OSI and TCP/IP(DoD) Model

What does Layer 7-5 of the OSI model provide Layer 4 (Transport)?

A PDU from Layers 7-5 containing data.

Layer 4 TCP/IP (DoD)

Application (Layer 5-7 of OSI model)

What happens when you go from bottom to top in a communication?

Decapsulation

Layer 6 OSI - Presentation

Defines data formats. Compression and encryption are defined at this layer.

Layer 3 OSI - Network

Defines device addressing, routing, and path determination. Device (logical) addressing is used to identify a host on a network (e.g. by its IP address).

Layer 5 OSI - Session

Defines how to establish and terminate a session between the two systems.

Layer 1 OSI - Physical

Defines how to move bits from one device to another. It details how cables, connectors and network interface cards are supposed to work and how to send and receive bits.

Layer 2 OSI - Data Link

Encapsulates a packet in a frame. A frame contains a header and a trailer that enable devices to communicate. A header, most commonly, contains a source and a destination MAC address. A trailer contains the Frame Check Sequence field, which is used to detect transmission errors. The data link layer has two sublayers: 1. Logical Link Control - used for flow control and error detection. 2. Media Access Control - used for hardware addressing and for controlling the access method.

What happens when you go from top to bottom in a communication?

Encapsulation

What is the PDU for the data link layer called?

Frame

Layer 2 TCP/IP (DoD)

Internet

Layer 1 TCP/IP (DoD)

Network Access (Layer 1 & 2 of OSI model)

What does OSI stand for?

Open Systems Interconnect

What is the PDU for the network layer called?

Packet

What is used at the transport layer to identify services or applications?

Port Addresses

What does PDU stand for?

Protocol Data Unit

What is the term used to describe data as is moves from one layer to another?

Protocol Data Unit

What is the PDU for the transport layer called?

Segment

Layer 4 OSI - Transport

Segments great chunks of data received from the upper layer protocols. Establishes and terminates connections between two computers. Used for flow control and data recovery.

What is Decapsulation?

The process of opening up encapsulated data that are usually sent in the form of packets over a communication network.

What is Encapsulation?

The process of putting headers (and sometimes trailers) around some data.

What do applications do?

They make requests.

What do services do?

They receive requests.

Layer 7 OSI - Application

This layer is the closest to the user. It enables network applications to communicate with other network applications.

Layer 3 TCP/IP (DoD)

Transport

How many directions are required to have successful communications in OSI-TCP/IP models?

Two (Bi-Directional)