Layer 5 Session Layer: The session layer establishes, manages, and terminates – communication sessions. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. Layer 4 - Transport Layer: The transport layer accepts data from the session layer and segments the data for transport across the network. Generally, the transport layer is responsible for making sure that the data is delivered error-free and in the proper sequence. Flow control generally occurs at the transport layer. Layer 3 - Network Layer: The network layer defines the network address, which differs from the MAC address. Some network layer implementations, such as the Internet Protocol (IP), define network addresses in a way that route selection can be determined systematically by comparing the source network address with the destination network address and applying the subnet mask. Layer 2 Data Link Layer: The data link layer provides reliable transit of data across a physical – network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. Network topology consists of the data link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Layer 1 Physical Layer: The physical layer defines the electrical, mechanical, procedural, and – functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications. The following figure illustrates some common LAN and WAN physical layer implementations.
Layer 5 – Session Layer: The session layer establishes, manages, and terminates communication sessions. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. Layer 4 - Transport Layer: The transport layer accepts data from the session layer and segments the data for transport across the network. Generally, the transport layer is responsible for making sure that the data is delivered error-free and in the proper sequence. Flow control generally occurs at the transport layer. Layer 3 - Network Layer: The network layer defines the network address, which differs from the MAC address. Some network layer implementations, such as the Internet Protocol (IP), define network addresses in a way that route selection can be determined systematically by comparing the source network address with the destination network address and applying the subnet mask. Layer 2 – Data Link Layer: The data link layer provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. Network topology consists of the data link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Layer 1 – Physical Layer: The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications. The following figure illustrates some common LAN and WAN physical layer implementations.
Network%20Topology.docx