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Comp247 data communications, Lecture notes of Computers and Information technologies

Macquarie University (MU)Computers and Information technologies

data communications

Typology: Lecture notes

2015/2016

Uploaded on 05/31/2016

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COMP247 Data Communications
Assignment 1, 2016
Due: Tuesday 5th April, 2016, 6 pm
Marks: 60
Value: 15%
44671172
Question 1:
Physical link:
The physical layer is the lowest layer of the internetwork layers, this layer contains the
information that unlike the other layers is physically moved across the network interface. The
role of this physical layer is to aid the other layers of transmitting data not only through cables
and interface cards when really the hardware must have a relation to the physical layer in order
to send data over the network, its main functions are establishment connections to a medium
through optic fiber cables or twisted pair cables. The physical layer provides the internetworking
layers with correctness in the sense that it provides specific means for transmitting raw bits
through the Ethernet protocol which is used to transfer information in packets called frames. An
Ethernet frame will encapsulate information from an upper level protocols. The Ethernet frame is
written in hexadecimal which is used to process information for the data link layer which will be
discussed later but the reliability of the physical layer comes through its topologies and the
different types that aid in how the physical layer will be able to aid the other layers. Topologies
are used in LAN (local area network), the main topologies are ring which isn’t reliable as one
broken device will disconnect the topology making it not efficient enough for it to be a part of a
system, bus topology another lacking topology as the main connection to the PC’s can be broken
or sabotaged making it unsecure and not robust, the best topology for a LAN is star as the main
server can be secured, it is easy to use but quite expensive. The compatibility and scalability of
the physical layer is through the synchronization of the transmitter as it travels through the layers
through the transmission medium to the receiver, the synchronization is at bit level. Line
configuration through point to point configuration and multipoint configuration each with their
own uses and qualities that make them the communication for a business or home. Point to point
is configured in pairs and is used to communicate between two certain nodes that is easily
capable of delivering data rates of up to 100 Mbps, it is easy to use, efficient and has it qualities.
It is able to achieve connectivity in rural environments for businesses or homes that live far out.
Multi point configuration is one node connected simultaneously too many other points, it
requires a base station to connect to and can transmit data rates up to 60Mpbs or more depending
on the design specifications. The system can be installed easily and can be used for wireless
devices much like a router this physical layer of connecting points is a major part of how the
other layers will be affected through speed, rate, connectivity and ease of use.
Data-link
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COMP247 Data Communications

Assignment 1, 2016

Due: Tuesday 5th April, 2016, 6 pm

Marks: 60

Value: 15%

Question 1:

Physical link:

The physical layer is the lowest layer of the internetwork layers, this layer contains the information that unlike the other layers is physically moved across the network interface. The role of this physical layer is to aid the other layers of transmitting data not only through cables and interface cards when really the hardware must have a relation to the physical layer in order to send data over the network, its main functions are establishment connections to a medium through optic fiber cables or twisted pair cables. The physical layer provides the internetworking layers with correctness in the sense that it provides specific means for transmitting raw bits through the Ethernet protocol which is used to transfer information in packets called frames. An Ethernet frame will encapsulate information from an upper level protocols. The Ethernet frame is written in hexadecimal which is used to process information for the data link layer which will be discussed later but the reliability of the physical layer comes through its topologies and the different types that aid in how the physical layer will be able to aid the other layers. Topologies are used in LAN (local area network), the main topologies are ring which isn’t reliable as one broken device will disconnect the topology making it not efficient enough for it to be a part of a system, bus topology another lacking topology as the main connection to the PC’s can be broken or sabotaged making it unsecure and not robust, the best topology for a LAN is star as the main server can be secured, it is easy to use but quite expensive. The compatibility and scalability of the physical layer is through the synchronization of the transmitter as it travels through the layers through the transmission medium to the receiver, the synchronization is at bit level. Line configuration through point to point configuration and multipoint configuration each with their own uses and qualities that make them the communication for a business or home. Point to point is configured in pairs and is used to communicate between two certain nodes that is easily capable of delivering data rates of up to 100 Mbps, it is easy to use, efficient and has it qualities. It is able to achieve connectivity in rural environments for businesses or homes that live far out. Multi point configuration is one node connected simultaneously too many other points, it requires a base station to connect to and can transmit data rates up to 60Mpbs or more depending on the design specifications. The system can be installed easily and can be used for wireless devices much like a router this physical layer of connecting points is a major part of how the other layers will be affected through speed, rate, connectivity and ease of use.

Data-link

The data link layer is the next layer of the physical layer and much like the physical layer it deals with the moving of data but this time across a physical link in a network. The main components to be overlooked in the data link layer include framing, physical addressing, and control of flow, error and access and how these can aid in the essential qualities of any system through correctness, reliability, robustness and security, compatibility and scalability, ease of use and efficiency. Framing essentially uses the previously explained point to point configuration by transmitting the data as a stream of bits. The framing is used when the bits are framed into discernible blocks of information to be transmitted through the data link layer, these frames have headers that ‘contain information such as error-checking codes.’^1 Framing contains correctness through the variable framing to create an efficient network but it also contains ‘unpredictable traffic flows and the inability to provide quality of service’^2 Physical addressing is the use of adding a header to a frame to give the sender or the receiver an address for the frame to follow. This labelling of information allows the network to easily use the frames and send it to where they need to go, the ease of use is in the simplicity of using a unique physical address with a particular destination location. The header is either the MAC address of the hardware address which is the physical address every single device is given for a network, there is also a use of security here as each address is unique meaning unless you are able to have the MAC address it is very difficult for the frames to be sent somewhere. The MAC address is very compatible with other devices and connecting to a network whether it be through point to point of multi point configuration each device with a unique MAC address, in the case of two devices with the same MAC address although it is highly unlikely it will unable to continue traffic through the host and the receiver most likely the address being borked. The control of flow, error and access are usually overlooked within the data link layer but its role of ensuring that no errors and all the handling of the transmission of data goes smoothly is crucial to the qualities of any working system. Flow control is good for allowing a transmitting station does not overflow a receiving with data through its efficiency and robustness. Error control is ‘achieved by adding a trailer at the end of the frame. Duplication of frames are also prevented by using this mechanism. Data link layers adds mechanism to prevent duplication of frames.’^3 Error control is reliable as it aids in error detection such as ARQ and FEC (forward error correction) by providing reliable information and incase something goes wrong it can be easily corrected.

Internet layers

Question 3:

1 http://www.linktionary.com/f/framing.html 2 http://www.linktionary.com/f/framing.html 3 http://www.studytonight.com/computer-networks/osi-model-datalink-layer