small number of locations and with a single carrier, while saving costs
and streamlining telecom operations, as shown in Figure 2.
Figure 2: Simplified
connectivity following the
introduction of an Enterprise
SIP deployment.
MPLS IP-VPN Network
Branch 2
Branch 1 Branch 3
Branch 4
Headquarters
Failover XO Communications
Branch 5
Regional Office
Branch 8 Branch 6
Branch 7
6 Solutions you want. Support you need.

7. XO Communications
Key Advantages and Business Benefits of Enterprise SIP
Not only does Enterprise SIP eliminate the need to buy and manage lines for each and every
location, it also streamlines the operation of the telecommunications infrastructure using a
centralized PBX, rather than managing multiple, disparate systems at the premise.
Key Advantages:
• Lower operating costs through centralizing communications facilities
• Reduce location equipment needs and connectivity requirements
• Enable flexible redundancy
• Allow bursting: capacity can be shared seamlessly and fluidly across the entire enterprise
when needed
“Not only does Enterprise • Use existing WAN for voice communications, resulting in more dynamic and efficient network
resource utilization
SIP eliminate the need to
buy and manage lines for
Business Benefits
each and every location, it
also streamlines the operation A primary and most important benefit that comes from Enterprise SIP is the degree
of control that a customer enjoys, and the flexibility that it makes possible.
of the telecommunications
infrastructure using a centralized 1. Consolidating voice and data over a single, converged IP network greatly reduces the cost and
PBX, rather than managing complexity of administration and management. Fundamentally, costs are reduced as the capacity
required for voice and data sessions is shared across the entire network.
multiple, disparate systems at the
premise.” 2. Centralizing the PBX equipment in one or a few sites results in capital savings, greater control over site
to site calling, and a unified customer experience. The headache of trying to control communications
across a myriad of premise configurations is gone, leaving only a router and phones at the premise.
3. Enterprise SIP allows for the consolidation of local and long distance inbound and outbound call-
ing across the entire enterprise, regardless of the calling and called parties’ physical locations.
4. Enterprise SIP makes bandwidth management easy. By allowing for instantaneously available
bandwidth on a demand basis, inbound and outbound calls always have adequate resources avail-
able to them.
5. And finally, Enterprise SIP allows for traffic prioritization: Voice can always be assigned the highest
priority among the various traffic types using the connection, thus guaranteeing assured quality-
of-service (QoS).
Of course these provide just a taste of benefits apparent to a business with
Enterprise SIP.
7

8. SIP for the Enterprise
Options When You Have a Private Network Already in Place
In many cases, companies have already invested in their own private networks, typically
MPLS IP VPNs, but sometimes Private Lines or even Dedicated Internet Access. Enterprise
SIP allows a company to take advantage of that investment by overlaying voice calling on the
existing network, further stretching the investment made. For example, XO even allows SIP to
be used with another carriers data network. Those same companies may have also invested
in VoIP as part of their evolution and now Enterprise SIP allows them to take advantage of
those investments through seamless integration of those assets into the mix. And because
the enterprise most likely has its own highly-skilled IT department with deep knowledge
of network and system performance, discrete control of network availability and service
performance can be conducted in-house. This results in differentiable quality-of-service and
assured business-class call quality across the enterprise.
Added Business Continuity
Network Survivability is critical to most companies, and because Enterprise SIP relies on IP,
a broad array of business continuity options become possible. These options are much more
difficult – and expensive – to deliver over the legacy switched network. If one route becomes
unusable or excessively congested, Enterprise SIP re-routes the connection across an
alternate route, with no change in quality of service.
Finally, because the service can be delivered by a single provider, far more flexible pricing is
available due to the consolidation of resources. The power accrues to the customer. It doesn’t
get much better than that.
Is an Enterprise SIP Solution Right for You?
So how do you know whether Enterprise SIP is an optimal solution for your
business? Ask yourself these questions:
1. Do you have more than five operating locations?
2. Does the geographically-dispersed nature of your company have you
using more than one carrier for your telecommunications needs?
3. Do you have inadequate leverage with your carriers?
4. Are you spending too much for long-distance connections and voice calling?
5. Are you spending too much capital on media gateways and PBX
network connections?
6. Are you uncomfortable with the level of survivability available in your network?
7. Could you get more value out of your IP-PBX installation?
If you answered ‘yes’ to one or more of these questions, then your business may be a viable
candidate for an Enterprise SIP solution.
The cost savings, added functionality and survivability alone make it a technology
progression that is worth serious consideration.
8 Solutions you want. Support you need.

9. Summary
1. Eliminate the need to purchase and manage multiple business lines from distinct service providers.
2. Consolidate local and long distance services and helps to accelerate the transition to VoIP less a
significant up-front investment.
3. Offer a high capacity connection to primary locations that in turn connect
to your private network, as required, to serve additional branches.
4. Take advantage of service delivered by a single provider, with far more flexible pricing due to the
consolidation of resources. The power accrues to you; the customer – it doesn’t get much
better than that.
About Steve Shepard
Dr. Steven Shepard, Ph.D. is president of the Shepard Communications Group. A professional writer, educator
and industry analyst with more than 25 years of experience in the technology industry, Dr. Shepard specializes
in international telecommunications issues, the social implications of technological incursion and the analysis of
financial issues related to technology-dependent businesses. He is the author of 45 books on a wide variety of
topics and regularly speaks to audiences throughout the world, and has clients in more than 50 countries.
Mr. Shepard can be reached at Steve@ShepardComm.com.
About XO® Enterprise and serves over 25,000 businesses with VOIP services.
In addition to providing integrated voice and data ser-
SIP
vices to businesses and enterprises, XO also powers
many other telecom providers’ VoIP infrastructure with
XO Communications has exper-
high volume VoIP Origination and Termination services.
tise in enterprise networking,
particularly with next-generation network architectures,
and makes for a powerful partner for your enterprise
connectivity needs. The XO® Enterprise SIP solution
For additional information:
provides a complete, end-to-end option for organiza-
tions with the challenge of interconnecting multiple Please visit XO Communications at www.xo.com or
geographically-dispersed locations. With over nine call directly at 888-718-7595 for more information or
years’ experience in owning and operating a VoIP-based a complimentary service evaluation.
solution, XO carries over 25 Billion VoIP minutes annually
© Copyright 2012. XO Communications, LLC. All rights reserved. 9
XO, the XO design logo, and all related marks are registered trademarks of XO Communications, LLC.

10. 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, carri-
ers, 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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© Copyright 2012. XO Communications, LLC. All rights reserved.
XO, the XO design logo, and all related marks are trademarks of XO Communications, LLC.