Int. J. Enterprise Network Management, Vol. 2, No. 3, 2008
301
Planning, designing and implementing an enterprise
network in a developing nation
Augustine C. Odinma*, Sergey Butakov,
Evgeny Grakhov and Felix Bollou
School of IT and Communications
American University of Nigeria
Yola Bypass, Yola, Adamawa State, Nigeria
E-mail: aodinma@yahoo.com
E-mail: Sergey.butakov@gmail.com
E-mail: Grakhov@gmail.com
E-mail: Bollou@gmail.com
*Corresponding author
Abstract: The enterprise network is the lifeblood of any Small to Medium
Enterprise (SME) with more than one site or supply chain partner. It enables
access to business information and allows for profitable and effective
communication flows between employees in different enterprise sites. Network
enterprise network equipment are mature and ubiquitous, but the quality of
services provided by similar networks varies from city to city and from country
to country. In particular, the quality variation gap between most of the cities in
some developing nations and their counterparts in advanced nations is very
wide. This is due to the lack in developing nations of an adequate IT
infrastructure, which is taken for granted in developed nations. Planning an
enterprise network in a developing nation is almost like planning it in the
middle of a desert. This paper briefly discusses the architecture of an enterprise
network. It examines the barriers to planning, designing and implementing an
enterprise network in some developing nations. This paper also compares the
services between a typical city in a developing nation and that in an advanced
nation and offers some recommendations for creating an enabling environment
for improvement.
Keywords: enterprise networking; network quality; Virtual Private Network;
VPN; MAN links; infrastructure barriers; enterprise network planning;
enterprise network design; enterprise network implementation.
Reference to this paper should be made as follows: Odinma, A.C., Butakov, S.,
Grakhov, E. and Bollou, F. (2008) ‘Planning, designing and implementing an
enterprise network in a developing nation’, Int. J. Enterprise Network
Management, Vol. 2, No. 3, pp.301–317.
Biographical notes: Dr. Augustine C. Odinma is a Professor of IT and
Communications at the American University of Nigeria. He was the Director of
Network Solutions for EMEA, Lucent Technologies. He was also a Senior
Manager – Capacity Management at AT&T Labs, NJ and a Professor of
Electrical, Telecommunications and Computer Engineering at Lagos State
University. He obtained his PhD in Telecommunications Engineering from the
University of London. His research interests are in communications network
planning and design, switching technologies, stochastic processes, data
characterisation and engineering management. He is a prolific writer and has
written many papers in the field. He has also chaired many professional
conferences internationally.
Copyright © 2008 Inderscience Enterprises Ltd.
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A.C. Odinma, S. Butakov, E. Grakhov and F. Bollou
Dr. Sergey Butakov has a PhD in Computer Science from Altai State
University, Russia. He is an Associate Professor of IT at the American
University of Nigeria. In 2000 he was recognised by Altai State Technical
University with the Best Young Scientist Award and in 2006 he received the
Excellence in Teaching Award from the American University of Nigeria.
In 2001–2004, he was Principal Researcher on two projects supported by
the Russian Foundation for Basic Research. He is interested in network
applications, data mining, artificial intelligence and neural networks.
Dr. Evgeny Grakhov has a PhD in Physics from Altai State Technical
University, Russia. He is an Associate Professor of IT at the American
University of Nigeria. He received grants from the President of the Russian
Federation and the International Soros Science Education Program following
research experiences in the field of computer modelling in the physics of solids.
He is interested in network applications, computer modelling in the physics of
solids, Database (DB) and DB applications design.
Felix Bollou is a faculty member in the School of Information Technology and
Communications, American University of Nigeria. He was Research Scientist
at the Institute for Innovation and Technology Management of Ryerson
University of Canada. Bollou is a PhD candidate at Aarhus School of Business,
Aarhus University, Denmark. He holds an Engineering degree in Computer
Science and a DESS (Master) from the Institute of Business Management,
University of Paris 1, La Sorbonne, France. Bollou’s research is in the areas
of information systems and applied economics. His current research focuses
on the impact of Information and Communication Technology (ICT) on
development in West African countries.
1
Introduction
Small to Medium Enterprises (SMEs) have a growing impact in this age of globalisation,
particularly in developing nations. An SME is said to be a major social and economic
contributor to the Indian economy (Ghose, 2001); it provides increasing production and
employment growth more than large enterprises do (Tuteja, 2001). This increasing
popularity has placed enormous pressure on SMEs to enhance the way they run their
business in order to be more competitive in the current global environment. Many
authors have argued that, in order to be competitive, SMEs in developing nations
inevitably need the right information at the right time (Sharma and Bhagwat, 2006;
Bhagwat and Sharma, 2007). Bhagwat and Sharma (2006) further argue that SMEs in
developing nations need a concentrated formulation and implementation of Information
System (IS) strategies in order to exploit the benefits of the system. In a study of SMEs in
India (Sharma et al., 2005), it was discovered that SMEs were not using all IS features
either due to limited appreciation of the IS, lack of IS awareness and management or the
cost of doing so. These were the reasons joint ventures or collaboration among SME
clusters was suggested (BarNiir and Smith, 2002; Berlak and Weber, 2004; Childe, 1998;
Jagdev and Thoben, 2001).
An SME is somewhat clumsy to define. It is often defined with respect to industry
type and sometimes by the number of employees in an enterprise. It is therefore not
surprising that each country has a somewhat different meaning (Ghose, 2001) of an SME.
Planning, designing and implementing an enterprise network
303
Furthermore, many writers believe that SMEs differ in so many ways from larger
enterprises (Sharma et al., 2005; Sharma and Bhagwat, 2006; Bhagwat and Sharma,
2006; Appiah-Adu and Singh, 1998; Berry, 1998; Marri et al., 1998).
There is unflinching agreement that IS/IT is essentially the key to SME success in
competing in the global market. An IS has been defined as an organised combination of
people, hardware, software, communication network and data resources that collects,
transforms and disseminates information within and among organisations (Sharma et al.,
2005). An IS provides integration of critical business information among supply chain
trading partners (Bhagwat and Sharma, 2007). These definitions presuppose effective
implementation of IT and telecom policies, which are necessary platforms for an IS to
thrive. Most of the commentary stresses prominently the need for ISs to be addressed
extensively in SMEs in India, but this view does not take into consideration
the fact that there are many developing nations where the IT and telecom infrastructure
is a bottleneck to IS implementation. There is no doubt that in India, there is a
well-entrenched IT/IS infrastructure in the system. This is not true for most developing
nations in sub-Saharan Africa. In most African countries, the IT/IS infrastructure that is
ubiquitous in advanced nations are very much lacking, if not nonexistent. Thus, this
paper will be concerned with barriers impacting IS/IT planning and implementation
for SMEs in some developing nations. This paper intends to address the IT/telecom
aspects of computer enterprise network management.
Enterprise networks are the bedrock of communication in SMEs. They allow
communication between several sites of a single company. Enterprise networks have
evolved dramatically in the last two decades. The evolution has been fuelled by advances
in Digital Signal Processing (DSP) technology, optical communications, packet
technology, traffic and network convergence, etc. Voice and real-time video, unlike data,
are time sensitive and traditionally can only be carried by Pulse Code Modulation (PCM)
coded medium (Black, 1997). The data network is not optimised for time-sensitive
traffic. Traditionally, voice traffic is transported using a channel capacity of 64 Kbps (E0)
and multiple channels are used to support video, which is image intensive. This means
that for any enterprise network to support voice, video or data traffic, lease lines,
which are multiples of DS0/E0, would be purchased from traditional telephone
companies. In the last decade, advances in DSP led to sophisticated codecs, and lower bit
rates such as 8, 16 and 32 kbps are now being used to code voice using Code Excitable
Linear Predictor (CELP). The coding of data (Pawlita, 1992), video (Verbiest et al.,
1988; Odinma-Okafor, 1991; Odinma-Okafor and Cosmas, 1992; Grunenfelder et al.,
1990) and voice (Brady, 1965; Gruber, 1992) has constituted a major active area in the
past few decades, but most recently variations of JPEG and MPEG were developed for
moving picture and audio. These coders ensure the transmission of hi-fi music and the
synchronisation of moving pictures with the associated audio. Traditionally, voice and
data have separate networks, but the advances in DSP and packet technologies have led
to convergent traffic sources and networks. So, enterprise network architecture has
evolved from separate networks for each traffic type for each enterprise site to a
converged network per site.
Data switches are essential for enterprise network connectivity. The X.25 was the first
of the many data switches we have today. X.25 was developed at the time of poor
transmission media and it contains an error control mechanism, which in turn slows the
processing of data. As the transmission medium improved, the Frame Relay (FR) was
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A.C. Odinma, S. Butakov, E. Grakhov and F. Bollou
developed. FR and Asynchronous Transfer Mode (ATM) switches use virtual links to
connect enterprise networks together. We review the impact of FR and ATM in enterprise
networking in different environments.
Another major technology that impacted enterprise networks is optical
communication technologies. Advances in this field have seen the development, among
others, of Optical Cross-Connect, Add/Drop Multiplexers, Wave Division Multiplexers
(WDM) and Dense WDM (DWDM), which turn a single fibre link to multiple
virtual links in the higher Gbps range. This has led to city rings, national rings and
undersea cables that enable enterprise networks to span within and across cities and
also national boundaries. The owners of the rings can now sell high-speed bandwidth
pipes to corporations for the linking of their enterprise networks at negotiated and
discounted prices.
Though packet networks are not optimised for voice traffic, voice over packets or IP
thrives in the enterprise networks. The Voice over Internet Protocol (VoIP) in an
enterprise network environment emulates the traditional circuit-switched voice quality
levels very well. Most companies that span several geographic areas in advanced
nations use their own VoIP in their enterprise network for employees to make voice calls
to their different branch offices. Moreover, Quality of Service (QoS) is guaranteed in an
enterprise environment because all the network elements are owned by the same
corporation. Established QoS mechanisms such as Differentiated Service (DiffServ),
Integrated Services (IntServ) and Multi-Protocol Labelling Switch (MPLS) can be
combined, as suggested elsewhere (Milonas, 2000; Weiss, 1998; Odinma and Oborkhale,
2006), in enterprise network environments such that quality is guaranteed.
It is true that enterprise network technology has evolved considerably, but this is not
necessarily true in developing nations. Most developing nations are bedevilled with
telecom and power infrastructure problems such that designing and planning enterprise
networks in such countries is like constructing the network in the middle of the desert.
This presupposes that quality cannot be guaranteed; the set-up cost is comparatively and
unnecessarily humongous; VoIP would be unstable and of low quality; and services
deteriorate seriously due to weather conditions because of total reliance on unguided
media such as microwave and satellite technologies.
This paper reviews the architecture of an enterprise network. It further discusses in
detail some of the technologies that have impacted enterprise networks positively and
negatively the world over. Bandwidth, private virtual circuits and lease lines are
discussed. Barriers to the proper implementation of enterprise networks in developing
nations are discussed. We also discuss a case study from the American University of
Nigeria (AUN), which typifies some of the problems most developing nations experience
in enterprise network design and implementation. Finally, we offer recommendations
and conclusions.
2
Enterprise network architecture
An enterprise network is a network of Local Area Networks (LANs) located in different
sites of a corporation that cuts across major towns, cities or even state boundaries. It
enables employees in different sites to access the enterprise network resources
irrespective of where they are, as if they were local. Corporations can now use their own
enterprise networks to deliver VoIP communication, but with adequate lease lines or
Planning, designing and implementing an enterprise network
305
Virtual Private Network (VPN) links purchased from telecom service operators. Figure 1
shows an imaginary enterprise network with three sites. Each of the sites contains local
network facilities and the sites can be linked via a lease line, satellite, VPN, etc. The
company wishing to use VoIP would need to include a gatekeeper and gateway
equipment in the networks. However, because the infrastructure for enterprise networks
is universal, meaning that enterprise network equipment used in the UK would give
similar service in Nigeria, we concentrate more on those aspects that differentiate the
services in different countries. Throughout this paper, the illustrations assume that the
imaginary enterprise network under discussion has sites in New York (NY), New Jersey
(NJ) and Atlanta (AT). NY and NJ are relatively close to each other, but NY and AT as
well as NJ and AT are very far apart. NY and AT are assumed to be much larger sites
than NJ.
Figure 1
Architectural representation of an enterprise network
Authenticate
GK
Authenticate
GW
GK
GW
Lease Line/
VPN
Server
PCs
Server
PCs
Site A
Site B
Le
as
e
DN
N/IS
Li
ne
VP
Authenticate
GK
GW
Server
PCs
Site C
3
Impact of packet technology and packet switches
Until the late 1960s, Circuit Switching (CS) was the method of communication between
networks (DeMartino, 2006). CS establishes and dedicates network resources for each
traffic flow for the duration of the connection (Odinma, 2005; Odinma, 2006a). It has the
advantage of providing better QoS because of guaranteed resources for the duration of
the connection. Unfortunately this leads to the inefficient use of resources. On the other
hand, Packet Switching (PS) technology does not require circuit establishment for
communication purposes as network resources are dynamically allocated to traffic flows
based on demand. PS requires additional information (Odinma, 2002; Stalling, 1997) for
routing, flow control and error corrections. However, this additional overhead has
negligible effects compared to the savings based on efficient utilisation of switching
resources. PS can be connection or connectionless oriented. With connectionless-oriented
PS, several packets representing a given information can traverse different routes to get to
the desired destination. Packets are rearranged to maintain the original order at the distant
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A.C. Odinma, S. Butakov, E. Grakhov and F. Bollou
end as the arrival may not be sequential. In connection-oriented PS, virtual circuits are
established for a particular traffic flow before transmission of information can begin. In
interconnecting enterprise networks using PS, virtual circuits are inevitable and are
usually purchased from service providers.
There are four packet technologies that are worth mentioning, some of which
currently form the packet core switching elements. The packet technologies are X.25, FR,
ATM and multiservice switches. PS is robust, scalable and flexible (Odinma, 2002). It
offers much more revenue opportunities than the circuit-based approach. However, this
comes at a cost too. The traditional packet technology was optimised for data only and
not for voice. In order to carry voice, there are QoS issues to be addressed. The first
packet data network is X.25, which was published in 1976 by the International
Telecommunication Union (ITU) and until 1990, it was said to be the most widely used
protocol (Stalling, 1997). X.25 is a layer 3 protocol of the OSI stack. The protocol was
developed at a time when there were poor transmission facilities and the technology to
support high speed was a bottleneck. It was therefore designed with enormous control
features to make the best use of what was available, and as such it was a very slow
technology. The slow speed made vendors begin studies of the protocol now known as
Frame Relay (FR) to eliminate the effect of the control features in X.25 by actually
removing them. This was successful and in 1992 the enormous benefit of FR was
published (Harbison, 1992). FR was originally designed for a speed of 2 Mbps (ITU-T
I.233) and later for a maximum of E3/T3 Traffic. The FR Data Link Connection
Identifier (DLCI) identifies fractional T1/E1 links used as the backbone for early
enterprise networks.
Data rates of E1/T1 and E3/T3 were considered very high speed two decades ago,
but as technology advanced and demand for high-bandwidth broadband services
increased, it became obvious that another, faster technology was needed. In the late
1980s, a vision of a switching technology that would support high-speed and broadband
services was conceived (Minter, 1989). ATM was chosen to support the Broadband
Integrated Service Digital Networks (BISDNs). The ITU published the ATM standards in
1996. The technology is designed for high-speed transfer of voice, video and data
through public and private networks using cell relay technology. ATM is a very flexible
and scalable technology and it was originally designed to operate at a low access speed
and network-to-network speed of 155 Mbps and 622 Mbps respectively. Today, it can
switch data traffic in Gbps. If we take a sample page such as this one you are reading, a
Gbps is equivalent to sending over 37 000 pages per second. There are ATM switches
operating at 25 Gig and more. ATM supports both connection and connectionless
services, but the technology comes at a high cost. The ATM header also consumes
between 10%–20% transmission resources and it could not be commercially used for
end-to-end switching because it was too expensive as an access device. Moreover, most
of the different ATM switches from different vendors do not interoperate. ATM used
Virtual Path Identifier/Virtual Circuit Identifier (VPI/VCI) at varying rates to
interconnect enterprise networks.
Internet traffic is switched between networks by routers. When ATM was being
planned, routers could only support a maximum of 45 Mbps. This rate was certainly too
small for the IP core backbone or switching and ATM was touted as the ultimate
switching technology to carry IP data. But because ATM was too expensive for
end-to-end switching, other elements were used (Doshi et al., 1998). The implication is
that multiple switching technologies have to be used in a particular network, but this
Planning, designing and implementing an enterprise network
307
means that there will also be a need for managing different elements. Moreover, advances
in optical DWDM meant that the transmission links could now support rates that were in
Exabits per second (260 bps) – that is, more than 1016 bps. The resultant effect was that
attention turned to switches that would exploit the advances in technology to support IP.
There are now commercial Gbps routers and multiservice switches that would support IP,
which form the basis for the metro or national fibre rings that most enterprise networks
are connected to nowadays.
4
Links between enterprise network sites
4.1 Lease lines
The methods of linking enterprise network sites are well established. The main methods
are lease lines, VPNs, ISDN, Microwave, VSAT, etc. The lease lines, often referred to as
dedicated circuits or private circuits, were originally cat 1 or cat 2 cables rented from a
telephone company to interconnect different sites of an enterprise network as shown in
Figure 1. The cat cable provided the lower end of the digital hierarchy, such as E0/DS0 or
multiples thereof. In the 1990s most of the telephone companies started to change most of
their external plant to fibre and the cable TV companies began to sell lease lines ranging
from OC-1/STM-1 to rates in the Gbps. This made life easy for most corporations in the
advanced countries, as high bandwidths could now be rented to meet the demands of their
enterprise network.
4.2 Virtual private networks
A VPN is a cheap and secure way to link enterprise networks. VPNs tend to mean
different things to different vendors (Newton, 2000). Primarily, VPNs enable
corporations to construct part of their enterprise network using some parts of a Service
Provider’s (SP) network. The SP can be a telephone, cable TV or internet service
provider. VPN can support voice, data or video traffic only or a combination of all three.
In its simplest form, a VPN is a secure dial-up link through a phone company to gain
access to enterprise network sites, as shown in Figure 2. Dial-up is bandwidth limited and
cannot support recent enterprise network demands for ultrahigh speed. The FR of the
1980s and the ATM networks of the 1990s provided alternative high-speed links for
enterprise networks in those decades. Figure 3 gives an example of an FR link for our
imaginary enterprise network between its offices in NY and NJ, and ATM links between
NJ and AT or NY and AT. In FR networks, a Virtual Circuit (VC) is provided in the form
of encapsulation carrying DLCI and ATM using VPI/VCI. Depending on traffic
demands, ATM can support circuit emulation, Constant Bit Rates (CBRs) or Public
Switched Telephone Network (PSTN) voice grade services at adaptation layer 1.
Adaptation layer 2 supports variable bit rates demand such as real-time video, and with
layer 5 it can support data traffic along with VoIP. The most recent approach for linking
enterprise networks is metro rings, Ethernet metro or national rings (Odinma, 2006b).
The rings enable corporations with offices that span a metropolitan or several cities to use
VCs provided over IP or over Synchronous Optical Network/Synchronous Digital
Hierarchy (SONET/SDH). Figure 4 shows optical rings used to support an enterprise
network. The NY office can be connected to the national ring via a low-speed pipe of
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A.C. Odinma, S. Butakov, E. Grakhov and F. Bollou
DS3, OC-3/STM-1 or OC-12/STM-4 through a Bandwidth Manager (BWM), which
allows granularity of OC-48/STM-16 or OC-192/STM-64. Similarly, the AT office can
be connected to the national ring. The BWM acts as an optical cross-connect and
add/drop multiplexer. The Optical Translation Unit (OTU) is responsible for optical
translation within the ring. The LS and HS refer to low-speed and high-speed ingress and
egress pipes respectively. The diagram of Figure 4 also shows how an enterprise network
with offices in NY and NJ can be linked via a metro ring. It also shows how NY and AT
can be linked via a national ring.
Figure 2
Dial-up VPN
NY
NJ
PSTN
PLMN
ISP
VPN
AT
Figure 3
FR-ATM virtual connection
FR
NY
NJ
ATM
ATM
NY
LA
DC
AT
Network
AT
Planning, designing and implementing an enterprise network
Figure 4
Metro and national rings used for linking enterprise networks
DWDM
NY
OC-3
OTU
OC-12
HS
National Ring
OC-192 HS
NJ
LS
OC-3
-
AT
IP
…
OC–3 = 155.5 Mbps
OC-12
-
…
OC-192
OTU
BWM
LS
BWM
…
…
IP
DWDM
DWDM
OTU
Metro Ring
NY
309
OTU
DWDM
DWDM
DWDM
OC-192 = 10 Gbps
HS – High Speed Pipe (OC--48/OC-192)
OTU – Optical Translation Unit
LS – Low Speed Pipe (OC-3/OC-12)
BWM – Bandwidth Manager
4.3 Unguided media
The unguided media refers to wireless links for connecting enterprise networks. These
links are facilitated by microwave, VSAT, omni-directional antenna, infrared, etc. These
links degrade depending on terrain and weather conditions. The unguided media are
becoming obsolete and are hardly used today in advanced nations. Unfortunately, it forms
the major links employed in developing nations.
5
Quality of service in enterprise networks
QoS has remained a major concern in IP networks. The concerns are expressed in terms
of network ability to handle certain categories of network parameters such as throughput,
bandwidth availability, latency, jitters, packet losses and service availability. Throughput
is the total amount of useful and nonredundant information transmitted between two
endpoints. It is a function of the other mentioned categories of parameters. Bandwidth
refers to the ability of a network to manage the entire data stream of packets flowing
through it, particularly under congestion. Under heavy congestion, packets are randomly
discarded and services can be seriously indiscriminately degraded in the IP environment.
On the other hand, FR and ATM have a mechanism to handle dropped packets
efficiently. Latency describes the end-to-end traffic delays. This is a major concern for
real-time traffic. Jitters are the delay variations between packets and are very disruptive
to audio communication. It is the phase shift of digital pulses over a transmission
medium. The packet loss parameter is concerned with the reduction of packets discarded
under congestion, either through effective buffer management or preventive measures.
Different applications have different requirements regarding the handling of their traffic
in the network. Applications generate traffic at varying rates and generally require that
the network be able to carry traffic at the rate at which they generate it. The QoS
parameters would have to be properly managed and controlled in order to achieve
varying QoS performance levels for the various Classes of Services (CoS). The QoS
management and control are achieved with the aid of these QoS components: (1) Traffic
Classification, which is responsible for sorting data flows of different traffic into separate
CoS; (2) Service Level Agreement (SLA), the contract between the SP and the customer
for a specific CoS; (3) Admission Control and Policing, which is used by SPs to
manage CoS defined in the SLA and controls the ability of the network to refuse
customers’ resource requirements when demand exceeds capacity; and (4) Active Queue
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Management (AQM), which is responsible for managing network queues based on an
SLA. IP is a best-effort technology and two mechanisms, IntServ and DiffServ, have
been defined (Braden et al., 1994; Mankin et al., 1997; Blake et al., 1998; Baker et al.,
2001) for QoS management. A third de facto mechanism, which has been useful in
shaping traffic, is the MPLS. None of these mechanisms alone can provide full QoS and
hence IntServ has been combined with DiffServ (Weiss, 1998). Similarly, DiffServ and
IntServ have each been combined with MPLS (Odinma and Oborkhale, 2006).
5.1 Quality of service mechanism
IntServ supports two packet-forwarding methods: Guaranteed (GS) and Controlled load
(CS) services. GS is defined in IETF RFC 2212 and it enables the reservation of
bandwidth to meet particular service requirements. For example, a VoIP application
can reserve 64 Kbps end to end using GS. GS attempts to offer guaranteed end-to-end
quality in order to enable delay jitters and latency-sensitive applications to emulate
circuit-oriented services. CS is another IETF RFC 2211, which allows applications to
have low delay and high throughput even during times of congestion. For example,
adaptive real-time applications such as the playback of a recorded conference can use this
kind of service. In order to be effective, every element along the path must be GS or CS
aware, otherwise the reservation cannot be accomplished. IntServ uses PATH and RESV
messages for signalling, as shown in Figure 5. The PATH message, which is sent by
the application towards an RSVP receiver, describes the data to be sent and in return the
receiving end sends back an RESV message to the sender. The message indicates the
traffic profile. Generally, PATH messages traverse the network elements from the sender
to the receiver. Each RSVP-aware element in the path records the path information and
establishes state-flow in accordance with the PATH message (Baker et al., 2001). As the
RESV message returns to the sending end, each element examines the resources
requirement; if the element is unable to meet the requirement it rejects the RESV.
Figure 5
IntServ message
Data Traffic
Receiver
Router
Router
Router
Sender
RESV Msg
Path Msg
Unlike IntServ, DiffServ takes a stateless approach that minimises the need for nodes in
the network to remember anything about flows. DiffServ is a CoS model defined in RFC
2474 and it differentiates traffic by user, service requirements and other criteria. It marks
packets so that network nodes can provide different levels of service via priority queuing
or bandwidth allocation, or by choosing dedicated routes for specific traffic flows.
DiffServ uses a six-bit field in the Type of Service (TOS) field of IPV4 and that of the
Traffic Class (TC) field of IPV6, as shown elsewhere (Odinma and Oborkhale, 2006).
The six bit field, often referred to as a DiffServ Code Point (DSCP), is shown in Table 1
Planning, designing and implementing an enterprise network
311
and are capable of 64 DSCP or traffic markings. Network elements simply respond to
these markings on a Per-Hop Behaviour (PHB) basis without the need to negotiate paths
or remember extensive state information for every flow. In addition, applications do not
need to request a particular service level. The two standardised PHBs are as follows:
Expedited Forwarding (EF) and Assured Forwarding (AF).
Table 1
DiffServ code points
AF
Class 1
Class 2
Class 3
Class 4
Low drop precedence (1)
001010
010010
011010
100010
Medium drop precedence (2)
001100
010100
011100
100100
High drop precedence (3)
001110
010110
011110
100110
EF is represented by a single DSCP. The EF behaviour is intended to emulate a virtual
leased line, which is similar to the ATM CBR service. To minimise any delay that may
occur when congestion exists, this behaviour suggests using a marking or code point in
the DSCP field to identify traffic that should receive preferential link access.
Furthermore, because packets using the EF behaviour get treatment superior to that of all
other packets, the delay variation or jitter is minimised as well. When the packets get
through routers quickly even during times of congestion, the end-to-end delay they
experience is minimised. The second PHB, AF, uses four sets of DSCP values. Each set
corresponds to a delay class. Within each set, there are three DSCPs corresponding to
different drop precedence levels. Table 1 shows the DSCP values for each AF PHB
group. Each AF service class is distinguished by the level of forwarding resources
(bandwidth and queue space) it receives at each hop. To prevent possible reordering of
packets belonging to application flows within a service class, an AF-compliant router
must not map different service classes into the same queue and is not allowed to
distribute packets belonging to a single service class across multiple queues.
In MPLS, labels are assigned to IP flows. The frames associated with the flows can
then be transported across packet or cell-based networks and switched based on the labels
rather than being routed using IP address look-up. In IP networks, a packet is forwarded
through the network on a hop-by-hop basis and the forwarding decision is made by
looking up the packet destination IP address against the routing table to determine the
next hop. In contrast, packets are forwarded in MPLS by using labels. A Forwarding
Equivalence Class (FEC) is used by a router at the edge of the MPLS network to attach
labels to packets. The packets are then forwarded through the MPLS network based on
their associated FEC by swapping the labels through the routers, or switched at the core
of the network to their destination. In the following section we discuss implementation
problems of the above mentioned technologies in a developing nation environment.
6
Enterprise networks in developing nations
Planning and implementing enterprise networks is cost intensive for developing
countries. This is predominantly due to infrastructure problems such as incessant power
outage and inadequate and unreliable bandwidth for linking different network sites. It is
for the same reason that QoS cannot be guaranteed. The enterprise network architecture is
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A.C. Odinma, S. Butakov, E. Grakhov and F. Bollou
mature, tried and tested in developed nations, but cannot at the present time provide a
similar service set in developing nations. We examine some of the barriers to a reliable
enterprise network and present a case study from the networking experience of AUN with
its Metropolitan Area Network (MAN) or remote sites.
6.1 Incessant power outage
Power supplied by the power authorities is very epileptic in most developing nations. In
Nigeria, when there is power, it could be interrupted several times a day. Moreover, there
are usually many days in a week without power. This implies that personal electric
generators are required by businesses. Most businesses have two or three electric
generators. This increases the capital expenditure (capex) associated with the business
and because there are enormous fuel requirements on a daily basis, the operational cost
(opex) is increased as well. The enterprise network under such an epileptic power
environment requires extra protection. The incessant nature of power interruptions
coupled with the fluctuation in the voltage level requires extra protection for enterprise
network server farms. In the case of AUN, in addition to stabilisers and Uninterrupted
Power Supply (UPS), the power is passed through a battery that can still sustain the
network infrastructure for more than 24 h if all else fails. In advanced countries where the
probability of power failure is negligible, the UPS would have sufficed; the additional
battery requirement increases the capex for a developing nation.
6.2 Inadequate linking infrastructure
One of the major problems that hinder the implementation of an enterprise network is
inadequate infrastructure to meet the bandwidth demands of the various services and that
of linking network sites. The telephone company only sells lease lines of E1 and
fractional E1s in only a few major cities, but those who purchased the lease lines
complain that they are very unreliable. That is understandable because the poor power
supply also affects the telephone company. There are often no carriers in developing
nations with ATM or FR networks across the board and, as such, private VCs are not
available for linking the enterprise networks. ISDN basic and primary rates that could
support SME enterprise networks are not available from any phone company in most of
the African countries, and certainly not in Nigeria. There is no fibre metro ring or
Ethernet metro in the majority of African cities and there are only limited national rings
in some African countries. Government policies make it unattractive for companies to
embark on metro ring construction due to right of way costs. The importance of
bandwidth cannot be overemphasised and that was why it was suggested (Odinma,
2006b–c) that tax-free infrastructure importation and right of way costs should be
reduced in order to encourage operators to construct metro rings.
6.3 Quality of service issues
The low rate available to link the enterprise network means that certain levels of services
cannot be supported in most developing nations. This is true because an end-to-end
connection is only as good as its weakest link (Milonas, 2000). As we mentioned earlier,
the DiffServ, IntServ and MPLS are only possible if the routers in the traffic flow route
Planning, designing and implementing an enterprise network
313
support these mechanisms. These include routers in the enterprise network as well as
those in the ISP network, as shown in Figure 6, where the enterprise routers are enabled
for RSVP, but the ISP routers enabled for DiffServ. Since the QoS cannot be guaranteed,
it is obvious that VoIP cannot be reliable. Since there is a heavy reliance on unguided
media, weather conditions can degrade the service sporadically and also the QoS.
Figure 6
Two enterprise sites linked via ISP
Enterprise
R
R
Enterprise
R
R
Site A
Enable RSVP MSG
7
R
R
R
R
Site B
ISP
Disable RSVP MSG
R
Reserv. Data Packet
DiffServ Data packet
MAN-enterprise case study
This case study typifies some of the problems associated with the implementation of
enterprise networks for SMEs. AUN is in the north-eastern part of Nigeria. It has 12
buildings for expatriate staff and another eight remote sites that are spread across the
city with distances ranging from 300 m to approximately 10 km from the university
communications centre. Although some of the buildings are far away from the university
communications centre, they do cluster together. Each of the buildings is a LAN within
the AUN enterprise network. The problem was to link these separate LANs efficiently in
a cost-effective manner such that a QoS similar to that obtainable in advanced nations is
maintained for the expatriate staff and other remote site users.
There was no lease line from the local telephone company or VPN from FR or ATM
service providers in Yola, Nigeria, where AUN is situated. The university cannot
construct fibre links to all the 20 remote sites because it is cost prohibitive. There are also
no cable TV companies, as one would find in the USA or the UK, with which to
negotiate bandwidth. The only option left is to use unguided media, such as satellite,
microwave antennas, omni-directional antennas, wireless bridge, VSAT, etc. In Figure 7,
we show that it costs about three times to link the 20 remote sites within the AUN
enterprise network than it would have been if we were in a city in an advanced nation,
such as London, using the British Telecom (BT) price list. Moreover, in Figure 7, we also
compare the AUN cost with the possible cost of MAN in Barnaul City, South-west
Siberia, Russia. It has already been emphasised that since we used unguided media, the
quality degrades seriously due to weather conditions. This is made even worse because
the antennas are operating in the reserved frequency spectrum for the Industrial,
Scientific and Medical (ISM) radio band. Indeed, there are periods when access to
the internet from the AUN faculty houses is impossible, in spite of all the measures
taken to make the AUN MAN segment robust. In Table 2, we give a checklist of
services available in advanced nations in comparison to that obtainable in Nigeria, a
developing nation.
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A.C. Odinma, S. Butakov, E. Grakhov and F. Bollou
Figure 7
Comparison of MAN costs in three cities
MAN links per city
300000
250000
$
200000
CapEx
150000
OpEx
100000
50000
0
London
Barnaul
Russia
Yola
Nigeria
City
Table 2
Comparison of service availability
Nation
Service type
Advanced
Developing
ISDN
Many SP
N/A
Lease lines
Many SP
In few cities, but unreliable
FR SP
Many SP
N/A
ATM SP
Many SP
N/A
OC or STM
Up to Gbps
N/A
Metro ring
Many SP
N/A
National ring
Many SP
Under construction
Unguided medium
Minimally used
Predominant
8
Conclusions
No SME can survive in this world of globalisation without proper access to information
and proper information exchange between its employees. It is important to note that
developing nations have different levels of IT and telecom infrastructure. While India, for
instance, with a good level of infrastructure, is concerned about the adoption of IS by
SMEs, another developing nation is concerned with infrastructure that would create an
enabling environment for IS and IT usage. Enterprise networks create a very vital
enabling environment for SMEs, one that has many business sites to access proper
business information in order to thrive. This paper described the enterprise network
architecture and services. It examined the barriers that inhibit effective quality
Planning, designing and implementing an enterprise network
315
information exchange in an enterprise environment in a developing nation in Africa. It
further compared a city in a developing nation with one in advanced nations, the UK and
Russia. The enterprise network equipment is mature, but due to poor infrastructure in
developing nations, quality cannot necessarily be guaranteed. Moreover, the cost of
planning and implementing the enterprise network profile in a city in a developing nation
compared to a similar one in an advanced nation is in the order of magnitude of more
than 3 to 1. This is due to an epileptic power supply and lack of other network facilities in
developing nations. In Nigeria, for example, there are no fibre metro rings or Ethernet
metro rings in any of the major cities, contrary to what is obtainable in major cities in
advanced nations. As a result, reliable high-speed bandwidth cannot be negotiated in a
cost-effective manner to link the networks. Moreover, the lease lines offered by local
telephone companies are limited to a few cities and are unreliable. There is no operator
offering modern VPN services such as FR or ATM services. Network sites can only be
linked via unguided media, which are not very secure and lacking in QoS.
In order to create an enabling environment for SMEs to thrive, the government
of the developing nations must create measures that address the barriers to enterprise
networks discussed in this paper. Network operators must be encouraged to construct
fibre rings in major cities by giving them tax-free holidays on the importation of
equipment that would enhance the overall national bandwidth supply. The governments
in developing nations must keep telecommunications infrastructure in their priority list
and should ensure that the right of way charges for underground cables are not
prohibitive or discouraging to operators.
References
Appiah-Adu, K. and Singh, S. (1998) ‘Computer orientation and performance: a study of SMEs’,
Manage, December, Vol. 36, No. 6, pp.385–394.
Baker, F., Iturralde, C., Le Faucher, F. and Davie, B. (2001) Aggregation of RSVP for IPv4 and
IPv6 Reservations, IETF RFC 3175.
BarNiir, A. and Smith, K. (2002) ‘Interfirm alliance in the small business: the role of social
networks’, J. Small Bus. Management, Vol. 40, No. 3, pp.219–232.
Berlak, J. and Weber, V. (2004) ‘How to make e-procurement viable SME suppliers’, Prod. Plan.
& Control, Vol. 15, No. 7, pp.671–677.
Berry, M. (1998) ‘Strategic planning in small and high tech companies’, Long Range Plan, Vol. 31,
No. 3, pp.455–466.
Bhagwat, R. and Sharma, M.K. (2006) ‘Management of information system in India SMEs: an
exploratory study’, Int. J. Enterprise Network Management, Vol. 1, No. 1, pp.99–124.
Bhagwat, R. and Sharma, M.K. (2007) ‘Information system architecture: a framework for a cluster
of Small and Medium Sized Enterprises (SMEs)’, Prod. Plan. & Control, June, Vol. 18, No. 4,
pp.283–296.
Black, U. (1997) Emerging Communications Technologies, 2nd ed., New Jersey: Prentice Hall.
Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. and Weiss, W. (1998) An Architecture for
Differentiated Services, IETF RFC 2475, December.
Braden, R., Clark, D. and Shenker, S. (1994) Integrated Services in the Internet Architecture:
An Overview, RFC 1633, June.
Brady, P.T. (1965) ‘A technique for investigating on-off patterns of speech’, Bell Syst. Tech.
Journal, Vol. XIV, January.
316
A.C. Odinma, S. Butakov, E. Grakhov and F. Bollou
Childe, S.J. (1998) ‘The extended experience – a concept of cooperation’, Prod. Plan. Cont.,
Vol. 9, No. 4, pp.320–327.
DeMartino, K. (2006) ‘Equivalent of fast circuit switching and connection-oriented packet
switching’, Annual Review of Communications, IEC, Vol. 59, December.
Doshi, B.T., Dravida, S., Harshavardhana, P. and Qureshi, M.A. (1998) ‘A comparison
of next-generation IP-centric transport architectures’, Bell Labs Tech. Journ.,
October–December, pp.66–85.
Ghose, A.K. (2001) ‘SMEs and environmental protection’, Productivity, Vol. 42, No. 2,
pp.210–216.
Gruber, J.G. (1992) ‘A comparison of measured and calculated speech temporal parameters
relevant to speech activity detection’, IEEE Trans. Comms., April, Vol. COM-30, No. 4.
Grunenfelder, R., Cosmas, J., Manthorpe, S. and Odinma-Okafor, A. (1990) ‘The characterisation
of video codecs as autoregressive moving average processes and related queuing system
performance’, IEEE J-SAC, April, Vol. 9, No. 3, pp.284–293.
Harbison, F. (1992) ‘Frame relay: technology for our time’, LAN Technology, December.
Jagdev, H.S. and Thoben, K.D. (2001) ‘Typological issues in enterprise networks’, Prod. Plan.
Cont., Vol. 12, No. 5, pp.421–436.
Mankin, A., Baker, F., Braden, R., O’Dell, M., Romanow, A., Weinrib, A. and Zhang, L. (1997)
Resource ReSerVation Protocol (RSVP) Version 1 Applicability Statement, IETF RFC
2208, September.
Marri, H., Gunasekaran, A. and Grieve, R. (1998) ‘An investigation into the implementation of
computer integrated manufacturing in small and medium sized enterprises’, Int. J. Advanced
Manuf. Tech., Vol. 14, pp.935–942.
Milonas, A.C. (2000) ‘Enterprise networking for the new millenium’, Bell Labs Tech. Journ.,
January–March, Vol. 5, No. 1, pp.73–93.
Minter, S. (1989) ‘Broadband ISDN and Asynchronous Transfer Mode (ATM)’, @ IEEE
Communications Magazine, September, Vol. 27, No. 9.
Newton, H. (2000) ‘Newton’s telecom dictionary: covering telecommunication, networking,
information technology, the internet, fiber optics, RFID, wireless, and VoIP’, CMP Books,
21st ed., March.
Odinma, A.C. (2002) ‘Advances in media convergence for information systems’, Assoc. of Telecom
Comp., NICOMM2002, Abuja, 11–13 November.
Odinma, A.C. (2005) ‘Telecom networks convergent architecture & migration strategies for
operators’, NSE Tech. Trans., October–December, Vol. 40, No. 4, pp.1–12.
Odinma, A.C. (2006a) ‘Circuit and packet switching implications for telecom operators’,
NSE Tech. Trans., January–March, Vol. 41, No. 1, pp.57–66.
Odinma, A.C. (2006b) ‘Optimisation of ICT backbone infrastructure for enhanced services’,
5th Intern. Nigeria Telecom Forum, Abuja, Nigeria, 19–20 September.
Odinma, A.C. (2006c) ‘ICT infrastructure technological development: an essential tool for
economic self-reliance’, NSE Intern. Conf., Gateway 2006, Abiokuta, December.
Odinma, A.C. and Oborkhale, L. (2006) Quality of Service Mechanisms and Challenges for IP
Networks, PJST, May, Vol. 7, No. 1.
Odinma-Okafor, A. (1991) ‘The characterisation of variable rate video signals’, PhD thesis in
Telecommunications Engineering, The University of London.
Odinma-Okafor, A. and Cosmas, J. (1992) ‘Impact of time series and counting process approaches
to video source modelling’, 9th UK Teletraffic Symposium, IEE, April.
Pawlita, P.F. (1992) ‘Traffic measurements in data networks: recent measurement results and some
implications’, IEEE Trans. Comms., April, Vol. Com-30, No. 4.
Sharma, M.K. and Bhagwat, R. (2006) ‘Practice of information system: evidence from selected
Indian SMEs’, J. Manuf. Tech. Management, Vol. 17, No. 2, pp.199–223.
Planning, designing and implementing an enterprise network
317
Sharma, M.K., Bhagwat, R. and Dangayach, G.S. (2005) ‘Practice of performance measurement:
experience from Indian SMEs’, Int. J. Global Small Bus., Vol. 1, No. 2, pp.183–213.
Stalling, W. (1997) Data and Computer Communications, 5th ed., New Jersey: Prentice Hall.
Tuteja, S.K. (2001) ‘Partnership for SME development: ancillarisation/sub-contracting’,
Productivity, Vol. 42, No. 2, pp.247–251.
Verbiest, W., Pinno, L. and Voeten, B. (1988) ‘The impact of ATM concept on video coding’,
IEEE Journal on Selected Areas in Communications, December, Vol. 6, No. 9,
pp.1623–1632.
Weiss, W. (1998) ‘QoS with differential services’, Bell Labs Tech. Journ., October–December,
pp.48–62.