Annex A Lesson 2 - The OSI and TCP/IP Models

The pathway that the data takes as it travels from source to destination.

Channel.

Layer 7 of the OSI Reference Model. Provides the means for end-to-end connectivity between individuals and data networks. Also provides network services to a users application.

Application

Layer 4 of the TCP/IP Reference Model. Represents data to the user, plus encoded and dialog control.

Application.

Layer 2 of the OSI Reference Model. Provides means for exchanging data frames over a common media. Detects and possibly corrects errors that may occur in the physical layer. Responsible for the physical addressing, topologies and flow control.

Data Link.

A person or device that receives data and reads it.

Destination.

Enables routers to exchange route information, compare path information and then to select the best path to the destination network. Examples include Open Shortest Path First (OSPF), and Border Gateway Protocol (BGP).

Routing Protocols.

Used for the automatic detection of devices or services on a network. Examples include Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS).

Service Discovery Protocols.

Layer 5 of the OSI Reference Model. Establishes, manages, and terminates sessions between two communicating hosts. Synchronizes and manages the data exchanges between 2 devices.

Session.

Three common elements of communication.

Source, Destination, and Channel.

A person or device that sends data to another person or devices.

Source.

Layered models used to describe network operations.

TCP/IP Reference Model and Open System Interconnection (OSI) Reference Model

Most relevant protocol suite used today across all devices and within the Information Technology industry.

Transmission Control Protocol/Internet Protocol (TCP/IP) Suite.

Layer 3 of the TCP/IP Reference Model. Supports communication between various devices across diverse network.

Transport.

Layer 4 of the OSI Reference Model. ensures that messages are delivered error-free, in sequence, and with no losses or duplications. Provides messages segmentation, message acknowledgement, message traffic control, and session multiplexing.

Transport.

Three delivery methods of communication.

Unicast, Multicast, and Broadcast.

Data is sent to a single destination on a network.

Unicast.

Data is sent to one or multiple destinations on a network.

Multicast.

Layer 1 of the TCP/IP Reference Model. Controls the hardware devices and media that make up the network.

Network Access layer

Enables 2 or more devices to communicate over one or more networks. Examples include Internet Protocol (IP), Transmission Control Protocol (TCP), Hyper Text Transfer Protocol (HTTP), and many more.

Network Communications Protocol.

Secures data to provide authentication, data integrity, and data encryption. Examples include Secure Shell (SSH), Secure Sockets Layer (SSL), and Transport Layer Security (TLS).

Network Security Protocols.

Layer 3 of the OSI Reference Model. Controls the operations of the network, deciding what physical path the data should take based on network conditions, priority of services, and other factors. Consists of four basic processes such as addressing end devices, encapsulation, routing and decapsulation.

Network.

Layer 1 of the OSI Reference Model. Defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between sources and destination. It controls things such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other similar attributes.

Physical.

Layer 6 of the OSI Reference Model. Provides the common representation of the data transferred between Application layer services.

Presentation.

Viewed in terms of layers, with each higher-level service depending on the functionality defined by the protocols shown in the lower levels.

Protocol Stack.

A group of inter-related protocols necessary to perform a communication function.

Protocol Suite.

Specific set of rules a network has to follow. Used by end devices and intermediary devices for exchanging data.

Protocols.

Layer 2 of the TCP/IP Reference Model. Determines the best path through the network.

Internet.