Chapter 9 Ethernet

                Ethernet as it is being introduced is the predominant LAN technology used today in the world, because of its great impact to the overall performance of a network. According to the history, it was Robert Metcalfe and his co worker at XEROX who developed this technology and they have dedicated many years of their lives for about 30 years of developing this ethernet technology. The OSI model upper layers function protocols were being defined and maintained by the International Engineering Task Force (IEFT), while the functional of the lower layers ,specifically the Data Link Layer  and the Physical Layer were maintained by many international organizations. Here the ethernet is being comprised of the standards at these lower layers. In 1980 the standards of ethernet were first established, and these standards work at the Data Link lower layer and Physical layer.

                The Data Link Layer is further subdivided into two sublayers, the logical link layer and the Media Access Control layer. The ethernet standard 802.3 works at the lower layer of the Data Link layer and to the Physical layer for addressing scheme and recognizing bit stream or a frame, but this has limitations and there comes the logical link layer that resolve these limitations. Logical Link layer connects or communicates to the upper layers of the OSI model. This media access control has many features, it use for frame delimiting and error detection and for managing collisions on a shared media. MAC uses the CSMA/CD method on a shared media where traffic is heavy and collision percentage is high. If ever collision occurs at the media CSMA/CD detects the collision and then prompts the node to retransmit the frame that failed. MAC address also plays a role on the network, every node connected to a network should have MAC address, it is used To determine the destination node of the frame in a network. The ARP or the Address Resolution Protocol help to address the issue of IPv4 addresses. ARP table stores the IPv4 addresses and MAC address and match these addresses in order to send the frame to the end devices. Ethernet LAN technology offers ethernet hubs to cater number of hosts connected to them on a LAN, but these two have different characteristics and features. Hubs and switches have the same function. Hub is an intermediary device where in multiple nodes can be connected to it in a shared media environment. Designated bandwidth in a hub-based ethernet network is being divided to number of nodes in that particular network segment, since the frame from other network will be receive by the hub port it will then send it to all the nodes causing traffic and occasionally a collision. As the number of nodes increases in a hub-based network the bandwidth will decrease and at the same time the throughput also decreases. The switch based. Ethernet network addressed those issues, switch manages a segment of the network to be collision free environment. Its port in the switch has its own designated bandwidth, thus it increases throughput.

chapter 11

The planning and design process of a network contribute to the installation of successful and functional network. These include the proper selection of the LAN and WAN media types, their associated cables and connectors. By considering all of these, the interconnection of devices from end devices, to intermediary devices up to the network resources lead to an appropriate decision that could help to improve and enhance network performance. In addition to that determining the number of hosts and subnets in a network and planning for future growth also contribute for a good network design and planning.  Intermediary devices are important device in a network, they used to interconnect devices and even to other nieghboring networks whether a LAN or WAN network. Configuring these devices properly in a secure manner would mean a good network administration. Routers and switches are just hardware components that are always dependent to the software that operate them in order to function. Since cisco is considered the backbone of the networking today, they provide an operating system that would manage and operate on the different cisco devices. This OS is called the INTERNETWORK OPERATING SYSTEM. It is used for routers, LAN switches small wireless access point. It also provide basic services in routing and switching function, reliable and secure access to network resources as well as network scalability. Ordinarily, CISCO devices were generally accessed through the command line interface (CLI) and stored in a non-volatile memory called flash. Routers and even switches can be accessed through different methods for the purpose of configuring these devices. The different access methods such as console, telnet/ SSH and by the use of AUX port offers various features and work at different environment. Each method uses security features to avoid unauthorized access. Some of these access methods work with or without active networking services present. The network administrator is a person who has primary control of the network configuration especially network configuration and also defines desired functionality of a CISCO device.  There are two types of configuration files: the start-up configuration file and the running configuration file. These configuration files are stored in a non-volatile random access memory. The CLI uses hierarchical structure for the modes of configuring CISCO devices. The major modes involved were user executive mode, privileged executive mode and the global configuration mode. Each mode is used to perform a specific function and has particular set of commands that are available when in that mode. This hierarchical structure mode provides security support at each mode level for authentication. Each mode has its own set of commands that are used to configure CISCO devices. The commands are the combination of keywords use to execute after the configurations. A command may be used to show the configuration or do some actions to the router and it could also help to show commands to guide the administrator of the appropriate command to be used by the context help command. There are also types of error messages in order to inform the users of the errors they committed. All configurations made must be stored in NVRAM for future access and configuration. Routers and switches have what we called interfaces and each interface must be configured with the right IP address and subnet mask in order to connect each other and send a packet within a network. After configuring all the CISCO devices with appropriate ip addresses and other information there is a need to test the connectivity, this is possible by pinging other devices in a network. Documentation is very helpful to facilitate monitoring and troubleshooting network performance, this is done through creating a network baseline that conduct a study of the network at regular intervals to ensure that the network is working as designed 

Chapter 10 Planning and Cabling Network

                     

                     Far beyond our imagination, people today are living in what we called an information era, where in information significantly play a great role in almost every aspect of our lives.  We communicate in various forms in order to capture information relevant to every organization or individual to support day to day transactions and activities. People today in different locations utilized the advancement of technology, where in digital and electronic devices were sprouting everywhere supporting human network. Cell phones, computers and ipads were just a few to mention. But the question is how these particular devices interact to each other in data network or data communication?

                     In order to send and receive message, a connection between two or more devices should be established and intermediary devices are needed to guide the message to the destination. Since Ethernet is the predominant LAN technology in our modern generation it should be complimented with the right and proper connection, intermediary device and the type of media in order to create or assemble a functioning network.

                  The pathway or the passage way where the data passes through in order to arrive in a fast, reliable and consistent manner is always dependent to the type of media used in a network. Therefore there is a need to examine the type of media their roles and how they function in different environments. Before designing a network, a type of media is important to establish a connection and in order to maintain a concrete connection there should be development management connection.      

              The type of media, the right cable to use and the associated connectors were subject to consideration in designing a network whether it uses a wireless, fiber optic, or copper connection. There are a lot of factors to consider in choosing a media. The first thing we should put in mind is the usability of the media, does it conform or define the needs and requirements of an organization? The second thing is the cost when choosing a media, the geographical location and the building structure. The selection of devices and the design of the network addressing scheme is also important in a LAN or WAN network. The appropriate device or intermediary devices just like routers, switches and hubs greatly affect the performance of the network. Making a LAN and WAN connection must be based on the needs and type of organization and recognizing the number of hosts in a network must also consider future expansion or growth and must depend on the number of end devices on a network. Subnetting is also helpful in order to reduce broadcast traffic. Subnet design helps to improve performance of the different departments in an organization, because one subnet may serve for a particular function. Addressing scheme is also helpful in facilitating configuration and troubleshooting of a network by this every device assumes a particular function just like a general user, administrator computer, a server and intermediary devices can easily be recognize through the help of addressing scheme. In designing a LAN Or WAN network there must be a consideration on the location where those network devices must be placed, example to this is the telecommunication room where intermediary devices were placed and maintained. The working area also, because it can affect to the performance of a network, especially if the working area where cables and other media are placed are exposed to various interferences just like electromagnetic and radio frequency interference. The performance of each device on a network is greatly dependent to other devices, to the design, location and building structure of an organization  

Chapter 8 Physical Layer

                  The Open System Interconnectivity (OSI) model is a set of standard often follows in networking society for data communication. It is also called a reference model, because other networking models are being referenced to OSI model standard and structured. OSI model is composed of 7 layers and each layer conforms to a protocol that govern data communication over the network. One of the layers of OSI model is the physical layer, this layer provides a means of transmitting of bits across the network media that make up the data link layer frame. The basic work of the physical layer is to accepts a complete frame from the data link layer and encodes it as a sequence of signals that are transmitted onto the local media. The frame is the PDU of the data link layer it is composed of groups of bits and each bit represents a signal. The signal represented by the bit may vary according to the type of media being used by the network and the three basic forms of network media are the copper cable, fiber optic, and wireless media. Each media has different physical characteristics that significantly affect the process of delivering a data along the local media and it also represents  different kinds of signal, copper cable uses electrical signal, fiber optic uses also light wave signals and wireless medium uses radio frequency signal to represents a bit. When the physical layer encodes the bits into the signals for a particular medium for a successful delivery, but in order to recognize that particular passes through a media has successfully received by receiving device, there is a must to distinguish the end and the beginning of the next frame. The physical layer has three fundamental functions, the physical component, data encoding and signaling. Physical component is comprises of electronic devices, media and connectors that help to transmit and carry the signals to represent the bits. Physical component standard was being set or defined by some of the international organizations like the international Organization for Standardization(ISO), Institute  of Electronic and Electrical Engineers(IEEE) and American National Standards Institute . The second function of the physical layer is the data encoding , a method of converting stream of data bits into a predefined code, in order to create a predictable pattern of code to recognized by both the sender  and the receiver . The last is the signaling that uses binary bits the 0's and 1's on the media as a signal whether it is electrical pulses, light or wireless signals. 

               When studying the physical layer we need also to consider the speed and the data transfer and how it is being measured. Data transfer can be measured into three different ways, the bandwidth,throughput, and goodput. Each measured the capacity,speed and the usable data in transfering data. Cabling is an important factor to consider also in data communication for a successful,faster and less interference of data transmission. Cabling resolved the problems of external interferences like the electronic noise that corrupt and distort the data on the medium. Cabling can be Aa UTP, STP, and Coaxial cabling. All of these has different physical characteristics and features to cater different needs of organization. It plays an important role in the ohysical layer but it may also cause hazards if not properly configured and if not installed in a building correctly.