Protocol Paper

NTC/362 Fundamentals of Networking

Protocol Paper

Introduction
Switching, whether it is packet or circuit, is an essential portion of any network. By not using the right equipment, or using it properly, you can cause massive lag time or jitter within your own system. This will result in packet collision, loss of data, and could result in loss of business.

Open Systems Interconnection Protocol Model

In order for two computers to be able to interchange data and information, they first must establish communicate with each other. Protocols allow for this communication to take place (Goleniewski). The Open Systems Interconnection (OSI) Model gives a logical design that is used for communication between systems. The OSI Model is layered with seven subcomponents: Application (7), Presentation (6), Session (5), Transport (4), Network (3), Data Link (2) and Physical (1). Each one of these layers presents a collection of services. These services are provided to the layers that are above and below that specific layer. In addition to these, the OSI Model also details the transfer of computer packets using layer protocols (Goleniewski).

The Application layer has the role of maintaining the exchange of information between a computer’s programs and services on the network. The Presentation layer makes it possible for software applications to read information by formatting it. Support for connections between sessions is handled through the Session layer. It also takes the role of handling administrative tasks and providing security. When transmission errors occur, it is the transport layer that corrects the issue. Then it reliably delivers that information to the target destination. The Network layer serves as a routing service by identifying computers on the network and directs the information throughout the network. To prepare data for transfer through a network, the Data Link layer groups that data into containers. Once the ones and zeros are in the container, the movement of information is allowed between two devices. The Physical layer handles the connection between the computer and the transmission medium. The transference of electrical and optical information is also through this layer. In order for information to be transferred throughout a network, it must make its way through each of the seven layers of the OSI Model.

Circuit Switching
First of all, we need to understand that circuit switching needs a dedicated point to point for successful transmission. Typically, according to the text, there are two forms of this, a WAN (Wide Area Network), or Customer Premises Equipment (CPE). One of the easiest ways to achieve this is a point to point where only two nodes are involved; however, this does not work well for long when the system begins to grow. Essentially, when information is transmitted, it starts at the DTE (Data Terminal Equipment), its physical interface, through the transmission channel, through the ending physical interface, and then, finally, to the DTE on the other end. For a normal example, Kudler is transmitting over a T100 line (copper twisted pair). Their computer, the DTE, takes their signal and converts it from digital to analogue, via the modem, so it can be transmitted over the line. However, since they have a large volume of data trying to move at once, they need to have a multiplexer, typically 24 channels and this will allow them to determine how that data rate is allocated. These lines are leased, so they should be able to use an intelligent multiplexer to use dynamic bandwidth allocation. So the information passes from the terminal, into the modem for conversion, into the PBX across the PSTN. Since the line is tied to this one circuit, it can’t be used by anything else until it is done with the conversation. This is why it is important for the company to use certain things at their disposal, like an intelligent mux and possibly dynamic alternative routing, to help alleviate some of the congestion problems during peak hours that have been causing them delays.

Packet Switching Packet switching is when the data is not sent in one full chunk, like circuit, but is broken up into smaller packets and then reassembled on the other side. According to the text, it was designed to “support bursty traffic data, which stays connected of a long time, but transmits low volume.” (Goleniewski, 0215). In essence, packet switching is a store and go type of system. You don’t need the dedicated line because the system holds the information based upon priority and then transmit when the system is open. This can cause lag times in certain areas. In the sense of this network, one connection is made and the subsequent packets that follow only need the header and they will be pushed through the virtual circuit to the end destination. Most of these systems, ATM and Frame Relay, were used for low bandwidth applications such as email, documents, etc. The largest problem with this system is distance. The farther it travels, the more delays it may encounter going from node to node. All of the packets are collected at the terminal end of the transmission and reassembled. In the Kudler realm, this may not be a bad feature since we could take a Frame Relay based on a hub and spoke design. We could allocated higher bandwidth for the cashiers during peak hours and allow them to get through the system faster and this would cut costs on the leased lines.

Advantages and disadvantages of circuit/packet switching
Packet switching protocols consist of frame relay packet switching and X.25. Both X.25 and Frame Relay provide connection-oriented packet switching, also known as virtual circuit switching. A major difference between X.25 and Frame Relay packet switching is that X.25 is a reliable protocol, based on node-to-node automatic repeat request, while Frame Relay is a non-reliable protocol; maximum packet length is 1000 bytes. Any re transmissions must be carried out by higher layer protocols. The X.25 protocol is a network layer protocol, and is part of the X.25 protocol suite, also known as the OSI protocol suite. It was widely used in switching networks during the 1980s and early 1990s, for example as an alternative to circuit mode terminal switching, and for automated teller machines.
Frame relay is a further development of X.25. The simplicity of Frame Relay made it considerably faster and more cost effective than X.25 packet switching. Frame relay is a data link layer protocol, and does not provide logical addresses and routing. It is only used for "semi-permanent" connections, while X.25 connections also can be established for each communication session. Frame Relay was used to interconnect LANs or LAN segments, mainly in the 1990s by large companies that had a requirement to handle heavy telecommunications traffic across wide area networks ("Packet Switching", 2013).
Some advantages of packet switching are its security and it takes advantage of the bandwidth being used to its full potential. It is not affected by line failure, it just redirects the signal. Devices of different speeds can still communicate. Some disadvantages are that under heavy use there can be a delay. Data packets can become lost or corrupted during transmission. Protocols are need for a reliable transfer. Some advantages of circuit switching are that the circuit is dedicated to the call. Its guaranteed the full bandwidth for the duration of the call. It will not lose quality during the transmission. It is easier and less expensive to double the capacity of a packet switched network a circuit network is heavily dependent on the number of channels available. Circuit-switched technologies, which take four times as long to double their performance/cost, force ISPs to buy that many more boxes to keep up.

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