Data Elements

Data Elements

Introduction:

In this blog post, I will be explaining the different types of data elements and why it is important. In addition to the explanations, I will also give its uses and why it is used. The data elements are:

• Cyclic Redundancy Check
• Encapsulation – Frames, Packets
• Datagrams
• Address
• Sequencing

Moreover, I will provide and show diagrams where appropriate for my points to be easier explained. In general, data elements are essentially data being broken up into manageable chunks. Additionally, although data is broken up into smaller sizes, additional information are set along with it which decreases the speed slightly but improves accuracy.

Cyclic Redundancy Check:

CRC (Cyclic Redundancy Check) is a checksum algorithm that is used whilst data packets are being transmitted across a device; this is to identify error detection and hopefully error correction. To do this, CRC will use a technique known as polynomial where it will divide the data (usually with a fixed divisor) and obtain a result. Furthermore, as the calculation is very specific, there will be a remainder. This remainder will be sent along with the data and will be re-calculated by the recipient device from the data it receives. This leads to error detection as if the comparison is incorrect, the data must have been corrupted during transmission. As a result, error correction will take place. Despite the importance of it improving the accuracy more than parity checks (counts the number of binary 1’s with an odd or even protocol), this increases the size slightly and thus slows the speed by a small percentage.

Encapsulation – Frames, Packets:

When large files are sent across the network to another device for download e.g. a video, the file will not only be split into smaller individual parts for convenience but also to assist in reliability. This is where encapsulation takes place as the frames will contain (encapsulate) each packet with a segment which holds user data and IP address. A common example is the Ethernet frame. Encapsulation is compulsory and is an important requirement because it gives the packet its destination, (see figure 1). Without this additional information the data would not be able to find its destination or know who to request a resend from.

Figure 1: Encapsulation

Datagrams:

When a file is sent, it is split into smaller manageable chunks – this can be in packets or in datagrams (consider datagram as a cousin to packets). However, datagrams are not reliable because it does not send an received acknowledgement (confirmation) to the sender of the data file, apart from this its function is identical to as of a packet – however this difference makes datagrams less reliable.

The difference between packets and datagrams is that packets are sent via TCP (transmission control protocol) and IP, this makes it reliable as it is only sent if the if it is connection-orientated (if it sends acknowledgement) whereas datagrams are sent through a UDP (user datagram protocol) and IP. This works by sending the data through different routes throughout the network and not having reliability as a priority.

Address:

Each device’s storage and components has its own unique identifier to the network; this is known as its address. Addresses are needed and are used by the devices because it is where the data will be transmitted to/sent from, like a destination for the data to go to or leave. This is also useful and is used by people who would like to access a specific array of a computer.

The main types of addresses are physical addresses and logical address. Physical addresses are an address that is given when the device is manufactured or hard coded; therefore it has its own identity and destination to where data goes to. This is useful for networks with computers that will be there in the long term. An example would be a MAC address.

On the other hand, a logical address is an address that is given (assigned) to the device every time by a server on a network. This address is more likely to be changed for security purposes; an example of a logical address is an IP address - a unique number that identifies a computer on the internet.

Sequencing:

When a file is split into packets and they sent from the device to the recipient, each packet will need to be reassembled at the end in chronological order for it to function accordingly. This is because without sequencing, the packets are not organised at the end and the data will be out of order – this is heavily dependent on the speed of the connection as well as the route it takes when it is sent through the network, (see figure 2). To avoid putting the data in the wrong order when the recipient device receives the data, they will beforehand add an identifier/sequence data element to let it know which order it goes.

Harvard Referencing: (In order of reference)
- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited.
- Figure 1: core0.staticworld, 2009. Encapsulation Frames Packets Segments. [Online] Available at: <http://core0.staticworld.net/images/idge/imported/article/nww/2009/07/01fig05-100277629-orig.jpg> [Accessed 22 January 2015].

Bibliography: (In alphabetical order)
- webopedia, 2015. CRC. [Online] Available at: <http://www.webopedia.com/TERM/C/CRC.html> [Accessed January 21 2015].

Communication Models & Protocols

Communication Models & Protocols:

Introduction:

In this blog post, I will be explaining about the uses of communication models as well as what they are in general - such as the OSI model (Open System Interconnect) and the TCP/IP (Transmission Control Protocol/Internet Protocol. In addition, I will provide diagrams.

Afterwards, I will provide an explanations for the main protocols used in networks. Some protocol standards that the IEEE (Institute of Electrical and Electronic Engineering) looks after are:

• Wi-Fi (802.11g, 802.11n)
• Bluetooth
• 3G and 4G
• Wireless Security Protocols (WEP, WPA)

In general, communication protocols are essentially communication methods which can be interpreted as a rule or instructions to how data and information are transferred from one device to another. Communication protocols are very important because they are required in order for successful interactions between devices and models to be carried out, or otherwise it will not work as overall its purpose is to provide compatibility. Moreover, they each serve a role/function such as to aid a particular area, or help minimise risks etc – these “protocol standard has to be agreed” (Anderson et al, 2011) which means that in order for successful data transmission; the protocols set in place must go through its procedure accordingly. Examples of protocols shown below include the TCP (transmission control protocol) and IP (internet protocol) model. Hence the name, these protocols were invented to help the internet.

OSI Communication Model:

The OSI communication model (also referred to ‘Open System Interconnect’) is a seven layered model which is created as a method of explaining to people about the network’s structure and to ensure communication is reliable between network devices for all platforms for compatibility purposes. See figure 1 for a brief description of each layer.

• Layer 1, Physical: This is where all the hardware is located such as the cables for the transfer of binary data to the second layer. An example would be Ethernet.
• Layer 2, Data Link: This layer contains the addresses that give a unique identity to the device; this controls the access of data as well as permission to send data. An example of a physical address is a MAC address.
• Layer 3, Network: In this layer, the routing takes place by creating connection lines that link one node to another node – allowing data to be transferred.
• Layer 4, Transport: This layer has the responsibility to transport data from one place to the other without harmful data (viruses) to be imported with the aid of firewalls and protocols to detect data corruptions (acting as a traffic control too).
• Layer 5, Session: With this layer, the user will have the ability to open “multiple browser, chat and email windows open simultaneously without any conflicts in the data transmitted” (Anderson et al, 2011) as it manages the connections between applications (programs).
• Layer 6, Presentation: Hence the name of the layer, this layer presents by converting the data from the application to formats we can use and view, e.g. images in the file format of .JPEG.
• Layer 7, Application: This is the closest layer the user can interact with as this can control, monitor, and access the network services (explained in ‘Network Software’ blog). Moreover, this also allows application to send emails, use web browsers and have file transferred with the user’s command. Common examples would include HTTP, HTTPS and FTP.

Figure 1: OSI Model

TCP/IP Communication Model:

TCP/IP (also referred to ‘Transmission Control Protocol/Internet Protocol’) is a model which is identical to the OSI model but mainly represents how the internet works instead, differing it. Additionally, TCP/IP was created with the help of various other protocols (TCP and IP) whilst following the generic structure of the OSI model, resulting in four layers to also distinguish tasks for simplicity, (see figure 2).

Figure 2: OSI vs TCP/IP Comparison

Wi-Fi:

Wi-Fi is a wireless signal and is an important protocol because it allows data to be transferred and received between the router and the DTE (data terminal equipment) device, such as laptops, tablets and phones to connect to the internet. The IEEE (Institute of Electrical and Electronic Engineers) has many manages/controls which allow one system to communicate to another, one of which is 802.11g, and 802.11n: Wireless LAN (Wi-Fi). There are also other types such as a, b, g and n that defines connection speed of each. Additionally, a couple more examples of the 802 standards includes:

• 802.3 (Ethernet): Ethernet are found in cables and this could be considered as most reliable (speed wise) due to it being able to transmit data across multiple networks quickly.
• 802.5 (Token Ring): Operates within topologies such as a ring. Token ring performs token passing by sharing the ‘ring’ in turns and this avoids the impacts of data collision as each node will have its own access at some point.
• 802.15.1 (Bluetooth): Bluetooth is a standard method of transmitting data from one device to the other without the need for cables. This heavily relies on the line of sight and requires the devices to be within a certain radius and thus is slower than the others.

Bluetooth:

Bluetooth is another IEEE standard (802.15.1) for devices to communicate to each other. However, this only functions within a short radius of networking devices (e.g. if two mobile phones are nearby). This allows easy share of data to communicate between devices and also requires low power, making it convenient and a useful protocol.

3G and 4G:

3G and 4G are both similar protocols that allow devices such as smartphone to communicate and send data. As technology advances, improved generations (G) are produced to increase efficiency and speed. Usually GSM (Global System for Mobile Communications) gives the access to connect to their network for the ability to communicate via voice and data, 3G is the example of this as it allows both data and voice communication at the same time whereas 4G is the improved version of 3G with a promising speed from “10Mbps to 300Mbps”, (Anderson et al, 2011). 

Wireless Security Protocols (WEP, WPA):

To connect to a wireless network, the user must connect with no security and this will ensure connectivity according to the standards. As a result of this, other people have the chance to steal bandwidth/information from many homes and commercial wireless networks, resulting in slower connection.

Due to the lack of security, a wireless security protocols such as WEP (wired equivalent privacy) was invented to tackle this issue for LAN. WEP does this by encrypting every packets of the file as it is transmitted from the device to its destination, end to end. However, it was discovered that this is not the case as WEP only works in the first two layers of the OSI model – not promising full security. This led to WPA (Wi-Fi protected access) which is essentially an improved protocol of WEP by improving the encryption process as well as having additional new features.

Harvard Referencing: (In order of reference)
- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited.
- Figure 1: compnetworking.about, n.d. Basics_OSIModel. [Online] Available at: <http://compnetworking.about.com/library/graphics/basics_osimodel.jpg> [Accessed 21 January 2015].
- Figure 2: dret, n.d. OSI vs Internet. [Online] Available at: <http://dret.net/lectures/services-fall06/img/osi-vs-internet.gif> [Accessed 21 January 2015].

Bibliography: (In alphabetical order)
- webopedia, 2015. OSI Layers. [Online] Available at: <http://www.webopedia.com/quick_ref/OSI_Layers.asp> [Accessed 21 January 2015].
- support.microsoft, 2015. The OSI Model’s Seven Layers Defined and Functions Explained. [Online] Available at: <http://support.microsoft.com/kb/103884> [Accessed 21 January 2015].
- webopedia, 2015. TCP/IP – Transmission Control Protocol/Internet Protocol. [Online] Available at: <http://www.webopedia.com/TERM/T/TCP_IP.html> [Accessed 21 January 2015].
- webopedia, 2015. WEP – Wireless Equivalent Privacy. [Online] Available at: <http://www.webopedia.com/TERM/W/WEP.html> [Accessed 21 January 2015].
- webopedia, 2015. WPA – Wi-Fi Protected Access. [Online] Available at: <http://www.webopedia.com/TERM/W/WPA.html> [Accessed 21 January 2015].

Access Methods

Access Methods:

Introduction:
In this blog post I will be explaining about the different types of access methods by stating what they are for and why they are used. Additionally, I will include diagrams and examples to help enhance my explanations and help validate my points. Take into account that these access methods are all working within a LAN. The access methods are:

• CSMA/CD (Carrier Sense Multiple Access/Collision Detection).
• CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance).
• Token Passing

Overall, access methods are required to notify which node or device will then send its data in turn. This is to avoid data collision, however if it does occur then the device will be using collision detection method and thus attempts to solve it by using collision avoidance method. These are mainly used because collisions are unpredictable due to the file sizes the data carry within the network and are vulnerable wherever; they reduce the changes of failure.

CSMA/CD:

CSMA/CD is the abbreviation for Carrier Sense Multiple Access/Collision Detection. This access method constantly checks whether the traffic of data in the data line is free in all devices. Furthermore, CSMA/CD is created to tackle problems created mainly by Ethernet. This is because it allows any device on the same network to send data whenever and this ends up with a collision when two or more devices’ data collide. CSMA/CD functions in logical steps to intercept this right after the data collision:

1. It firstly checks whether or not the data line has any traffic (if any data is currently being sent across the network by a device).
2. Assuming there is no traffic; CSMA/CD will allow the device to send data.
3. It will then wait for the recipient to send an acknowledgement (confirmation) that the data has been successfully transmitted across.
4. However, if a data collision has occurred then no acknowledgement will be sent back. This triggers the CSMA/CD to wait a random amount of time (within a second).
5. It will return to step one where it checks for the data line to see if it has any traffic. This will repeat until the data is successfully sent – normally the first reattempt works.

I have created a flowchart to represent this, see figure 1.

Figure 1: CSMA/CD Flowchart

CSMA/CA:

CSMA/CA is the abbreviation for Carrier Sense Multiple Access/Collision Avoidance. This access method/protocol commonly takes place before CSMA/CD to avoid collision data as much as possible by informing the other nodes to not transmit data, unlike CSMA/CD where it only performs when CSMA/CA fails.

1. Before any data is sent, is the connection line available to prevent data collision?
2. If other devices are transmitting data across the network, then wait a random amount of time and go back to step 1.
3. If the connection line is free, the data packet will be sent.
4. If the recipient device receives the file, acknowledgment and confirmation takes place. Then it returns to step 1 and repeats until the file is sent.
5. However, if CSMA/CA fails then CSMA/CD will take place.

Token Passing:

For devices to communicate, an access control method has been designed to control which device communicates (sends data). This is where token passing mainly takes place in the ring network/topology to allow each node to communicate in turn, (see figure 2). However, as the ring network expands this can cause an issue especially when big talkers are present.

Big talkers are usually servers that communicates more (sends more data) than others, causing traffic. This links to CSMA/CA and CSMA/CD as it can help this problem.

Figure 2: Token Passing in Ring Topology

Harvard Referencing: (In order of reference)
- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited.
- Figure 1: Chan, D. 2015. CSMA/CD Flowchart by Danny Chan. [Online] [Accessed 20 January 2015].
- Figure 2: manishasanyal.blog, 2012. Token Passing Ring Topology. [Online] Available at: <http://manishasanyal.blog.com/files/2012/08/ring_topology.gif> [Accessed 20 January 2015].

Bibliography: (In alphabetical order)

- webopedia, 2015. CSMA/CA. [Online] Available at: <http://www.webopedia.com/TERM/C/CSMA_CA.html> [Accessed 20 January 2015].

Network Software

Network Software

Introduction:

In this blog post, I will be explaining what network software in general is and why it is used for what purposes:

• Network Software (NOS)
• Connection Software

Network Software (NOS):

The NOS (also refers to ‘Network Operating System’) is essentially a computer platform in conjunction with servers, giving it ultimate access and controllability over the network in general – allowing computers and devices to connect to the network - LAN in most cases, (see figure 1).

Main examples include well known network software’s such as Microsoft Windows’ server domain control (where similar devices within the same network have an identical address like a MAC address for easier controllability). In addition to this, it usually contains components including greater processor, hard drive storage disk space, improved wireless/wired cards and wireless/wired adapter for sufficient and substantial amount of internet bandwidth.

Despite its beneficial yet expensive components, it can handle tasks and perform other services such as managing the printer, files, and databases and give a specific amount of access to the internet/browser for devices. This is because it is a server that executes management. An example of this is when the user is required to log in when they use a computer; this is to connect to the network to access files which the network operating system runs e.g. databases.

Figure 1: NOS (LAN)

Network Connection Software:

The NCS (referred to as ‘Network Connection Software’ or a client) is a software that provides the connection to access services the NOS (Network Operating System) runs, such as its printer control and management, (see figure 2). It is like an assistant that can access the settings. Examples of NCS are its access privileges to files, databases, web servers, and even email servers hosted by Google Mail.

This is also beneficial to the main operating system of the network because it can reduce the impact of the physical network itself as it can help carry out other tasks. Furthermore, this makes it efficient and therefore results in a good data flow, with minimal data collision. You can almost consider network connection software’s similar to operating systems, however this is dependent on how much access it is administered prior. This is because the clients allow connections for the access of services by the NOS.

Figure 2: NCS (Printer Management)

Harvard Referencing: (In order of reference)
- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited. P.304.
- Figure 1: teach-ict, n.d. A LAN. [Online] Available at: <http://www.teach-ict.com/images/a_lan.jpg> [Accessed 20 January 2015].
- Figure 2: res2.windows.microsoft, n.d. Microsoft Windows Network Connection Software Management. [Online] Available at: <http://res2.windows.microsoft.com/resbox/en/windows%207/main/eeaf834f-12b1-47c9-a3e4-5fbfc053ef3f_66.jpg> [Accessed 20 January 2015].

Bibliography: (In order of alphabet):
- webopedia, 2015. NOS – Network Operating System. [Online] Available at: <http://www.webopedia.com/TERM/N/network_operating_system_NOS.html> [Accessed 20 January 2015].
- ehow, 2015. Networking Software. [Online] Available at: <http://www.ehow.com/about_5507248_networking-software.html> [Accessed 20 January 2015].

Network Services

Network Services

Introduction:

In this blog post, I have worked with other members of a group to explain how different network services operate as well as providing its advantages and limitations for each.  I worked with: Connor P, Sami, H, Liam B, and Ben C. The network services I will be talking about are:

• Packet Switched
• ISDN (Integrated Services Digital Network)
• ADSL Broadband (Asymmetric Digital Subscriber Line)
• WAP (Wireless Access Protocol).

Packet Switched:

Packet switches is a mechanism which sends network traffic in small manageable data units across the system. When you would like to send a file across to somebody else, the file breaks down into smaller sizes like 2MB for example and sends it across the internet in manageable chunks for it to rebuild itself at the end to display the following information.

The benefits of packet switches is that it only functions when there is a group of routers or WAN switches all interconnected, this is reliable because if one line of the branch fails then the data you would like to send (packet switches) will redirect to a different route line. You would use packet switches to direct traffic via a variety of routes such as through a mesh topology which is efficient in speed.

Furthermore, big companies with lots of employees would use this as it is much better than having cables due to the amount of cost and space it would require, therefore if they have many customers it means it is easy for it to be expanded.

However, the limitations for this is the time it requires for the data packages to be put back together as it is broken up in the first place and is not ideal for emergencies. Furthermore, it usually splits into packets of 600 bytes (60k approx.) so if a file is 512 bytes, it will require two packets doubling the time needed. This links to how some packets may not reach its destination and end up lost within the connection lines of mesh, slowing down every other packet.

Another limitation is if the main cloud fails down the whole mesh topology will follow.

Figure 1: Packet Switching

ISDN:

ISDN stands for integrated services digital network. It is an old circuit switched system for simultaneous digital transmission of voice, video, data and other network services (it is still in use for some places but technology has advanced and grown out of it slightly). ISDN was the first solution to transfer data and bypass the limitations set by the public telephone system in 1980’s.

The benefits of ISDN are that it can hold multiple connections by having separate channels for data. This gives it the capability to send voice and data simultaneously. It can also be used for ‘other signals’ by other organisations for different purposes.

Another benefit of ISDN network line is that it could be provided in two different ways. The first way is BRI (basic rate interface) and the second way is PRI (primary rate interface). BRI is for smaller businesses and smaller remote sites whereas PRI is for larger businesses, communities and organisations. This is because BRI can have two channels of approximately 60kb, each for voice and data communication signals. On the other hand, PRI can have 30B channels of 64K, allowing up to “30 voice lines” which are suitable for business purposes, (Anderson et al, 2011).

In addition to this, nowadays the modern ISDN connections are considered faster than traditional dial up connections because more development and research has been invested.

The limitations are that ISDN can be very costly because it requires specialised digital devices.  This network service would be used for connections in remote sites, or for customers such as a small business or home users.

Additionally, a limitation is the resources you send outside to the other networks will not be permanently available to other internet users; this is because ISDN functions in a way where you send video, voice, and data that cannot be retrievable afterwards.

Lastly, the last limitation of ISDN would be that modern ADLS (asymmetric digital subscriber line ) connections can transfer a lot more data in one go and are cheaper to maintain, putting ISDN below it as it has “no balance or symmetry”, (Anderson et al,  2011).

Figure 2: ISDN

ADSL Broadband:

Broadband, (referred to asymmetric digital subscriber line) has high speed for data transmission in which a single line or cable is capable of carrying large amounts of data at once. The most common form of broadband connections is cabled modems which provide a continuous connection to homes and businesses.

The benefits of broadband are that it is considerably faster than its predecessor baseband with technological advancements. Furthermore, another benefit is that it is easy to set up nowadays as technology has advanced to the stage where the entire physical network infrastructure is all built into one ‘hub’ – making it easier to handle for people with no prior knowledge of the communication devices. The third benefit is that different service providers now offer different packages making it easy to find the right one for you for the right purpose such as if it was purchased for a business or if it was purchased for residential purposes.

One limitation of broadband would be if you have two systems connected to the broadband but one is further away and one is nearer, the connection strength is prioritised towards the nearer system. This is because it doesn’t include a switch to regulate signal strength to all systems. Another limitation would be that the advertised download and upload speeds are rarely what they’re advertised to be. This means that you could be paying £100 a month for a 100MB/s speed when realistically you’re only getting 10MB/s (the density of area and other interference can be a role).

Lastly, ADSL Broadband is not well suited for all internet applications. This is because the ADSL "pipeline" to send data is quite small. Internet applications such as websites and VPN (Virtual Private Networking) are not well suited for ADSL Broadband as the way data is transmitted is different than usual. It may also be improved only if it has fibre optic cables rather than copper wires as then it travels faster.

Figure 3: Broadband

WAP – Wireless Access Protocol:

Wireless access protocol is a specification that allows users to access information and sends data with DTE (data terminal equipments) which are hand held only, such as a smartphone, communicator, or a mobile phone. To have the internet and display the webpage of a specific website that uses HTTP, the hand held device (smartphone) requests data through the internet to the HTTP server. At the server, it will return the requested data and resend it to the WAP server gateway (gateway connects two different networks) where this server will receive, process, and respond. The WAP server will then transmit the data back through the internet to the assigned device it requested from - allowing it to view the webpage it desired, (see figure 4). Overall WAP is a network service/structure that delivers, receives and transmits data across networks for emails, chats, and the internet to hand held devices.

The benefits of wireless access protocol are that improvements and advancements are being designed as time progresses, such as the upgrade from 3G to 4G – increasing the overall internet speed of how fast data transfers massively. Another benefit is the convenience of this network service for mobiles, this is because it copes well with small amounts of data such as for emails and text messages.

The limitations of wireless access protocol is the speed of the WAP system as it can be slow in general, taking some time to load up a page possibly due to other interference and by users in the same network. This limitation links with the first one; the speed and storage space of the device is a factor because it is also not suitable for large amounts of data such as large files alike animations as the bandwidth is incredibly huge, making it inconvenient and not recommended as a result. The third limitation to WAP is the cost of the set up as well as its maintenance cost because the design and creation of a mobile network has to live up to its expectations of many users – for example, a user will only get the amount of usage they paid for 3G whereas 4G is a slightly increased amount, this means that the market and businesses limit the amount they give. As mentioned about network service providers, WAP such as 3G and 4G are still used because it is convenient and is an easy method of internet access and communications in public such as phone calls. However as technology advances, 3G will be less likely to be used as 4G progress its way up due to being a successor of 3G.

Figure 4: Wireless Access Protocol

Harvard Referencing: (In order of reference)
- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited. P.304.
- teach-ict, n.d. Packet Switching. [Online] Available at: <http://www.teach-ict.com/technology_explained/packet_switching/packet_switching.html> [Accessed 16 January 2015].
- Access Points – Compnetworking.about.com, 2015. WAP Information [online] Available at: <http://compnetworking.about.com/cs/wireless/g/bldef_ap.html> [Accessed 01/2015]
(Conceptdraw.com, 2014)
- Access Points – Conceptdraw.com, 2014. WAP [online] Available at: <http://www.conceptdraw.com/examples/access-points> [Accessed 01/2015]
- Figure 1: webclasses, n.d. Packet Switch Diagram. [Online] Available at: <http://www.webclasses.net/3ComU/intro/units/media/figures/unit04/PacketSwitched.gif> [Accessed 16 January 2015].
- Figure 2: mynetfone, n.d. ISDN Diagram. [Online] Available at: <https://www.mynetfone.com.au/media/images/diagrams/QuadroISDN_diagram.jpg> [Accessed 16 January 2015].
- Figure 3: aitelephone, n.d. Broadband Diagram. [Online] Available at: <http://www.aitelephone.com/broadband-phone-diagram.gif> [Accessed 16 January 2015].
- Figure 4: althos, n.d. WAP Server Operation. [Online] Available at: <http://www.althos.com/sample_diagrams/ag_WML_WAP_Server_Operation_low_res.jpg> [Accessed 18 January 2015].

Bibliography: (In order of alphabet):
- orbit-computer-solutions, n.d. Wireless Routers. [Online] Available at: <http://orbit-computer-solutions.com/Wireless-Routers.php> [Accessed 16 January 2015].
- wcape.school, n.d. ISDN. [Online] Available at: <http://www.wcape.school.za/handbook/isdn.htm> [Accessed 16 January 2015].
- learning.ericsson, 2002. WAP. [Online] Available at: <http://learning.ericsson.net/mlearning2/project_one/wap_article.html> [Accessed 18 January 2015].
- wirelessdictionary, 2009. Wireless Access Protocol – WAP [Online] Available at: <http://www.wirelessdictionary.com/wireless_dictionary_WAP_definition.html> [Accessed 18 January 2015].

Network Topologies

Network Topologies:

Introduction:
Each network is different and this requires a structure, also known as ‘topology’, this is the layout of the network devices. In this blog post I will be explaining about the different network topologies which are listed below (these are the most common ones).

• Bus
• Ring
• Star
• Tree (or hierarchical)
• Mesh

With each topology, I will identify its use of operation, its advantages and limitations. In addition, I will also use suitable diagrams to further enhance my explanations.

Bus:
The bus is an old historical topology which allows easy connection for different devices to the network by having a single core cable (bus) running through the middle, (see figure 1). By having this structure laid out conveniently, the advantages of the bus topology is that it allows new devices to be added easily because the core cable can be extended. Furthermore, this is also beneficial for LAN because it is used within the same geographical area. On the other hand, the limitations for the bus topology is that one half of the system and devices on one side will not work if cut, making it unable to communicate from the first device to the last.  Despite the above limitation, the whole line can also be disrupted if the core cable has an issue, therefore the network stops working. Data collisions may also take place if the traffic of the data overflows.

Figure 1: Bus Topology

Ring:
The ring topology is a very well operated network as each network has an equal share of bandwidth. It works together in harmony as each node has the opportunity to communicate by taking in turns, ultimately meaning that there will be no overflow of data as only one is used at a time, (see figure 2). This allows an overwhelming advantage/benefit as it is very well structured and organised. This leads to another benefit of it as being convenient to add more nodes/computers. However, the limitations are that there is a chance one node may send more data by communicating more, slowing down the network overall. Additionally, using this topology also means that there is less privacy and the security is greatly limited due to each node being able to see the traffic of its adjacent neighbours next to it. Lastly, because each node is connected, it can affect the system if either one node or if the central hub fails.

Figure 2: Ring Topology

Star:
The star topology is when different nodes are all connected and linked directly to the centre, known as the ‘hub’ such as a router for data transfer and connection. The router in the middle can control all of the other nodes as they work together indirectly, (see figure 3). The benefits of this topology are if one part of the system gets cut off, it will not affect the others. Moreover, if each node has its own cable running directly to the core router, then that means the chances of data collisions are greatly reduced. Nonetheless, the limitations are simple – if the main router hub gets dislocated, the whole of the network will also go down and fail. This also makes it unbeneficial and therefore a limitation because the amount of cables required can be costly to set up despite its reliability.

Figure 3: Ring Topology

Tree (or hierarchical):
This topology is convenient when it represents a hierarchy of an organisation, company, or business as it can represent how the system is laid out for different fields of importance in the form of a tree shape (or a star/bus), see figure 4. It is formatted in a logical order as the core centre at the top, and leading down is expansions and a variety of branches for the nodes. The advantage of this topology is it allows components to be added easily due to its organised layout. Another benefit of the tree topology is if one connection line or node is down, it can be easily identified as the structure is well defined. Nevertheless, one limitation is that the centre still has the properties of a star, so if the main hub fails, the whole system will too. Another limitation is the maintenance as the costs are high due to its size and complexity of cables needed to run this network structure.

Figure 4: Tree Topology

Mesh:

The mesh topology is a series of connections for multiple and varied paths for the data to travel to, generally attached to each other node so that it allows data to be relayed from one place to the other in the quickest route possible, (see figure 5). The benefit of mesh is the ability for the system to keep functioning to communicate and thus relay more data even if one connection line fails, suitable for high data traffic. In conjunction with the above benefit, it also allows easy identification of its whereabouts if one node and or line fails. However, to set up the network to be structured in a mesh topology, it will require a lot of complex set up and maintenance as it expands forwardly, this is also because of the excessive amount of cables needed. Additionally, as it expands continuously as time progresses, the second limitation is many connection lines may become redundant as other connection lines may be faster than others, (no longer needed) and this will mean some cables are wasted, increasing overall costs.

Figure 5: Mesh Topology

Harvard Referencing: (In order of reference)
- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited. P.305.
- Figure 1: bbc, 2014. Bus Topology. [Online] Available at: <http://www.bbc.co.uk/staticarchive/9933e41867b45fa9319fa74db5ac7f33b71d44c8.gif> [Accessed 15 January 2015].
- Figure 2: studydroid, n.d. Ring Topology. [Online] Available at: <http://studydroid.com/imageCards/0p/ld/card-26916531-back.jpg> [Accessed 15 January 2015].
- Figure 3: mattytv, 2012. Star Topology. [Online] Available at: <http://www.mattytv.com/blog/wp-content/uploads/2012/06/star.png> [Accessed 15 January 2015].
- Figure 4: ecomputernotes, n.d. Tree Topology. [Online] Available at: <http://ecomputernotes.com/images//thumb474-Tree-Topology-9b75e7959710e5df73e20d5806405a51.jpg> [Accessed 15 January 2015].
- Figure 5: brainbell, n.d. Mesh Topology. [Online] Available at: <http://www.brainbell.com/tutorials/Networking/images/01fig06.gif> [Accessed 15 January 2015].

Bibliography: (In alphabetical order)
- ianswer4u, 2011. Mesh Topology Advantages and Disadvantages. [Online] Available at: <http://www.ianswer4u.com/2011/05/mesh-topology-advantages-and.html#axzz3Ovjx0358> [Accessed 15 January 2015].

Networks

Networks:

Introduction:
In this blog post I will be describing and explaining the different types of networks. Additionally, I will also provide suitable diagrams and examples wherever appropriate. The networks are:

• WAN (Wide Area Network)
• LAN (Local Area Network)
• Wireless

Figure 1: WAN

WAN (Wide Area Network):
Wide area network (WAN) works the same way as LAN does but is ultimately a larger network overall. By larger it means the network covers more than just one area such as a residential home like LAN, and rather has the size of more than one location. However, as networking in general improves over the years, WAN has expanded to spread beyond to crossing countries and continents, which have becoming international. An example would be many different users from around different countries or the world can connect to a wider area of a network and share information to each other such as employees working in the same company but different branches (see figure 1). Moreover, different examples of WAN include the internet and satellite links.

Figure 2: WAN

LAN (Local Area Network):

A local area network (LAN) is essentially a WAN but covers a smaller range of area as defined by its geographical reach, often limited and used usually by a small building such as a house, college, and a store etc. This is because businesses and systems can be more secure if only a small amount of people who access it there uses the devices and information/data they share, which means it is unnecessary to have a larger network, (see figure 3). As LANs are usually only located to one site of a network, it can also connect to other LANs to form a WAN as a result, (see figure 2). Despite the limited area of reach it provides, it is used by a lot of individual groups because it is much faster for transferring data due to its closeness.

Figure 3: LAN

Wireless:
Wireless is a piece of communication device (such as a wireless router) which allows connectivity for all types of wireless devices, (see figure 4). An example includes smartphones and laptops as it transmits and receives data consistently without the need of cables by using radio waves. Furthermore, wireless network are used because it is more low-priced than having to purchase cables such as Ethernet, making it cost-effective for businesses or larger organisations. Usually, all devices without a cable should have a wireless adapter that connects to the Wi-Fi – the signal between the router and the device itself.

Figure 4: Wireless

Harvard Referencing: (In order of reference)

- Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D. 2011. Information Technology Level 3 Book 1 BTEC National. Harlow: Pearson Education Limited. P.304.
- Figure 1: materi.palcomtech, n.d. WAN2. [Online] Available at: <http://materi.palcomtech.com/admin/cms_images/WAN2.jpg> [Accessed 15 January 2015].
- Figure 2: bbc, 2015. WAN Wider Area Network. [Online] Available at: <http://www.bbc.co.uk/staticarchive/17d1c375cab9c86e64c0b5987e1d6fc5109739c3.gif> [Accessed 15 January 2015].
- Figure 3: bbc, 2014. LAN Local Area Network. [Online] Available at: http://www.bbc.co.uk/staticarchive/30dd6ccf1df35e81482db0b2e1f3f62edd760733.gif [Accessed 15 January 2015].
- Figure 4: eusso, n.d. Wireless Router Network Diagram. [Online] Available at: <http://www.eusso.com/Models/Wireless/UGL2430-RT/Diagram-3.jpg> [Accessed 15 January 2015].