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3. computer networking
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An Open Source VoIP Solution for Healthcare
Capstone Research Project Report
April 25, 2015
Partha Pratim Roy
Subhamoy Pati
Suriaa Mathivanan
Debasmita Hazra
Interdisciplinary Telecom Program
University of Colorado Boulder
Abstract — This paper explores the feasibility of an open
source Voice over IP (VoIP) solution in rural healthcare.
The impact of technology on healthcare organizations has
expanded manifold as it helps them to streamline their
various processes. With the emergence of VoIP, many
healthcare organizations have moved from the legacy
Private Branch Exchange (PBX) systems, to VoIP systems.
This shift has observed significant reduction in the system
down time, and an improvement in the response time while
tackling any emergency situation. However, these
technologies have not yet been adopted to the full extent in
rural areas as well as in many developing countries due to
the high cost of deployment and maintenance of VoIP
systems. This research suggests that open-source systems
can be used to build a low-cost but effective VoIP solution.
This paper demonstrates an implementation using
Asterisk open source framework over wired and wireless
network infrastructure. The wireless solution is deployed
using open source DD-WRT firmware. The cost benefits of
the solution is compared to both traditional PBX systems
as well proprietary solutions. The results can lead to
potential increased adoption of VoIP in economically
constrained rural hospitals and maximize efficiency in
delivery of healthcare.
Keywords - VoIP, PBX, Asterisk, Open source, Wireless
I. INTRODUCTION
i. STATEMENT OF THE PROBLEM
The impact of technology on healthcare organizations has
expanded manifold as it helps them to streamline their various
processes. With the emergence of Voice over IP (VoIP), many
healthcare organizations have moved from the legacy Private
Branch Exchange (PBX) systems, to VoIP systems. This shift
has observed significant reduction in the system down time,
and an improvement in the response time while tackling any
emergency situation. However, these technologies have not
yet been embraced completely in rural areas as well as in
many developing countries due to the exorbitant cost of
deployment and maintenance of VoIP systems. This research
suggests that open-source systems can be used to build a lowcost but effective VoIP solution.
Jeffrey D. Dimaio
Adjunct Faculty
Interdisciplinary Telecom Program
University of Colorado Boulder
ii. RESEARCH QUESTION
Can a customized Open source VoIP solution be provided
for the rural healthcare community that is not only cost
effective, but also meets the requirements of the healthcare
organization? The following sub-problems have been
identified to answer this question:
A. Which VoIP features are most important for a rural
healthcare organization?
The healthcare focused VoIP solutions available in the
market today provide a wide array of features, but it
comes with a huge price tag. Considering a rural hospital
with low capital to invest on VoIP solutions, it is
important to identify which features are absolutely vital to
that organization. Collecting these requirements helps to
understand what type of Open Source products can be
used to cater their needs.
B. Can customized solution meet the requirements of rural
healthcare industry?
Healthcare industry has some specific requirements like
integration with other technologies like Electronic Health
Record (EHR), Nurse Call Communication System and
Patient Monitoring Systems. Further the VoIP solution
needs to provide additional benefits in form of better
collaboration among medical professionals and make
critical staff more accessible. Unless the benefits provided
by the Open Source VoIP solution meet the basic
requirements and provide greater efficiency, there will be
no motive to adopt it over legacy PBX’s.
C. Can our customized solution be cost effective?
The proposed solution needs to tackle cost concerns on
two fronts. Firstly we would need to analyze what the cost
incentives are to adopt an open source solution compared
to the existing proprietary options, and secondly, what the
cost savings are from transitioning to a VoIP solution
over traditional PBX.
1
D. Is the proposed Open Source solution easy to deploy?
Since the target audience for this Open Source VoIP
solution is rural healthcare facilities, it is imperative to
make the solution very easy to deploy, with minimum
operational overhead. However since this project will
involve open source coding and integration modules, it
may appear complex to the end-user.
II. LITERATURE REVIEW
The problem that persists today is that most VoIP based
proprietary healthcare solutions provided by Cisco, ShoreTel,
and Ascom comprise of closed and expensive components.
Contrary to this, the relatively inexpensive open source
solutions have not yet fully demonstrated their role in
resolving healthcare issues like nurse calls. Initially, legacy
telecom vendors started controlling the PBX systems [2]. With
the advent of IP PBX systems, companies like Cisco and
ShoreTel entered the market and there was a considerable shift
from hardware based PBX systems to software based PBX
systems [2]. However, this gave rise to proprietary constraints,
such as lack of flexibility and stability in product versions, and
caused less savings. The backend code for the proprietary
systems is closely guarded and any change to the same would
be released in accordance with the developing company’s own
interests. Chava and Ilow’s paper on integration of open
source and enterprise PBX system discusses the same with an
example of the Cisco Call Manager or the CCM, which is the
software-based call processing equipment of the Cisco IP
Telephony Solution [3]. It is also a part of the Cisco
Architecture for Voice, Video and Integrated Data or AVVID
[3]. The CCM necessitates the usage of Cisco’s Unity box for
an overall unified messaging system, which sends voice, fax
messages and emails to a single inbox [3]. Open source is
continuing to reshape these barriers and provide easily
available Application Programming Interface or APIs for
development by any interested party.
Open source IP PBX systems allow for modification of
the data systems by those who have the will to change the
existing, freely available source code to suit the company
needs. The IP PBX market currently has several open source
options in the form of Asterisk, SipXecs, Clearwater, and
XorCom. The source code of these Imaging Software or ISO
can be very easily downloaded from the market frontiers such
as tribox CE, elastix, FreePBX, and PBXinaflash [4]. As
compared to the commercialized VoIP products, the
mentioned Software ISO are available without a simultaneous
call license fee, per user license fee, or a phone license fee,
and are free from any mandatory support and maintenance
contracts [4]. Additionally, support for these software are also
available easily both via free and paid options.
Another advantage of open source facilities is that it has
customization capabilities unlike proprietary solutions [4].
Asterisk and other solutions like FreePBX, trixbox,
PBXinaFlash allow integration of services like click-to-dial,
databases, and other customer management tools [4]. All these
can easily be configured in the Command Line Interface of
any of the open source systems [4]. Contrary to this,
proprietary solutions do not provide access to their CLI and
any modifications can be brought about only via the
application’s web Graphical User Interface or GUI, and by the
system’s developers alone [4].
Open source systems started with the embrace of the
software depended modules, thereby gearing the drive towards
inexpensive and innovative alternatives to hardware based
solutions. Intel’s Host Media Processing software is one of the
earliest mainstream examples [3]. Using Intel’s software,
regular purpose computer platforms were able to create
applications involving both video and voice.
While proprietary systems are more robust compared to
open source systems, there are certain limitations to the same.
The ShoreGear 120/24 is specially designed for 120 IP users
or 24 analog users. Depending on the density of the location,
these gears can be customized accordingly [5]. However,
additional technical support is required every time the slightest
of modifications is required in the software. It is agreed upon
that most proprietary systems have an established global
presence. However, they also have serious restriction on the
choice of hardware and are fraught with stringent license
requirements. Cisco is one of the leading market frontiers in
PBX healthcare systems. Even then, it is bound to its own
products. While digital T1/E1 packet voice trunk network
runs on Cisco 2600 series and Cisco 3600 series routers, the
two-port T1/E1 digital voice port adapter modules operate on
Cisco 7200 series and Cisco 7500 series routers [6].
Correspondingly, Cisco MC3810 multiservice concentrators
are mostly observed in case of digital voice modules. Similar
is the case with ShoreTel [6]. This system comes with the
whole ShoreGear Voice Switches and ShoreWare Director
V.6 [6]. On the other hand, Asterisk is a completely open
source PBX software system that can run on Debian, Free
BSD, Linux and Centos [3]. Additionally, it can operate on
almost all equipment that is compliant with VoIP standards,
employing comparatively inexpensive hardware. For VoIP
purposes, Asterisk doesn’t require any additional hardware. It
even supports an extensive range of hardware devices for
establishing interconnection with either digital or analog
telephone equipment [3]. Digium is the most noted hardware
vendor for Asterisk products. However, these products are
equally compliant with vendors like RedFone and Sangoma
[3]. It even replaces the traditional switch network as a Public
Switched Telephone Network or PSTN gateway, soft switch,
and voicemail server, Plain Old Telephony Service or POTS
gateway, voicemail server, and music on hold server [3].
Open source solutions also provide the advantage of
interoperability with almost every VoIP endpoint in the
market, spanning Peripheral Component Interconnect or PCI
cards, Gateways Wi-Fi Phones, Session Initiation Protocol
Digital Enhanced Cordless Telecommunications or SIP DECT
solutions, etc [4]. This interoperability also allows the
mapping of the open source based PBX system to any phone
model and manufacturer.
Apart from Asterisk, there are other popular open source
applications in the domain of IP PBX systems like sipXecs,
OpenSIPS, Clearwater etc. Their common features include
unified messaging, voice messages and presence features, all
of which can be heavily used to improve the healthcare sector.
In addition to that, applications like SipXec follows a
2
centralized distribution system along with Point to Point
routing which provides for unlimited simultaneous calls and
improved voice quality and even prevents the Private
Automatic Branch Exchange (PABX) from becoming a single
point of failure [7]. Another relatively less popular open
source PABX is Yate, whose kernel is written in C++ but
supports Python scripting. Additionally, Yate provides
Interactive Voice Response, conferencing and allows VoIP-toPSTN gateway among other services [7]. FreeSWITCH is a
switching engine that is usually interfaced with other open
source PABX systems like sipXecs, CallWeaver, Yate or
Asterisk. It is also independent of the operating systems,
ranging from Solaris, Linux, Windows, and the BSDs [7]. It is
with the help of such platform independent and flexible open
source solutions that this proposal aims to resolve some major
healthcare issues.
III. RESEARCH METHODOLOGY
To research the solutions to the above mentioned sub
problems we implemented the following methodology.
Firstly, we researched some of the common barriers to
entry in VoIP and current state of the art in market. To
understand the needs of the rural healthcare organization we
decided to conduct a short survey at a private eye care hospital
in eastern India. Disha Eye Hospitals and Research Centre is a
chain of multi-specialty eye care hospital with locations in
both urban and rural areas. We interviewed IT administrators
as well as hospital staff of nurses and doctor. Based on their
feedback we determined the current challenges they face with
legacy phone system and their needs. Second, to analyze the
feasibility of an all open source based VoIP solution, we
deployed a lab set up.
To build our network infrastructure we decided to use the
following hardware and software.
Table 1 - Hardware and software requirements
HARDWARE
 Dell PowerEdge R805
Server
 Cisco 3800 Router
 Cisco Catalyst 3560 Switch
 Linksys E1200 Wi-Fi
Wireless Router
 TP-LINK Wireless N300
Home Router
 Raspberry Pi B+
SOFTWARE
 VMware Esxi 5.1
 Ubuntu 12.04
 Asterisk
Communications
Framework
 OpenLdap
 Zoiper (desktop and
phone app)
Secondly, we deployed the network infrastructure as
shown below to implement our open source asterisk based
VoIP solution and test out the requirements suitable for the
rural healthcare organizations.
Figure 1 - Network Diagram of Deployed Infrastructure
3
Thirdly, to enable mobility to the hospital staff we
deployed a wireless network. We used open source firmware
DD-WRT to build the underlying wireless infrastructure in
order to facilitate mobility for VoIP solution [11]. We used
cheap wireless routers flashed with DD-WRT open source
firmware making them robust. DD-WRT leverages full
hardware capabilities of the devices. Routers with this were
used in different network modes including Access points
(Wireless Gateways), Repeater bridge (wireless range
extender with wireless WAN) and Client bridge mode
(wireless range extenders) to provide full wireless coverage.
The default wireless parameters were adjusted to provide
better performance.
Finally, to quantify the cost savings from our open
source VoIP solution we first performed cost analysis of
transitioning to a VoIP based system from legacy TDM based
phone systems. We based this cost analysis on three
parameters, fixed monthly cost, one time installation cost and
yearly cost. For this research we assumed our rural hospital to
have 50 employees, out of which 10 are remote workers.
Based on the result we then calculated our Return on
Investment (ROI). Next, we compared the cost of our
customized open source VoIP solution against proprietary
solutions like Avaya, Cisco and Nortel based on the Total Cost
of Ownership (TCO) of each model. This comparative study
was based on the requirements of a small healthcare
organization having 20 end users. The cost from the vendors
are quotes received from them for the deployment. For this
research we focused on the infrastructure cost perspective as
currently we do not have a maintenance and onsite support
capability.
IV. RESEARCH RESULTS
Our research showed that VoIP is gradually being adopted
in healthcare sector as shown by the industry wise sale of
VoIP below.
Figure 2 - Demographics of VoIP Market [12]
However rural healthcare has its own set of challenges
and to understand that we surveyed an eye hospital in eastern
India. Based on our interaction with the staff at Disha Eye
Hospital and Research Centre, below is our survey result:
Table 2 – Survey Analysis
Survey Question
Answer
Do you have
access to
Internet?
Yes, a data circuit of 1 mbps
bandwidth is provisioned.
Have you
deployed VoIP?
No current VoIP infrastructure.
What are the
factors that have
led you to not
deploy VoIP?
Primary reason is cost of
implementation, secondly lack of
expertise in deploying and
maintaining VoIP solution.
What are some
of the issues that
you wish
technology could
manage for you?
I. Better call handling capacity –
Currently many patients are
unable to talk to the receptionist
because the receptionists are busy
speaking to someone else on the
phone.
II. Ability to collaborate with remote
doctors and patients – Some of
the rural branches of Disha Eye
Hospital lack senior doctors. In
some cases it becomes necessary
to refer a complicated patient to
city hospitals.
III. Integrating patient monitoring
systems – Currently the patient
monitoring systems are separate
entities deployed on the hospital
premises. An ability to bring them
under a common IT infrastructure
to provide “smart healthcare” is
desired.
Next we set up a lab network using Asterisk Open source
framework as our communication server. Based on our survey
result we decided to implement not only basic calling feature
but also collaboration tools like video and Voicemail. By
configuring support for H.264 and H.263p codec, our VoIP
system is able to support video calling. We were able to
support voicemail capability by simple configuration of
voicemail.conf and modifying user context in extensions.conf
configuration file. We also enabled ring group feature on our
asterisk system to support ring to simultaneous end devices.
To ease the automation of adding end users, we successfully
integrated OpenLdap [13], which is an open source light
weight active directory, with our Asterisk PBX.
Further our open source VoIP solution is compatible with
IP based patient monitoring systems. Using raspberry pi we
implemented an SIP based panic button which when pressed
would send an alert email to configured mail addresses as well
as a call to an emergency number 100 configured on our
Asterisk PBX. We were able to achieve mobility for VoIP
solution by deploying a robust underlying wireless
infrastructure. Transmission power, sensitivity, channel
4
bandwidth were altered to increase the signal to noise ratio
allowing increased coverage by at least 100 hundred more
meters and better performance. With the extenders in bridge
mode, the layer two domain is extended to cover the complete
infrastructure, thereby, alleviating the issues related to hard
hand-off (IP address change) during roaming between access
points. The results of our first and second part cost analysis is
given below.
Table 3 - Average Monthly cost of traditional PBX v/s IP PBX (VoIP)
Description
Quantity
Legacy circuits required
SIP Trunks
DID Trunks
1
17
50
Existing Network and PBX
costs (Monthly)
$450.00
N/A
$100.00
Long Distance Charges
220
$330.00
20 min / emp /
month
10
1
N/A
Audio Conferencing
Remote Worker Costs
Move, Add, Changes
Maintenance and Service
Facilities Cost (power, insurance,
space allocation, etc)
N/A
TOTAL
On site VoIP PBX and SIP Trunking
$0.00
$425.00
$0.00
N/A Long distance charges are
included in the Trunk Charge
$240.00
$0.00
$874.90
$50
$208.33
$0.00
$0.00
Included in equipment cost
$1200
$300
$3453.23
$725
Table 4 - Initial one-time cost of deploying Traditional PBX
One-time costs of traditional
PBX
Alcatel OmniPCX 4200,
including 3 DLC 8 extension
cards and CTI add on module
Alcatel 4019 digital business
phones
One-time costs ADSL
(modem/installation)
Protection against power
outage: APC Smart-UPC SC
420
Amount
Price
Subtotal
1
$1716
$1716
50
$160
$8000
1
$556
$556
1
$100
$100
TOTAL
$10,732
Table 5 - Cost of Open Source VoIP solution against proprietary solutions for 20 phone system [12]
One-time cost of IP PBX
Quantity
Price
Subtotal
Digium G200 VoIP Gateway
1
$1,995.00
$1995.00
Asterisk based Server
1
$420
$420
TP Link PoE Switch
4
$45
$180
Grandstream GXP 1400 IP
Phones
50
$40
$2000
TOTAL
$4595
5
Table 6 – Acquisition Cost of Open Source VoIP solution against proprietary solutions for 20 phone system [14]
Asterisk Based
Open Source
solution
$800 (no license
fee)
Acquisition Cost
Cisco
Alcatel Omni PCX
Shoretel
Avaya IP Office
Phones (including
license cost)
$8,100
$5840
$8160
$6160
Equipment
$10,681
$18,850
$12,158
$18,992
$2595
Installation/
training
$12,000
$3576
$4291
$3823
$3000 (training
cost per person)
TOTAL
$30,791
$28,446
$24,609
$28,975
$6395
V. DISCUSSION OF RESULTS
From the results we are able to prove that using open
source Asterisk communication framework we can set up a
VoIP system suitable for healthcare requirements. The
impact analysis of implementing a feature like video
conferencing is that now rural healthcare staff can connect
with their peers in cities and get real time consultation on
issues. Using ring group, an incoming call can now be
configured to either ring a set of phone numbers
simultaneously or ring phone 1, then phone 2 (if line 1 is
busy) and rest of the configured numbers sequentially. This
will be useful in emergency calling and reception areas. For
example, in case a nurse wants to speak to a doctor
immediately she will ring a helpline number, the call will
ring the phone of all the configured doctors and then
whoever picks up the call first will answer it.
By deploying our solution over both wired and wireless
infrastructure, we have enabled mobility in a dynamic work
environment. Thus, this will allow users with smartphones
to talk on the move by installing readily available free
Session Initiation Protocol (SIP) endpoint applications like
3cx and Zoiper. This also presents an opportunity for
hospitals to cut costs on hardware based phones.
Figure 3 – Cost Analysis of Traditional vs. IP PBX
6
The cost analysis of traditional PBX based system v/s
our IP based PBX solution shows a huge impact in savings
(fig. 4) for a healthcare organization. The five year ROI
calculation shows that we can save up to 78% with open
source VoIP implementation. This boosts our argument that
VoIP can be a cost effective solution in the long run for a
healthcare organization. The comparative analysis of our
open source VoIP implementation to proprietary solutions
shows that open source can be a much cheaper alternative
than enterprise solution from big vendors. The graph in
Figure 4 shows that our solution is almost 74% cheaper than
the nearest competitor (Shoretel). However, it is to be noted
that when you buy a proprietary solution you get customer
support for the product, but our solution currently has no
support organization.
VI. CONCLUSION AND FUTURE RESEARCH
The rural healthcare community is still a laggard in
adoption of VoIP technology primarily due to concerns over
cost. Through our research we have demonstrated how open
source VoIP platform can be leveraged to build cost
effective solution for a small to midsize healthcare facility.
We have performed cost analysis of our solution against
enterprise solutions like Cisco and Avaya and compared the
cost savings for a similar set of features. Our research is
based on both wired and wireless infrastructure, thus
providing the necessary flexibility in a healthcare
organization. The solution presented will not only reduce
operational expense of the organization but also enable rich
multimedia features. The open nature of the components
involved makes the solution vendor neutral, which will
enable greater adoption of VoIP in developing countries
where proprietary solutions are not available or too costly to
afford. Furthermore, although the solution is designed for
rural healthcare, the benefits can be easily realized in other
underprivileged sectors like rural education and cooperatives.
Future research should encompass the current
limitations of the solution, such as maintenance and fault
resolution. As rural organizations face a shortage of talented
IT staff, a support network will be required to facilitate
management of our proposed VoIP solution. The support
network will be a not-for-profit organization and can be
funded by NGO’s working for rural development. The
support organization can become a strategic partner of
existing open source organizations like GNU Health, to
bolster adoption open source VoIP. However the feasibility
of such an organization needs to be analyzed. Further
research needs to be done on developing healthcare specific
“apps” that can run on top of our VoIP solution and provide
greater functionality like health profiling, and electronic
exchange of patient information over unsecure medium. A
long term strategic direction would be to host the VoIP
solution
on
cloud
platform.
Offering
Unified
Communications as a Service (UCaaS) would ease the
burden of onsite maintenance and support. However it
would also bring interesting challenges and the results are
yet to be seen.
VII. REFERENCES
[1]. M. Daniel, and M. Emma, “Delivering Voice over IP
Networks”, Wiley Computer Publishing, 1st edition, 1998,
ISBN 0-471-25482-7
[2]. “The evolving role of hardware as a key enabler of open
source telephony in the business market,” InfoSecToday, J.
Arnold and Associates, Jul 2006. Available:
http://www.infosectoday.com/ITToday/SangomaWPJuly06.
pdf
[3]. K.S. Chava and J.Ilow, “Integration of open source and
enterprise IP PBXs,” in Proc. of the 3rd International
Conference on Testbeds and Research Infrastructure for the
Development of Networks and Communities, May 2007, pp.
1-6.
[4]. G. Smith, “The upsides and downsides of open source
voip systems,” Jun 2010. Available:
http://www.voipsupply.com/blog/voip-insider/open-sourcevoip-systems-pros-cons/
[5]. W. Rash, “Easy management makes shoretel pbx a
delight,’ in InfoWorld, vol.28, Trade Publications, 2006,
pp.36.
[6]. “Configuring pbx interconnectivity features”, in Cisco
IOS Voice, Video, and Fax Configuration Guide. Available:
http://www.cisco.com/c/en/us/td/docs/ios/12_2/voice/config
uration/guide/fvvfax_c/vvfpbx.html
[7]. R. Gedda, “Five open source to IP telephony projects to
watch,” in CIO Magazine, Oct 2009. Available:
http://www.cio.com.au/article/323016/five_open_source_ip
_telephony_projects_watch/
[8] M. Ahmed and A.M Mansor ,"Cpu dimensioning on
performance of asterisk voip pbx,” in Proc. of the 11th
communications and networking simulation symposium
(CNS '08),New York, pp. 139-146, 2008, doi:
10.1145/1400713.1400737
[9] A. D. Keromytis, “Voice over IP: Risks, threats and
vulnerabilities,” in Proc of the Cyber Infrastructure
Protection (CIP) Conference, June 2009.
[10] V. K. Gurbani and V. Kolesnikov, “A Survey and
Analysis of Media Keying Techniques in the Session
Initiation Protocol (SIP),” IEEE Communications Surveys
and Tutorials, 2011.
[11] DD-WRT. Com, Main page- DD-WRT, [online].
Available: http://www.dd-wrt.com/wiki/index.php/
[12] J. Jones. (2014, Aug 18). voip software small business
buyer, Buyerview [Online]. Available:
http://www.softwareadvice.com/voip/buyerview/report2014/
[13] The OpenLDAP Project, OpenLDAP software, [online]
2014. Available: http://www.ittc.ku.edu/~krsna/citing.htm#
7
[14] Evaluating the total cost of ownership for small to
medium business voip phone systems, Savatar, 9 Harcourt
Street Boston, MA, pp. 1-9. Available:
http://www.adtran.com/pub/Library/White_Papers/Evaluati
ng_the_Total_Cost_of_Ownership_for_Small_to_Medium_
Business_VoIP_Phone_Systems___Savatar.pdf
VIII. ACKNOWLEDGEMENT
Our sincere thanks to Prof. Jeff Dimaio for his
insightful comments and expertise that greatly supported
this project. We would also like to thank Prof. Jose Santos
for assisting us with his valuable advice and with the
hardware required for our research. We are also thankful to
the staff of Disha Eye Hospitals and Research Centre for
their kind co-operation and participation in the survey that
helped identify the goals of this effort. We extend our
sincere thanks to Dr. David Reed for his constant guidance
and supervision in pursuit of the successful completion of
the research work.
DSCP
Differentiated Services
Code Point
EHR
Electronic Health Record
GUI
Graphical User Interface
HIPPA
Health Insurance Portability
and Accountability Act
PABX
Private Automatic Branch
Exchange
PBX
Private Branch Exchange
SIP
Session Initiation Protocol
VoIP
Voice over IP
QoS
Quality of Service
WAN
Wide Area Network
WLAN
Wireless Local Area
Network
Appendix 1: List of resources
Hardware
Asterisk SIP Server PoE
switch, 3rd Party Sip Phones
Firewall
Juniper/ Cisco/ Checkpoint
User Administration
OpenLDAP
Voice Gateway
Cisco with PRI card slots
Software
Avaya Call manager, DDWRT (Linux based
alternative Open Source
firmware for WLAN
routers)
Appendix 2: List of Acronyms
API
Application Programming
Interface
AVVID
Architecture for Voice,
Video and Integrated Data
CCM
Cisco Call Manager
8