Subjects

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Chapter 8 (Physical)

In data networking, the OSI Physical Layer is responsible to transmit ultimately the data over network communication media. But, if we talk about OSI Physical Layer, there are some roles and purposes  describe in it. One of its purpose is relatively in network and identifying  the basic elements which enable to fulfill its function.  Inside this physical layer, there is something that make this layer functional - this are bit, signaling, associated hardware components, encoding, media characteristics, proper cabling, and radio waves.If we tackle OSI physical layer, we faced so many things, like for example- its protocol and services, its signaling and encoding, characteristics and uses of network media.

The OSI Physical layer provides the means to transport across the network media the bits that make up a Data Link layer frame and it’s purpose is to create the electrical, optical, or microwave signal that represents the bits in each frame.There are three basic forms of network media – copper cable, fiber, wireless. This network media carry the frame as a multiple entity. The media carries signals, one at a time, to represent the bits that make up the frame. The OSI physical layer standards specify signal connector and cabling requirements. There are three fundamental function of OSI Physical Layer – physical components, data encoding and signaling. The physical components are the electronic hardware devices, media and connector. The data encoding composed of converting  stream of bit to data codes. The signaling concern on what type of media used for signaling and what is the best. Measuring of data transfer its either – goodput, throughput, bandwidth. The bandwidth data transfer measurement determine the flow of data at a given period of time. The throughput data transfer of measurement determine the transfer of bit across the media at a given period of time. The goodput data transfer measurement determine the usable data transfer over a given period of time.

The copper media are composed of – coaxial cable, unshielded twisted pair cable and rj-45 connection. Cable  with shielding or twisting of the pairs of wires are designed for minimizing signal degradation cause to electronic noise.The UTP cable has a outer jacket which protect the copper wire from physical damage and has twisted pair to protect the signal from inference and has a color coded plastic installation that electronically isolates wire from each other and identify its pair. There are wiring convention of UTP this are – crossover, straight- through and rollover. Two types of copper cable  - coaxial cable and shielded twisted pair.

There are some copper media safety that everyone must observed – electrical hazard and fire hazard. There are wireless media standard  and types – wifi that use wifi router so that computer and cellphone can connect, Bluetooth and wimax . The wireless access point  example is the router and the wireless adapter example is the wireless LAN card (Atheros and Broadcom).

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Chapter 9 (Trends of LAN Technology)

In our modern times, the common use our LAN Technology now is Ethernet. The question is- Why is Ethernet is the most widely use in the field of LAN Technology as of now?

In order to answer the above question, we first discuss  on how the Ethernet generate. Do you know that the first LAN structure is the Ethernet version. There are many answer of the above question but I think that is one of the reason why Ethernet become a widely used LAN Technology. If we think there are long time to develop and develop, the Ethernet LAN so that it will become popular.

The LAN standard starts the number of 802. The Ethernet standards start of 802.3 which passed the standards. The Layer 1 and the lower portion of Layer 2 of the OSI model is the responsibility of the IEEE 802.3 standards addressing. The media access layer (MAC) is found in the half lower layer of data link with its concerned of the physical components that will being use to communicate the information and prepares the data for transmission over the media. The Data Link sublayers support significantly to computer communications and technological compatibility. The Layer 1 touches signals, bit streams that travel on the media, physical components that put signals on media, and various topologies. The Logical Link Control (LLC) sublayer is independent of the communication physical equipment . The LLC sublayer functions describe by the IEEE 802.2 standard, and the MAC sublayer and the Physical layer functions describe by the 802.3 standard. Logical Link Control handles the communication between the networking software, and the lower layers and  the upper layers.

As for the Ethernet frame size, its standard level the minimum frame size as 64 bytes and its maximum is 1518 bytes. The source MAC address identifies the frame originating interface and the destination MAC address serve as an identifier of the said recipient. The unicast MAC address is the unique address for sending a frame from a single transmitting device to single destination device. The multicast address is a group of address that can only be used as the destination of a packet. The broadcast address contains a destination IP address that has all ones  in the host portion.

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Chapter 10 (Think and Connect)

In normal human communication, you must think the word or phrase you say and the ears is serve as a connection so that you can perform a formal communication. Same in the field of computer networking, there is thinking and connection to perform a successful communication.

As for the computer networking, we must think what kind of end devices, intermediary devices and cable or wireless connection so that everything is harmonize and synchronize in its function. Let me take some example- not all switches match the interfaces of the internet, not all cable or wireless connection match when we connect switches to host, switch to router and router to router. Now, what shall we do? We must think the appropriate materials that are going to use in connecting the networking devices. 

Important Factors

                It is important to choose the exact, correct and appropriate LAN Device. How? The router is the first most important LAN device used in interconnect networks.Why? Because the router have the ability to broken up broadcast domains and collision where other devices can’t do.  We can determine the right router to deploy by matching the Ethernet interfaces to the technology of the switch at the center of the LAN. The UTP cable and fiber optics will help the router to connect to the LAN media.

                Previously, we discuss  the internetwork devices (router)  but now the intranetwork devices.  The two intranet devices are Hub and Switch. As for the Hub, it receives signal from the devices,regenerate the said signals, send it over all ports and create a logical bus. Remember that switches is more expensive than switches. How about the switch? What is it? The switches will receive a frame, regenerate its bit of frame and segment the network into multiple collision domains.

                Determining the devices? Consider this factor – cost (kantidad), speed (gikusgon), expandable, manageable type of ports and operating system features.  

                In planning and cabling networks, consider the work area, telecommunication room, backbone cabling and distribution cabling. It is important? Yes,because the factors in determining the devices will depend on it.

                There are types of media – UTP, fiber-optics, wireless. Every type has its advantage and disadvantage,so you consuder this – cable length, cost, bandwith, ease of installation and susceptible to EMI/RFI.

                In making LAN connection, it’s undergo in UTP cabling  and determining type of interfaces (either straight-through or cross-over). Remember this, straight-through used in switch to router, computer to switch and computer to hub while cross-over used in switch to switch, switch to hub, hub to hub, router to router, computer to computer and computer to router.

                In making WAN connection, take this forms – telephone line RJ-11 connectors for dial-up or DSL connection and 60 pin serial connection.  There are some device that maintain the link between sending and receiving device – DCE (supplies clocking service to other device) and DTE (receive clocking service).

                The number of host in a network will depends on the requirements. Why? Every device has a require IP address. The end device – user computers, administrator computers,servers and others (include printers,IP phone, IP cameras). The network device – router LAN and router WAN. Management network device – switches and wireless network point. There is a formula in determining no. of host in a network ( 2 to the nth power minus 2 (2^n-2). Remember, the network address and broadcast address – cannot be assigned to host.

                In dividing subnets, the reason is to manage broadcast traffic, different network requirements and security.

                There are some categories of the host- there is general users, special users, network resources, router LAN interfaces, router WAN interfaces, router WAN links and management access.

                In this chapter, calculation of IP address and addressing was perform.

                                                   

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Chapter 11 (Build, Visualize, Examine and Try)

In a network, you can build a Ethernet-based local area network  if you have a computer connected to switches and vice versa, switches connected to router and vice versa and computer connected to router and vice versa. Its already finish? No. Why? Because you must configure and test  to make sure that the connection is successful and that’s the trend of this chapter – Configuring and Testing Your Network.

Configuring a Network

In configuring a network, you need an OS same to our present  computers – it needs an Operating System (OS) to perform its capabilities. The question is – What do you call the OS of a Network? Absolutely, the Internetwork Operating System (IOS).  There are some kind of OS in a Network but this chapter explain and discuss the Cisco Internetwork Operating System.

What is inside in this Cisco Internetwork Operating System?

The Cisco Internetwork Operating system  provide a basic routing and switching function, reliable and secure access to networked resources and network scalability. And you can access the above CISCO IOS services through command line interface (CLI). The flash memory serve as a storage of IOS file.  

Through this, the function of the devices will totally increase.

Accessing the CLI environment use method of console,telnet or SSH and AUX port. The console use a below speed limit of serial connection to automatically connect a computer  or terminal to its console port on the router switch while the Telnet or SSH is unlike the console that remotely accessing the CLI environment . The AUX is nearly the same to the Telnet but its remote connection is via telephone dial-up connection.

There are two kinds of configuration files in CISCO Network device- the running configuration file and the startup configuration file. Both are very useful configuration because the running configuration file is perform during the current operation of the device and the start-up configuration file is perform as a back-up configuration and loaded when a device is started.

In order to perform successfully the network configuration, they designed a modal operating system  where modes are become popular in configuring network. The modes are – user executive mode, privileged executive mode, global configuration mode and other specific configuration modes. All of this mode are designed to perform the different specific task inside the Cisco IOS.

In a human, the name is serve as an identity of a person as well as in the network. As for the networks, it is important that you put a device names.

Most individual want to limit the device access of the other people. Now, configuring password is the most important. And those password are said to be secret.

Testing Net work

Testing the network point the validity of the network connection. There are some techniques of testing the network – using ping and then the host,router or server IP address. There is also testing the interface assignment that will verify the router interface. You can also test also local network  and  gateway and remote connectivity using ping.