CISCO CHAPTER 4

  OSI Layer Explanation

   Physical Layer
  This is the simplest layer; related to electrical (and optical) connections between equipment. Binary data is encoded in a form that can be transmitted through network media, for example cables, transceivers and connectors related to the Physical layer. Tools such as repeaters, hubs and network cards are on this layer.


  Data-link Layer
  This layer is slightly more "intelligent" compared to the physical layer, as it provides more tangible data transfer. As a link between the network medium and the higher-level protocol layer, the data link layer is responsible for the final packet of binary data coming from the higher level to the discrete packet prior to the physical layer. Will send frames (blocks of data) through a network. Ethernet (802.2 & 802.3), Tokenbus (802.4) and Tokenring (802.5) are protocols at the Data-link layer.


  Network Layer
  The main task of the network layer is to provide a routing function so that packets can be sent out from the local network segment to a destination that resides on another network. IP, Internet Protocol, generally used for this task. Other protocols such as IPX, Internet Packet eXchange. The Novell company has programmed several protocols, such as SPX (Sequence Packet Exchange) & NCP (Netware Core Protocol). This protocol has been entered into the Netware operating system. Some functions that may be done by Layer Network

• Divide the binary data stream to discrete packets of a certain length
• Detecting Error
• Fix the error by resending the damaged package
• Controlling the flow

  Layer Transport
  Data transport layer, using protocols such as UDP, TCP and / or SPX (Sequence Packet eXchange, this one is used by NetWare, but specifically for IPX-oriented connections). The transport layer is the center of the OSI-mode. This layer provides reliable and transparent transfer between the two end points, this layer also provides multiplexing, flow control and error checking and fix.


  Layer Session
Layer Session, as the name implies, is often misunderstood as a logon procedure on the network and related to security. This layer provides services to two layers above it, Coordinate the communication between the entity layer it represents. Some protocols on this layer: NETBIOS: a session interface and protocol, developed by IBM, that provides services to the presentation layer and application layer. NETBEUI, (NETBIOS Extended User Interface), a development of NETBIOS used in Microsoft networking products, such as Windows NT and LAN Manager. ADSP (AppleTalk Data Stream Protocol). PAP (Printer Access Protocol), which is contained in the Postscript printer for access on the AppleTalk network.


  Layer Presentation
  The presentation layer of the OSI model performs only a single function: the translation of the various types in the system syntax. For example, a connection between PC and mainframe requires the conversion of EBCDIC character-encoding format to ASCII and many factors to consider. Data compression (and possible encryption) is handled by this layer.


  Application Layer
  This layer is the most "smart", the gateway is on this layer. Gateway does the same job as a router, but there is a difference between them. The Application Layer is the primary link between applications running on a single computer and the resources network that requires access to it. The Application Layer is the layer where the user will operate on it, protocols such as FTP, telnet, SMTP, HTTP, POP3 are on the Application layer.

 EXPLANATION OF CHARACTERISTICS AND TECHNOLOGY PROPERTIES

  Definition of Wireless

  Wireless Technology or wireless technology, or more often abbreviated wireless technology is electronics that operate wirelessly. Wireless technology can be used for communication, and controlling, for example for communication, known as wireless communication ie information transfer, any form, remotely without the use of cable such as mobile phone network wireless and satellite computers. Remote wireless control is one example of wireless technology. For example the use of TV remote, control car, and remote to open the garage door of the car. Communities are already familiar with wireless technology. Both because people use the phone or because many start to access the Internet through a hotspot service.

Characteristics of Wireless Systems

Components / Elements
  Access Point (AP)
AP in addition to connecting the Internet with a local network, also serves as Filtering, Firewall, and Router, and have a Different Covering.
"Covering" Is the Area Area that AP can reach
"Router" is a pointer for sending data on target.
"Firewall" is a network device that serves to limit data transfering