Network management (HND in Networking)

Network Management
Naresh Loganathan Page 1
Table of Contents
Task 01..............................................................................................3
1.1..........You are thinking about creating a network solution for a small business of
approximately 15 users. You can use Wi-Fi or cable network. Describe which
method you suggest? Give reasons to your answer. .....................................3
Wired or Cable Network diagram ..........................................................3
Benefits of wired connection ...............................................................3
Benefits of wireless connection ............................................................4
Legacy infrastructure and mixed environments .........................................5
WLAN vs LAN ..................................................................................5
LAN and WLAN Security ....................................................................6
LAN and WLAN Availability .................................................................6
Wired vs Wireless.............................................................................7
Task 1.2 .............................................................................................8
What are the required devices to setup the network in Task 1.1? Describe the
security methods you applied, performance and cost to establish the network....8
WIRELESS ROUTER............................................................................8
Wireless Router Functions...................................................................8
NETWORK INTERFACE CARD.................................................................9
Network Interface Card Functions .........................................................9
ETHERNET CABLE ........................................................................... 10
Task 1.3 ........................................................................................... 11
Describe what Network Operating System (NOS) is and what are the additional
features available compared to client Operating System (OS). ..................... 11
NOS REMOTE LOGIN ........................................................................ 12
Task 02............................................................................................ 13
Task 2.1 ........................................................................................... 13
The 7 layer network management model and list Protocols and a device operates
on layers of the 7 layer model. .......................................................... 13
OSI 7 Layers Reference Model For Network Communication......................... 13
Characteristics of Layered Protocols: ................................................... 14
Layer 7 Application layer.................................................................. 15
Layer 6 Presentation Layer ............................................................... 17
Layer 5 Session layer....................................................................... 18

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Layer 4 Transport layer.................................................................... 19
Layer 3 Network layer ..................................................................... 21
Layer 2 Data link layer..................................................................... 23
Layer 1 Physical layer...................................................................... 24
Task 2.2 ........................................................................................... 26
Briefly explain the peer to Peer network (Workgroup) model and Client Server
network (Domain) model. ................................................................. 26
Peer-to-peer network...................................................................... 26
Client/ server network .................................................................... 27
Task 03............................................................................................ 32
Task 3.1 ........................................................................................... 32
Design a total network solution for a company which has around 25 computers
and have 2 servers respectively one for web server and the other one for file
sharing propose and Internet connectivity. This design must reflect a high
availability on all aspect of the networking starting from LAN to WAN. ........... 32
Task 3.2 ........................................................................................... 33
Compare and contrast OSI and TCP/IP proposed network management standards
................................................................................................ 33
Distinguishing Points ....................................................................... 33
TCP/IP Model................................................................................ 34
OSI Model .................................................................................... 35
Task 3.3 ........................................................................................... 37
Describe the responsibilities of Network Administrator. ............................. 37
Equipment upgrades ....................................................................... 37
Configuration................................................................................ 37
Software upgrades ......................................................................... 38
Patches....................................................................................... 38
Performance maintenance ................................................................ 38
Ho-hum chores.............................................................................. 38
Software inventory......................................................................... 38
Designing the Network..................................................................... 39
Setting Up the Network.................................................................... 39
Maintaining the Network .................................................................. 39
Expanding the Network.................................................................... 39

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Task 01
1.1 You are thinking about creating a network solution for a small business of approximately 15
users. You can use Wi-Fi or cable network. Describe which method you suggest? Give
reasons to your answer.
This task provides evidence for P14.1.1
Wired or Cable Network diagram
Benefits of wired connection
It is easy enough to see why enterprises want to remain wired – control and security, reliability
and speed are the primary benefits of using physical connections. It is also relatively cost-
effective, as the price of cabling – even at the lengths needed to cover an average office – is
pretty cheap.
One great advantage of having a wired infrastructure, which seems particularly relevant in
today’s mobile world, is the control it provides. If a physical connection is needed to access the
corporate network, the business is in full control of who and what gets online. While this has

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obvious security benefits of keeping unauthorized visitors out of your network, it also means
your network will not be overloaded with non-business critical traffic.
Wireless or Wi-fi Network Diagram
Benefits of wireless connection
While a physical infrastructure may be good from a management point of view and offer cheap
deployment, having all those wires running throughout a building can be costly and awkward to
maintain. For example, if a business increases its workforce, all those new workers will need
physical connections at their desk – connections that will need to be manually set up. Any
breakages in the wired connection will also have to be manually fixed as there is no software
solution to a broken Ethernet pin.

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With the explosion in mobile devices over the last few years – Apple alone has sold around 100
million iPads since the tablet was introduced in 2010 – many workers are bringing their own
devices into the office. It is vital these employees have access to the corporate network to get
the most out of them, and that means giving them wireless access. As well as being able to use
their own devices, wireless infrastructure means freedom to move around the office, from desk
to desk or meeting room to meeting room.
According to the above scenario I like to suggest use both Network method.
Legacy infrastructure and mixed environments
There are pros and cons to having a wireless and a wired enterprise and it is fair to say that
wireless becoming the norm is still some way off. For example, there is too much legacy
infrastructure in place to rip it out and replace it with a wireless set up.
A combination of wired and wireless is the way forward, at least for now. That way a business
can satisfy the needs of its mobile workers and ensure all security, control and reliability
requirements are met.
Having a mixed environment does not need to mean a nightmare from a management point of
view. Cisco, for example, recently unveiled its new Unified Access platform, which brings
together wired and wireless connections in one switch. The 5760 Unified Access WLAN
controller enables wireless connections to be managed on top of existing wired infrastructure.
Juniper Networks also integrates wireless LANs with existing wired infrastructure, giving
businesses the best of both worlds.
Managing both together means businesses can run the same policies across the wired and
wireless infrastructure, meaning business will see the benefit of having both while, hopefully,
reducing the negatives associated with either installation.
WLAN vs LAN
LAN stands for Local Area Network, which is a collection of computers and other network
devices in a certain location that are connected together by switches and/or routers that
facilitate the communication of the network elements. Each computer or network element is
connected to the switches/routers via a UTP cable. The added letter in WLAN stands for
wireless. This is a type of network where the data is not transmitted via cables but over the air
through the use of wireless transmitters and receivers.
WLANs are deployed in areas where a wide number of computers may connect to the network
but not at the same time. Places like coffee shops often add WLAN to their shops to entice more
customers who do not stay for extended periods. Even at home where you have a somewhat
fixed number of computers that connect to the network, WLAN is also preferred as it gives users
the freedom to move around the house and carry their laptops with them without needing to fuss
with cables. For areas where the computers are pretty much fixed, a wired LAN is very desirable
due to the advantages that it offers.

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First off, a wired LAN is much faster compared to a WLAN. Most wireless routers nowadays are
limited to a theoretical maximum speed of 54mbps while a contemporary wired LAN has a
bandwidth of 100mbps. Gigabit network equipment can even ramp this up to 1000mbps or
1Gbps. This might not be such a big issue for browsing the internet or sending email but when
you are copying large files, it can take a while with a WLAN.
WLANs are also vulnerable to attack as just about anyone with a strong enough transceiver is
able to detect the signal. Access can then be achieved by breaking the encryption used by the
router through certain software. The information that is being transmitted through the WLAN can
also be collected by malicious person and used in a variety, often destructive, ways. In order to
intercept data in a wired LAN, you need to physically connect to a switch or a router.
LAN and WLAN Security
In theory, wireless LANs are less secure than wired LANs, because wireless communication
signals travel through the air and can easily be intercepted. To prove their point, some
engineers have promoted the practice of wardriving, that involves traveling through a residential
area with Wi-Fi equipment scanning the airwaves for unprotected WLANs. On balance, though,
the weaknesses of wireless security are more theoretical than practical. WLANs protect their
data through the Wired Equivalent Privacy (WEP) encryption standard that makes wireless
communications reasonably as safe as wired ones in homes.
No computer network is completely secure and homeowners should research this topic to
ensure they are aware of and comfortable with the risks. Important security considerations for
homeowners tend to not be related to whether the network is wired or wireless but rather
ensuring:
the home's Internet firewall is properly configured
the family is familiar with the danger of Internet "spoof emails" and how to recognize them
the family is familiar with the concept of "spyware" and how to avoid it
babysitters, housekeepers and other visitors do not have unwanted access to the network
LAN and WLAN Cost
Wireless gear costs somewhat more than the equivalent wired Ethernet products. At full retail
prices, wireless adapters and access points may cost three or four times as much as Ethernet
cable adapters and hubs/switches, respectively. 802.11b products have dropped in price
considerably with the release of 802.11g, and obviously, bargain sales can be found if shoppers
are persistent.
LAN and WLAN Availability
Wireless LANs suffer a few more reliability problems than wired LANs, though perhaps not
enough to be a significant concern. 802.11b and 802.11g wireless signals are subject to
interference from other home appliances including microwave ovens, cordless telephones, and
garage door openers. With careful installation, the likelihood of interference can be minimized.

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Wireless networking products, particularly those that implement 802.11g, are comparatively
new. As with any new technology, expect it will take time for these products to mature.
Wired vs Wireless
Wired Wireless
Installation moderate difficulty easier, but beware interference
Cost less more
Reliability high reasonably high
Performance very good good
Security reasonably good reasonably good
Mobility limited Outstanding

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Task 1.2
What are the required devices to setup the network in Task 1.1? Describe the security methods
you applied, performance and cost to establish the network.
WIRELESS ROUTER
A wireless router is a device in a wireless local area network (WLAN) that determines the next
network point to which a packet should be forwarded toward its destination. A wireless router
works in the same way as the router in a hard-wired home or business local area network
(LAN), but allows greater mobility for notebook or portable computers. The individual computers
are equipped with small wireless transceivers that can be plugged into either a Universal Serial
Bus (USB) port or a PC card slot.
For home and business computer users who have high-speed Internet connections, a wireless
router can also act as a hardware firewall. This is true even if the home or business has only
one computer. Many engineers believe that the use of a router provides superior protection
against hacking because individual computer IP addresses are not directly exposed to the
Internet. A wireless router also does not consume computer resources as a firewall program
does.
Wireless Router Functions
In technical terms, router, be it wired or wireless, functions like a layer 3 gateway i.e. that it
connects various networks and then it operates at the network layer of the OSI model.
Wireless routers operate either in wired Local Area Network (LAN), wireless LAN or a network
which is a mixture of wired and wireless. Most of the wireless routers have features like LAN
ports, Wide Area Network (WAN) ports, which is used in connecting to a wider area network,
and wireless antennae, which helps in connecting with wireless devices like wireless access
points, wireless repeaters and wireless bridges.
Wireless router is used by wireless devices as their hub while mini-LAN, which is present in the
router, is connected as a single device to the remaining LAN. Wireless routers can function both
in a point-to-point mode and point-to-multipoint mode. Wireless devices must be set to the same
service set identifier and radio channel to which the wireless router is connected.

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NETWORK INTERFACE CARD
A network interface card (NIC) is a computer circuit board or card that is installed in a computer
so that it can be connected to a network. Personal computers and workstations on a local area
network (LAN) typically contain a network interface card specifically designed for the LAN
transmission technology, such as Ethernet or token ring. Network interface cards provide a
dedicated, full-time connection to a network. Most home and portable computers connect to the
Internet through as-needed dial-up connection. The modem provides the connection interface to
the Internet service provider.
Network Interface Card Functions
The purpose of a LAN Card is to create a physical connection to the network; to provide an
open 'door', as it were. The first interface supported by a LAN Card is a physical interface of
how the cable plugs into the card. This interface is well defined in technical documentation,
which is why standard network cables fit most standard LAN cards. The second function of a
LAN Card is to provide a data link. There is a theoretical model in computer networking
called OSI - Open Systems Interconnection. This model, or a way of explaining networks,
includes 7 layers. The first two layers are the physical layer and data link. Each layer of the
OSI model allows for other layers to be independent. Upgrading or changing one layer does
not affect others. This means that if plugins change for all LAN cards, other elements like the
protocols don't have to change.
The data link function of a LAN Card provides hardware-level sending and receiving of
network binary data. Zeros and ones flow from the network into the network card. The card
can recognize this flow and it can even check for errors. When you turn on a computer with a
LAN Card, it will have two lights, one green and one orange. The orange light will come on
when the data link layer is activated. This means that the cable works, there is a network
connected, and data bits are flowing. The second light, the green light, comes on once the
next layer the network layer is activated (such as an IP network).

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ETHERNET CABLE
Ethernet is a physical and data link layer technology for local. Ethernet was invented by
engineer Robert Metcalfe.
When first widely deployed in the 1980s, Ethernet supported a maximum theoretical data rate of
10 megabits per second (Mbps). Later, so-called "Fast Ethernet" standards increased this
maximum data rate to 100 Mbps. Today, Gigabit Ethernet technology further extends peak
performance up to 1000 Mbps.
Higher level network protocols like Internet Protocol (IP) use Ethernet as their transmission
medium. Data travels over Ethernet inside protocol units called frames.
The run length of individual Ethernet cables is limited to roughly 100 meters, but Ethernet
networks can be easily extended to link entire schools or office buildings using network
bridge devices.

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Task 1.3
Describe what Network Operating System (NOS) is and what are the additional features
available compared to client Operating System (OS).
Initially, computers were built to operate as a singular entity; having discrete resources and
individual operating system. Although the use of multiple computers to solve a single problem is
not unheard of, it is often a human’s job to subdivide the problem into manageable chunks that
the computers can separately work on.
A distributed OS is just an improvement of the original concept. But instead of a human cutting
up the job, the OS is smart enough to know which computers are overloaded and which ones
are idle. It would then balance the tasks available so that each computer in the group is sharing
equal load. This is good for maximizing the usefulness of each computer. The drawback though
is that you would need to upgrade all the units every so often to maintain a reasonable level of
performance. There is also some software that is simply not compatible with distributed
computing. They are not optimized to take advantage of multiple processes, and as such can
only be processed by one computer.
The appearance of network operating systems is a direct result of the need to cut costs and
control each computer in the system. Network OS does not reside on every computer, the client
only has enough software to boot the hardware and contact the server. All the subsequent
operations are done on the server, and the only role of the client is to relay the input and output
between the server and the user. This is very effective in controlling the installed software since
clients do not have the capability to add or remove software. A network OS requires a very
minimal amount of hardware on the client, although the server should be capable to handle the
demands of multiple users. This means that you would not need to upgrade the clients as long
as you keep the server properly maintained. This even led to the creation of thin clients or
devices that cannot function on their own but are meant to work with network OS.
Depending on the needs and resources of your company, a distributed or network OS might be
worth looking into. Each has its own advantages and disadvantages that you should take into
consideration. A distributed OS could cost a bit more than a network OS, but a network OS
cannot handle computation intensive programs due to the stress it puts in the server. The
decision is up to you in picking a better solution that what you currently have.

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NOS REMOTE LOGIN
Each user uses its own operating system. When a user wants to access any other machine, he
must require some kind of remote login to access the other machine.
The user knows the location of the files on their own systems, and they use file transfer
commands to transfer these files from one machine to another.
Let's have a look at advantages and disadvantages of Network operating system;
Advantages
Servers are highly stable.
Security is managed by server.
Up gradation of system is easy.
Remote access to server is possible.
Disadvantages
High Cost.
Great dependency on server.
Regular maintenance is required.
Network Operating System Operating System
Control over file placement is done by
user.
Control over file placement is done by
system itself.
Various machines are included and
each machine has its own user IDs.
Various machines are included and
there is single system wide mapping.
Each computer system schedules and
run its own processes.
A single process running on one
machine may have its sub-processes
running on other machines.
Follows two-tier client server
architecture.
Follows n-tier client server architecture.
Huge dependency on server. No dependency on any machine.
Medium Processing speed. Fast processing.

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Task 02
Task 2.1
The 7 layer network management model and list Protocols and a device operates on layers of
the 7 layer model.
OSI 7 Layers Reference Model For Network Communication
Open Systems Interconnection (OSI) model is a reference model developed by ISO
(International Organization for Standardization) in 1984, as a conceptual framework of
standards for communication in the network across different equipment and applications by
different vendors. It is now considered the primary architectural model for inter-computing and
internetworking communications. Most of the network communication protocols used today have
a structure based on the OSI model. The OSI model defines the communications process into 7
layers, which divides the tasks involved with moving information between networked computers
into seven smaller, more manageable task groups. A task or group of tasks is then assigned to
each of the seven OSI layers. Each layer is reasonably self-contained so that the tasks
assigned to each layer can be implemented independently. This enables the solutions offered
by one layer to be updated without adversely affecting the other layers.
The OSI 7 layers model has clear characteristics. Layers 7 through 4 deal with end to end
communications between data source and destinations. Layers 3 to 1 deal with communications
between network devices.
On the other hand, the seven layers of the OSI model can be divided into two groups: upper
layers (layers 7, 6 & 5) and lower layers (layers 4, 3, 2, 1). The upper layers of the OSI model
deal with application issues and generally are implemented only in software. The highest layer,
the application layer, is closest to the end user. The lower layers of the OSI model handle data
transport issues. The physical layer and the data link layer are implemented in hardware and
software. The lowest layer, the physical layer, is closest to the physical network medium (the
wires, for example) and is responsible for placing data on the medium.

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Characteristics of Layered Protocols:
Above Figure shows Headers and the OSI protocol layers.
When a device transmits data to the network, each protocol layer processes the data in turn.
Consider the network layer for the sending device. Data to be transmitted is received from the
transport layer. The network layer is responsible for routing and must add its routing information
to the data. The network layer information is added in the form of a header, which is appended
to the beginning of the data. The term Protocol Data Unit (PDU) is used to describe the
combination of the control information for a layer with the data from the next higher layer. Each
layer appends a header to the PDU that the next higher layer receives. The data field for each
layer consists of the PDU for the next higher layer. The physical layer does not encapsulate in
this manner because the physical layer manages data in bit form.

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07. Application layer
06. Presentation layer
05. Session layer
04. Transport layer
03. Network layer
02. Data link layer
01. Physical layer
Layer 7Application layer
Application layer is the level of the protocol hierarchy where user-accessed network processes
reside. An TCP/IP application is any network process that occurs above the transport layer. This
include all the processes that the users directly interact with, as well as other processes at this
level that users are not necessarily aware of.
The Application Layer provides the services user applications needed to communicate through
the network.
Here are several examples of user application layer services:
• Electronic mail transport.
• Remote file access.
• Remote job execution.
• Directories.
• Network management.
Application Layer Protocol Functions
Application layer ISO OSI protocols are used by both the source and destination devices during
a communication session. In order for the communications to be successful, the application
layer protocols implemented on the source and destination host must match. Protocols establish
consistent rules for exchanging data between applications and services loaded on the
participating devices. Protocols specify how data inside the messages is structured and the
types of messages that are sent between source and destination. These messages can be
requests for services, acknowledgments, data messages, status messages, or error messages.
Protocols also define message dialogues, ensuring that a message being sent is met by the
expected response and the correct services are invoked when data transfer occurs. Many
different types of applications communicate across data networks. Therefore, Application layer
services must implement multiple protocols to provide the desired range of communication
experiences. Each protocol has a specific purpose and contains the characteristics required to
meet that purpose. The right protocol details in each layer must be followed so that the functions
at one layer interface properly with the services in the lower layer. Applications and services
may also use multiple protocols in the course of a single conversation. One protocol may
specify how to establish the network connection and another describe the process for the data
transfer when the message is passed to the next lower layer.

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Ap
plication Layer Services and Protocols
A single application may employ many different supporting Application layer services; thus what
appears to the user as one request for a web page may, in fact, amount to dozens of individual
requests. And for each request, multiple processes may be executed. For example, a client may
require several individual processes to formulate just one request to a server. Additionally,
servers typically have multiple clients requesting information at the same time. For example,
a Telnet server may have many clients requesting connections to it. These individual client
requests must be handled simultaneously and separately for the network to succeed. The
Application layer processes and services rely on support from lower layer functions to
successfully manage the multiple conversations.
Protocols: FTP1
, HTTP2
, SMTP3
, DNS4
, TFTP5
, NFS6
, TELNET7
Application layer network devices
When most people think of Application Layer protocols like HTTP, SMTP, or POP3, they also
think of software applications which are the interface for these applications. But this is not
always the case. With a little thought we can easily think of examples where the interface for the
applications are hardware implementations. For example, take many of today's cordless phones
which are capable of connecting to one's VoIP account. Now while there is software on these
phones it is easy to imagine that the majority of the work is done by hardware. In fact, your
voice is collected by a microphone and hardware processes it so that it is compatible with the
proprietary VoIP application protocol by hardware inside the phone. This hardware can be either
an Application Specific Integrated Circuit (ASIC) or a Field Programmable Gate Array (FPGA).
Another example of a hardware implementation of an Application Layer protocol is found
within Bluetooth. Bluetooth, in its entirety, covers many layers of the OSI Reference Model but
we will focus on the application layer implementation. Within Bluetooth devices you can find
many applications falling within the Application Layer. One such application is one which would
allow a wireless ear piece, like the one shown in Figure 1, to communicate with a cell phone in
your pocket. In this case, the ear piece, which has a Bluetooth chip inside, will convert the signal
it receives from the phone to a form acceptable to the speaker completely through hardware.
Likewise, the ear piece will receive a signal of your voice from the microphone and convert it to
a form acceptable to the Bluetooth chip which will then send the signal to your phone. This is all
done through hardware.

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Layer 6 Presentation Layer
The presentation layer is layer 6 of the 7-layer Open Systems Interconnection (OSI) model. It is
used to present data to the application layer (layer 7) in an accurate, well-defined and
standardized format. The presentation layer is sometimes called the syntax layer.
The presentation layer is responsible for the following:
Data encryption/decryption
Character/string conversion
Data compression
Graphic handling
The presentation layer mainly translates data between the application layer and the network
format. Data can be communicated in different formats via different sources. Thus, the
presentation layer is responsible for integrating all formats into a standard format for efficient
and effective communication.
The presentation layer follows data programming structure schemes developed for different
languages and provides the real-time syntax required for communication between two objects
such as layers, systems or networks. The data format should be acceptable by the next layers;
otherwise, the presentation layer may not perform correctly. Network devices or components
used by the presentation layer include redirectors and gateways.
Presentation layer protocols
The OSI presentation layer protocol (ISO-PP) is for the information transit between open
systems using connection oriented or connectionless mode transmission at the presentation
layer of the OSI 7 layer model. An application protocol is specified in terms of the transfer of
presentation data values between application entities (PS users), using the User data parameter
of presentation service primitives.
The Presentation Layer has two functions it carries out on behalf of PS users:
negotiation of transfer syntaxes
transformation to and from transfer syntax.
The function of transfer syntax negotiation is supported by presentation protocols.
Transformation of syntax is a function contained within a presentation entity and has no impact

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on presentation protocol design. For connectionless mode transmission, the sending
presentation entity selects the transfer syntaxes. No transfer syntax negotiation occurs.
A set of presentation data value definitions associated with an application protocol constitutes
an abstract syntax. For two application entities to communicate successfully they must have an
agreement on the set of abstract syntaxes they intend to use. During the course of
communication they may decide to modify this agreement. As a consequence, the set of
abstract syntaxes in use may be changed. The abstract syntax specification identifies the
information content of the set of presentation data values. It does not identify the transfer syntax
to be used while presentation data values are transferred between presentation entities, nor is it
concerned with the local representation of presentation data values.
The Presentation Layer exists to ensure that the information content of presentation data values
is preserved during transfer. It is the responsibility of cooperating application entities to
determine the set of abstract syntaxes they employ in their communication and inform the
presentation entities of this agreement. Knowing the set of abstract syntaxes to be used by the
application entities, the presentation entities are responsible for selecting mutually acceptable
transfer syntaxes that preserve the information content of presentation data values.
Protocols: ASCII8
, EBCDIC9
, MIDI10
, MPEG11
, JPEG12
Presentation layer network devices
The Presentation Layer is responsible for converting the data sent over the network from one
type of representation to another. For example, the Presentation Layer can apply sophisticated
compression techniques so fewer bytes of data are required to represent the information when
it's sent over the network. At the other end of the transmission, the Transport Layer then
uncompressed the data.
The Presentation Layer also can scramble the data before it's transmitted and then unscramble
it at the other end, using a sophisticated encryption technique.
Layer 5 Session layer
In the Open Systems Interconnection (OSI) communications model, the Session layer
(sometimes called the "port layer") manages the setting up and taking down of the association
between two communicating end points that is called a connection. A connection is maintained
while the two end points are communicating back and forth in a conversation or session of some
duration. Some connections and sessions last only long enough to send a message in one
direction. However, other sessions may last longer, usually with one or both of the
communicating parties able to terminate it.
For Internet applications, each session is related to a particular port, a number that is
associated with a particular upper layer application. For example, the HTTP program or daemon
always has port number 80. The port numbers associated with the main Internet applications
are referred to as well-known port numbers. Most port numbers, however, are available for
dynamic assignment to other applications.

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Session layer protocols
The session layer provides the mechanism for opening, closing and managing a session
between end-user application processes, i.e., a semi-permanent dialogue. Communication
sessions consist of requests and responses that occur between applications. Session-layer
services are commonly used in application environments that make use of remote procedure
calls (RPCs).An example of a session-layer protocol is the OSI protocol suite session-layer
protocol, also known as X.235 or ISO 8327. In case of a connection loss this protocol may try to
recover the connection. If a connection is not used for a long period, the session-layer protocol
may close it and re-open it.
It provides for either full duplex or half-duplex operation and provides synchronization points in
the stream of exchanged messages.Other examples of session layer implementations include
Zone Information Protocol (ZIP) – the AppleTalkprotocol that coordinates the name binding
process, and Session Control Protocol (SCP) – the DECnet Phase IV session-layer
protocol.Within the service layering semantics of the OSI network architecture, the session layer
responds to service requests from the presentation layer and issues service requests to the
transport layer.
Protocols: SQL13
, RPC14
Session layer network devices
According to the OSI Model, the session layer is where connections are established, managed,
and torn down. For connection-oriented network protocols, understanding how the session layer
works, and what symptoms would help you identify when it's not working, is an important part of
your job as a network administrator. However, because TCP doesn't respect the OSI model, we
have to sort of carve TCP/IP out of this conversation, which really limits its practical application
in most environments.
When you think about session-oriented communications vs. connectionless conversations, you
might compare them to a telephone conversation vs. using a walkie-talkie. With a telephone,
you call the person who you want to talk to, establish a connection -- or session -- and then you
hang up, severing the connection once the conversation is completed. With a walkie-talkie, you
simply speak into the device and hope that the person on the other end is listening and that they
respond in kind. There's no session established.
Two session-oriented protocols that you are still likely to see on production networks
are Netbios and RPC. These protocols are commonly used within Microsoft-based LAN
environments. However, problems with these protocols are seldom seen and when they are,
since they're used on the LAN, it's unlikely that the problem is network related. More likely, it's
an application problem.
Layer 4 Transport layer
The transport layer is the layer in the open system interconnection (OSI) model responsible for
end-to-end communication over a network. It provides logical communication between
application processes running on different hosts within a layered architecture of protocols and
other network components.

Network Management
The transport layer is also responsible for the management of error correction, providing quality
and reliability to the end user. This layer enables the host to send and receive error corrected
data, packets or messages over a network and is the network component that allows
multiplexing.
As the transport layer is built on top of the network layer, it is important to know the key features
of the network layer service. There are two types of network layer services: connectionless and
connection-oriented. The connectionless network layer service is the most widespread.
Transport layer protocols
This chapter provides an overview of the most important and common protocols of the TCP/IP
transport layer. These include:
I. User Datagram Protocol (UDP)
II. Transmission Control Protocol (TCP)
By building on the functionality provided by the Internet Protocol (IP), the transport protocols
deliver data to applications executing in the IP host. This is done by making use of ports. The
transport protocols can provide additional functionality such as congestion control, reliable data
delivery, duplicate data suppression, and flow control as is done by TCP.
I. User Datagram Protocol (UDP)
UDP is a standard protocol with STD number 6. UDP is described by RFC 768 – User
Datagram Protocol. Its status is recommended, but in practice every TCP/IP implementation
that is not used exclusively for routing will include UDP.
UDP is basically an application interface to IP. It adds no reliability, flow-control, or error
recovery to IP. It simply serves as a multiplexer/demultiplexer for sending and receiving
datagrams, using ports to direct the datagrams. Demultiplexing based on ports UDP provides a
mechanism for one application to send a datagram to another. The UDP layer can be regarded
as being extremely thin and consequently has low overheads, but it requires the application to
take responsibility for error recovery and so on.
II. Transmission Control Protocol (TCP)
TCP is a standard protocol with STD number 7. TCP is described by RFC 793 – Transmission
Control Protocol. Its status is recommended, but in practice, every TCP/IP implementation that
is not used exclusively for routing will include TCP.
TCP provides considerably more facilities for applications than UDP, notably error recovery,
flow control, and reliability. TCP is a connection-oriented protocol, unlike UDP, which is
connectionless. Most of the user application protocols, such as Telnet and FTP, use TCP.
The two processes communicate with each other over a TCP connection.
Protocols: TCP15
or UDP16

Network Management
Transport layer network devices
The device will maintain a routing table whose size is dependent on thesize of the WAN and the
device will ensure that overall security of thenetwork is maintained.
This can be implemented by making the device support V-WAN. Bysupporting V-WAN
the device can also work on the security function of aswitch, with regard to each router
and the network below each router.
The device will update its routing table automatically. This means that it will maintain a
database of the routers connected to it. This will be updatedat stipulated time interval .
This ensures that it is well aware of thenetworks connected to it and indirectly the hosts
present in each network.
Layer 3 Network layer
The most significant protocol at layer 3 (also called the network layer) is the Internet Protocol, or
IP. IP is the standard for routing packets across interconnected networks--hence, the
name internet. It is an encapsulating protocol similar to the way Ethernet is an encapsulating
protocol. If we view the original check as a unit of data needed to be sent, we now have two
envelopes required to do the transmission--the check first goes into an IP envelope, and then
the entire IP envelope (known as a packet) is placed into an Ethernet frame.
The format of an IP packet is documented in RFC 791. The most significant aspect of the IP
protocol is the addressing: every IP packet includes the IP source address (where the packet is
coming from) and the IP destination address.
Network layer protocols
Among the seven layers in the OSI reference model, layer 3 belongs to the network layer. There
are some important network layer protocols that you should know of. Protocol is nothing but a
set of rules that determine how messages are being exchanged between different computers.
Let us now briefly consider five important protocols that are related to the network layer
message transfers. They are:.
Protocols: IPv4, IPv6, CLNP, IPSec, and ICMP
IPv4:
IP stands for Internet Protocol while v4 indicates that it is the version 4. Here, version 4 refers to
the fourth revision of the Internet Protocol that was later widely deployed. There exists an IPv4
header structure that is the basis for network layer transfer of packets. This is one of the most
important network layer protocols.
IPv6:
This is also an Internet Protocol that is of version 6. Though IPv4 is widely used these days, it is
expected that this IPv6 is going to take over the rest of the attention. Hence, it is called the next
generation protocol. There are just a few basic differences between both the protocols. The
address space of IPv6 is larger than that of the IPv4.

Network Management
CLNP: CLNP stands for Connectionless Network Protocol. The service that this protocol
renders is called CLNS. This routes the messages to their destination independently.
IPSec: Internet Protocol Security is one such protocol that enables encryption and also
authentication of every IP packet that moves in the data stream. Encryption and authentication
are two techniques to ensure secure message transfer from the source to the destination.
ICMP: ICMP stands for Internet Control Message Protocol. This particular protocol is very
important among all the network layer protocols. This is used by the operating systems of
network computers to send error messages indicating that a particular service was not available
or the connection to a router failed, etc.
Network layer network devices
The network layer does not care much about the type of data it is moving, the path it takes, or
the different media that it moves over. Typically, you are allowed to change physical media
types at this layer. To connect different network types, you need an interconnection device that
supports data links for different network types.
Such a device includes different media connections on either side and, like the router in the
following figure, can connect gigabit Ethernet on one side of the device to something foreign,
such as Token Ring, on the other side.
Just as the data link layer has addresses that it uses to identify other devices with which your
computer communicates, these are hard to understand addresses and they are only valid for
the current network segments (the area between two routers). This area between routers is also
referred to as a data link because it is the only place where the local devices can communicate
with each other, using MAC addresses (or data link layer addresses).
The network layer of the OSI model also uses addresses, but these are network layer
addresses and their specific format is based on the network layer protocol being used. Internet
Protocol (IP) represents a common network layer protocol.
At the network layer, IP uses IP addresses to determine which two devices are communicating.
The relationship between the network layer and the data link layer is that all communication
over a data link will always be performed using data link (MAC) addresses, so as the network
layer sends data down to the data link layer, it must also tell the data link layer what the
destination MAC address is for this data.

Network Management
Layer 2 Data link layer
Different data link layer specifications define different network and protocol characteristics,
including physical addressing, network topology, error notification, sequencing of frames, and
flow control.
Physical addressing, is not to be confused with network or IP addressing. The physical address
defines how devices are labeled in the data link layer. This physical address is most commonly
called the Media Access Control (MAC) address. The MAC address is a unique number
assigned by the manufacturer. This numbering system is actually administered by one of the
networking governing bodies.
Network topology consists of the data-link layer specifications that often define how devices are
to be physically connected, such as in a bus or a ring topology. Error notification alerts upper
layer protocols that a transmission error has occurred, and the sequencing of data frames
reorders frames that are transmitted out of sequence. Finally, flow control moderates the
transmission of data so that the receiving device is not overwhelmed with more traffic than it can
handle at one time.
Switches and bridges use MAC addressing to make networking decisions and therefore these
types of equipment function on the data link layer.
Data link layer protocols
The basic function of the layer is to transmit frames over a physical communication link.
Transmission may be half duplex or full duplex. To ensure that frames are delivered free of
errors to the destination station (IMP) a number of requirements are placed on a data link
protocol. The protocol (control mechanism) should be capable of performing:
I. The identification of a frame (i.e. recognise the first and last bits of a frame).
II. The transmission of frames of any length up to a given maximum. Any bit pattern is
permitted in a frame.
III. The detection of transmission errors.
IV. The retransmission of frames which were damaged by errors.
V. The assurance that no frames were lost.
VI. In a multidrop configurationSome mechanism must be used for preventing conflicts
caused by simultaneous transmission by many stations.
VII. The detection of failure or abnormal situations for control and monitoring purposes.
It should be noted that as far as layer 2 is concerned a host message is pure data, every single
bit of which is to be delivered to the other host. The frame header pertains to layer 2 and is
never given to the host.
Protocols: IEEE 802.222
, 802.323
, 802.524

Network Management
Data link layer network devices
The Data Link Layer is concerned with local delivery of frames between devices on the same
LAN. Data Link frames, as these protocol data units are called, do not cross the boundaries of a
local network. Inter-network routing and global addressing are higher layer functions, allowing
Data Link protocols to focus on local delivery, addressing, and media arbitration. In this way, the
Data Link layer is analogous to a neighborhood traffic cop; it endeavors to arbitrate between
parties contending for access to a medium.
When devices attempt to use a medium simultaneously, frame collisions occur. Data Link
protocols specify how devices detect and recover from such collisions, and may provide
mechanisms to reduce or prevent them.
Delivery of frames by layer 2 devices is affected through the use of unambiguous hardware
addresses. A frame's header contains source and destination addresses that indicate which
device originated the frame and which device is expected to receive and process it. In contrast
to the hierarchical and routable addresses of the network layer, layer 2 addresses are flat,
meaning that no part of the address can be used to identify the logical or physical group to
which the address belongs.
Layer 1 Physical layer
The Physical Layer is the first and lowest layer in the seven-layer OSI model of computer. The
implementation of this layer is often termed PHY.
The Physical Layer consists of the basic hardware transmission technologies of a network. It is
a fundamental layer underlying the logical data structures of the higher level functions in a
network. Due to the plethora of available hardware technologies with widely varying
characteristics, this is perhaps the most complex layer in the OSI architecture.
The Physical Layer defines the means of transmitting raw bits rather than logical data packets
over a physical link connecting network nodes. The bit stream may be grouped into code words
or symbols and converted to a physical signal that is transmitted over a hardware transmission
medium. The Physical Layer provides an electrical, mechanical, and procedural interface to the
transmission medium. The shapes and properties of the electrical connectors, the frequencies
to broadcast on, the modulation scheme to use and similar low-level parameters, are specified
here.
Within the semantics of the OSI network architecture, the Physical Layer translates logical
communications requests from the Data Link Layer into hardware-specific operations to affect
transmission or reception of electronic signals.

Network Management
Physical layer protocols
CSMA/CD - Carrier Sense Multiple Access / Collision Detect
CSMA/CA - Carrier Sense Multiple Access / Collision Avoid
FDMA - Frequency Division Multiple Access
MSK - Minimum Shift Keying
GFMSK - Gaussian-Fitered Minimum Shift Keying
TDMA - Time Division Multiple Access
CDMA - Code Division Multiple Access
B8ZS - Binary 8 Zero Substitution
2B1Q - 2 Binary 1 Quaternary
PCM - Pulse Code Modulation
QAM - Quadrature Amplitude Modulation
PSK - Phase Shift Keying
SONET - Synchronous Optical NETworking
Protocols: IEEE 802.323
, 802.524
Physical layer network devices
I. Cables
II. Connectors
III. Repeaters
IV. Passive Hub
V. Simple Active Hub
VI. Transmitters
VII. Multiplexers
VIII. Receivers
IX. Transceivers
X. Couplers

Network Management
Task 2.2
Briefly explain the peer to Peer network (Workgroup) model and Client Server network (Domain)
model.
Peer-to-peer network
In a peer-to-peer network, there are no specific servers, and there is no hierarchy among the
computers. All the computers are equal and therefore are known as peers. Each computer
functions as both a client and a server.And there is no administrator responsible for the entire
network. The user at each computer determines what data on that computer is shared on the
network.
Computers in a peer-to-peer network are called peers. In a peer-to-peer network, all computers
are considered equal; they all have the same abilities to use the resources available on the
network. Each computer can function both as a client and a server. Computers are not
dedicated to function as servers. They use the network to share resources among the
independent peers. The computer whose applications are required by the other networked
computers functions as a server. The other computers function as clients. Therefore, a
dedicated administrator is not assigned for network management.
A peer-to-peer network is a small group of people using a network. Peer-to-peer networks
members usually perform similar tasks, which necessitates the sharing of resources. The peer-
to-peer networks support 10 computers. The users in a peer-to-peer network are located in the
same geographical area. Operating systems, such as Microsoft Windows 98 or Microsoft
Windows XP, can be used to set up a peer-to-peer network. Additional software is not required
because peer-to-peer networking is built into the systems.
Another important point of peer-to-peer networks is that the users of each computer plan and
control the security of their resources. The users determine the resources on their computers,
which can be shared on the network. The shared network resources, such as disk space,
printers or faxes, can be used by anyone who has access to the network. This is possible only if
the shared network resources are not password protected. Peer-to-peer networks have weak
and intrusive security because a central server is not used to administer and secure the
network. In addition, some users may not implement security.
A peer-to-peer network does not support a central login process. This implies that a user who
logs on to one peer can access any shared network resource, which is not controlled by a
specific password. Peer-to-peer networks are relatively simple. Because each computer
functions as a client and a server, there is no need for a powerful central server or for the other
components required for a high-capacity network. Peer-to-peer networks can be less expensive
than server-based networks.
Peer-to-peer networks are simple and inexpensive to install and maintain. The cost of
implementing peer-to-peer networks is low because a central server is not used to administer
the network. In addition, the components for a high-capacity network are not required in a peer-
to-peer network.

Network Management
In a peer-to-peer network, the users handle administration. This means that all the users need
to be trained in how to share files, folders, and printers. In a peer-to-peer network, suddenly
shutting down your computer can cause one of your colleagues to be unable to print.
Peer-to-peer networks are appropriate for environments where all the users are located in the
same geographical area and the network security is not an important factor. In addition, these
networks are useful when the network expansion is limited.
Advantages of a peer-to-peer network
Less initial expense.
Setup - An operating system (such as Windows XP) already in place may only need to
be reconfigured for peer-to-peer operations.
Disadvantages of a peer-to-peer network
Decentralized - No Centralized server.
Security - Does not provide the security available on a peer-to-peer network.
Client/ server network
In a server-based network, clients rely on the services that the server provides, such as file
storing and printing. Client computers are generally less powerful than server computers.
A server-based network using network operating system is that the networks are organized into
domains. A domain is a collection of networks and clients that share security information.
Domain security and logon permissions are controlled by special servers called domain
controllers. Users cannot access the resources of servers in a domain until a domain controller
has authenticated them.

Network Management
In server-based networks, a network administrator centrally manages the resource security. The
administrator defines and manages user access to network resources.
Another beneficial of server-based networks is central file storage. Server-based networks
provide easy backup of critical data. Data backup is another useful characteristic of server
based networks.
Server based networks can support a larger number of users than peer-to-peer networks. To
support a large number of users, server-based networks use monitoring and network
management tools. Servers must perform varied and complex tasks.
Advantages of a client/server network
Centralized - Resources and data security are controlled through the server.
Security - More security then Peer-to-peer network.
Flexibility - New technology can be easily integrated into system.
Interoperability - All components (client /server) work together.
Accessibility - Server can be accessed remotely and across multiple platforms.
Disadvantages of a client/server network
Expense, requires initial investment in dedicated server.
Maintenance, large networks will require a staff to ensure efficient operation.
Dependence, when server goes down, operations will cease across the network.

Network Management
compares the features of client/server networking (such as with Novell NetWare, Windows NT
Server, and Windows 2000/XP) with peer-to-peer networking (such as with Windows for
Workgroups, Windows 9x, Windows Me, and Windows NT Workstation). This table will help you
decide which type of network is appropriate for your situation.
Table 10.1. Comparing Client/Server and Peer-to-Peer Networking
Item Client/Server Peer-to-Peer
Access
control
Via user/group lists of permissions. A
single password provides user access to
only the resources on that list; users can
be given several different levels of
access.
Via password lists by resource. Each
resource requires a separate
password. All-or-nothing access is
used. No centralized user list exists.
Security High, because access is controlled by
user or by group identity.
Low, because knowing the password
gives anybody access to a shared
resource.
Performance High, because server doesn’t waste time
or resources handling workstation tasks.
Low, because servers often act as
workstations.
Hardware
cost
High, because of specialized design of
server, high-performance nature of
hardware, redundancy features.
Low, because any workstation can
become a server by sharing
resources.
Software
cost
License fees per workstation user are part
of the cost of the Network Operating
System server software (Windows
NT/2000/XP Server, Novell NetWare).
Free; all client software is included
with any release of Windows 9x,
Windows NT Workstation, Windows
2000 Professional, Windows Me, or
Windows XP.
Backup Centralized when data is stored on
server; allows use of high-speed, high-
capacity tape backups with advanced
cataloguing.
Left to user decision; usually mixture
of backup devices and practices at
each workstation.
Redundancy Duplicate power supplies, hot-swappable
drive arrays, and even redundant servers
are common. Network OS normally is
capable of using redundant devices
automatically.
No true redundancy among either
peer ―servers‖ or clients. Failures
require manual intervention to correct
with high possibility of data loss.

Network Management
Difference between client/server and peer-to-peer networksIn terms of security
and cost
There’s a huge difference between client/server and peer-to-peer networks. For instance, a
peer-to-peer network has no central server. Each workstation on the network shares its files
equally with the others. There’s no central storage or authentication of users. Conversely, there
are separate dedicated servers and clients in a client/server network. Through client
workstations, users can access most files, which are generally stored on the server. The server
will determine which users can access the files on the network.
Peer-to-peer networks should be installed in homes or in very small businesses where
employees interact regularly. They are inexpensive to set up (comparatively speaking);
however, they offer almost no security. On the other hand, client/server networks can become
as big as you need them to be. Some support millions of users and offer elaborate security
measures. As you can imagine, client/server networks can become very expensive.
Peer-to-peer networks
Peer-to-peer networks are appropriate only for very small businesses or for home use. A peer-
to-peer network can support about ten clients (workstations) before it begins to suffer from some
serious performance and management problems. Usually, peer-to-peer networks are composed
of a collection of clients that run either Windows NT Workstation or Windows 98. Windows 3.11,
Windows 95, and Windows 2000 Professional also support peer-to-peer networking.
The concept behind peer-to-peer networking is to share files and printers as inexpensively as
possible; therefore, there’s no main server on the network. Instead, each client functions both as
a client and as a server simultaneously. Since users are allowed to control access to the
resources on their own computers, however, security becomes very risky in a peer-to-peer
environment. There’s no central security or any way to control who shares what. Users are free
to create any network share points on their computers. The only security on a peer-to-peer
network is at the share level. When users create network shares, they may implement no
security, which means that anyone can have full access to the share, or they may assign a
password to the share. Depending on which networking platform you use, a user may be able to
assign one password to a share for read-only access and another password for full control over
the share.
Although this arrangement may sound somewhat secure, it isn’t. The computer that contains the
shared resources doesn’t check on who’s trying to access those resources. Any user can
access them as long as the user knows the password. If someone happens to write down a
password, anyone who finds that password can access the share.
Client/server networks
There are an almost infinite variety of client/server networks, but all of them have a couple of
things in common. For one thing, all have centralized security databases that control access to
shared resources on servers. In the world of Windows, the server usually runs NetWare,
Windows NT, or one of the Windows 2000 Server products. The server contains a list of
usernames and passwords. Users can’t log on to the network unless they supply valid
usernames and passwords to the server. Once logged on, users may access only those
resources that the network administrator allows them to access. Thus, client/server networks
possess much more security than do peer-to-peer networks.

Network Management
Client/server networks also tend to be much more stable. In a peer-to-peer network, certain
shared resources reside on each user’s machine. If users decide to monkey around and crash
their computers, they could seriously affect their peer-to-peer network (where coworkers depend
on resources that reside on other users’ machines). On most client/server networks, however,
shared resources reside on the server, where they’re safe from curious users. If a user happens
to erase a shared resource from the server, you can rely on the nightly backup. (It’s very difficult
to back up a peer-to-peer network every night.)
The primary downside to a client/server network is its cost. Servers can become very
expensive. For example, you could pay over $800 for a copy of Windows NT Server and five
client licenses, and that price doesn’t even include the cost of the hardware, which must be
more powerful than a standard workstation. Additionally, client/server networks require an
employee to manage them. Unless you have someone in your office who’s trained in NetWare
or Windows NT Server and in all of the issues that are involved in client/server networking, you’ll
have to hire someone from the outside. And believe me when I say that qualified networking
professionals don’t come cheap.

Network Management
Task 03
Task 3.1
Design a total network solution for a company which has around 25 computers and have 2
servers respectively one for web server and the other one for file sharing propose and Internet
connectivity.This design must reflect a high availability on all aspect of the networking starting
from LAN to WAN.
This task provides evidence for P14.2.3, P14.3.1, P14.3.3, P14.4.

Network Management
Task 3.2
Compare and contrast OSI and TCP/IP proposed network management standards
Transmission Control Protocol is used by Internet applications like email, world wide web, FTP,
etc. TCP/IP was developed by the Department of Defence (DOD) to connect various devices to
a common network (Internet). The main purpose behind developing the protocol was to build a
robust and automatically recovering phone line failure while on the battlefield. On the other
hand, Open Systems Interconnection was developed by the International Organization for
Standardization (ISO). This model was made up of two components, namely, seven-layer model
and the subset of protocols.
Distinguishing Points
Both the TCP/IP and OSI model work in a very similar fashion. But they do have very subtle
differences too. The most apparent difference is the number of layers. TCP/IP is a four-layered
structure, while OSI is a seven-layered model.

Network Management
TCP/IP Model
The Internet Protocol Suite, popularly known as the TCP/IP model, is a communication protocol
that is used over the Internet. This model divides the entire networking functions into layers,
where each layer performs a specific function.
This model gives a brief idea about the process of data formatting, transmission, and finally the
reception. Each of these functions take place in the layers, as described by the model. TCP/IP
is a four-layered structure, with each layer having their individual protocol. Let us have a look at
the four layers:
Link Layer
As the name suggests, this layer includes the physical and logical connections from the host's
link. It is also known as Network Access layer and Network Interface layer. It explains how the
data is transmitted from the host, through the network. The physical connectors like the coaxial
cables, twisted pair wires, the optical fiber, interface cards, etc., are a part of this layer. This
layer can be used to connect different network types like ATM, Token ring, Ethernet, LAN, etc.
Internet Layer
This layer is also known as the Network Layer. The main function of this layer is to route the
data to its destination. The data that is received by the link layer is made into data packets (IP
datagrams). The data packets contain the source and the destination IP address or logical
address. These packets are sent on any network and are delivered independently. This
indicates that the data is not received in the same order as it was sent. The protocols at this
layer are IP (Internet Protocol), ICMP (Internet Control Message Protocol), etc.

Network Management
Transport Layer
This layer is responsible for providing datagram services to the Application layer. This layer
allows the host and the destination devices to communicate with each other for exchanging
messages, irrespective of the underlying network type. Error control, congestion control, flow
control, etc., are handled by the transport layer. The protocol that this layer uses is TCP
(Transmission Control Protocol) and UDP (User Datagram Protocol). TCP gives a reliable, end-
to-end, connection-oriented data transfer, while UDP provides unreliable, connectionless data
transfer between two computers.
Application Layer
It provides the user interface for communication. This is the layer where email, web browsers or
FTP run. The protocols in this layer are FTP, SMTP, HTTP, etc.
OSI Model
The Open Systems Interconnected (OSI) model divides the network into seven layers and
explains the routing of the data from source to destination. It is a theoretical model which
explains the working of the networks. It was developed by the International Organization for
Standardization (ISO) for their own network suite. Here are the details of OSI's seven layers:
Physical Layer
As the name suggests, this is the layer where the physical connection between two computers
takes place. The data is transmitted via this physical medium to the destination's physical layer.
The popular protocols at this layer are Fast Ethernet, ATM, RS232, etc.
Data Link Layer
The main function of this layer is to convert the data packets received from the upper layer into
frames, and route the same to the physical layer. Error detection and correction is done at this
layer, thus making it a reliable layer in the model. It establishes a logical link between the nodes
and transmit frames sequentially.
Network Layer
The main function of this layer is to translate the network address into physical MAC address.
The data has to be routed to its intended destination on the network. This layer is also
responsible to determine the efficient route for transmitting the data to its destination. While
doing so, it has to manage problems like network congestion, switching problems, etc. The
protocols used here are IP, ICMP, IGMP, IPX, etc.

Network Management
Transport Layer
This layer provides end-to-end delivery of data between two nodes. It divides data into different
packets before transmitting it. On receipt of these packets, the data is reassembled and
forwarded to the next layer. If the data is lost in transmission or has errors, then this layer
recovers the lost data and transmits the same.
Session Layer
This layer is responsible to establish and terminate connections between two communicating
machines. This connection is known as a session, hence the name. It establishes full-duplex,
half-duplex and simplex connection for communication. The sessions are also used to keep a
track of the connections to the web server.
Presentation Layer
The data conversion takes place at this layer. The data that it receives from the application layer
is converted into a suitable format that is recognized by the computer. For example, the
conversion of a file from .wav to .mp3 takes place at this layer.
Application Layer
This layer provides a user interface by interacting with the running application. E-mail, FTP, web
browsers, etc., are the network applications that run on this layer.
The entire communication industry stands on the backbone of TCP/IP and OSI reference model.
It is absolutely vital to learn the above differences, if anyone wants to be an expert in the field of
communication.

Network Management
Task 3.3
Describe the responsibilities of Network Administrator.
Simply put, network administrators administer networks, which means that they take care of the
tasks of installing, configuring, expanding, protecting, upgrading, tuning, and repairing the
network. Network administrators take care of the network hardware, such as cables, hubs,
switches, routers, servers, and clients, as well as network software, such as network operating
systems, e-mail servers, backup software, database servers, and application software.
On a big network, these responsibilities constitute a full-time job. Large networks tend to be
volatile: Users come and go, equipment fails, cables break, and life in general seems to be one
crisis after another.
Smaller networks are much more stable. After you get your network up and running, you
probably won’t have to spend much time managing its hardware and software. An occasional
problem may pop up, but with only a few computers on the network, problems should be few
and far between.
Regardless of the network’s size, all network administrators must attend to several common
chores:
Equipment upgrades
The network administrator should be involved in every decision to purchase new computers,
printers, or other equipment. In particular, the network administrator should be prepared to lobby
for the most network-friendly equipment possible, such as new computers that already have
network cards installed and configured and printers that are network ready.
Configuration
The network administrator must put on the pocket protector whenever a new computer is added
to the network. The network administrator’s job includes considering what changes to make to
the cabling configuration, what computer name to assign to the new computer, how to integrate
the new user into the security system, what rights to grant the user, and so on.

Network Management
Software upgrades
Every once in a while, your trusty operating system vendor (in other words, Microsoft) releases
a new version of your network operating system. The network administrator must read about the
new version and decide whether its new features are beneficial enough to warrant an upgrade.
In most cases, the hardest part of upgrading to a new version of your network operating system
is determining the migration path — that is, how to upgrade your entire network to the new
version while disrupting the network or its users as little as possible. Upgrading to a new
network operating system version is a major chore, so you need to carefully consider the
advantages that the new version can bring.
Patches
Between upgrades, Microsoft releases patches and service packs that fix minor problems with
its server operating systems. For more information, see the section ―Patching Up Your
Operating System and Software‖ later in this chapter.
Performance maintenance
One of the easiest traps that you can get sucked into is the quest for network speed. The
network is never fast enough, and users always blame the hapless network manager. So the
administrator spends hours and hours tuning and tweaking the network to squeeze out that last
2 percent of performance.
Ho-hum chores
Network administrators perform routine chores, such as backing up the servers, archiving old
data, freeing up server hard drive space, and so on. Much of network administration is making
sure that things keep working and finding and correcting problems before any users notice that
something is wrong. In this sense, network administration can be a thankless job.
Software inventory
Network administrators are also responsible for gathering, organizing, and tracking the entire
network’s software inventory. You never know when something is going to go haywire on Joe in
Marketing’s ancient Windows 2000 computer and you’re going to have to reinstall that old copy
of WordPerfect.

Network Management
Designing the Network
The first phase in the life cycle of a network involves creating its design, a task not usually
performed by new network administrators. Designing a network involves making decisions
about the type of network that best suits the needs of your organization. In larger sites this task
is performed by a senior network architect: an experienced network administrator familiar with
both network software and hardware.
Setting Up the Network
After the new network is designed, the second phase of network administration begins, which
involves setting up and configuring the network. This consists of installing the hardware that
makes up the physical part of the network, and configuring the files or databases, hosts, routers,
and network configuration servers.
The tasks involved in this phase are a major responsibility for network administrators. You
should expect to perform these tasks unless your organization is very large, with an adequate
network structure already in place.
Maintaining the Network
The third phase of network administration consists of ongoing tasks that typically constitute the
bulk of your responsibilities. They might include:
Adding new host machines to the network
Administering network security
Administering network services, such as NFS services, name services, and electronic
mail
Troubleshooting network problems
Expanding the Network
The longer a network is in place and functioning properly, the more your organization might
want to expand its features and services. Initially, you can increase network population by
adding new hosts and expanding network services by providing additional shared software. But
eventually, a single network will expand to the point where it can no longer operate efficiently.
That is when it must enter the fourth phase of the network administration cycle: expansion.
Several options are available for expanding your network:
Setting up a new network and connecting it to the existing network using a machine
functioning as a router, thus creating an internetwork
Configuring machines in users' homes or in remote office sites and enabling these
machines to connect over telephone lines to your network
Connecting your network to the Internet, thus enabling users on your network to retrieve
information from other systems throughout the world
Configuring UUCP communications, enabling users to exchange files and electronic mail
with remote machines.

Network Management

Network management (HND in Networking)

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