Layer 2 (Data Layer) is below it.
Layer 4 (Transport Layer) is above it.
The OSI Layer is made up of 7 layers. The layers start out in the following order:
7. Application Layer - Responsible for identifying and establishing the availability of the communication partner and determining if sufficient resources for the communication exist. It also handles synchronizing communication between applications. This layer is closest to the end-user and how user interacts with the software applications. Examples are; (FTP, WWW, Telnet, SMTP, and Search Engines.) [DATA]
6. Presentation Layer - Provides a variety of coding, decoding, encrypting, decrypting and conversion functions that are applied to the application layer data. These functions ensure that information sent from the application layer of one system will be readable by the application layer of another system. (TIFF, GIF, PICT, ASCII, EBCDIC, MPEG, MIDI, HTML, and Quicktime, data).
5. Session Layer -Responsible for coordinating communications between systems, which is accomplished by connection establishment, data transfer and connection termination.( PC, SQL, NFS, NetBIOS names, AppleTalk, ASP, X Window, DECnet SCP DATA).
4. Transport Layer - Manages the flow of data between parties across a network. This layer provides error checks to guarantee error-free data delivery. (TCP, UDP, SPX ,SEGMENT).
3. Network Layer - Responsible for routing transmissions between computers,(IP, IPX, AppleTalk DDP, DATAGRAM, Routers, and Brouters).
2. Data Link Layer- Defines the format of data on the network. It handles physical and logical connections to the packet?s (data frame) destination using a network interface. (HDLC, PPP, IEEE 802.2, 802.3, & 802.5, FDDI, ATM, FRAME, NICs, Bridges, and Brouters). [Logical Link Control and Media Access Control Sub-Layers].
1. Physical layer - Defines the medium itself; like cables Thinnet, Thicknet, UTP, and STP. [BITS, NICs, Hubs, and Repeaters] (Also called the Foundation Layer.)