As VoIP standards mature and ven- by gabyion


									                                                                                                             Enterprise VoIP

Anatomy of an Implementation
Guerin C. Goldsmith and Hsiaosu Hsiung

                                                                s VoIP standards mature and ven-          with the transition’s complexities.

                                                       A        dors promise more stable tech-
                                                                nologies and products, organiza-
                                                                tions have rushed to overhaul their
                                                       telecommunications service. Many have
                                                       found a disappointing gap, however. The
                                                                                                            The project was enterprise-wide, and
                                                                                                          operational standards were high: No ser-
                                                                                                          vice interruption would be tolerated. Oth-
                                                                                                          er than presenting each user with a new
                                                                                                          phone, the change to VoIP service was
What does it take to                                   new technology is far from plug-and-play,          to be completely transparent: Employees
                                                       and its implementation can be fraught with         would not have to alter their dialing pat-
successfully execute                                   problems if you make that assumption.              terns or telephone use. Following these
   a VoIP project?                                        Noblis recently discovered this when it         mandates, Noblis successfully imple-
                                                       decided to upgrade its private branch ex-          mented a VoIP system in fall 2005 with no
 Meticulous planning                                   change (PBX) equipment to VoIP technol-            disruption to normal business operations.
and consideration of                                   ogy. The project provided a realistic envi-
                                                       ronment in which to identify and address
the user perspective                                   VoIP’s technical challenges and gain both          System planning
can overcome many                                      hands-on experience with an emerging                 Figure 1 shows the resulting system,
                                                       technology and application insights from           which is layered over the data network.
  problems, as this                                    a client perspective. Among the many les-          SBC is the local exchange carrier, and
case study illustrates.                                sons learned was that judiciously apply-           AboveNet in Reston, Virginia, provides
                                                       ing tested project management methods—             the alternative facility for the call man-
                                                       chiefly, careful planning and risk assess-          ager cluster. VoIP calls between station
                                                       ment—was the best antidote to dealing              sets at Noblis’ Fairview Park (FVP) facil-

                                                         • VoIP implementation planners must deeply understand implementation details and installation
                                                           nuances. Companies without that knowledge should hire a system integration contractor.
                                                         • A table of failure scenarios can help the project team speculate about risks and instill confi-
                                                           dence in management that mitigation approaches are in place.
                                                         • A system design that minimizes transition headaches and meshes well with business op-
                                                           erations must consider call plans, interconnection services, security, and support for analog
                                                         • A phased approach to VoIP transition allows for a period in which users are on both the PBX
                                                           and VoIP systems. Noblis found that two weeks of dual use was enough time to identify and fix

    Vo i c e o v e r I n t e r n e t P r o t o c o l                                                                                                        9
                                            Cisco 4507R                Cisco 4507R                  Site Access Switches/Routers
         Noblis User                                                                          Cisco 3750 or Cisco 2650XM, Cisco 2821
                                            Closet Switch              Closet Switch

                                                                                                 Field Office
                               Ethernet                                                                                                Analog Line              Local and
                                                                                                                                                              Long Distance
                                                                                                      Router         Software
                                Cisco 6500                                      Cisco 6500
                                Core Switch                                     Core Switch
         PSTN                                                                                                                                             AboveNet
                                                                                                                                                      (Backup Location)
                              Cisco 3845                Ethernet                 Cisco 3845
         SBC                                                                                  ATM Fractional
        Network                                                                                   DS3
         Local                                                                                                                                    Router          Software
                                                                                                                SBC MPLS

         AT&T                                                                                                                                       Call
                                                         Call                                                                                     Manager
          Long                                         Manager
        Distance                                                                                                                                  Cluster
                                           Media        Cluster
                                          Gateway      MCS 7835

Figure 1. VoIP network architecture in the VoIP project. The Noblis VoIP network consists of two layers implemented by closet switches and core switches,
all with redundancy. Redundant closet switches are on each floor at the Falls Church, Virginia, (FVP) facility; a second call manager server is in Reston,
Virginia. The VoIP system interconnects to the local exchange carrier (SBC) and to AT&T through VoIP media gateways. At FVP, VoIP calls made to locations
not on the VoIP network are completed through SBC for local calls and through AT&T for long distance calls.

ity in Falls Church, Virginia, and between              data network also made it easier to con-                           In house or contract?
FVP and remote sites are completed over                 verge voice and data features, such as                                Planning for a VoIP implementation
SBC’s Multi-Protocol Label Switching                    voicemail. Noblis then baselined the ex-                           demands careful coordination with all
(MPLS) network. The VoIP network at                     isting data network to determine what ad-                          parties involved in the VoIP system in-
each remote site is composed of a site ac-              ditional upgrades or modifications would                            stallation and deployment, which in turn
cess router, which provides connectivity                be needed to support VoIP.                                         requires a deep understanding of imple-
to the public switched telephone network                   As part of network baselining, Noblis                           mentation details and installation nu-
(PSTN) and MPLS network through me-                     reviewed its business operations and list-                         ances. Not having internal resources with
dia gateways. A site switch provides local              ed features and functions that the PBX                             that level of understanding, Noblis de-
area network (LAN) interconnectivity to                 provided, as well as desired new features                          cided to hire a systems integration con-
all user VoIP station sets and other VoIP               and functions that only the new VoIP sys-                          tractor, SBC, which would be responsible
equipment at the site.                                  tem would offer. The project team looked                           for installing and testing the VoIP equip-
   As Figure 2 shows, the project team de-              at the existing infrastructure’s ability to                        ment and for transitioning voice service
voted the first three months to planning,                meet these new functions, including any                            from the PBX. SBC essentially became
during which they made several key de-                  impact on wiring and cabling, heating;                             the prime contractor, subcontracting work
cisions about desired features, equipment               ventilation, and air conditioning. The                             to the VoIP equipment vendor. SBC also
vendors, migration strategy, and risk miti-             team also examined the power availabili-                           helped identify features and functions that
gation.                                                 ty and power supplies for VoIP equipment                           the initial inventory overlooked and used
                                                        and station sets.                                                  the final inventory in its planning.
Functions and features                                     Another task was to take inventory of                              Some organizations might have enough
  As one of the first steps in planning,                 the infrastructure, which involved identi-                         internal expertise to test, install, and acti-
an enterprise must decide if the VoIP net-              fying all the planned locations of station                         vate the VoIP equipment themselves and
work should support both data and voice                 sets, such as desktops, hallways, lobbies,                         will not have to hire an integration con-
or voice alone. Noblis decided to imple-                cafeterias, phone banks, laboratories,                             tractor. However, all organizations will
ment its VoIP system using the company’s                waiting areas, common areas, restrooms,                            need a VoIP equipment vendor and will
data network—in part, because it had                    conference rooms, equipment rooms, and                             generally have to investigate vendors,
made earlier upgrades to the data network               elevators. It was also important to de-                            create a candidate list of four or five, and
to ensure that network equipment would                  termine the locations of analog lines for                          conduct a cost-benefit analysis to select
support network quality of service and                  devices, such as modems and facsimile                              a winner. Any such vendor investigation
different data traffic classes. Using the                machines.                                                          should include

10                                                                                                                                   Vo i c e o v e r I n t e r n e t P r o t o c o l
     Jan 2005          Feb 2005               Mar 2005           Apr 2005          May 2005           Jun 2005         Jul 2005         Aug 2005

Figure 2. VoIP project timeline. Planning is key to a successful effort, including selecting equipment vendors and setting up communication channels so
that everyone understands the new services.

• a survey of each vendor’s product features                 vice impairments, the project team created          call plans, interconnection services, secu-
  and comparison against the organization’s                  a table of possible failure scenarios. For          rity, and support for analog devices.
  features list;                                             each scenario, the team listed the failure’s
                                                             impact and the means of mitigating its ad-          Call plans
• enough technical discussion with vendors to                verse consequences. The team used this ta-             Because number, dialing, and routing
  ensure that engineering and support staff un-              ble both to speculate about failure scenari-        plans can significantly affect both the VoIP
  derstand how the products would operate in                 os and to instill confidence in management           system implementation and the organiza-
  their organization; and                                    that mitigation approaches were in place.           tion’s business operations, the path of least
                                                                                                                 resistance is to maintain as much similarity
• an assessment of the vendor’s past installa-                                                                   between the old plans and the VoIP plans
  tions that might be similar to the one planned,              System planning action items:                     as is feasible. Users can then retain the
  including a list of references.                                                                                extension numbers and dial calls as they
                                                               • Decide if the VoIP system will support          did with the PBX. This arrangement will
                                                                 data as well as voice.                          make the transition to VoIP service much
   For its VoIP equipment vendor, Noblis                                                                         smoother. The dialing plan must also ac-
chose Cisco, which had supplied the com-                       • Choose an integration contractor or
                                                                                                                 commodate 911 calls, which need enough
pany’s data network equipment. Choosing                          decide to test, install, and deploy the
                                                                                                                 location information for emergency re-
the same vendor eliminated cross-vendor                          VoIP system yourself.
                                                                                                                 sponders to locate the caller.
interoperability problems between data                         • After determining the desired functions            Noblis was able to preserve all existing
and voice network equipment and gave the                         and features, choose a VoIP equipment           plans except that it had to change the prefix
company a contractor it knew had exten-                          vendor.                                         of the 10-digit number used to place calls
sive experience with VoIP systems. Cisco                                                                         to remote sites. The VoIP system also pro-
also provided input into the features and                      • Create a table of failure scenarios and         vides enough information for 911 respond-
functions list and used the final inventory                       use them to identify risk mitigation ap-        ers to find the exact room in which the call
to plan equipment deployment and create a                        proaches.                                       was made.
bill of materials.                                                                                                  Sometimes it is not possible or efficient
                                                                                                                 to retain the existing call plans. If an orga-
Risk mitigation                                                                                                  nization must revise the plan, it should do
  Typically, VoIP systems have at least one
                                                             Design and engineering
                                                                                                                 so as early as possible because any changes
or two nonnegotiable requirements. For                          A system design that minimizes transi-           will affect the network equipment configu-
Noblis, these were voice quality and sys-                    tion headaches and meshes well with busi-           ration and business operations. Revisions
tem reliability and availability. To prepare                 ness operations is fundamental to a VoIP            also add a component to user training: fa-
for VoIP equipment-related failures or ser-                  project’s success. Considerations include           miliarizing users with the new plan.

          Vo i c e o v e r I n t e r n e t P r o t o c o l                                                                                                  11
Directories                                     available for the desired speed of connec-       Table 1. Support methods for analog devices.
   Any VoIP implementation will involve         tion between the off-site user and Noblis’
the use of directories. The decision is         LAN. For these reasons, Noblis decided
whether to maintain an enterprise-wide          not to implement the softphone until it                                                Method
directory or to implement multiple stand-       could resolve security and performance is-                           Media gateway             Terminal adaptor
alone directories. If the choice is multiple    sues, and to date the softphone has yet to be                       and RJ-11 wiring           and RJ-45 wiring
directories, the enterprise must find a means    implemented.
to synchronize their contents.                                                                                    Lower initial cost         Must maintain only

   Noblis elected to operate with separate      Analog devices                                                                               RJ-45 wiring
directories. One reason was the poor per-          In most organizations, the VoIP system
                                                                                                                                             Easy to move or add
formance of the Lightweight Directory           must also support existing analog devices,                                                   analog devices
Access Protocol interface between the           such as facsimile machines and modems.
VoIP system’s directory and the multiple        Table 1 shows two support methods. One
enterprise versions of MS Active Directo-       method is to connect the analog device to                         Must maintain both         Higher initial cost

ry, which caused users to experience long       the VoIP system’s media gateway using the                         RJ-11 and RJ-45
delays while browsing the VoIP directory.       existing RJ-11 wiring. The other method is
Instead, the VoIP system maintains its own      to deploy an IP terminal adaptor adjacent                         Difficult to relocate the
directory, which is synchronized offline         to the analog device that would convert the                       device

with the company’s separate version of          analog signal to a digital signal. The digital
Active Directory. The resulting directory       signal, in turn, would connect to the LAN
system works somewhat differently from          through an RJ-45 wall jack, on which the         or cutover, will unfold, troubleshooting
Noblis’ original plan to use an enterprise-     VoIP system operates. With the second            equipment and settings, establishing a
wide directory, but it effectively avoids the   method, users can more easily move the           backup and recovery mechanism, training
problematic interface.                          analog device throughout the facility or add     users, and instituting proven project man-
                                                analog devices, but the initial cost is higher   agement practices.
Interconnection                                 because each device requires a terminal
   Telecommunication services for inter-        adaptor.                                         Schedule
connecting on- and off-network locations           Noblis elected to use the existing RJ-11         Perhaps the best way to develop a
directly affect the VoIP system’s perfor-       wiring because it did not foresee the need       VoIP implementation schedule is to cre-
mance, cost, and security. As Figure 1          to move existing analog devices or add new       ate a work breakdown structure (WBS)
shows, Noblis decided to use the PSTN to        ones.                                            that covers all the activities associated
connect to off-network users and SBC’s                                                           with implementing the VoIP equipment
MPLS network to connect the FVP and on-                                                          and migrating service. A WBS details the
network remote sites. The MPLS network            Design and engineering action items:           tasks involved, assigns responsibilities
makes it possible to implement quality of                                                        to accomplish the tasks, and establishes
service, which means that the network can         • Consider keeping the existing number,        anticipated timelines to complete them.
support real-time application issues, such          dialing, and routing plans to make the       SBC used Microsoft Project to automate
as voice traffic.                                    transition to VoIP service easier.           the WBS, making it easier to manage. The
                                                                                                 team frequently reviewed the WBS to en-
Security                                          • If you can’t keep the existing dialing       sure that the project stayed on schedule
   The scope of security measures and the           and routing plans, make any revisions        and used it to plan workarounds if certain
means to implement them depend heavily              as early in the project as possible to       tasks were delayed.
on the VoIP network infrastructure. If the          ensure that they are well designed and          SBC also held weekly meetings with all
Internet is the site-to-site transport mecha-       engineered.                                  interested parties, and Noblis’ intranet car-
nism, a firewall to handle network address         • Select a plan for handling directories.      ried the status of all activities on a shared
translation will be needed, as well as a                                                         team site. Any implementation or deploy-
means to handle intrusion detection and           • Choose the site interconnection service.     ment problems were discussed during
prevention applications.                                                                         the weekly meetings, and decisions were
                                                  • Review security measures and accom-
   Although the mobility of computer-based                                                       reached on the spot.
                                                    modations for 911 calls.
telephones, or softphones, offers great flex-
ibility, it also presents additional security     • Decide how to support analog devices.        Cutover
and performance concerns. 911 calls are an                                                         The cutover can be done all at once or in
issue because the needed number identifi-                                                         phases. In the phased approach, some us-
cation would come from where the call is                                                         ers are put on the VoIP system, while oth-
handled (the FVP location on the VoIP net-
                                                Implementation issues                            ers remain on the existing system. The two
work), not where the call is placed. Also,        Implementation issues include making           user groups must be able to communicate
the required voice bandwidth may not be         a schedule, deciding how the transition,         during this dual-use period.

12                                                                                                                    Vo i c e o v e r I n t e r n e t P r o t o c o l
   Noblis felt that the phased approach was                 echo. Network administrators were able        User training
a better choice because it helped gel users’                to trace the cause to the clock references       Regardless of the implementation de-
confidence that the VoIP system would                        for the media gateway and primary rate in-    tails, any transition to VoIP services is
operate reliably. Moreover, any problems                    terface that connects the media gateways      likely to require user training. The enter-
would affect only a few users, and network                  with the PSTN. Because the clocks were        prise must consider the type of training and
administrators would have time to fix them                   not synchronized, the media gateway’s         training materials needed, whether training
before rolling the system out completely.                   echo cancellation logic could not func-       should be formal or informal, and whether
Noblis decided to have a dual-use period                    tion properly. VoIP administrators solved     it should be done in-house or by the VoIP
of two weeks, which it felt was ample time                  the problem by replacing the primary rate     contractor.
to identify and fix problems and acquaint                    interface card with one that could properly      Noblis employed a train-the-trainer strat-
users with new features.                                    attain synchronization.                       egy, in which SBC, in concert with Cisco,
   After user training, the company al-                        The exact troubleshooting context will     provided training to select CIM staff, in-
lowed users to retain their old station sets                differ across organizations, but regardless   cluding those responsible for maintaining
but also provided new ones, which users                     of the specific problems, a good practice is   the VoIP system. The CIM trainers then
were expected to try out. Inbound calls                                                                   conducted formal employee training in a
could be made to either system. Users’                                                                    pilot demonstration at the FVP site using
extensions remained the same, but the                                                                     actual station sets, with which they dem-
exchange codes for the PBX and VoIP                                                                       onstrated common operational features of
systems were different. At the end of the                       Regardless of the                         the VoIP system. Individuals then used the
two weeks, the transition to the new VoIP                                                                 sets at their seats as trainers showed them
system was considered complete, and                              implementation                           how to activate features. CIM trainers also
network administrators removed the old                              details, any                          traveled to remote sites to provide similar
station sets. By this time Noblis’ Corpo-                                                                 training and answer questions.
rate Information Management (CIM) staff                         transition to VoIP                           In addition to the formal training, train-
had gained experience operating the new                          services is likely                       ers handed out wallet-sized user guides to
system, and users had had enough experi-                                                                  all employees along with a pamphlet ex-
ence in using the new phones to grasp the                         to require user                         plaining feature operation in greater detail.
phone’s operation and features.                                       training.                           Employees could also find these training
   CIM staff then sent out a notice to PBX                                                                materials on the Noblis intranet.
voicemail users that their messages would
be retained only until the company de-                                                                    Project management
commissioned the PBX voicemail system                                                                        From a management perspective, a VoIP
in several weeks. At that time, the VoIP                    to have the vendor meet with the organiza-    system project is no different from any
system would be operable, and voicemail                     tion’s technical staff to review all equip-   other project that requires enterprise-wide
would go to the new system only.                            ment settings and connections.                coordination. Noblis followed best practic-
   This cutover strategy worked well, and                                                                 es, such as ensuring that all parties accept
users accepted the change without undue                     System recovery and backup                    the implementation plan and will adhere
complaint. However, phased migration                           For rapid network recovery, a distrib-     to it, thoroughly examining activity work-
might not be suitable for all organiza-                     uted VoIP system architecture makes sense     flow, and establishing workaround plans
tions, since dual-use might not be feasible.                because all call processing and gateway       to accommodate changes in planned tasks.
Noblis had a separate area code that it could               equipment then has alternative connec-        Of utmost importance is the need to estab-
map to the same numbering plan as the 610                   tion paths to other telecommunications        lish communication channels at all levels
area code. This situation made it possible                  networks, such as the PSTN. Noblis’ VoIP      so that individuals know from whom they
to operate the old and new systems simul-                   system architecture uses redundant call       should take direction and from whom they
taneously. Not all companies will have the                  manager clusters and alternate paths to       should seek help. Everyone should also un-
luxury of a second area code and will need                  both the interexchange carrier and SBC.       derstand when problems or issues should
to resort to an all-at-once, or flash, cutover                  It is vital to back up VoIP databases,     be escalated, to whom, and the proper pro-
to the new VoIP system. Organizations that                  such as directories, as well as numbering     cedure for doing so.
are unsure about which approach is bet-                     and dialing plan databases. Noblis opted to      Other best project management practices
ter—phased or flash—should ask the VoIP                      use its existing backup procedures—part       address the inevitable planning deviations.
equipment vendor how it would conduct                       of its Continuity of Operations Plan—for      The team must set up a mechanism for re-
the transition from the current voice envi-                 VoIP system corporate and user files. The      viewing what motivated the deviations and
ronment to the new VoIP system.                             plan describes when to implement backup       their impact on schedule and cost, as well
                                                            procedures and when to resume normal          as how plans might be revised. Again, con-
Troubleshooting                                             operation. Network administrators make        sensus and follow-up will ensure that the
  During implementation, some Noblis                        daily backup files and take them to an off-    implementation proceeds according to the
users experienced a few seconds of voice                    site location for safekeeping.                agreed-on revisions.

         Vo i c e o v e r I n t e r n e t P r o t o c o l                                                                                           13
                                                  tion testing duplicates initial testing, but in
                                                  a real-world setting. It attempts to ensure
  Implementation action items:                                                                          Testing action items:
                                                  that all the equipment interconnections are
                                                  sound and that the network infrastructure
  • Develop an implementation schedule                                                                  • Conduct initial testing of VoIP system
                                                  is adequate.
    using a work breakdown structure.                                                                     components using all potential calling
                                                     Similarly, Noblis’ engineering staff and
                                                                                                          scenarios. Be sure that all appropriate
  • Decide if cutover will be phased or occur     CIM members—those ultimately respon-
                                                                                                          parties review and agree on the test pro-
    all at once and establish suitable training   sible for the VoIP installation and deploy-
    to ease the transition on users.              ment—prepared and reviewed the verifica-
                                                  tion test procedures. CIM and Noblis’ en-             • Conduct verification testing to baseline
  • Have a vendor meet with the project           gineering staff conducted the verification               system performance after installing the
    team to review all equipment settings         tests at the FVP facility. Testers simulated            system but before making it operational.
    and connections.                              the environment using equipment and net-
                                                  work connections like those in the opera-             • Conduct acceptance testing to identify
  • Incorporate network and system redun-         tional network.                                         and resolve operational problems. Make
    dancy and have a plan for backing up the                                                              sure that users have a backup service
    files associated with the VoIP system.         Acceptance                                              at this time.
                                                     Acceptance testing, which occurs after
  • Use project best practices to manage                                                                • Document all test plans and results,
                                                  the system becomes operational, ferrets out
    workflow and handle any deviations.                                                                    particularly for verification testing, which
                                                  any unanticipated problems. If the existing
                                                  voice system is still in operation, it can be           establishes the system’s baseline per-
                                                  a fallback if the VoIP system experiences a             formance.
                                                  major failure. Acceptance testing is the last
Testing                                           step to ensure the VoIP system’s integrity
  Testing includes developing a compre-           and viability.                                         he technology to enable a VoIP system
hensive test plan, test procedures, and a
test schedule. The test plan should cover
how to test the VoIP system equipment.
                                                     For Noblis, acceptance testing did not
                                                  involve formal procedures. Rather, engi-
                                                  neering staff and CIM members exercised
                                                                                                    T    has undergone significant advances in
                                                                                                         reliability and ease of implementa-
                                                                                                    tion, but activating a VoIP system within
Procedures should detail the actual equip-        the system to ensure that the functions and       an enterprise still requires careful planning,
ment settings and configurations to be test-       features operated according to their speci-       execution, and testing. It also requires ap-
ed, test sequences, and expected results. A       fications and reported any operational ab-         preciating the technical culture shock to
good strategy is to make the test schedule        normalities to Noblis’ help desk where net-       management, staff, and technical support
part of the project WBS.                          work administrators analyzed and resolved         personnel as they shift to a VoIP system.
                                                  the call problems after the level one trou-       An organization must strive to view the re-
Initial                                           ble desk operators took the calls. The help       quirements and service transition through
   Initial testing should be done in a labora-    desk continues to maintain a list of all VoIP     the users’ eyes so that individuals will em-
tory setting, in which the individual VoIP        operational troubles that stem from VoIP          brace the new VoIP service.
system components are tested as they              equipment malfunction. All solution strate-
would be configured when installed. Tests          gies are kept in a lessons learned database,
evaluate the components’ ability to handle        which CIM members access to maintain
all potential call types and use switch and       and troubleshoot the VoIP system.                 Guerin C. Goldsmith is a principal engineer
                                                                                                    at Noblis, where his experience includes
function settings that would occur in the                                                           telecommunications, VoIP, digital transmission,
real environment.                                 Test documentation                                IP-based video teleconferencing, analog/digital
                                                                                                    video technology and production, and program
   Noblis’ initial test procedures were             Test documentation is important in all          management. He received an MSEE from the
based on inputs from Cisco (its equipment         testing phases, but it is especially impor-       University of Illinois. Contact him at ggoldsmi@
vendor), SBC (its systems integrator), and        tant for verification testing, since testers
its CIM and engineering staff. All inter-         are recording the system’s performance at
ested parties reviewed these procedures at        the beginning of its life cycle. Such knowl-      Hsiaosu Hsiung is a senior fellow at Noblis, where
                                                                                                    his experience includes large-network simulation
SBC’s facility before any testing began,          edge is useful in activating equipment war-       and design, next-generation Internet, VoIP,
and Noblis’ engineering staff participated        ranties or in reviewing any performance           electronic commerce, secured access control
                                                                                                    technologies, Internet Protocol cyber attack,
in the actual testing.                            service level agreements in contractor or         public key infrastructure technologies, and data
                                                  vendor agreements.                                communications. He received an MS in computer
                                                                                                    science from the University of Connecticut.
Verification                                         Noblis documented test results and              Contact him at
  Verification testing occurs after the            equipment settings for the tests, which it
equipment is installed but before it be-          retains with other as-built drawings and
comes operational. In essence, verifica-           system documentation.

14                                                                                                                   Vo i c e o v e r I n t e r n e t P r o t o c o l

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