M5: Communication Protocols

Module 5 CISCO Networking Basic: About Protocols

Protocol

are rules that make communication—human or digital—clear, organized, and successful. It is defined by standard. It includes the message format, message size, timing, and encapsulation.

Standard

is a defined set of rules for how something must be done. In networking, standards ensure:

• Devices use the same protocols

• Information is sent and received in a consistent way

• Different devices (PCs, phones, tablets) can communicate smoothly

Internet Engineering Task Force

Creates and manages internet standards. It publishes RFC. It tracks every stage of a standard’s development.

Requests For Comments

The document that IETF records and publishes the Internet standard.

Ethernet Protocol

Controls communication between network interface cards (NIC‑to‑NIC) on the same local network. Handles how devices send data within a LAN.

Internet Protocol

Moves data from the original source to the final destination, even across multiple networks. Ensures the message reaches the correct address.

Transmission Control Protocol

Ensures data is delivered reliably and in the correct order. Re‑sends missing packets and re‑orders out‑of‑sequence packets.

HyperText Transfer Protocol

Controls the transfer of web content, especially HTML pages. Used when you browse websites.

Layered Model

It help us understand how protocols work together and how each layer interacts with the ones above and below. They make networking easier to design, explain, and upgrade.

4 Layers of TCP/IP Model

1. Application

2. Transport

3. Internet

4. Network Access

Encoding

Data is converted into bits. Bits are encoded as sound, light, or electrical signals depending on the medium. Receiver decodes the signals back into data

Application Layer

In TCP/IP Protocol stack it uses HTTP. This layer handles what the user interacts with (websites, apps, services)

Transport Layer

In TCP/IP Protocol stack it uses TCP. This layer provides reliable delivery, error checking, and correct ordering of data.

Internet Layer

In TCP/IP Protocol stack it uses IP. This layer handles addressing and routing so data reaches the correct destination.

Network Access Layer

In TCP/IP Protocol stack it uses Ethernet. This layer controls how data is sent over the physical network (NIC to network communication).

OSI Model

Created by the ISO (International Organization for Standardization).
Used to describe and troubleshoot network functions. Types of model that is used to explain how network communication works. It shows what must happen at each stage of ANY network communication

7. Application

OSI Layer (Top-Bottom). Process‑to‑process communication. Where applications access network services. PDU: Data

6. Presentation

OSI Layer (Top-Bottom). Ensures a common data format. Handles encryption, compression, translation. PDU: Data

5. Session

OSI Layer (Top-Bottom). Manages dialogues between devices. Opens, maintains, and closes sessions. PDU: Data

4. Transport

OSI Layer (Top-Bottom). Segments, transfers, and reassembles data. Provides end‑to‑end communication. PDU: Segment/Datagram

3. Network

OSI Layer (Top-Bottom). Moves data between end devices. Handles addressing and routing. PDU: Packet

2. Data Link

OSI Layer (Top-Bottom). Moves frames across a shared medium. Handles MAC addressing and error detection. PDU: Frame

1. Physical

OSI Layer (Top-Bottom). Electrical, mechanical, and signaling rules. Sends raw bits over cables, radio, fiber. PDU: Bits

TCP/IP Model

It shows how its own protocols work.