Design and Conﬁguration of Context-aware VoIP Telephony Systems

Slawomir Nasiadka

Gdansk University of Technology, Narutowicza 11/12, Gdansk, Poland

Keywords:

Context, Context-aware, VoIP, Telephony, Design, Conﬁguration.

Abstract:

Voice over IP is a widely used concept with regard to a realization technology of different types of telephony

systems, including those that are used in enterprises. Such systems consist of a call processing component and

a set of desk endpoints that are pervasive from a user perspective. Those endpoints are usually not mobile,

but in result can deliver a much greater set of functions needed in an everyday ofﬁce work (e.g. secretary

and attendant features). Those functions also make VoIP telephony systems well suited for using a context

information to adapt to the situations of their users. The paper presents an approach to designing such systems

from a context-aware point of view and organizing a conﬁguration of their objects. A sample deployment has

been prepared and evaluated.

1 INTRODUCTION

A context (Krawczyk and Nasiadka, 2011) with re-

gard to a communication between people can be used

in different ways (Schilit et al., 2007). However, they

mostly regard cell phones and extension of their ca-

pabilities to interpret context data. Apart from those

devices there is also a group of telephony systems

(TS) used within enterprises and smaller companies.

They consist of distributed or centralized call process-

ing system and a set of desk endpoints (or softphones)

that are pervasive from a user perspective. Those end-

points can deliver a much greater set of functions that

are needed in an everyday ofﬁce work (e.g. secretary

and attendant features) than cellular phones. Such

TS systems are often VoIP (Johnston, 2009) based

solutions. As enterprises are global and hire great

number of people located worldwide, those systems

can become very large and complex. Nevertheless,

they are supposed to offer their users a context-aware

functionality. Delivering it can be challenging from

a design and conﬁguration point of view. The aim

of this article is to propose a new approach to design-

ing enterprise telephonysystems and conﬁguring tele-

phony objects (e.g. endpoint devices) using informa-

tion about their context. There has been prepared a

sample deployment of a VoIP TS enhanced with the

environment based on the system for dynamic ser-

vice integration described in (Dziubich et al., 2012).

Thanks to the presented approach the design process

regarding context-awareness can be systemized and

TS can dynamically adapt to changes in its and its

users environment.

The reminder of the article is constructed as fol-

lows. Section 2 describes state of the art regarding

context-aware behavior of telephony devices. In sec-

tion 3 there is presented a model of a VoIP telephony

system (VoIP TS). Section 4 describes how a context

is used in VoIP TS across its layers. In Section 5 there

is introduced a new approach to designing and con-

ﬁguring context-aware VoIP TS. This approach has

been used to prepare a sample deployment which is

described in Section 6. This section also brieﬂy de-

scribes experimental results regarding introduction of

that approach. Section 7 summarizes the paper.

2 RELATED WORK

The vast majority of publications regarding context-

aware telephony refer to mobile interruptions. They

address the problem of cell phones ringing at inap-

propriate moments (such as in a theater). In the pa-

per (Schmidt et al., 2000) authors propose a mech-

anism that addresses this issue. Each mobile phone

user can choose a state which expresses if he is will-

ing to receive calls. Callers can then check what

is the status of the person to whom the call is to

be made and decide whether to make a call. An-

other approach is presented in the publication (Raento

et al., 2005), where authors describe a framework that

allows to automatically collect information about a

context of a mobile phone user. This context can

Nasiadka S..

Design and Conﬁguration of Context-aware VoIP Telephony Systems.

DOI: 10.5220/0004314100420048

In Proceedings of the 3rd International Conference on Pervasive Embedded Computing and Communication Systems (PECCS-2013), pages 42-48

ISBN: 978-989-8565-43-3

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

then be presented in various forms to the caller who

can decide whether to continue with the call. How-

ever, such an approach means sharing certain pri-

vate information (e.g. location) about people. The

paper (Khalil and Connelly, 2006) draws attention

to this aspect and describes what are people prefer-

ences regarding providing information about their sit-

uation. Described publications touch different aspects

of VoIP telephony systems (including design, tools

and frameworks), however they mostly regard mobile

phones which greatly differ from enterprise VoIP sys-

tems. Another approach has been described in (Chi-

han et al., 2012), where authors concentrate on creat-

ing a framework for developing context-aware com-

munication systems. That work focuses on communi-

cation services, but lacks the analysis of how a design

and conﬁguration of particular objects existing in a

telephony system should be organized with regard to

context-awareness.

Some commercial systems (like Cisco Uniﬁed

Communications Manager) already use context data.

For instance, Cisco softphonesmay be used by mobile

users in different locations where the same distributed

VoIP TS is deployed. Because of using VoIP technol-

ogy the current location can be easily recognized (e.g.

by the IP address) by the TS and during a registra-

tion of an endpoint and it can be assigned a different

set of conﬁguration entries than in its home location.

That set of entries can inﬂuence mainly on its dial-

ing capabilities (e.g. allowing dialing only internal

calls) and on a codec it uses to encode a voice stream.

A context can also be used during assigning different

call routing rules. E.g. depending on a current time,

an endpoint may have different dialling restrictions.

During work hours it can be allowed to dial any type

of numbers, but after work hours only internal and

emergency calls are allowed. However, commercial

products make use of only limited context data and

only in some particular conﬁguration aspects.

3 VoIP TELEPHONY SYSTEM

MODEL

Telephony systems can be described using a layered

model which is shown in Figure 1.

The lowest layer (endpoints layer) represents

physical devices that are used by users to make calls

(phones, softphones). That layer also includes gate-

ways to Public Switched Telephone Network (PSTN)

and other devices or software that are used as termina-

tion points of media streams (such as media resources

- like transcoders, conference bridges, and so on).

Those devices register to a TS through a register (reg-

Figure 1: A telephony system layered model.

istry layer), which includes information about values

of parameters describing endpoints. Those parame-

ters may represent a location of a device, its codec or

video capabilities and so on. They are used in the pro-

cess of call routing and establishment. That process is

actually the most important one in every TS and is lo-

cated in a separate layer - call routing layer. Based on

the information from the registry the call routing pro-

cess, routes and establishes calls between endpoints

based on the input from a caller. The top layer - ap-

plication layer - represents applications that utilize the

call routing and establishment process, such as Au-

tomatic Call Distribution (ACD) or Auto Attendand

(AA). Within each of the presented layers there have

to be conﬁguration, security and safety mechanisms

available.

A VoIP Telephony System (VoIP TS) is a tele-

phony system that uses the Internet Protocol (IP) as

a transport protocol for voice and signalization pack-

ets. On the one hand it simpliﬁes the management

of the infrastruture, but on the other hand it causes

difﬁculties in guaranteeing proper QoS characteristics

- mainly regarding latency, jitter and queue manage-

ment (Verma, 2011). That is why across all the lay-

ers of the ISO/OSI model (Tanenbaum, 2010) there

have to be introduced advanced QoS mechanisms

(like LLQ - Low Latency Queuing). Another feature

that is available to users in VoIP TS systems is a mo-

bility of endpoints. Wherever a particular endpoint is

connected to the IP network, if only it can communi-

cate with its VoIP TS, it can register and function with

the same settings as in the home location. That gives

users a consistent experience and allows administra-

tors to easily manage a whole telephony infrastruc-

ture. Moreover, those endpoints also provide addi-

tional functionalities like access to web applications.

As it can be observed the usage of the IP protocol

mostly incluences on the endpoints and registry lay-

ers. Often the QoS mechanisms are controlled by the

call routing layer.

Deploying a VoIP TS is a complex process which

most important parts are a design and a conﬁguration

of particular TS mechanisms and objects across all

DesignandConfigurationofContext-awareVoIPTelephonySystems

the layers of the TS layered model (see Figure 1).

Those parts are organized according to the user re-

quirements which may regard a context-awareness.

Because those requirements may be formulated late

by the users during the deployment (e.g. based on

the experience of using a partly deployed TS system)

an agile-based approach is necessary. To introduce a

new approach to designing and conﬁguring a context-

aware VoIP TS there will be analyzed a sample VoIP

TS deployment. Its initial set of requirements is sum-

marized in Table 1.

Table 1: Initial set of requirements for the sample VoIP TS

deployment.

Id Requirement

1 200 users in different locations (geograph-

ically distributed)

2 a redundancy (2 sites)

3 a local PSTN access and a toll bypass

functionality

4 Direct Dial-In (DDI) numbers for users

5 calling to international numbers should be

available only for a particular group of

users

6 a Voice Mail account for each user

7 an ability to move users between loca-

tions and an automatic adjutsing of conﬁg-

uration parameters of their endpoints (e.g.

codecs)

8 after work hours all incoming calls should

be routed directly to cell phones or voice

mail when no answer

9 an administration should only be allowed

for users with appropriate skills

10 a line description, a presentation and a

phone language should change after a user

logs into a workstation

Some of the requirements regard functionalities

that don’tdepend on context(like number of usersand

telephony numbers that they use). However, some of

them are context-aware (with ids 7 - 10). How a con-

text can be utilized in TS VoIP systems is described

in the next section.

4 CONTEXT IN VoIP TS

With regard to context-awaresystems there can be de-

ﬁned two types of input data (Krawczyk and Nasi-

adka, 2011). In case of a context-aware VoIP TS the

ﬁrst one is related to the user input which is a tele-

phony number that the user enters to reach a called

party (called DNIS number). The second one is the

data that create context which can inﬂuence on differ-

ent aspects of the TS behavior that are spread among

layers from the model presented in Figure 1.

4.1 Endpoints

Endpoints can perform sensing, processing and act-

ing functions. This is possible because in a VoIP TS

they need to perform complex operations during each

call (e.g. a TCP/IP connection establishment, encod-

ing voice). Hence, they are equiped with a processor

and memory which can also be utilized to perform

additional operations, that are not directly related to

the telephony. Those operations can be context-aware

(e.g. switching a device to an idle mode after a par-

ticular amount of inactivity time). Thanks to this, the

usage of a VoIP enterprise telephony makes the space

where it is deployed intelligent (Intelligent Space -

IS). That is further used in such concepts as intelli-

gent buildings, where telephony endpoints are used

as interfaces for users to non-telephony systems (like

controlling an air condition or a room automation).

4.2 Registry

A registry that contains all the information about end-

points also needs to allow to enhance them with con-

text data. Moreover, it should be possible to change a

conﬁguration of entries based on the current context.

That is crucial e.g. for mobile users, who can con-

nect an endpoint to the infrastructure anywhere they

are. Depending on a location and other context data

the informationcontained in the registry should be ap-

propriately changed, so that e.g. a codec negotiation

and call routing mechanisms can behave correctly.

4.3 Call Routing

Because of the use of the IP protocol for transporting

media packets, different quality issues in a VoIP TS

may arrise. Hence, depending on the situation in the

network layer (which may also be included in a con-

text) and information contained in the registry, the call

routing mechanism has to establish connections dif-

ferently to maximise a quality of calls (e.g. in case of

a total Wide Area Network bandwidth saturation the

VoIP TS system should use external PSTN circuits to

establish long distance calls). Other type of context

PECCS2013-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

data that can be used during execution of processes

from this layer is the current time.

4.4 Applications

A behavior of additional call handling applications

(e.g. Interactive Voice Response, Voice Mail, Auto

Attendant) may be different depending on an ANI

number, a time, data, a proﬁle of a caller and so on.

A management and administration of the system and

a login and logout functionality for users also creates

context that can be used by applications.

Because endpoints provide an access to function-

alities and information anytime and anywhere, they

can be treated as pervasive devices. As a result, the

layered model presented in Figure 1 can be divided

into a pervasive part, which consists of the endpoints

layer and a ubiquitous part, which consists of the reg-

istry, the call routing and the applications layer. That

reﬂects the nature of enterprise telephony systems,

where endpoints are distributed among users (they are

physically close to them and each user has his own

endpoint) and the rest of the system is logically cen-

tralized but accessible anywhere users need.

From the set of requirements presented in Table 1,

last four of them regard context-awareness. To deliver

a system which meets those requirements it is nec-

essary do go through the process of its deployment

which mainly includes design and conﬁguration.

5 DESIGN AND

CONFIGURATION APPROACH

FOR CONTEXT-AWARE VoIP TS

A deployment of a context-awareVoIP TS can be sys-

temized with the usage of the layered model presented

in Figure 1. A resulting approach is organized accord-

ing to the Agile method. Firstly, the requirements

for a new VoIP TS deployment have to be assigned

to the particular layers of the TS model. Next, each

of the requirements needs to have assigned a priority

expressing its importance from the user perspective.

Based on the analysis, for each requirement there can

be assessed a time that is needed to prepare a nec-

essary conﬁguration. The conducted analysis should

include a necessary design of a part of the VoIP TS

(which will satisfy the requirements) as well as inter-

ferences with the already deployed parts of the sys-

tem. The design that regards context-aware require-

ments should include deﬁning a situation (particular

context) to which appearance in the space the VoIP

TS will react, and also which conﬁguration changes

in the TS will take place. Based on the priorities, as-

sessments and time constraints the deployment pro-

cess can be divided into separate iterations. After

each iteration is completed, there is delivered a use-

ful from the user perspective functionality that can be

tested and accepted. That also allows users to intro-

duce new or correct previously speciﬁed requirements

along with the progress of the deployment, which is a

common situation during VoIP TS deployments. The

organization of the sample deployment which resulted

from implementing described approach is presented

in Table 2 (context-aware requirements are marked

with ’(c)’).

Comparing to the initial set of requirements (see

Table 1) a one additional requirement has been for-

mulated by users. After they used a partly deployed

system (delivered in the ﬁrst iteration) users decided

that when someone logs out from a workstation, an

ofﬁce phone should switch to a stand-by (idle) mode

and should require an authorization for making calls.

That requirement (with id 11(c)) appeared during the

second iteration and its realization has been planned

for the third iteration. Within each iteration after the

design is completed, a necessary conﬁguration needs

to be prepared.

VoIP TS systems may need to behave differently

depending on their (and their objects) context. Hence,

a particular object (apart from the initial conﬁguration

needed to satisfy context-unaware requirements) may

need to be reconﬁgureddepending on context data de-

livered by sensors (i.e. endpoints - see Section 4 or

other sources). Nowadays, such context-aware recon-

ﬁguration can be based on a limited set of parameters

(most often a time and a location). However, VoIP

TS systems can be deployed in different environments

and the deﬁnition of a context can change between

deployments. That is why a VoIP TS should have a

capability of deﬁning a context and based on it - re-

conﬁguring its particular objects. Context data can be

sent by sensors using a SIP protocol (Pan et al., 2003)

(in a form of additional headers) which is widely used

in the telephony signalization.

Regarding an aspect of context-awareness, VoIP

TS systems can be modelled using the CAA model in-

troduced in (Krawczyk and Nasiadka, 2011). As such

their architecture can be extended with components

needed to execute CAA applications. Those compo-

nents are responsible for context analysis, commu-

nication with sensors, knowlegde base management

and changing conﬁguration. The implementation of

such extension for a particular VoIP TS deployment

has been described in the next section.

DesignandConfigurationofContext-awareVoIPTelephonySystems

Table 2: An organization of design and conﬁguration tasks in the sample deployment.

Requirement

Layer Priority (1 -

highest)

Time assessement in

MD - ManDay

Iteration

number

1, 2 application layer 1 25MD 1

3 call routing layer 1 5MD 1

4, 5 registry layer 1 7MD 1

6, 9(c) application layer 2 11MD 1

7(c) registry layer 1 5MD 2

8(c) call routing layer 2 1MD 2

10(c) registry layer 2 10MD 2

11(c) endpoints layer and registry

layer

2 5MD 3

6 IMPLEMENTATION

To see how the presented approach behaves in a real

life scenario, there was prepared a sample deploy-

ment of a VoIP TS. It was organized according to

Table 2. The deployment was based on the Cisco

Uniﬁed Communications Manager (CUCM) 8.5 plat-

form. That platform already has some context-aware

mechanisms built into the registry and the call rout-

ing layers but they are too limited to fulﬁll all the re-

quirements presented in Table 2 (i.e. requirements

9, 10 and 11 were not satisﬁed). Hence, those

mechanisms were enhanced by the introduction of an

execution environment for CAA applications (later

called CAAEE) which was based on the system for

dynamic service integration described in (Dziubich

et al., 2012). The resulting structure of the deployed

system is presented in Figure 2.

The CAAEE environment consists of a base ser-

vices environment component, a context analysis

component, an action execution component and a

knowledge base component. The base services en-

vironment component communicates with custom

.NET applications (installed on user workstations)

which deliver context data. The data included a name

of a user that logged in (or logged out) to the work-

station associated with the endpoint (an association

was conﬁgured in the CUCM) and a current time.

It was then analyzed in the context analysis compo-

nent. Based on the analysis, a particular conﬁgura-

tion change was applied (through the action execu-

tion component of the CAAEE) to the telephony ob-

ject using the AXL (Administration XML) interface.

Based on the context-aware requirements there were

designed the following rules which were further im-

plemented in the CAAEE (each entry is in a form: a

situation - a necessary change in the conﬁguration):

• a user has logged out from the workstation - make

a copy the CSS of the phone along with its parti-

tions and patterns belonging to the partitions, en-

able the Forced Authorization Code setting on the

patterns and set the new CSS on the phone; set the

idle URL on the phone,

• a user has passed a training on the CUCM and

gained a knowledge about the CUCM conﬁgura-

tion - change the user proﬁle in the CUCM so that

the user can save conﬁguration changes,

• a user has logged in to the workstation - change

the CSS of the phone to the one that contains par-

titions that don’t force an authorisation, (if exists)

delete the CSS forcing an authorization, unset the

idle URL, set a new line description, a presenta-

tion and a language settings.

The endpoints (Cisco 7965 IPPhones) sent their

IP address directly to the CUCM during registration.

Based on this information an appropriate Device Pool

was chosen. That allowed to adjust conﬁguration

paramters for the endpoint according to its location

which was determined based on the IP address. Addi-

tionally, a current time was also analyzed internally

by the CUCM call routing process for each routed

call. That analysis was performed on a partition level

and enabled changes in the routing so that after work

hours all incoming calls were routed to a voice mail

or cell phones.

The use of CAAEE allowed to satisfy all the re-

quirements that were identiﬁed in the Table 2. Some

of them could be satisﬁed without that additional

PECCS2013-InternationalConferenceonPervasiveandEmbeddedComputingandCommunicationSystems

CAA Execution

Environment

(CAAEE)

Telephony system

Call routing layer

Application layer

Registry layer

Endpoints layer

Security, Safety, Quality

Phones (endpoints)

Applications

Context

data

(

)

Configuration

Context

data

Figure 2: The structure of the sample context-aware VoIP TS system.

component - particularly context-unaware require-

ments (with ids 1 - 6) as well as context-aware ones

for which the CUCM built-in mechanisms were sufﬁ-

cient (requirements with ids 7 - 8). It is worth to men-

tion the latter regarded the call routing which is a real-

time task. It can be expected that the use of a context

during execution of those tasks can be limited only to

built-in mechanisms as the additional analysis of con-

text data can make them last unacceptably long. How-

ever, a conﬁguration of those tasks (which doesn’t

have to be completed in a real-time) can successfuly

be enhanced with a context-awareness. Hence, the

CAAEE could be used for changing conﬁguration of

telephony objects across all the layers from the lay-

ered model presented in Figure 1. A particular change

of the conﬁguration needed to satisfy requirements

with ids 9, 10 and 11 took about 3 seconds (measured

from the time the situation appeared in the IS to the

time that the new conﬁguration was sent through the

AXL interface). In case of the CUCM platform it is

also important that after some conﬁguration changes

the endpoint has to be restarted. However, as those

changes are done rarely (login and logout from the

workstation) it wasn’t annoying for users.

7 CONCLUSIONS

The paper presents a new approach to designing (and

more generally deploying) and conﬁguring context-

aware enterprise VoIP telephony systems. Thanks to

this approach a deployment process can be system-

ized and agile-oriented. To prove that the proposed

approach is useful there has been prepared a deploy-

ment based on a commercial VoIP telephony solu-

tion. The implementation showed that a VoIP TS can

be succesfully designed according to the presented

method and that a proposed mechanism of changing

a conﬁguration based on the current context is useful

and feasable for users. For the sample deployment

there was used a currently available system for con-

text analysis and adaptaion action execution. It al-

lowed to dynamically change a conﬁguration of par-

ticular telephony objects so that they behave more

convenient from the end user perspective (they adapt

to the current situation).

It is worth to mention that the proposed organiza-

tion of a design and a conﬁguration processes signif-

icantly differ from those that are used currently. This

is because interactions between objects cannot be ex-

plicitly expressed within a conﬁguration. They need

to be taken into account by designing an appropriate

contexts based on which a particular conﬁguration is

chosen. That is why it may be more difﬁcult to deploy

a VoIP system and test it before running in production.

A requirement for new supporting tools arises in this

area.

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