Network Layer (Layer 3) defines end-to-end delivery of data packets and defines logical addressing to accomplish this. It also defines how routing works and how routes are learned. The OSI Reference Model fragments a packet into smaller packets to accommodate media with smaller The Millionaires Maker maximum transmission unit sizes. The Internet Protocol (IP) is the cornerstone of the Transmission Control Protocol/Internet Protocol (TCP/IP) suite and the most frequently used network layer protocol. Other examples include: IPX, AppleTalk DDP, NetBIOS, NetBEUI and ICMP.
Data Link Layer (Layer 2) is the channel between the computer's networking hardware and networking software. This layer is concerned with getting data across one particular link or medium. The data link protocols define delivery across an individual link. These protocols are necessarily concerned with the type of media in use. To implement a data-link layer protocol, the following hardware and software is needed: Network interface cards (NICs), which are also called Network adapters; Network adapter drivers;
Network cables and ancillary connecting hardware; and Network hubs. NICs and hubs are designed for specific data-link layer protocols, and it cannot mix with other products or different kinds of protocols. Some network cables are protocol-specific, while others can be used with different protocols. The most popular data-link layer protocol is Ethernet while Token Ring is also common. Data-link layer protocol specifications include the three basic elements: A format for the frame, A mechanism for controlling access to the network medium, One or more physical layer specifications for use with the protocol Examples include: IEEE 802.3/802.2, HDLC, Frame Relay, PPP, FDDI, ATM, and IEEE 802.5/802.2.
Physical Layer (Layer 1) deals with the physical characteristics of the transmission medium. Connectors, pins, use of pins, electrical currents, encoding, and light modulation are all part of different physical layer specifications. It defines the nature of the network's hardware elements. It also defines what kind of network interface adapter should be used and the hub that should be used. Different kinds of copper or fiber optic cable can be used, and a wide variety of wireless solutions. Usually when a LAN is set up, the physical layer specifications are related to the data-link layer. The data-link layer protocol, Ethernet, helps with the different kinds of options in the physical layer. Examples includes: