Enterprises that are adopting unified communications (UC) platforms such as Microsoft Office Communication Server (OCS) must carefully consider and plan how UC will affect their LAN and WAN infrastructures, as well as how their networks may either hinder or improve the performance of a UC solution. Everything from bandwidth considerations, to firewall topology, to end-user habits and experiences must be taken into consideration. If done correctly, enterprises can realize great productivity gains with new levels of collaboration, both internally and with external parties. Reduction of WAN and LAN infrastructure, built to maximum capacity in support of past IP telephony or voice/data convergence efforts, can also reduce costs and lessen management complexity in the long run.

1. Network Considerations for Microsoft
OCS Deployments
by Phil Hochmuth and Zeus Kerravala | November 2009
Executive Summary
Enterprises that are adopting unified communications (UC) platforms such as Microsoft Office Communication Server (OCS) must carefully
consider and plan how UC will affect their LAN and WAN infrastructures, as well as how their networks may either hinder or improve the
performance of a UC solution. Everything from bandwidth considerations, to firewall topology, to end-user habits and experiences must be
taken into consideration. If done correctly, enterprises can realize great productivity gains with new levels of collaboration, both internally and
with external parties. Reduction of WAN and LAN infrastructure, built to maximum capacity in support of past IP telephony or voice/data
convergence efforts, can also reduce costs and lessen management complexity in the long run.
This report examines four case studies of enterprises that have deployed Microsoft OCS Enterprise Voice and evaluates the cost-saving
opportunities, best practices and challenges around each organization’s deployment.
Table of Contents
I. UC as a Strategic Collaboration/Communications Platform vs. PBX Replacement 2
II. Case Studies of OCS Deployments 2
III. OCS and Your Network: Recommendations and Best Practices 8
IV. OCS Costs and Benefits: A Breakdown of Potential Savings 11
V. Conclusions 12
VI. OCS Enterprise Voice Deployment FAQs 13
This custom publication has been sponsored by Microsoft.
© Copyright 2009. Yankee Group Research, Inc. All rights reserved.

2. Network Considerations for Microsoft OCS Deployments
I. UC as a Strategic Collaboration/ important trend—among these examples is that these enterprises
Communications Platform vs. are deploying UC and OCS as more of an application, independent
PBX Replacement of the network layer, as opposed to a service tied intrinsically to a
Layer 2/3 infrastructure or to proprietary, purpose-built endpoints.
The adoption of enterprise IP telephony systems throughout
the 2000s led to wide-scale replacement of PBX systems with IP The second half of this report breaks down best practices in
PBXs and phones. During this transition, enterprise architectures network-related aspects of OCS deployments, based on lessons
were modified to basically re-create circuit-switched TDM voice learned from the enterprises profiled in the case studies. At the
infrastructures on top of IP networks. Enterprises saw cost end, a TCO guide and FAQ section serve as handy references to
savings from IP/TDM network convergence and management help enterprises and partners know what to expect when rolling
consolidation in return for large and often costly upgrades in LAN out this technology.
and WAN infrastructure to support vendor requirements such
as QoS and traffic segmentation. Traditional IP telephony systems
II. Case Studies of OCS Deployments
do not provide deep integration of telephony with desktop and Many enterprise UC platforms begin as pure IP telephony solutions,
line-of-business applications, do not incorporate the concepts of with features such as unified messaging (voice/e-mail), presence
identity and presence, and may have challenges providing a quality and IM/chat added incrementally though the lifecycles of various
experience on networks where the enterprise does not have end- products. Microsoft OCS differs from other solutions in that it
to-end control (i.e., the Internet). This latter limitation is becoming had no previous IP telephony platform as its base. Components
increasingly important as enterprise workforces become more of the OCS architecture came out of its predecessor, Live
dispersed and mobile. Communications Server (LCS), a solution designed to deliver
all channels of UC in a single integrated package. Each UC tool
Microsoft has taken a different approach, providing IP telephony
included was considered an equally important piece to the entire
functionality as part of an integrated communications software
solution, rather than just a feature added over time. While OCS
suite based on the concepts of identity and presence. Over the
was initially criticized as lacking enterprise-grade telephony features
past decade, the company has built upon its investments, from the
and resilience, the 2007 R2 release of the product introduced these
earlier days of Computer/Telephony Integration (CTI) to H.323
capabilities and positioned OCS as an option to replace incumbent
NetMeeting conferencing, messaging and video, and culminating in
IP telephony solutions within an enterprise.
its current OCS platform.
The following four case studies chronicle how companies across
Microsoft OCS is a UC platform based on Microsoft Windows
various industries are deploying, or plan to deploy, OCS 2007 R2. In
server technology that incorporates enterprise telephony and
each deployment example, the respective companies implemented
messaging along with presence management. The client technology
OCS alongside some existing traditional IP telephony deployment.
consists of Microsoft Office Communicator (for IM, voice, video and
The case studies build toward a “net” conclusion, with regard to
presence) running on both PCs and dedicated telephony endpoints
best network architecture practices for deploying OCS Enterprise
from third-party partners. OCS uses a back-end server technology
Voice as identified by the deploying company.
based on industry standards, such as the Session Initiation Protocol
(SIP), as well as advanced media capabilities on endpoints using both
Case Study 1: Manufacturing Company
standard codecs and a codec developed and licensed by Microsoft.
A global manufacturing company with plans to deploy Microsoft OCS
This Yankee Group report examines the experiences of four
2007 to tens of thousands of employees across the U.S. and worldwide
large organizations that have deployed Microsoft OCS, taking into
is currently in the early phases of its rollout. The firm has plants and
account their drivers for adopting the technology, their approach to
offices primarily in North America, but it also has a worldwide reach. It
the deployment, and how they overcame obstacles and issues along
connects most sites with an MPLS WAN backbone.
the way—particularly from a network-centric and voice-quality
troubleshooting point of view. The common thread—and the most
2 © Copyright 2009. Yankee Group Research, Inc. All rights reserved.

3. November 2009
Business Driver Behind OCS The company currently supports its companywide deployment
of OCS for IM, presence and conferencing in its three main data
The manufacturer was one of the first large adopters of IP centers, and it is in the process of adding voice services to these
telephony technology at the beginning of the decade, when it made data centers. OCS servers are in the same locations as its Exchange
a mass transition from TDM telephony to Cisco’s then-branded infrastructure, which is centralized in two data centers; this is
AVVID IP telephony architecture and later to Cisco CallManager different from its current Cisco CallManager infrastructure, which
and Cisco Unified Communications Manager. It was ahead of the requires dozens of server clusters in locations worldwide in order
curve with IP telephony in the early 2000s, and the company is to support the total end-user population.
continuing this trend with UC as it enters the next decade.
The manufacturer’s OCS Enterprise Voice deployment is
Unlike the IP telephony migration, the switch to OCS is focused fully interoperable with its pre-existing Cisco CallManager
on improving business processes, as opposed to just moving voice infrastructure. Currently, Cisco ISR routers are used to connect
traffic from one medium (TDM) to another (IP) or one vendor all OCS calls to the PSTN via a SIP trunk feature. No upgrade was
(Cisco) to another (Microsoft). The manufacturer wants to bring required on the Cisco side to support this because the SIP trunking
multiple communications channels under one common interface at capabilities are based on a Session Border Controller (SBC) feature
the endpoint (whether mobile or desk-bound) along with a single native in the Cisco IOS routing software the company uses. The
back-end server and management infrastructure. The firm also interoperability is transparent to users because the dial plans did
wants to put underutilized desktop processing resources toward not have to be changed.
telephony, with the goal of reducing the company’s total telephony
endpoint/dial-tone footprint. For every employee, the company Issues Experienced and the Approach to Solve Them
currently supports approximately 2.5 “PSTN units” (i.e., desktop
Overall, the manufacturing company has experienced no major
phones, soft phones with assigned numbers, etc., that can reach the
network-configuration issues that have affected the performance
PSTN). This was the result of years of slow migration from TDM
or quality of OCS. The company attributes this both to the robust
to IP telephony, which ultimately left the company with a complex
network infrastructure and the independent underlying nature of
mixed environment that led to a sprawling, overprovisioned voice
OCS itself, which largely operates independent of its underlying
environment. By consolidating telephony endpoints with OCS,
transport technology and does not rely on network-based controls,
where voice services are tied to end-user identity and endpoint
such as RSVP or network segmentation, to ensure quality.
PCs, the manufacturer plans to drive that number back down to one
PSTN unit per employee, with a correlated benefit on costs. What Worked Well
Methodology for Rollout Because of the manufacturer’s existing Cisco deployment (which
it will retain for the next several years), it already has an extensive
The manufacturing company’s OCS deployment is extensive,
QoS and VLAN structure for segmenting voice traffic and providing
although not complete. Each user in the 100,000-employee
priority queuing and express forwarding on its Cisco LAN and
company has Office Communicator on his or her desktop and
WAN infrastructures. This will remain because the firm is working
connects to a centralized OCS infrastructure for IM and presence.
to map its current QoS architecture to the OCS voice traffic.
About 300 employees have been using OCS Enterprise Voice for
about a year, and the company’s goal is to expand to 2,000 end-
users by the end of 2009. By the end of 2010, it expects to be at
12,000. The long-run goal is for the ratio of OCS users to Cisco IP
phone desktop users to be close to 50-50.
© Copyright 2009. Yankee Group Research, Inc. All rights reserved. 3

4. Network Considerations for Microsoft OCS Deployments
“In my opinion, if [you] already have [QoS] installed,” says the Business Driver Behind OCS
manufacturing company’s lead architect for enterprise voice and
UC, “you should be making OCS fit into your QoS architecture.” For years, the consulting firm has envisioned a unified platform for all
To achieve this, the company is mapping the DiffServ priority tags channels of enterprise communications, from telephony, conferencing
assigned to OCS voice traffic and mapping this traffic to existing and real-time chat to voice and e-mail. The company says it bought
VLAN and QoS architectures—a relatively simple configuration into early iterations of IP telephony with an eye toward this ultimate
exercise. This strategy is the result of two factors: The goal, but the reality of solutions offered over the last five to seven
manufacturing company still has a very large deployment of Cisco IP years was that they were basic PBX replacements that transported
telephony, which requires separate VLANs and express forwarding voice using IP networks instead of circuit-switched TDM networks.
settings for LAN-based IP telephony; and VLAN separation and In the interim between IP telephony and true UC, the consulting firm
QoS still offer troubleshooting and delivery guarantees over LAN had to fill in gaps, such as multimedia Web conferencing and instant
links that the company does not want to leave up to chance upon messaging, with outside services and tools, such as conference hosting
the first rollout of OCS. providers or consumer-based IM solutions pushed mainly by the
company’s own employees.
With more employees using PCs and mobile devices as primary
voice interfaces, the number of desktop phones will shrink over Methodology for Rollout
time; as a result, the manufacturing firm will also be able to begin
The consulting firm is on a rapid pace to roll out OCS throughout
gradual reduction of Power over Ethernet (PoE) switch ports
its organization and plans to completely transition from its legacy
deployed in wiring closets throughout its enterprise. Currently,
Nortel PBX platforms to Microsoft OCS Enterprise Voice by
every Cisco IP telephone connects to a PoE switch port, which
the end of the year. Of the 6,500 employees in the organization,
provides both power and network connectivity. Since PoE adds an
approximately one third now use OCS for all communications. The
approximate 20-30 percent premium to the cost of a switch port,
consulting firm’s CIO estimates that it will have all of its end-users
reducing the need for PoE to desktops could save the company
on OCS by the November/December 2009 time frame.
millions in infrastructure costs in the long run.
OCS Enterprise Voice still connects externally via Nortel PBXs,
“Net” Conclusions which act as a gateway for OCS SIP traffic and the PSTN. The
Enterprises will want to leverage their already deployed extensive firm plans to be off this hybrid architecture within the next three
IP telephony infrastructures. The QoS and native SIP functionality to six months because it expects its regional telco to make pure
within the OCS server stack was a key component to this SIP-based trunking services available soon. The SIP trunking service
company’s migration strategy; the company was able to integrate would tie the OCS Enterprise Voice infrastructure directly into the
OCS users with its incumbent Cisco infrastructure without altering carrier’s SIP-based VoIP network, eliminating the need for PSTN/
dial plans or introducing other changes that would make the OCS SIP gateways.
environment seem bolted on. This also allowed the manufacturer to The firm is moving its 20 offices from Nortel telephony to full
use its existing Cisco SIP-trunking gateway infrastructure instead of Microsoft OCS support at a rate of one office about every two
purchasing new equipment. weeks. Each office had its own IP PBX platform and connected to
the PSTN via a local trunk (although internal calls were routed
Case Study 2: Europe-Based Consulting Firm
over the company’s WAN). As the offices move from Nortel
One Europe-based consulting firm is among the most aggressive to Microsoft for voice, the main number and all internal direct
deployers of OCS Enterprise Voice of the four companies profiled. inward dialing (DID) numbers are rerouted through the company’s
With more than 6,500 employees across 20 offices, the firm is using headquarters, where its main data center for OCS is hosted. This
OCS to centralize disparate islands of telephony across its locations allows the firm to reduce receptionist staff at each of its offices and
and to provide advanced collaboration features to its employees and reassign the workers to other support positions within the firm.
partners via OCS federation.
4 © Copyright 2009. Yankee Group Research, Inc. All rights reserved.

5. November 2009
The company is deploying Polycom USB-based handsets, which how we are different from an efficiency standpoint compared to
connect to end-users’ laptops, to every desktop in the firm. The our competitors, which is crucial in this economic environment,”
Polycom phones are certified with Office Communicator clients says the firm’s CIO. The fact that the company was able to provide
and OCS in general. all this without any complex or expensive network upgrades
is a testament to both the firm’s existing high-end network
Issues Experienced and the Approach to Solve Them infrastructure and the unobtrusiveness of the OCS platform.
The consulting firm has experienced no real network-related issues
“Net” Conclusions
in its OCS deployment so far. Assigning dual 100 Mbps Ethernet
WAN pipes to each location gave the OCS deployment plenty of While he realizes that not every enterprise can roll out a metro
bandwidth and low latency, which ensured quick call setups and Ethernet WAN to all of its sites, the consulting firm’s CIO says
good voice quality. that investing in a high-bandwidth network was one of the main
factors of success behind his firm’s OCS Enterprise Voice rollout.
One of the only issues end-users have complained about
A largely tech-savvy employee base and very large network pipes
during the rollout was the issue of resource contention on
allowed the firm to roll out OCS Enterprise Voice at a very rapid
desktop endpoints—particularly among users with older model
clip—a pace the CIO says actually led to slow days in IT, given how
PC hardware and OSs. The firm’s CIO says that calls can be
quickly he is able to turn over offices. “Sometimes we have [IT
interrupted when end-users copy large files to or from their PCs
staff] not doing anything for a few days at some offices, because the
over the network while having an OCS voice conversation. Even
change went so smoothly. It makes me think we should have been
though the firm will use USB-based handsets, which can boost
more aggressive with our timetable.”
voice quality and offload voice processing from the PC to the
device’s digital signal processor (DSP), voice and data packets will Case Study 3: Global Energy Company
still contend for bandwidth at the endpoint level. The CIO says
the company plans to move to Windows 7-based workstations in The next enterprise operates in over 140 countries and currently
2010; this will entail upgrading processors and memory on many supports more than 15,000 users on Microsoft OCS Enterprise
older machines that were having the resource contention issue. He Voice. The company also has an extensive TDM-based PBX system
anticipates the upgrade will improve performance for simultaneous from Nortel and other vendors, as well as IP telephony systems
voice and data applications. from Nortel. The company is also upgrading its self-managed,
heterogeneous hub-and-spoke WAN architecture to a common
What Worked Well AT&T-hosted MPLS VPN network.
Immediate results of the quick OCS rollout include a more Business Driver Behind OCS
productive consultancy team, which is driving more customer
interactions—and more billable hours, according to the firm’s The energy company wanted to consolidate the management of its
CIO. Desktop sharing and click-to-dial integration for conferencing voice infrastructure, which was spread across more than 270 PBXs
and chat are used frequently by consultants giving presentations throughout the world. The company also sought a unified desktop
to clients on-site. Instead of deferring to other colleagues for client experience for all communications channels—e-mail, voice
questions beyond their own scope and making notes to follow up, messaging, chat, telephony and video. The company is also keen
the consultants can now quickly conference their colleagues into on extensive use of federation with OCS to allow for greater
live presentations via the Office Communicator client. Presence connectivity with key external partners.
allows the consultants to see who is available, and connections
are made with a click of the mouse. “This capability lets us show
© Copyright 2009. Yankee Group Research, Inc. All rights reserved. 5

6. Network Considerations for Microsoft OCS Deployments
Methodology for Rollout As with the consulting firm, the only recurring issue the energy
company faces is with voice quality on older PC endpoints (i.e.,
In initially deploying OCS 2007 over the WAN, the energy Windows 2000 Professional, which is still widely used throughout
company’s network team calculated the average number of users the organization). If employees use CPU-intensive applications on
and the average number of projected phone calls employees make these desktops or copy large files to or from their PCs while on an
on a daily basis. It then calculated the bandwidth that would be audio conferencing call, this leads to interference in voice quality,
consumed on average per site. Based on that, the firm determined which can make calls sound choppy. Also similar to the consulting
the sites where it could enable Enterprise Voice and video services firm, the energy company anticipates these issues will lessen as
in the short term, prior to network upgrade. The company also it upgrades its end-users to Windows 7 in the near future. Also,
factored in other bandwidth consumption and usage factors, such general user awareness about running multiple applications or
as its global, centrally hosted deployment of SAP, which is accessed downloading/uploading large amounts of data will also increase as
by over 200 sites worldwide. During that phase, the company the deployment matures.
hosted OCS 2007 from its data centers in Amsterdam, Houston
and Singapore to serve its worldwide client base. What Worked Well
No significant changes to the LAN were necessary to initially Overall, according to the energy company’s IT architect, voice
accommodate OCS because the deployment was tailored to the quality is an improvement over any previous IP telephony or
in-place network. Although sites have existing VLAN and QoS TDM voice solution due to the wideband (16 kHz) audio used
architectures in switches to support Nortel-based IP telephony, on peer-to-peer voice connections over the LAN. While some
these will be abandoned when OCS becomes the predominant initial users complained about voice quality at some sites where
voice application. On the WAN side, QoS will be used to prioritize underprovisioned WAN links were used, the advanced media
OCS voice traffic on the AT&T MPLS WAN. capabilities built into OCS endpoints have done well in adjusting for
resource contention on the WAN.
Beyond this initial deployment, AT&T (acting as the energy
company’s outsourcer for network and telephony) is upgrading “Net” Conclusions
the deployment from OCS 2007 to OCS 2007 R2 and rolling
out a global MPLS network to virtually every site. The goal is to Upgrades to the WAN (to MPLS), as well as usage analysis and
eventually enable OCS for Enterprise Voice and video at every site. right-sizing of branch office links, were among the most critical
AT&T will deploy dual MPLS links to each site for link redundancy. aspects of the energy company’s project and have led to the success
For smaller sites that do not warrant dual MPLS links, the company of this rollout so far. At this point, process and implementation
will deploy local resiliency capabilities such as voice gateways, timing challenges were the only drawbacks in the company’s rollout;
which will allow the sites to make outbound PSTN calls in the as for the technology, it has worked as advertised and has required
event of a primary MPLS link failure. Since AT&T will be managing minimal network reconfiguration or workarounds. Looking back,
the OCS deployment on behalf of the company, the OCS server says the IT architect, the company probably would not have rolled
infrastructure will be deployed at AT&T data centers in Europe, the out its OCS deployment in parallel with moving to AT&T for hosting
U.S. and Southeast Asia. and an MPLS network overhaul. Performing major simultaneous
changes to the network introduced complexity and delays that
Issues Experienced and the Approach to Solve Them could have been avoided had the project been taken on piecemeal.
The IT architect at the energy company jokingly says the greatest
challenges are keeping up with end-user demands to deploy OCS
more widely to more sites and to enable new features such as
mobile device support.
6 © Copyright 2009. Yankee Group Research, Inc. All rights reserved.

7. November 2009
Case Study 4: European Study 1, which must support parallel Cisco/Microsoft OCS voice
Telecommunications Company infrastructures into the foreseeable future. (The manufacturing
company’s engineering team says the configuration effort will be
A regional telecommunications company operating in Europe has worth the benefit of being able to segment OCS traffic in VLANs or
plans to deploy OCS Enterprise Voice across 120 office locations. apply Layer 2 QoS controls to the traffic.)
The company uses almost all Cisco IP telephony today, as well as
circuit-switched and packet-based telephony systems from Siemens, Issues Experienced and the Approach to Solve Them
Nortel and Alcatel in a few offices. Most non-Cisco sites have TDM-
The major network reconfiguration the carrier faced was related to
based equipment.
its extensive internal network of Check Point firewalls—a complex
Business Driver Behind OCS infrastructure with multiple zones and VPN segments. This had to
be re-engineered when OCS was deployed. Firewalls prevented
The company wanted to leverage its ubiquitous Windows desktop the any-to-any connection environment necessary for OCS, which
environment to include voice, messaging and presence applications meant some employees could initiate chat or voice sessions, but
under one umbrella. What really pushed the idea of OCS as the others could not call or message back due to zone restrictions. This
main voice platform was the 2008 acquisition of a smaller Web was alleviated by configuring the Check Point firewalls with rules
conferencing service provider. The acquired company had used OCS that permitted bi-directional signaling and codec traversal for OCS
more aggressively, with a full deployment of OCS Enterprise Voice traffic. Also, the Microsoft OCS Mediation Server—a critical piece
to its 300 users. The company had started with Microsoft LCS and of infrastructure to the deployment—was hosted in a data center
stuck with the technology as it evolved into OCS. While it is not that could not be accessed by all users. The Mediation Server was
yet deployed to all employees’ desktops, Office Communicator is moved to another data center that permitted wider access.
used by a majority of workers on their mobile devices, including
Windows Mobile and RIM BlackBerry. What Worked Well
Methodology for Rollout The software stack and corrective codecs for voice allowed
the carrier to deploy OCS Enterprise Voice without any major
The carrier’s own deployment of OCS IM and presence started in configuration changes to its LAN or WAN environments. The
late 2007 with 50 users and quickly expanded to 600 users by mid- customer decided that voice quality could be adequately assured
2008. It now has 17,000 employees accessing the system for IM and via endpoint software and close monitoring of voice streams via the
presence. The carrier also uses federation with its partners via OCS. Quality of Experience (QoE) Monitoring Server—a platform for
Two redundant data centers host the OCS server infrastructure ongoing voice traffic and call quality monitoring and reporting that is
inside the carrier. Multi-gigabit WAN connections link all three part of the OCS Enterprise Voice suite. This allowed the company to
of these data centers. External PSTN connections are all routed provision voice as just another application or feature of its merged
through a Nortel Communication Server (CS) 2100—an IP PBX OCS infrastructure, rather than having to treat the voice rollout as a
still used to support a large portion of employees with Nortel IP separate, laborious process of network testing and fine-tuning.
phones. The CS 2100 resides in one of the two data centers.
“Net” Conclusions
The carrier did little network engineering to augment the
Since bandwidth was not a great concern—considering that the
performance of OCS voice. It relies on the OCS codecs and
carrier could provide as much as it needed from its own network—
endpoint software to provide voice quality, as opposed to
the carrier was able to rapidly migrate and build out its OCS
implementing separate VLANs or QoS prioritization on the WAN
environment, moving relatively quickly from small OCS deployment
or LAN. While the company did have a QoS/VLAN infrastructure
to integration with the larger organization, which had previously
in place for its existing IP telephony deployment, OCS will not
used LCS. The end-user interface made migration simple from
be mapped to this scheme. This is because the company plans
an end-user-adoption standpoint: Workers just kept using Office
to quickly move off its existing IP telephony platform to OCS
Communicator on endpoints.
Enterprise Voice, unlike the manufacturing company profiled in Case
© Copyright 2009. Yankee Group Research, Inc. All rights reserved. 7

8. Network Considerations for Microsoft OCS Deployments
III. OCS and Your Network: Each user we spoke with used a centralized deployment model for
Recommendations and Best Practices hosting OCS servers for the entire enterprise; in most cases, OCS
was deployed alongside the company’s existing Microsoft Exchange
The previous case studies highlight the drivers behind each messaging infrastructure. If enterprises had already deployed OCS for
company’s OCS deployment, the issues and challenges they presence, IM and conferencing, they deployed OCS Enterprise Voice
faced and examples of how network configurations and existing services within this infrastructure instead of deploying additional
environments can affect an OCS rollout. Next, we examine some servers in more locations in order to support enterprise telephony.
specific issues around network planning and deployment using
best practices drawn from the experiences of the four profiled In the case of the manufacturing company, the firm is hosting OCS
companies and the OCS user community at large. from three data center sites in North America. This gives the
company localized geographical coverage for sites near each data
Complete a Pre-Deployment Network Assessment center and provides redundant OCS resources in case of a server
or site outage. This is the current approach used by all customers
Each enterprise profiled assessed the capabilities of its network prior
interviewed in this paper: to have an entire off-line failover site
to rolling out OCS Enterprise Voice. A critical first step in assessing
waiting to assume the burden of all voice traffic in the event of a
the network is to determine bandwidth availability and average
primary site failure. Although real-time failover features, where OCS
call usage per site. Provisioning voice and determining bandwidth
sessions would be seamlessly handed off from a failing site to a live
needs for a small-scale pilot deployment—perhaps to a group of
site, are not yet supported, the manufacturing company says it has
IT professionals testing the system, or to a select group of power
enough faith in Microsoft’s OCS road map to deploy only three sites
users—can be done by looking at call detail records from an existing
in anticipation of this feature in future revisions of the platform.
PBX or IP telephony system to gauge usage patterns. If an entire
branch office or department is being moved into production with In addition to centralizing data center resources for enterprise
OCS, however, pre-determining how the network will handle this telephony, enterprises can use an OCS deployment as an
new type of traffic and call volume on a more detailed level is critical. opportunity to right-size and optimize their WAN deployments
for branch offices. As was the case with the energy company and
In the case of the global energy company, call capacity and
European carrier, local gateways can still be used to provide backup
bandwidth planning were part of the deployment process. The
dial tone.
energy company calculated the number of users at its various
remote sites and factored in the average monthly volume of calls At the time of our interviews, the enterprises’ deployments of
made from these locations. The company’s IT group also assessed OCS Edge Services were in various stages. The manufacturer
overall interest in video among the locations and factored this used Edge Services to federate its OCS resources with key
into the estimates. The company then looked at the total available partners and customers; separate remote access or authentication
bandwidth for each site to determine if it would be ready as-is for infrastructures were not needed in order to share presence,
an OCS Enterprise Voice deployment, or if more lines or larger conferencing and IM with outside partners.
pipes needed to be provisioned.
Full Edge Services deployments are on the road map for each of
Analyze Topology Schemes these companies. This will allow the organizations to further migrate
away from legacy IP telephony and remote access infrastructure,
Each enterprise interviewed for this report uses a centralized such as IPSec VPN tunneling, to access OCS resources, which is a
deployment model for its OCS Enterprise Voice setup. This is one method still widely used (e.g., the manufacturing company). Edge
of the main drivers for OCS in general—centralization of voice Services will allow mobile and external users to access OCS without
call processing instead of dispersed islands of PBXs at remote VPN tunneling; also, internal users will be able to access external
sites, or up to a dozen quasi-centralized IP PBXs, as in the case OCS users directly from the OCS Edge Services infrastructure at
of the manufacturing company with its multiple Cisco Unified the network demarcation point.
Communications Manager clusters.
8 © Copyright 2009. Yankee Group Research, Inc. All rights reserved.

9. November 2009
If You Have QoS, Use It tools (from vendors such as Qovai, NetQoS and Clarus Systems)
that delivered automatically generated mean opinion score (MOS)
Each enterprise used QoS mechanisms, mainly DiffServ, to prioritize analysis of voice call quality by sampling traffic streams.
voice media packets traversing WAN links. However, they used
little traffic shaping or prioritization on LAN connections for The issue with such approaches was that they separated two
Microsoft OCS Enterprise Voice. If practical to the customer, types of metrics: one on the performance of packet delivery of
Microsoft generally prescribes wiping VLAN segmenting and 802.1p an IP network; the other on the sound quality of packetized voice
prioritization from a LAN architecture overall, with the idea that delivered over an IP network. It was up to network engineers to put
right-sizing the network for bandwidth and latency has greater impact these two areas of management together in order to troubleshoot
on quality for less cost. Further, Microsoft’s RTAudio codecs and and fine-tune enterprise IP telephony deployments. The fact that
features such as Forward Error Correction (FEC) can compensate vendors of IP telephony gear did not supply such tools with their
for less-than-optimal network conditions or constraints. systems also muddled the issue and forced end-users to do extra
work to find measurement and management tools that were
Of course, QoS and other flow management techniques can still certified with their respective IP telephony platforms—or pay high-
be considered. Enterprises can keep in place their predefined QoS priced, specialized consultants to do this.
schemes from previously deployed IP telephony products, such as
Cisco Unified Communications Manager or Nortel Communications Microsoft’s QoE server takes into account multiple factors that can
Server 1000. This was the case with the global manufacturer, which affect voice quality and system performance as perceived by end-users.
had a complete network-based QoS architecture already built on To start with, it goes beyond simple, passive network taps or probes;
both the LAN and WAN to segment and prioritize IP voice signaling the server has the ability to gather statistics on the overall quality of
and payload traffic. The company plans to map OCS Enterprise an individual’s connection or group’s connections, taking into account
Voice traffic into the same 802.1p traffic prioritization and 802.1Q both the performance of voice traffic on the wire and the experience
VLAN tagging scheme it currently has. of the end-user at the endpoint. Active monitoring, trend analysis and
end-user complaint mediation features are also included.
In the case of the energy company, a QoS architecture is already
in place for the worldwide deployment of SAP, which the company Some of these enterprises looking for a cross-platform view used
hosts from central data center locations in Europe, North America a secondary tool for the measurement and monitoring of voice
and Asia. As it transitions these data centers to AT&T and moves quality and overall network performance in conjunction with the
to the carrier’s global MPLS IP VPN, it will continue with its current Microsoft QoE server. It’s no surprise that the carrier Yankee
prioritization of SAP over the WAN (using DiffServ controls Group interviewed, for whom running and optimizing networks is a
mapped to MPLS switch labels) and will incorporate OCS voice core business, is the biggest proponent of this approach.
traffic into this scheme as well. The energy company considers SAP
The European regional carrier uses traffic measurement tools from
and OCS to be the two highest-priority traffic types for operating
Ipanema Technologies to analyze multiple types of RTP traffic and a
its business and will prioritize both flows over all others.
variety of codecs traversing the carrier’s network. Along with this
Become Familiar With Ongoing Management and method, the carrier uses Microsoft QoE server to specifically measure
Monitoring Tools OCS traffic as well. This combined approach gives the provider a large-
picture view of how OCS fits into the network as a whole, with the
Another common denominator among the enterprises interviewed QoE server used for OCS-specific management and monitoring.
is extensive use of the QoE server as the centerpiece of their
ongoing voice quality management and monitoring strategy. In past Overall, use of a secondary tool is recommended for enterprises,
IP telephony deployments, users typically had to rely on third-party as opposed to solely relying on the QoE server for voice
tools for supporting management and quality assurance of real-time troubleshooting and monitoring. Tools to consider are those
communications traffic on an enterprise network. These tools were that can analyze OCS Enterprise Voice traffic; certified partners
based in one of two camps: network-related products for measuring providing such tools include NetQoS and Psytechnics. Such tools
packet loss and jitter of IP traffic streams, and voice quality analysis can provide a good secondary analysis outside the QoE metrics
used by the Microsoft platform.
© Copyright 2009. Yankee Group Research, Inc. All rights reserved. 9

10. Network Considerations for Microsoft OCS Deployments
Consider Network Services Provisioning and Security and network considerations are not only focused on
Carrier-Provided SLAs enterprise boundaries, but on internal network segments as well.
As shown in the case of the regional European carrier, a firm that
Many enterprises that are centralizing voice delivery for the first operates an extensive internal firewall infrastructure can run into
time with OCS are also crafting service level agreements (SLAs) trouble when deploying OCS if it does not account for how voice
with carriers around IP voice. In the case of the global energy traffic will traverse various security zones across an organization.
company, for example, this is the first time global voice delivery It is essential to place critical OCS infrastructure components on
could be included in an SLA with a carrier, since the company’s voice segments of the network that are accessible to all employees.
infrastructure in the past was made up of over 270 PBXs connected
to the PSTN by various providers. In general, firewalls, traffic inspection gateways and other in-line or
out-of-band security appliances that will be traversed by OCS traffic
The energy company, which has run a centralized, global should only enforce policy at the routing layer. Firewalls should be
deployment of SAP for several years, has had various SLAs with configured to recognize and allow pass-through of traffic across key
its data carriers for delivering that traffic to branch offices. Now external and internal user ports, such as Ports 5061, 5062 and 443
that both voice and applications traffic will be delivered over a for OCS Access and Audio/Video Edge Servers and Ports 443 and
single pipe (the AT&T MPLS network) and from a single source 8057 for Web Conferencing Edge Servers.
(AT&T’s regional hosted data centers), the company is working
with the carrier to craft SLAs that will take into account whether OCS’s end-to-end security model includes secure real-time
OCS voice traffic is delivered at a rate below the acceptable level protocol (SRTP), which secures the audio stream of OCS Enterprise
of the SLA. This is where the QoE server comes into play directly Voice communications using a 128-bit AES encryption standard
as a potential revenue-saving opportunity. The QoE server can be to prevent against conversation interception or other tampering
used to flag voice traffic that falls below a certain quality threshold with the RTP stream. Also, transport layer security (TLS) protocol
from both a network and endpoint perspective. The company is is used to secure SIP-based signaling, which prevents protocol-
working with AT&T to extract some of the network-related metrics based spoofing attacks at the signaling protocol layer. With these
and parameters measured by the QoE server to use those as a safeguards in place at the OCS Enterprise VoIP application layer,
foundation for the SLAs. enterprises deploying OCS Enterprise Voice should adopt a more
open, any-to-any topology model for connectivity—at least in
Prepare Security Validation and Firewall Topology, terms of the pieces of their OCS infrastructures. Enterprises with
Configuration Adjustments past experience in IP telephony and security best practices will also
have to rethink previous methods of cloistering segments of the
Some enterprises faced security challenges related to firewall
network exclusively for voice, or extensive use of access control
topology and architecture during their OCS deployments. Firewalls
lists for blocking access to IP PBXs, or limiting what types of traffic
and IP telephony have a history of not playing well together. In early
endpoints can receive and send.
VoIP deployments, network engineers had difficulty getting firewalls
and technology schemes such as network address translation Another general rule of thumb followed by all enterprises
(NAT) to work well together. To this point, many enterprises have interviewed for this report is the inclusion of their respective
avoided this issue by using VPN tunneling to connect VoIP clients security teams in the planning and testing of OCS infrastructure.
or resources on opposite sides of a firewall. The issue is also being Federation and the prospect of opening up internal directories
addressed by the development of standards that will allow for more to external partners was a serious undertaking from a security
seamless inter-network VoIP connectivity; among these efforts is standpoint in each case study. The enterprises all required sign-off
the Interactive Connectivity Establishment (ICE) protocol, used in from their respective IT security teams to complete this, as well
OCS, for firewall and NAT traversal of SIP-based VoIP traffic. as an audit of what types of communications and resource sharing
would be allowed among federated partners.
10 © Copyright 2009. Yankee Group Research, Inc. All rights reserved.

11. November 2009
IV. OCS Costs and Benefits: A Breakdown The consolidation of call control, as well as external telephony
of Potential Savings connections, will also help reduce the number of PSTN gateway
interfaces the company currently uses. Prior to OCS, even Nortel-
Enterprises are moving to Microsoft OCS Enterprise Voice to based VoIP sites that included multiple offices connecting to an IP
improve end-user productivity, add powerful collaboration tools PBX still required an external PSTN gateway link for outbound and
such as video and presence, and make business-to-business incoming calls. Putting the OCS servers into the AT&T data center,
communications more open. This does not mean these enterprises where OCS can connect directly to AT&T’s SIP trunking service,
aren’t interested in finding ways to cut existing infrastructure costs will also consolidate this entire infrastructure of hundreds of
with OCS as well. This section analyzes some areas for cost savings, gateways down to essentially three in AT&T’s data centers in Asia,
based on some of the experiences of the four organizations profiled. North America and Europe.
Network Right-Sizing Endpoints
Organizations such as the global energy company are realizing Another powerful cost-saving force in the realm of equipment
increased savings and management cost efficiencies by re-evaluating reduction is the use of PCs as IP telephony endpoints, which allows
the bandwidth requirements for all branch office voice connections for reduction of IP phones on desktops. This was cited as a driver
and redeploying WAN links accordingly. Previously, the energy for the four organizations we talked to for this report. In the case of
company managed a complex tangle of varying point-to-point the manufacturing company, the goal is to get the number of phones
MPLS and VPN circuits across its multiple locations. Obviously per employee down from a range of about 2.5-to-1 to around 1-to-
this infrastructure was deployed prior to the OCS rollout, so the 1—that is, each employee’s desktop PC would become his or her
bandwidth provided did not take into account the actual calling telephony endpoint as well. The manufacturing company estimated
patterns and voice bandwidth utilization of these sites; as a result, that its total IP phone reduction could be in the tens of thousands
many sites were overprovisioned in terms of WAN bandwidth of handsets.
requirements for voice, while links at other sites were unnecessarily
squeezed. Above most other cost-saving factors, the exercise of While most of the cost of the phones has already been depreciated,
evaluating how much network bandwidth will be required for OCS the move to a phoneless desktop will save the manufacturing
Enterprise Voice and readjusting the infrastructure accordingly is company millions of dollars on desktop phone replacement costs
among the most powerful cost-saving aspects of an OCS rollout. in the long run. Considering the list price of a new Cisco IP phone
starts at $250 for a basic-feature handset, the manufacturing
Back-End Equipment company would be saving as much as $10 million for an enterprise-
wide upgrade, which would include between 80,000 and 100,000
Server consolidation and equipment reduction will be a very large
employees. There is also a potential for cost savings on the
cost-reducing factor among many of the enterprises interviewed.
network side, as fewer phones will require fewer PoE ports, which
In the energy company’s case, it will decommission more than 200
could result in lower future LAN switch acquisition costs. Energy
PBXs and other IP telephony gear at its remote sites throughout the
consumption will also be reduced, since the company will no longer
duration of the rollout, as sites come online with OCS voice. Taking
be required to inject power as broadly over its structured cabling
into consideration the cost of ongoing maintenance, lease of some
plant. Additionally, the company would be able to provision remote
equipment and other factors, this move will, over time, equate to a
workers, teleworkers and even external contractors or partners
savings in the tens of millions of dollars annually.
with OCS Enterprise Voice-based telephony without having to
deploy expensive VPN, remote access and hardware telephony
endpoints to these constituents.
© Copyright 2009. Yankee Group Research, Inc. All rights reserved. 11

12. Network Considerations for Microsoft OCS Deployments
Advanced Application Services save money or consolidate resources. The underlying theme among
all the enterprises is the decoupling of enterprise voice services
Conferencing is one of the most dominant cost-saving drivers from the network infrastructure; the long-promised goal of “voice
named by the enterprises as part of the OCS feature set. In the as just another application” is starting to become realized in many of
case of the Europe-based consulting firm, the company’s 6,000 these organizations. If done correctly, great organizational TCO and
employees had frequently used external conferencing services end-user productivity gains are possible.
for both internal and external meetings. The use of various
conferencing provider services left employees working on platforms To that end, however, enterprises are still faced with getting
with inconsistent interfaces, while requiring users to track call-in OCS Enterprise Voice to work on their networks. While
numbers and manage various downloadable plug-ins to support an OCS Enterprise Voice offers many advanced features that can
array of meeting platforms shared with external partners and with compensate for network congestion and low bandwidth, such as
members of their own organization. In addition, employees were software and codecs that provide error correction and audio quality
being charged for these various services, which made funding and improvement, careful consideration must still be given to how OCS
accounting of costs difficult across the various business units using Enterprise Voice is deployed throughout an enterprise. Deployment
the services. plans must still tackle several issues in order for implementation
to succeed, including network topology, integration with legacy
Centralized conferencing covers all channels used by the company: telephony systems, endpoint device scenarios and bandwidth
Web, voice and video with integrated chat and desktop sharing. The considerations—especially for branch and remote offices. Based on
central platform also provides a common interface familiarity across the experiences of the OCS Enterprise Voice deployers detailed in
the organization, as well as easier conferencing setup tools; any type this report, the following conclusions can be drawn:
of conference can be easily initiated from a voice, chat, e-mail or
video communications session. Network considerations should be included in a
deployment plan
Also, federation allows the company to easily set up conferences—
including Web, video and voice—with other federated partners, OCS Enterprise Voice introduces new bandwidth management,
customers and external parties. This allows the company to voice quality assurance and other technologies that allow the
continue to keep its travel costs down while lowering its costs service to boldly go where enterprises have feared to send IP
further by using the internally hosted OCS platform instead of an telephony in the past—in particular, on high-latency and/or
outside provider. Additionally, the wideband audio of the OCS bandwidth-constrained connections for remote or mobile users.
conferencing platform provides a superior quality to previous This capability opens up new possibilities in terms of use cases
solutions, making such meetings more resonant and productive. and deployment scenarios, such as right-sizing WAN connections
and reducing VoIP-specific network constructs, such as VLAN/
Among enterprises in general, Web and video conferencing is also
QoS architectures and PoE switch infrastructures. Nevertheless,
seen as the greatest cost-saving component among all the areas of
simply throwing OCS Enterprise Voice onto an existing network
UC. According to Yankee Group's Anywhere Enterprise: Large—
is not recommended unless bandwidth and latency are already
2009 Transforming Infrastructure and Transforming Applications
well provisioned in the network. Careful consideration must be
Survey, Wave 1-4, this is regarded as the No. 1 cost-reducing factor
given to network topology (such as internal and external firewall
of a UC deployment among enterprises that have deployed or are
and security zone boundaries), deployment of services relative to
considering UC.
geographical location of remote users and branch offices, and where
V. Conclusions QoS and traffic prioritization schemes might be applicable, such as
over low-bandwidth or long-distance WAN connections. The good
Each featured enterprise’s deployment of OCS Enterprise Voice news is that the major Herculean tasks facing IP telephony projects
uses a different approach from past efforts around network voice/ of the past—complete LAN/WAN redesigns and upgrades, or
data convergence or IP telephony. Users of the platform see OCS as introduction of new QoS protocol schemes such as RSVP—are no
a strategic step forward and as a business-enabling communications longer part of the equation.
tool, as opposed to a tactical implementation of a technology to
12 © Copyright 2009. Yankee Group Research, Inc. All rights reserved.

13. November 2009
• Consolidation is key: All of the enterprises interviewed for gateway infrastructure in order to allow OCS clients to make
this report used their OCS Enterprise Voice deployments as external calls over the PSTN. This is where the flexibility of OCS
an opportunity to consolidate voice communications into a can be used to adapt to existing polices without cumbersome
centralized service delivered from a small number of locations. changes. Existing QoS schemes, set up for legacy IP telephony
Distributed call control servers, gateways or other VoIP-enabling systems, can remain in place to support workers as they
CPE can be minimized, reducing equipment costs, management transition from old platforms to OCS Enterprise Voice. For
complexity and overall TCO. To that end, those who have organizations looking at long-term mixed environments of IP
deployed the technology should regard OCS Enterprise Voice telephony and OCS Enterprise Voice, OCS traffic can be mapped
as a service similar to e-mail, corporate IM or other centralized to existing traffic-shaping and network segmentation schemes
applications and services. Replicating this central infrastructure for VoIP, provided that such setups do not interfere with OCS
over a small handful of data centers—anywhere from two to features and functions.
four—is also the consensus approach taken by the enterprise
• Endpoint endgame: Enterprises should also consider
deployments highlighted in this report. By doing this, deployers
how—or if—they will transition employees who use IP
ensure that all OCS services will remain available in the event
desktop handsets to PC-based Office Communicator clients
of a network or data center failure. At the same time, they are
with headsets. Doing so can lead to a quick cost reduction and
also anticipating future advancements that will allow for live-site
simplification of network architecture: The former is achieved
redirection and global live failover scenarios in future iterations
by decommissioning expensive IP handsets on desks; the latter
of OCS Enterprise Voice.
is realized by decreasing the need for LAN switch-based PoE
• Measure, monitor, adjust, repeat: Each enterprise in to power phones at every desktop. Another consideration
this report found real value with the QoE server as a tool for is end-user acceptance. Workers used to lifting a receiver to
measuring all aspects of end-user voice quality experience—from make a phone call may find the transition hard to make; options
network performance in terms of packet delay, latency and to help with this include USB-attached handset devices that
congestion, to perceived audio quality on endpoints. Unlike tools are compatible with Office Communicator software. If some
used to measure performance and quality of IP telephony in pre- employees are heavy mobile phone users, such workers could
deployment or ongoing integration scenarios, the QoE server is be encouraged to use their mobile devices as primary voice
designed to be an ongoing tool used frequently in tight conjunction endpoints while at their desks or out of the office.
with OCS Enterprise Voice for maintenance and monitoring.
Enterprises going into an OCS deployment should regard this VI. OCS Enterprise Voice Deployment FAQs
platform as a future everyday OpenView- or Unicenter-like The following is a list of common issues or concerns, presented in
systems management tool, not as a specialized piece of network question form, that the four case-study organizations faced around
troubleshooting equipment brought out only during deployment their respective deployments of OCS Enterprise Voice, specifically
tests or to fix specific problems on the network. regarding network issues.
• Build upon existing engineering: Like any major technology
displacement, the introduction of OCS Enterprise Voice will
require some parallel coexistence of previous enterprise voice
systems. At the very least, enterprises will initially have to
tie OCS Enterprise Voice servers to existing IP PBX or VoIP
© Copyright 2009. Yankee Group Research, Inc. All rights reserved. 13

14. Network Considerations for Microsoft OCS Deployments
What common network-related trouble spots might backup scenarios, where multiple instances of OCS Enterprise
I expect to see upon deployment? Voice can serve various groups of end-users, with each set covering
for the other if one group of servers becomes unavailable. Most
Among the four enterprises examined in this paper, one major
enterprises deploying OCS Enterprise Voice today are building their
network-related trouble spot highlighted was the deployment
network and data centers toward this future model in anticipation
of OCS Enterprise Voice across an infrastructure that is heavily
of the OCS road map.
segmented via firewalls and other access control gateways. For
security and compliance purposes, many organizations use these What are the bandwidth requirements of OCS codecs?
tactics to create secure zones for segmenting various departments,
or for keeping public and private LANs and extranet zones A peer-to-peer enterprise OCS voice call, using the Wideband
segmented from each other. When deploying OCS Enterprise Voice, RTAudio (16 kHz) codec, consumes 35 Kbps of bandwidth per
however, enterprises must consider how OCS traffic will traverse user. When video is added to an internal peer-to-peer call, another
security zones. Also important to consider is the deployment 260 Kbps of bandwidth is consumed. A server-hosted RTAudio
of OCS servers throughout the enterprise, taking into account narrowband (8 kHz) connection, which connects end-users to the
whether or not all users will be able to access the servers, given PSTN, consumes 30 Kbps of bandwidth. For conferencing, OCS
their security zone. The “any-to-any” collaborative nature of OCS uses the Polycom Siren protocol, which consumes 22 Kbps of
can run into a brick (or fire) wall very quickly if these issues are not bandwidth per participant endpoint, and an additional 260 Kbps
worked out before wide-scale rollout. of bandwidth when video is added. PSOM, the Web conferencing
and collaboration protocol used in OCS, consumes 10 Kbps.
How does OCS support QoS? For an example of a real-use scenario, putting together multiple
protocols, a remote conferencing session with video, conferencing
OCS supports the DiffServ model for QoS, and this is the
and collaboration would consume approximately 292 Kbps of
recommended approach if enterprises determine that a low-
bandwidth. Here is an area where enterprises must take care in
bandwidth or a highly congested WAN connection used to provide
capacity planning and bandwidth allocation for their deployments,
OCS Enterprise Voice services could be improved with traffic
since sites that use older, lower bandwidth links, such as fractional
engineering. In general, enterprises deploying OCS Enterprise Voice
T-1 or ISDN, could become saturated quickly if multiple audio and
view QoS as a best practice for WAN connections; on LAN links,
video conferencing features are spun up quickly.
QoS is less critical. While some enterprises deployed previous 802.1p
packet prioritizing schemes on their LANs for legacy IP telephony How is the QoE Monitoring Server used in
systems, generally, enterprises are finding that such controls are not my network?
necessary for peer-to-peer LAN connections with OCS.
Microsoft’s QoE Monitoring Server is a centralized repository for
What are the available disaster recovery networking statistics about the performance of OCS voice and video traffic on
plans for OCS today, and what is on the road map? the network. OCS servers and endpoint clients generate data on
the performance of their call sessions, and this data is collected
Currently, OCS provides client redirection failover capabilities,
by a centralized QoE Monitoring Server. The server takes into
allowing clients to connect and re-register with secondary OCS
account multiple factors that can affect voice quality and system
servers in the event that primary servers become unavailable due to
performance as perceived by end-users. This includes multiple types
hardware, software or network failures. This type of failover does
of mean opinion score (MOS) metrics, such as voice quality being
not allow for seamless continuation of communications. Calls and
sent and received by endpoints, and network-wide voice quality
conferences with external parties are dropped in such a scenario.
reflected in MOS data. Basic network performance metrics, such
However, the OCS road map includes capabilities that would allow
as delay, jitter, packet loss and traffic degradation, are also factored
for seamless, live-call failover of voice traffic, as well as active/active
into QoE Monitoring Server reporting.
14 © Copyright 2009. Yankee Group Research, Inc. All rights reserved.

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