TCP/IP Protocols Layers

The Physical Layer

contains the protocols relating to the physical medium on which TCP/IP will be communicating.

Four categories of physical layer protocols

1 Electrical/optical protocols describe signal characteristics such as voltage or photonic levels, bit

timing, encoding, and signal shape.

2. Mechanical protocols are specifications such as the dimensions of a connector or the metallic

makeup of a wire.

3. Functional protocols describe what something does. For example, “Request to Send” is the

functional description of pin 4 of an EIA-232-D connector.

4. Procedural protocols describe how something is done. For example, a binary 1 is represented on

an EIA-232-D lead as a voltage more negative than –3 volts.

The Data Link Layer

– contains the protocols that control the physical layer: how the medium is accessed and shared, how devices on the medium are identified, and how data is framed before being transmitted on the medium.

– Examples of data link protocols are IEEE 802.3/Ethernet, IEEE 802.5/Token Ring, and FDDI.

The Internet Layer

corresponding to the OSI network layer, is primarily responsible for enabling the routing of data across logical internetwork paths by defining a packet format and an addressing format.

The Host-to-Host Layer ( Transport Layer)

– corresponding to the OSI transport layer, specifies the protocols that control the internet layer, much as the data link layer controls the physical layer. Both the host-to-host and data link layers can define such mechanisms as flow and error control.

– The difference is that while data link protocols control traffic on the data link— the physical medium connecting two devices— the transport layer controls traffic on the logical link— the end-to-end connection of two devices whose logical connection traverses a series of data links.

The Application Layer

– corresponds to the OSI session, presentation, and application layers.

– the most common services of the application layer provide the interfaces by which user applications access the network.

Disclaimer: The materials used for this post is for personal notes on my preparations for the CCIE certifications. Source of notes were taken from Routing TCP/IP Volume 1.

NETWORK LESSON