What is PDU (Protocol Data Unit)
Following table explains about different PDUs at important layers of OSI model. Presentation and session layers are removed, because those layers are not much relevant these days.
|Layer Number||Layer Name||Description|
|Layer 7||Application Layer||Original data generated from network application.|
|Layer 4||Transport Layer||Original data with TCP/UDP headers containing sender’s and receiver’s TCP/UDP port numbers.|
|Layer 3||Network Layer||Data with TCP/UDP headers, with Network Layer header containing sender’s and receiver’s IP addresses.|
|Layer 2||Datalink Layer||Original data with TCP/UDP header, network layer header, and Datalink Layer header containing sender’s and receiver’s MAC addresses. Datalink layer adds a trailer also.|
|Layer 1||Physical Layer||Bits for network transmission.|