BILZ Daily Write

 the network layer manages device addressing tracks the location of devices on the network and determines the best way to move data which means that the network layer must transport traffic between devices that aren't locally attached. routers are specified at the network layer and provide the routing services within an Internetwork.  Two types of packets are used at the network layer data and route updates. Data packets:- used to transport user data through the internetwork. protocols used to support data traffic are called routed protocols examples of routed protocols are IP and IPv6  Route update packets:- used to update neighboring routers about the networks connected to all routers within the internetwork. protocols that send route update packets are called routing protocols examples of common ones are RIP, RIPv2, EIGRP, and OSPF route update packets are used to help build and maintain routing tables on each router. Network addresses  - protocol-specific network...

 the transport layer segments and reassembles data into a data stream. services located in the transport layer segment and reassemble data from the upper-layer application and unite it into the same data stream. they provide end to end transport services and can establish a logical connection between the sending host and destination host on an internetwork some of you are probably familiar with TCP and UDP already if so you know that both work at the transport layer and that TCP is a reliable service and UDP is not this means that application developers have more options because they have a choice between the tow protocols when working with TCP/IP protocols. NOTE - the term reliable networking can be used at the transport layer it means that acknowledgments, sequencing, and flow control will be used.  Flow Control:- # the segments delivered are acknowledged back to the sender upon their reception. # any segments not acknowledged are retransmitted. # segments are sequenced back...

  The session layer is responsible for setting up managing and then tearing down sessions between presentation layer entities. this layer also provides dialog control between devices or nodes.  simplex, half-duplex, and full-duplex to sum up the session layer basically keeps different applications data separate from other application data.

 the presentation layer gets its name from its purpose it presents data to the application layer and is responsible for data translation and code formatting. this layer is essentially a translator and provides coding and conversion functions.a successful data transfer is to adapt the data into a standard format before transmissin. the OSI has protocol standards that define how standard data should be formatted. tasks like data compression, decompression  encryption and decryption are associated with this layer. some presentation layer standards are involved in multimedia operations too.

 the application layer f the OSI model marks the spot where users actually communicate to the computer. this layer comes into play only when it appears that access to the network is going to be needed soon. take the case of internet explorer. you could uninstall every networking component from a system. such a TCP / IP  NIC card and so on and you could still use IE to view a local HTML document no problem but things would definitely get messy if you tried to do something like view an HTML document that must be retrieved using HTTP or nab a file with FTP or TFTP.

 OSI (open system interconnection). this model was created by the international organization for standardization (ISO )  the OSI model was meant to help vendors create interoperable network devices and software in the form of protocols so that different vendor networks could work with each other. Like world peace, it probably never happen completely.  Advantages of reference models  it divides the network's communication process into smaller and simpler components thus aiding components development design and troubleshooting.  it allows multiple vendor development through standardization of network components.  it encourages industry standardization by defining what functions occur at each layer of the model.  it allows various types of network hardware and software to communicate. it prevents change in one layer from affecting other layers so it does not hamper development  OSI specifications are to assist in data transfer between disparate hosts...