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Answer Sheet – Level 3 Networking Principles (7540-031) Assignment A
Task A1: Explain the difference between logical and physical network topologies.
A logical topology is how devices appear connected on a diagram or to the user, and a physical topology is how they are actually connected using cables and
wires. For example in a networks that uses shared Ethernet to connect to hubs instead of switches is a physical star topology, however the logical topology is a
bus topology because this is how it appears to be to a user.
Task A2: Describe how each of the following physical network topologies transmits data and specify appropriate cabling and connectors for each.
 Bus
 Star
 Ring
 Mesh
 Hybrid or Tree

Star
A start topology is shown in image 2. In a star topology network devices are connected to a central hub. Nodes communicate
across the network, transmitting data by passing data through the hub. Star topologies are made using Ethernet, fast Ethernet or
gigabit Ethernet using RJ45 connectors. However even though these use more wiring that the bus topology, they are better as
because each computer is connected to the hub, is one wire is damaged or broken it will only affect one computer, whereas on
the bus it would affect the whole network.

Ring
This is a ring topology (image3). A ring topology is logical topology, and means that all of the computers in the network are
connected in a closed off loop. Messaged travels around the ring in one direction to each computer. Sending and receiving data
can only happen with the use of using tokens. Tokens contain a piece of information with along with the data is send by the
source computer. This token then passes to the next node, which checks if the data has been sent to it by the source, if it has not
the computer will continue to send the data along the ring until it has found the correct recipient of the data. If another node
wants to send data they must wait until an empty token that reaches their computer. Most ring topologies will have the physical
cabling of a star topology.

Mesh
A mesh topology is shown in image 4. A mesh topology transmits data by having all devices connecting to every other device on the network. Every node
has a connection to another node. In a full mesh topology has a circuit connecting nodes to every other node on the network,
where as a partial mesh topology some nodes are organised as full mesh where as some are not. A mesh topology provides
redundancy and fault tolerance. Mesh’s can be wired topology’s, using Ethernet cables however this would be really expensive
so a lot of people create Wi-Fi meshes with 802.11 standard.

Hybrid or Tree
A Tree topology is shown in image 5. Tree topologies combine characteristics of the start and bus topologies. In a tree network
groups of star topology configured networks are connected to a linear bus backbone cable. Therefore this will use the same
wiring and method of data transmission as the bus and the star topologies. Tree topologies are a good choice for large
computer networks, as the topology devices the whole network into manageable chunks.
Task A3: Describe data communication systems hardware and software components that are typically used in constructing and configuring a LAN.
Include in your description a minimum of seven hardware and four software components.
When setting up a LAN network the following hardware and software is required for data communication. Starting with the hardware you need a
transmission channel, There are a few types of channel used for data communication in a LAN such as, twisted pair cable and coaxial cable. You will need
Network interface cards (NIC), these are used so that workstations can connect to the network. Servers will be needed as providing servers on a LAN
means that sharing expensive resources such as storage devices and printers can be possible. A server is a dedicated computer that controls one or more
resources. Some major types of server are a printing server, a modem server and a file server. Also Workstations, in network computers are the
workstations; these are the computers that users use when they are on the network. A LAN network also uses switches, a device that directs data
packages along a path and through the network to workstations/printers/etc. Lastly a LAN can also use a hub; hubs are central connecting devices in a
LAN network. Data arrives at the hub from one or more devices and is thrown out using just one cable.
LAN networks also require software to be able to function and communicate data. LAN’s require software such as network OS for systems and servers,
for example for a server you could use WindowsServer2008 R2, and for workstations you can use Windows 7 Enterprise. However licences must be
brought correctly to ensure the use of them is legal. LAN’s also need Networking protocol software, such as TCP/IP, Novell or IPX, this allows for protocols
to be managed and set up in the network. Application software, such as emails (outlook) and internet browsers need to be installed on workstations, this
is so that the email servers/webservers can connect to these applications to let users browse the web safely and to receive email. Lastly NIC drivers are
needed so that all the computers/servers can use the NIC correctly and connect to the network as it is a device, and needs a driver to make sure it works
correctly.
Task A4: Identify two wiring standards and explain the difference between them.
T568A and T568B are the two colour codes used for wiring RJ45 plugs. Both of these provide wiring schemes for terminating twisted pair copper network cabels
to RJ45 jacks. These are 4 pairs of twisted wires that are based on 4 colours orange, blue, brown and green with each colour having a condescending wire of the
same colour with white stripes on it. When untwisted the four pairs of wires result in eight individual wires, one for each pin of the jack plug.
The only difference between the two colour codes is that the orange and green pairs are interchanged. The T568A patter is preferred as it provides backwards
compatibility to both USCO wiring schemes. However the most used one is T568B because it matches the older ATA&T 258a colour code.
T568A and T568B should not be combined or interchanged. T568B is the preferred and most used wiring standard out of the two, however there are cases when
T568A components need to be connected to T568B components. In this case a crossover cable will need to be used to smoothly transfer between standards
without compromising data
T568A
White Green
T568B
White and Orange
Green
White and Orange
Blue
White and Blue
Orange
White and Brown
Brown
Orange
White and Green
Blue
White and Blue
Green
White and Brown
Brown
Task A5: Identify three wireless standards.
802.11 - 802.11 can only support a maximum network bandwidth of 2mbps which is too slow for most applications and a frequency of 2.4GHz. And 802.11
wireless products are no longer manufactured
802.11b - IEEE expanded on the original 802.11 to 802.11b. This supports bandwidth up 10 11mbps, comparable to Ethernet. It still uses the frequency of
2.4GHz. This standard can be interfered from microwaves, ovens, cordless phones and other applications using the same GHz.
802.11a- IEEE created a second extension to the original 802.11. 802.11a supports bandwidth up to 54mbps and signals in the frequency of around 5GHz
however the higher frequency meant that the range is shortened and also the signal had trouble getting through walls.
Task B1: Describe the function of each layer of the OSI model and explain how the layers relate to each other, including encapsulation and framing.
On the application layer data flow and encapsulation occurs when two nodes are connected in a network with shared transmission mediums. An application
running on a source device created some data. Then it moves along to the presentation layer where the application needs to add encryption to the data. Then
the data moves down to the session layer, here is when it appends the session ID and at this point the information is still just one block of data. Once in the
transport layer, it gets broken down into blocks of data called segments. Each segment gets a port number to identify which upper layer application and what
device needs to receive the data. Once through that data goes to the network layer, this later takes the segments and appends the source and destination IP
addresses, this is when a packet is created. Then the data goes down into the data link layer where the destination and MAC address is added, then at this point
the data is a frame. The frame is then sent to the physical layer where it is transferred into a signal, a signal that represents 0’s and 1’s, The NIC then prepared
those signals and sends them out.
Task B2: For each layer of the OSI model, describe the key features, protocols and standards.
Layer 1- Physical Layer. The physical layer is the physical part of the OSI model, meaning that it is all the wires and its job is to transmit the data of raw bit
streams over a physical medium. The physical layer has the following major functions, It defines topology, it defines the transmission mode (half duplex/full
duplex). It defines the protocol to establish a connection between two directly connected nodes. And finally it defines the electrical specifications of data
connection. It gives a relationship between a device and a physical transmission medium such as Ethernet or fibre optic. Examples include – Hubs, NICS and
cables.
Layer2- Data link. This layer is the next layer up, and is reliable for transmission of data between two nodes, connected by a physical layer. Therefore the physical
layer has to be there in order for the data link layer to start to begin to transmitting data. This is a reliable link between two nodes, because it detects and
corrects errors that occur on the physical layer. The data link used point to point protocol (PPP) and TCPIP. Examples include - Switches
Layer 3 - Network Layer. The network layer is there to structure and manage multi node network, including addressing, routing and traffic control. The network
layer provides the functional and procedural means of transferring variable length data sequences from one node to another connected to the same network. It
translates logical network address into physical machine address (IP to MAC). A network is a medium to which many nodes can be connected, on which every
node has an address and which permits nodes connected to it to transfer messages to other nodes connected to it by merely providing the content of a message
and the address of the destination node and letting the network find the way to route the message to the destination node. Examples include – Routers, layer 3
switches, IP.
Layer 4 – Transport layer. This layer is therefore reliable transmissions of data segments between points on a network, including segmentation,
acknowledgement, and multiplexing. This layer provides the means of transferring variable length data sequences from a source to a destination using TCP and
UDP. The transport layer makes a link more reliable as it will flow control, segment/desegment and error control the data passing. Protocols include – TCP, UDP
Layer 5 – Session layer. This layer manages communication sessions in the form of multi back and forth transmissions between nodes. This layer controls
dialogues and connections between computers. It manages the connections between logical and remote application. It will provide full duplex and half duplex
and establishes checkpoints termination and restart procedures. This layer is responsible for graceful close of sessions, as well as recovery. Protocols include –
NetBIOS, PPTP, Kerberos
Layer 6 – Presentation layer. This layer is the translation of data between a network service and an application. Including data compression and encryption. This
layer gives independence from data representation by translating between application and network formats. The presentation layer transforms data into a form
that can be read from the application layer. Protocols include – HTTPS, SSL
Layer 7 – Application layer. This layer is the final layer and is there to share resources, remote file access and virtual terminals. This is the layer closest to the end
user. This layer interacts with software application such ad outlook and internet browsers. Protocols include – SNMP, SMTP, FTP
Task C1: Describe the functions and key features of the four layers of the Internet Protocol (TCP/IP) model.
Each layer of the TCP/IP model has its own functions and key features. To begin with there is layer 1, network access. This layer is used to define the cabling, and
what topology the network is going to be (star, bus, mesh) . This is signalled by hardware devise such as coaxial cable and twisted pain cable. When a host wants
to place data on the wire, it will check the wire to find whether another host is already using the medium. If there is traffic already in the medium, the host will
wait and if there is no traffic, it will place the data in the medium. But, if two systems place data on the medium at the same instance, they will collide with each
other, destroying the data. The protocols in this layer include Ethernet, token ring and FDDI. Next there is layer 2 of the TCP/IP model, Internet. This layer is used
for packet switching, and it is to allow hosts to insert packets into any network and have them delivered to a destination. It is then the job of higher levels to
arrange these. The protocols in this layer include IP, ICMP and ARP. Next is Layer 3 the transport layer. The purpose of the transport layer is to permit devices on
the source and destinations hosts and to carry on a conversation. This layer defines the level of service and status of a connection when transporting data, this
layer used the protocols TCP and UDP, and is the same as the transport layer on the OSI model. Lastly Layer 4 the application layer, this layer defines TCP.IP
application protocols and how programs interface with the transport layer services to use the network, so basically this is how when things are transported they
go through and become data on applications on workstations. This layer includes protocols like DNS, HTTP, SSH, and FTP.
Task C2: Describe the protocols of each TCP/IP layer.
Each layer of the TCP/IP model uses protocols. To begin with there is layer 1, network access, the protocols in this layer include Ethernet, token ring and FDDI as
they are the cables and wiring standards that start everything off. The network has to start from something physical, therefore it’s these protocols that allow
things to be done further up the model. Next there is layer 2 of the TCP/IP model, Internet. The protocols in this layer include IP, ICMP and ARP. These protocols
are used for network addressing and by network devices, like routers, to send error messages indicating, for example, that a requested service is not available or
that a host or router could not be reached. Next is Layer 3 the transport layer. This layer used the protocols TCP and UDP, and is the same as the transport layer
on the OSI model. TCP reorders packets and is desirable for transmitting data. Lastly Layer 4 the application layer. This layer includes protocols like DNS, HTTP,
SSH, and FTP. These protocols allow you to access applications for example when you ask your email program (outlook) to download e-mails that are stored on a
email server, it will request the task to the TCP/IP application layer and the SMTP protocol.
Task C3: Explain how the TCP/IP model relates to the OSI model.
Similarities
•
They share a similar architecture, as both of them have layers and they directly connect to each other like the image to the right.
•
They share a common application layer; however the two can complete different services depending on the model.
•
Both models have comparable transport and network layers.- This can be illustrated by the fact that whatever functions are performed between the
presentation and network layer of the OSI model similar functions are performed at the Transport layer of the TCP/IP model
•
Knowing both models is required by industry professionals.
•
Both models assume that packets are switched; therefore individual packages can take individual paths.
Differences
•
TCP/IP combines the presentation and session layer issues into its application layer.
•
TCP/IP is considered to be a more credible model- This is mainly due to the fact because TCP/IP protocols are the standards around which the internet
was developed therefore it mainly gains creditability due to this reason.
•
The OSI model has 7 layers whereas the TCP/IP model has 4.
•
The TCP model is a simpler model and this is because of the fact it has less layers.
This form can be handwritten or completed electronically.