The Open Systems Interconnection Model Sherese Harrell Rebecca

The Open Systems Interconnection Model Sherese Harrell, Rebecca Meinhold, Peter Mella, Brenden Tourelle

Application Layer Physical Layer Presentatio n Layer The OSI Model Data Link Layer Session Layer Network Layer Transport Layer

The Application Layer Where users actually communicate to the computer Provides a user interface Responsible for identifying and establishing the availability of the intended partner

Communication in the Application Layer The application layer facilitates communication between software applications and lower-level layers of the OSI model Application Protocols In this example, the Word application is not part of the application level, but instead communicates with application-level protocols

The Presentation Layer Provides independence from data Transforms into the form that an application accepts Formats and encrypts data to be sent over a network Sometimes called the syntax layer This layer allows different operating systems to exchange data

The Session Layer MANAGES The session layer allows processes to communicate over a network ESTABLISHES TERMINATES CONNECTIONS BETWEEN APPLICATIONS

Communication Session Here is how communication happens between end user applications Data Network

The Transport Layer This layer accepts data from the Session layer & manages end-to-end delivery Checksums Flow Control Gauges which transmission to use depending on how fast the recipient can accept data Determines whether the arriving data unit exactly matches the data that was sent Connectionless Protocol More efficient, useful when data must be transferred quickly

Connection Oriented Protocols What is connection oriented programming? It is a protocol that establishes a connection before transmitting data SYNCHRONIZATION-ACKNOWLEDGEMENT SYNCHORNIZATION ACKNOWLEDGEMENT Web server Sends responds a packet to the request SYNto with connect a SYN-ACK to to Responds to server with an ACK indicate that server the server is willing to make a connection ACK SYN 3 SYN-ACK

Segmentation in the Transport Layer We don’t have all day to wait for the units, so this speeds up the process Segmentation Reassembly Large data units broken into multiple smaller units called segments Reconstructing of the segments Sequencing Puts segments into the group they belong in

Network Layer Translates network addresses and decides how to route data from the sender to the receiver Accepts segments and adds addresses Becomes a packet Factors in delivery priorities, network congestion, quality of service, and cost of alt routes Process of determining the best path is routing Internet Protocol instructs the network where the HTTP request is coming from/where it goes Fragmentation subdivides segments from the Transport Layer

Physical Layer Fiber-Optic Signals issued as light pulses This layer manages signaling to & from The type of wire used physical network determines what type connections of method is used to send signals Wire Types Wireless Signals sent as electromagnetic waves Copper Signals issued over wire as voltage Physical Layer protocols… Detect and accept signals, then send them to Data Link Layer Set the data transmission rate and monitor data error rates

Data Link Layer Recipient’s MAC address Sender’s MAC address This layer divides data into distinct frames A frame is a structured package that includes raw data as well as the sender/receiver’s network addresses Data Frame Check Sequence (FCS) Frame

Data Link Layer Physical Addressing Manages Physical Medium Both parts work together to ensure that an initial The connection is Data set up. Link and is broken that. Layer data has been into two parts, MAC and received successfully LLC Media Access Control (MAC) Logical Link Control (LLC) Error Notification Acknowledgement Flow Control

MAC Addresses Keep in mind that no two MAC addresses will ever be the same Contain 2 parts 004005 - Organizationally Unique Identifier (OUI) 607 D 49 Device ID MAC addresses are also known as physical addresses, data link layer addresses, and sometimes hardware addresses

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