Protocol Data Units and OSI Model

Transport

defines services to segment, transfer, and reassemble the data for individual communications between the end devices, Port Addresses are encapsulated at this layer

Data-link

describe methods for exchanging data frames between devices over a common media, Physical Addresses are encapsulated at this layer

Physical

describe the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical connections for bit transmission to and from a network device

MAC

lower sublayer of the data-link layer defines the media access processes preformed by the hardware

Presentation

provides for common representation of the data transferred between Application layer services

Network

provides services to exchange individual pieces of data over the network between identified end devices, IP Addresses are encapsulated at this layer

Session

provides services to the Presentation layer to organize its dialogue and to manage data exchange

Application

provides the means for end-to-end connectivity between individuals in the human network using data networks

Frame

the data Link layer PDU

Data

the general term for PDUs used at the application layer

Packet

the network layer PDU

Bits

the physical layer PDU used when physically transmitting data over the medium

Segment

the transport layer PDU

LLC

upper sublayer of the data-link layer defines the software processes that provide services to the network layer protocols