;-----> (^_^)

A compliment is something like a kiss through a veil.
Victor Hugo

And now, this is the sweetest and most glorious day that ever my eyes did see.
Donald Cargill

Belief creates the actual fact.
William James

Believe you can and you're halfway there.
Theodore Roosevelt

Change your thoughts and you change your world.
Norman Vincent Peale

Clouds come floating into my life, no longer to carry rain or usher storm, but to add color to my sunset sky.
Rabindranath Tagore

Don't judge each day by the harvest you reap but by the seeds that you plant.
Robert Louis Stevenson

Every charitable act is a stepping stone toward heaven.
Henry Ward Beecher

Every moment and every event of every man's life on earth plants something in his soul.
Thomas Merton


Faith is love taking the form of aspiration.
William Ellery Channing

For a gallant spirit there can never be defeat.
Wallis Simpson

Give light and people will find the way.
Ella Baker

God always gives His best to those who leave the choice with him.
Jim Elliot

God sleeps in the minerals, awakens in plants, walks in animals, and thinks in man.
Arthur Young

Grace is the beauty of form under the influence of freedom.
Friedrich Schiller

Gratitude is the fairest blossom which springs from the soul.
Henry Ward Beecher

Great hopes make great men.
Thomas Fuller

Happiness is not something you postpone for the future; it is something you design for the present.
Jim Rohn

Happiness is the natural flower of duty.
Phillips Brooks

chapter 9

ETHERNET

   

      The first LAN in the world was the original version of Ethernet and it is now the prime LAN technology in the world that being designed by Metcalfe and his coworkers at Xerox for more than thirty years ago. The first Ethernet standard was published in 1980 by a association of Digital Equipment Corporation, Intel, and Xerox (DIX). This can be understood by the OSI model of its comprised standards at these lower layers. The OSI model separates the Data Link layer functionalities of addressing, framing and accessing the media from the Physical layer standards of the media.

      Ethernet operates across two layers of the OSI model. the Layer 1 involves signals and Layer 2 involves addresses limitations. Ethernet separates the functions of the Data Link layer into two distinct sublayers: the Logical Link Control (LLC) sublayer that implemented in software, and its implementation is independent of the physical equipment. And Media Access Control (MAC) sublayer is implemented by hardware, typically in the computer Network Interface Card (NIC).It is the lower part of Data Link layer.

      Ethernet was designed to accommodate multiple computers that were Interconnected on a shared bus topology. The first version of Ethernet incorporated a media access method known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). And it can managed the problems that result multiple devices attempt to communicate over a shared physical medium. Each computer was directly connected to the backbone.Hub was in the Legacy Ethernet that typically at the central point of the network segment. And this is created as a shared media. The Ethernet Beyond the LAN in the increased cabling distances enabled by the use of fiber-optic cable in Ethernet-based networks has resulted in a blurring of the distinction between LANs and WANs. Ethernet was initially limited to LAN cable systems within single buildings, and then extended to between buildings. It can now be applied across a city in what is known as a Metropolitan Area Network (MAN).

      The original Ethernet standard defined the minimum frame size as 64 bytes and the maximum as 1518 bytes is Ethernet Frame Size. This includes all bytes from the Destination MAC Address field through the Frame Check Sequence (FCS) field. While the MAC address value is a direct result of IEEE-enforced rules for vendors to ensure globally unique addresses for each Ethernet device.

      OSI Data Link layer (Layer 2) physical addressing, implemented as an Ethernet MAC address, is used to transport the frame across the local media. Although providing unique host addresses, physical addresses are non-hierarchical. They are associated with a particular device regardless of its location or to which network it is connected. In Ethernet, different MAC addresses are used for Layer 2 unicast, multicast, and broadcast communications. A unicast MAC address is the unique address used when a frame is sent from a single transmitting device to single destination device. With a broadcast, the packet contains a destination IP address that has all ones (1s) in the host portion. This numbering in the address means that all hosts on that local network (broadcast domain) will receive and process the packet. Multicast addresses allow a source device to send a packet to a group of devices. Devices that belong to a multicast group are assigned a multicast group IP address.

chapter 8

OSI Physical Layer

      Encoding of the binary digits to represent Data Link layer frames into signals and to transmit and receive these signals across the physical media (copper wires, optical fiber, and wireless) that connect network devices are the roles of OSI Physical layer.  It provides the means to carry across the network media the bits that make up a Data Link layer frame. This layer accepts a complete frame from the Data Link layer and encodes an of series of signals that are transmitted into the local media.

      The purpose of the Physical layer is to create the electrical, optical, or microwave signal that represents the bits in each frame. The media does not carry the frame as a single entity. The media carries signals, one at a time, to represent the bits that make up the frame. In identifying a frame, the devices on the media would not recognize when a frame has been fully received. In that case, the destination device would only receive a string of signals and would not be able to properly reconstruct the frame.

      Physical layer contains the three fundamental functions, the physical components, data encoding and signaling. Encoding is a method of converting a stream of data bits into a predefined code. Manchester Encoding, bit values are represented as voltage transitions. While Signaling  it  must generate the electrical, optical, or wireless signals that represent the "1" and "0" on the media. NRZ Signaling a simple method only suited for slow speed data links. NRZ signaling uses bandwidth inefficiently and is susceptible to electromagnetic interference.

      Symbols is a technique of encoding that use bit patterns. Code groups represent encoded data or control information. It is a consecutive sequence of code bits that are interpreted and mapped as data bit patterns. The symbols encoded onto the media are all unique. The symbols representing the data being sent through the network have different bit patterns than the symbols used for control. And these differences allow the Physical layer in the receiving node to immediately distinguish data from control information. The code groups have three types of symbols, Data symbols that represent the data of the frame as it is passed down to the Physical layer. Control symbols it is a special codes injected by the Physical layer used to control transmission. These include end-of-frame and idle media symbols. And the Invalid symbols that have patterns not allowed on the media. The receipt of an invalid symbol indicates a frame error.

Different physical media support the transfer of bits at different speeds. It can be measured in three ways: Bandwidth it is a capacity of a medium to carry data is described as the raw data bandwidth of the media. Throughput is the measure of the transfer of bits across the media over a given period of time. And Goodput to measure the transfer of usable data.

      In this chapter it identifies the different characteristics of the UTP (Unshielded Twisted Pair) cable, STP and Coaxial cable. UTP cabling, terminated with RJ-45 connectors, is a common copper-based medium for interconnecting network devices, such as computers, with intermediate devices, such as routers and network switches. STP uses two pairs of wires that are wrapped in an overall metallic braid or foil. The coaxial cable design has been adapted for different purposes. Coax is an important type of cable that is used in wireless and cable access technologies. Coax cables are used to attach antennas to wireless devices. The coaxial cable carries radio frequency (RF) energy between the antennas and the radio equipment.

IPv6

INTERNET PROTOCOL VERSION 6 (IPV6)

      

       In today's generation, the birth of technology is going faster and faster. And in order to connect the people in whole world it uses the internet. It is a system of interconnected computer networks globally that use a standard TCP/IP.
      The data transfer by the internet into small packets that independently route into the networks by an international communication protocol knows as the internet protocol. In each pocket data contains two numeric addresses that the source to the destination of devices.

      The problem of continues growing of internet is the more addresses needed that IPv4 became collapse. And the Internet Engineering Task Force (IETF) find a solution for this situation, they develop the Internet Protocol version 6 (IPv6). It is the newest version of the internet protocol (IP) that being designed to succeed the older Internet Protocol version 4 that being used publicly since 1981, and it is the currently foundation for most Internet Communication. It was released and published on December 1998 and described in Internet standard document RFC 2460.

      IPv6 is an internet layer protocol for packet switched internetworking and provides end to end datagram transmission across multiple IP networks. It uses the 128 bits addresses, 2¹²⁸ (approximately 340 undecillion or 3.4 x 10³⁸) addresses space supports. While the IPv4 allows only 32 bit, 2³² (4,294,967,296) addresses available.

      In this new version it allows for many more devices and users on the internet as well as the extra flexibility in allocating addresses and efficiency for routing traffic.  It offers more additional features than the previous edition. It simplifies the aspects of address assignment (stateless address auto configuration) network renumbering and router announcements when changing Internet connectivity providers. It also eliminates the primary need for network addresses translation (NAT), which gained widespread deployment as a effort to alleviate IPv4 address exhaustion.