1. The OSI Model An overview of the media layer (Physical, Data Link, Network) By Luke Shiffner

2. Layer 1: Physical Defines a relationship between a device and a physical medium. -This includes, Cables, Hubs, Repeaters, Network adapters, pins, voltage and many other types of physical mediums The physical layer is primarily concerned with the interaction between a single device with its medium

3. Functions of the Physical layer Establishing and terminating a connection to a communications medium Conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel. Flow control: The process where the communication resources are shared among multiple users

4. Examples of Physical layer Implementations RS-232 T1 E1 10BaseT 100BaseTX POTS SONET DSL 802.11 a/g/b/n PHY

5. Layer 2: Data Link Provides a functional way to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical layer. Transfers data between adjacent network nodes in a wide area network or nodes on a local area network This layer is subdivided into 2 more layers which will be covered briefly: Logical Link Control and Media Access Control

6. Sub-layer 1: Logical Link Control This sub layer protocols running atop the data link layer This layer also helps to deal with flow control, acknowledgement and error recovery.

7. Sub-layer 2: Media Access Control This layer refers to the structure of a frame, which is the data type associated with the Data Link layer. These frames contain Media Access Control (MAC) addresses. These MAC addresses act as a unique serial number for the networking devices using the layers, for example: Network adapters It also determines where one frame starts and where the other frame ends.

8. Examples of Data Link Implementations Ethernet VLAN ATM CDP FDDI Frame Relay HDLC PPP Token Ring

9. Layer 3: Network Transfers data sequences, of no particular length from a source to a destination via one or more networks while maintaining the quality of service requested by the Transport layer. This layer also performs routing functions as well as reporting delivery errors. Makes use of the IP (Internet Protocol) Logical addressing scheme. This is the most commonly known protocol of the Network layer

10. Functions of the Network Layer There are 2 important functions of this layer: Forwarding and Routing Forwarding is the relaying of packets from one network segment to another by nodes in a computer network. Routing is the process of selecting paths in a network to send data or physical traffic.

11. Examples of Network Implementations NBF, which stands for NetBIOS Frames, which is most commonly used as one of the layers for Microsoft Windows Networking Q.931, which is ISDNs connection control protocol, which can be related to TCP from the Internet Protocol stack.

12. Summary All of these layers make up a section of the OSI model called the Media Layer This layer is responsible for many imperative functions of the OSI model. This includes but is not restricted to, signal and binary transmission (Physical layer), Physical addressing such ass MAC and LLC (Data Link layer), and Determining packet paths and logical addressing (Network layer)

13. fin.