OSI Networking Layers By Victor Savastano Application Layer

OSI Networking Layers By Victor Savastano

Application Layer l Serves as an interface between the user and the network l Initiated by a communications application, such as an email, browsing or FTP program l Converts data into bits and attaches a header identifying the sending and receiving computer

Presentation Layer l Translates the data into a language the receiving computer can understand, such as ASCII l May also encrypt and/or compress data l Adds another header that specifies the language, along with any compression or encryption schemes

Session Layer l Establishes and maintains the communications session l The session is the period between establishing a connection, transmission of data, and termination of the connection

Transport Layer l Ensures that the data arrives correctly and in proper sequence l Adds a checksum, which is later used to be sure the data arrived unscrambled

Network Layer l The network layer routes the message from the sender to the receiver l Splits data into packets l Adds a headers that contains the packet sequence, the receiving computer’s address and routing information l Also manages network problems, by rerouting packets to avoid network congestion

Data Link Layer l Supervises the transmission of the data to the next network node l Contains information about the networking technology (Ethernet, token ring, etc. ) l Calculates checksum and keeps a copy of every packet until it ensures that the packet arrived undamaged to the next node

Physical Layer l Encodes the packets into a signal recognized by the medium that will carry the data (Ethernet, analog modem, etc. ) l Sends the packets along the medium to the receiving computer

References Vermaat, S. (2012). Discovering Computers: Your Interactive Guide to the Digital World (COMPLETE). Boston, MA: Course Technology