What is a digital network?
Modern digital technology allows different sectors, e.g. telecom, data, radio and television, to be merged together. This occurrence, commonly known as convergence, is happening on a global scale and is drastically changing the way in which both people and devices communicate. At the center of this process, forming the backbone and making convergence possible, are IP-based networks. The convergence is on going in all industries right now, and the security and surveillance industry is gaining tremendous benefits from joining.Services and integrated consumer devices for purposes such as telephony, entertainment, security or personal computing are constantly being developed, designed and converged towards a communication standard that is independent from the underlying physical connection. The cable network, for instance, first designed for transmitting television to the consumer, can now also be utilized for sending e-mail, surfing the Web or even monitoring a network camera sending live pictures from another continent. Furthermore, these features are also available over other physical networks, e.g. telephone, mobile phone, satellite and computer networks.
This basic tutorial introduces the central components of IP-based network technology, and in doing so it will demonstrate the tremendous benefits this new technology has to offer the security and surveillance market.
Basics in network communication
The Internet has become the most powerful factor guiding the ongoing convergence process. This is mainly due to the fact that the Internet protocol suite has become a shared standard used with almost any service. The Internet protocol suite consists primarily of the Internet Protocol (IP) and the Transport Control Protocol (TCP); consequently, the term TCP/IP commonly refers to the whole protocol family.
IP-based networks are of great importance in today's information society. At first glance, this technology might appear a bit confusing and overwhelming. Therefore, we'll start by presenting the underlying network components upon which this technology is built.
A network is comprised of two fundamental parts, the nodes and the links. A node is some type of network device, such as a computer or a camera. Nodes are able to communicate with other nodes through links, like cables. There are basically two different network techniques for establishing communication between nodes on a network: the circuit-switched network and the packet-switched network techniques. The former is used in a traditional telephone system, while the latter is used in IP-based networks.
A circuit-switched network creates a closed circuit between two nodes in the network to establish a connection. The established connection is thus dedicated to the communication between the two nodes. One of the immediateproblems with dedicated circuits is wasted capacity, since almost no transmission uses the circuit 100 percent of the time. Also, if a circuit fails in the middle of a transmission, the entire connection must be dropped and a new one established. For illustration purposes, take a look at a telephone connection over a circuit-switched network (Figure 1).
Figure 1: A circuit-switched network utilizes a dedicated closed circuit.IP-based networks on the other hand utilize a packet-switched network technology, which uses available capacity much more efficiently and minimizes the risk of possible problems, such as a disconnection. Messages sent over a packet-switched network are first divided into packets containing the destination address. Then, each packet is sent over the network with every intermediate node and router in the network determining where the packet goes next. A packet does not need to be routed over the same links as previous related packets. Thus, packets sent between two network devices can be transmitted over different routes in the event of a link breakdown or node malfunction (Figure 2)
.
Transmission Fundamentals
Analog data is expressed as continuously variable waves and thus takes on continuous values. Examples include voice and video. Digital data on the other hand is represented as a sequence of bits, or ones and zeros. This digitization allows any kind of information to be measured and represented as digital data. So, text, sound and pictures can be represented as a sequence of bits. Digital data can also be compressed to allow higher transmission rates (this will be covered in a coming tutorial) and it can be encrypted for secure transmissions. In addition, a digital signal is exact and any related noise can easily be filtered out. Digital data can be transmitted through three general types of media - metal such as copper, optical fiber or radio waves.
The techniques represented below offer the first building block for digital communications, the cable and antenna layer (Figure 3). This layer allows us to send and receive digital data over a wide variety of media. However, more building blocks are required for successful digital communication.
You might ask, "What is the difference between transmission and communication?" Consider an analogy from human speech. Think about the acoustic waves in the air generated by speaking. These waves are transmitted, but they are a long way from communicating. The words that come out must be organized to make any sense. If they come out too quickly or too slowly, the speaker will not be understood. If many people speak simultaneously no one is understood. If someone speaks a language you don't understand, information is lost. Speaking generates information, but it is not necessarily communicated, or understood.
Digital communication has similar problems that need to be overcome. The receiver must know how message bits are organized to understand the message. Additionally, some rules must specify what will happen if many network devices try to use a shared media simultaneously. The best way to ensure that network devices send and receive in compatible ways is to adhere to standardized protocols that define the rules and the manner in which the devices initiate and carry on communication.
The Local Area Network Infrastructure
Local Area Networks (LANs) are used for connecting network devices over a relatively short distance. Typically, a LAN operates in a limited space, such as an office building, a school or a home. LANs are usually owned and managed by a single person or organization. They also use certain specific connectivity technologies; often some type of shared media.
An important feature of a LAN is its topology, where the term topology refers to the layout of connected network devices on a network. We can think of topology as a network's shape. Network topologies can be categorized into the following basic types:
* The bus topology uses a shared
communication medium, often referred to as a common bus, to connect
all network devices (Figure 4). A device that wants to communicate
with another device on the network sends the packet onto the bus.
All devices that are connected to the bus will receive the sent
packet but the intended recipient is the only device that actually
accepts and processes the packets.
* The star topology features a logical communication center to which all network devices are directly connected. Each device requires a separate cable to the central point and consequently all packets will travel through the communication center (Figure 6).
The standardized protocols
utilize different network topologies together with the cable and
antenna layer to build different LAN architectures that are either
wired or wireless. These protocols offer the second building block
for successful digital communications, the transmission layer
(Figure 7).
Figure
7: Cable and antenna layer and the second building block Ð the
Transmission layer.
Interconnecting LANs in an IP-based
Architecture
So far, we have described how network devices
can communicate over different types of LANs. However, different
LANs are designed for different goals and needs. Hence, every so
often it is necessary to interconnect several LANs to allow
communication over the network boundaries. Such a geographically
scattered, interconnected collection of LANs is commonly referred to
as a Wide Area Network (WAN). Probably the most familiar WAN is the
Internet, which spans most of the globe.
The Internet
protocol suite is a layered protocol family where each layer
builds upon the layer below it, adding new functionality. The lowest
layer is concerned purely with sending and receiving data utilizing
the transmission layer. At the top are protocols designed for
specific tasks, such as sending and receiving motion pictures, sound
and control information. The protocols in between handle things such
as dividing the message data into packets and forwarding them
reliably between network devices.
The Internet
Protocol (IP) is the basis of the Internet protocol suite and is
the single most popular network protocol in the world. IP enables
data to be transmitted across and between local area networks, hence
the name: Inter-net Protocol. Data travels over an IP-based network
in the form of IP packets (data units). Each IP packet includes both
a header and the message data itself, where the header specifies the
source, the destination, and other information about the data. IP is
a connectionless protocol where each packet is treated as a separate
entity, like a postal service. Any mechanisms for ensuring that sent
data arrives in a correct and intact manner are provided by
higher-layer protocols in the suite. Each network device has at
least one IP address that uniquely identifies it from all other
devices on the network. In this manner, intermediate nodes can
correctly guide a sent packet from the source to the
destination.
The Transport Control Protocol (TCP) is
the most common protocol for assuring that an IP packet arrives in a
correct and intact manner. TCP provides reliable transmission of
data for upper layer applications and services in an IP environment.
TCP offers reliability in the form of a connection-oriented,
end-to-end packet delivery through an interconnected
network.
|
|
Figure 7: Cable and antenna layer and the second building block Ð the Transmission layer. |
Interconnecting LANs in an IP-based
Architecture
So far, we have described how network devices
can communicate over different types of LANs. However, different
LANs are designed for different goals and needs. Hence, every so
often it is necessary to interconnect several LANs to allow
communication over the network boundaries. Such a geographically
scattered, interconnected collection of LANs is commonly referred to
as a Wide Area Network (WAN). Probably the most familiar WAN is the
Internet, which spans most of the globe.
The Internet
protocol suite is a layered protocol family where each layer
builds upon the layer below it, adding new functionality. The lowest
layer is concerned purely with sending and receiving data utilizing
the transmission layer. At the top are protocols designed for
specific tasks, such as sending and receiving motion pictures, sound
and control information. The protocols in between handle things such
as dividing the message data into packets and forwarding them
reliably between network devices.
The Internet
Protocol (IP) is the basis of the Internet protocol suite and is
the single most popular network protocol in the world. IP enables
data to be transmitted across and between local area networks, hence
the name: Inter-net Protocol. Data travels over an IP-based network
in the form of IP packets (data units). Each IP packet includes both
a header and the message data itself, where the header specifies the
source, the destination, and other information about the data. IP is
a connectionless protocol where each packet is treated as a separate
entity, like a postal service. Any mechanisms for ensuring that sent
data arrives in a correct and intact manner are provided by
higher-layer protocols in the suite. Each network device has at
least one IP address that uniquely identifies it from all other
devices on the network. In this manner, intermediate nodes can
correctly guide a sent packet from the source to the
destination.
The Transport Control Protocol (TCP) is
the most common protocol for assuring that an IP packet arrives in a
correct and intact manner. TCP provides reliable transmission of
data for upper layer applications and services in an IP environment.
TCP offers reliability in the form of a connection-oriented,
end-to-end packet delivery through an interconnected
network.
 |
Figure
8: Cable and antenna layer, transmission layer and the third building block - The IP layer. |
To summarize, the Internet Protocol
suite provides an adaptation to the transmission layer protocols and
offers a standardized architecture for communication over an
interconnected collection of LANs, i.e. a WAN. This is a tremendous
advance, mainly because weÕre able to connect and communicate over
different physical connections in a standardized way. With IP as the
basis, the Internet Protocol suite provides the third building block
for successful digital communications, the IP layer (Figure 8).
Benefit from the IP-based Architecture
The
Internet Protocol suite brings together all transmission layer
protocols into a single, standardized protocol architecture, which
can be utilized by applications for different communication
purposes. As a direct result, any application that supports TCP/IP
will also be able to communicate over any IP-based
network.
It should be easy to see that this standardized
architecture has revolutionized network communication. An
ever-increasing number of applications that transfer text, sound,
live pictures and more utilize IP-based architecture. All these
applications and application protocols constitute the application
layer and provide the fourth, and final, building block for
successful digital communications (Figure 9).
Examples of
applications are such as fire alarms, access controls and
image/sound from CCTV.
 |
Figure
9: The last building block - the Application
layer. |
Convergence
Modern digital
technology allows for convergence where different services, and
combinations of these services, can be provided through
infrastructures that formerly accommodated only one type of service.
There are three major factors that create the conditions for
convergence: digital technology, transmission technology and
standardized communication protocols. Digital technology allows all
information Ð text, sound and motion pictures, for example Ð to be
represented as bits and transmitted as sequences of ones and zeros.
Transmission technology enables better utilization of available
capacity in different infrastructures. Consequently, services that
require high
capacity can be provided by infrastructures
previously able to deliver only simpler services.
Case
Study
So far we have discussed the structure of the IP-based
architecture, especially in comparison with traditional
circuit-switched networks. However, the preceding sections have not
contained any real applications that take advantage of this
architecture in the security and surveillance industry. IP-based
architecture creates great opportunities for new application
domains. Hence, applications that previously could not be realized
can now be successfully implemented. Additionally, application
domains built upon older technologies derive increased functionality
when utilizing IP-based technology. For illustration, consider an
application domain that has clearly taken advantage of IP-based
architecture: visual surveillance systems.
In today's
society, the demand for visual surveillance systems has been
steadily increasing. Different camera solutions are used for
monitoring activities in a variety of environments, such as shops,
enterprise buildings and prisons. Up until recently, Closed Circuit
Television systems (CCTV systems) were the only alternative for such
monitoring. These dedicated systems typically require their own
communication link between the camera and the monitor. This separate
link is expensive to buy, install and maintain. Camera images are
transmitted over the dedicated cabling network to time-lapse video
recorders or dedicated monitors at a control center. A modern
IP-based visual surveillance system on the other hand is not limited
in the same way as a traditional CCTV system. Enterprises can
install network cameras, IP-based visual surveillance cameras, fire
alarms or access control that plug directly into the enterprise
network. Such products have their own IP address, much like any
network device. The main differences between these systems and CCTV
systems are that video digitization is performed at the camera level
and the Internet Protocol suite is utilized for transferring the
pictures onto the network. This is beneficial since IP-based
networks are generally available in most buildings, and because
TCP/IP can be utilized with almost any existing network, there is
probably no need for extra cabling. A network security system, in
comparison with a CCTV system or other old type of alarm system,
also saves money by reducing the amount of dedicated equipment
needed to manage the security system. For example, no dedicated
monitors are required.
An IP-based solution also allows
images and alarms to be remotely stored and monitored over any
interconnected network, such as an Intranet or the Internet. This
alone creates huge advantages for enterprises that wish to outsource
the monitoring of their offices and facilities to a third party
surveillance and monitoring center. This center simply needs a
password and the IP-address to access live pictures, via the
Internet, from a site placed anywhere in the world. Moreover, the
IP-based architecture creates a new world in which different
applications can be completely integrated. For instance, motion
pictures can be distributed to other network solutions, such as
factory control management systems and access control
systems.
Conclusion
The Internet Protocol suite has
rapidly grown into a widespread, fundamental building block for
information exchange. As communication technology becomes
increasingly important, there is growing pressure to use this
technology to reduce costs without sacrificing any capabilities or
benefits. IP-based networks address many of the problems faced in
this complex environment, while providing an elegant solution that
meets present needs, as well as those to come. Ultimately, all forms
of communications, including data, alarms, voice, motion pictures
and entertainment, will converge into a common transporting
network.
The primary benefits of an IP-based network strategy
are the cost savings and operational improvements from using one
converged network instead of several smaller networks dedicated to
specific purposes, like data, alarms, voice and motion pictures. The
second most important group of benefits from network convergence is
in enabling new applications. New applications not only drive cost
reductions; they can also be a source of new revenue as they provide
value essential to enterprises and users.
Convergence is here
and the benefits are real. Now it's time to pick strategic partners
Ð those who understand the broad scope of needs and are committed to
meeting them - and take the first step towards an IP-based
future.
