Individual Assignment: Protocol Paper
NTC/362

Individual Assignment: Protocol Paper
Describe Open Systems Interconnection (OSI) protocol model. The Open Systems Interconnection (OSI) model is a seven-layer logical network architecture that is used to define the network protocol standards to enable OSI device to communicate to another by exchanging information. (Goleniewski, 2007) The seven layers in the OSI model include the physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer. Each layer has its own functions and responsibilities. The four lower layers of the OSI model contain the physical, data link, network, and transport layers. The physical layer is layer 1, which is the bottom layer of the OSI model. It transmits and receives signals, as well as specifying the physical details of Ethernet cables and other hardware behavior. The functions of the physical layer include managing hardware connections, handle sending and receiving of binary signals and encoding of bits. (Cengage Learning, 2011) The data link layer, layer 2, is responsible for managing access to the network and provides physical addressing, device-to-device delivery of frames, media access control, and MAC addresses. Layer 3 is the network layer, which handles the logical addressing and routing of PDUs across internetwork. It handles packet routing and access control through packet inspection. Transport layer is the 4th layer of the OSI model and it is responsible for delivery of data streams across the network. The transport layer not only ensures reliable delivery of data but it also breaks data into segments, handles sequencing and provides flow control. The upper layers of the OSI model consist of three layers which include the session layer, presentation layer, and application layer. Session layer is the 5th layer and is responsible for setting up, maintaining, and ending communication sequences across a network. Another important function of the session layer is to coordinate communication between applications. The presentation is the 6th layer, which functions in the application layer. The presentation layer informs the application layer of what type of data or graphics format to display. Its main responsibility is to translate platform-specific application formats into generic data formats for transmission or from generic data formats into platform-specific application formats for delivery to the application level. (Cengage Learning, 2011) The 7th layer of the OSI model is the application layer which provides interfaces that enable applications to request and receive network services. It handles error recovery for applications and allows access to network services for programs.
Below is an example of an OSI model and what each layer may consist of. (Mitchell, 2014)
Describe key concepts of circuit switching and packet switching. Identify the advantages and disadvantages of circuit switching and packet switching in term of performance, efficiency, speed and throughput potential, and end-to-end transmission reliability and predictability. Circuit switching and packet switching have traditionally occupied different areas. Circuit switched network were used primarily for phone calls and packet switched network handled data. In modern circuit switches, electronic signals pass through several switches before connection is established. During a call, no other network traffic would be able to use those switches. However, in packet-based switching networks, the message gets broken into small data packets that seek out the most efficient route as circuits become available. (Copeland, 2000) Packet switched and circuit switched networks use two different technologies for sending messages and data from one point to another. In packet switched networks, the message will get broken down into small data packets. The packets are then sent out from the computer and travel around the network looking for the most efficient route to ravel as circuits become available. A packet may go in a different route from another. Some of the advantages of using packet switching include security, availability, and recovery. In packet switching, bandwidth can be used to its full potential. Devices of different speeds can communicate, signals are redirected in case of line failure, and packet switching can still send e-mails and texts during crisis or disaster. (www.teach-ict.com, 2014) One of the disadvantages of using packet switching are the delays if there is heavy use or traffic. Data packets can experiencer corruption or loss of data. Packet switching is not reliable for some types of data, such as video streams because the packets may arrive out of sequence. Circuit switching involves three phases which is to establish, transfer, and disconnect. It differs from packet switching because a message is sent all together and arrives in the same order it was sent. An advantage of using circuit switching is that the circuit is dedicated to the call with no interference, as well as full bandwidth for the entire call. Unlike packet switching, a network switching network may become unstable or unavailable during a disaster. It is primarily developed for voice and not data traffic so it can be inefficient. Circuit switching can also take some time to set up.
Identify one example of circuit switch system and packet switch system respectively. List major protocols for each of these two in the framework of OSI model. An example of a circuit switched network is the telephone. Say a person calls someone and the party answers, you then establish a circuit connection. The circuit would function like such, no matter what devices you use to carry your call. Once you disconnect the call, the circuit will terminate. The major protocols that are used in the framework of the OSI model include physical, transport, and session. X.25 is an example of a packet switching network. It uses a suite of protocols, which works at the physical, datalink, and network layers of the OSI model. The X.25 was traditionally used to carry voice over analog lines. Many X.25 applications are now moving to Ethernet, which utilizes Internet Protocol (IP) as the network layer.

References
Cengage Learning. (2011). Guide to Networking. Cengage Learning.
Copeland, L. (2000, March 20). Packet-Switched vs. Circuit-Switched Networks. Retrieved from ComputerWorld: http://www.computerworld.com/article/2593382/networking/packet-switched-vs--circuit-switched-networks.html#social
Goleniewski, L. (2007). Telecommunications Essentials: The Complete Global Source, Second Edition. Boston, MA: Addison-Wesley.
Mitchell, B. (2014). Visual Networking Overview - The OSI Model. Retrieved from About.com Wireless/Networking: http://compnetworking.about.com/od/basicnetworkingconcepts/l/blbasics_osimod.htm www.teach-ict.com. (2014). Packet vs. Circuit Switching. Retrieved from Teach ICT: www.teach-ict.com