TCP/IP - Full Notes

📝 Notebook Notes (Quick Review)TCP/IP Model

The TCP/IP Model is the networking model used on the Internet.

Unlike the OSI Model (7 layers), TCP/IP has 4 layers.

🧠 Think:

OSI = Learning Model

TCP/IP = Real World

The 4 Layers

1. Application

  • User applications

  • Web browsing

  • Email

  • DNS

Protocols:

  • HTTP

  • HTTPS

  • FTP

  • SMTP

  • DNS

2. Transport

  • End-to-end communication

  • Reliability

  • Ports

  • TCP & UDP

Protocols:

  • TCP

  • UDP

3. Internet

  • IP addressing

  • Routing

  • Packet forwarding

Protocols:

  • IPv4

  • IPv6

  • ICMP

4. Network Access (Link)

  • Physical network

  • MAC addresses

  • Ethernet

  • Wi-Fi

  • Cables

Technologies:

  • Ethernet (802.3)

  • Wi-Fi (802.11)

TCP/IP vs OSI

TCP/IP

OSI

Application

7,6,5

Transport

4

Internet

3

Network Access

2,1

🧠 Memory Trick

Top = 3 become 1

Middle = Stay the same

Bottom = 2 become 1

⭐ Network+ Must Memorize

  • TCP/IP = 4 Layers

  • Internet uses TCP/IP

  • Application = OSI 7,6,5

  • Transport = OSI 4

  • Internet = OSI 3

  • Network Access = OSI 2,1

  • TCP/IP is the practical networking model

💻 Knowt Notes (Deep Understanding)What is the TCP/IP Model?

The TCP/IP (Transmission Control Protocol/Internet Protocol) Model is the networking model used by the Internet and most modern networks.

Like the OSI Model, it divides networking into layers so that each layer has a specific job.

The main difference is that the TCP/IP Model is simpler.

  • OSI Model = 7 layers

  • TCP/IP Model = 4 layers

The OSI Model is mainly used for learning and troubleshooting, while the TCP/IP Model is the one used in real-world networking.

Exam Tip: CompTIA expects you to know both models and how they relate to each other.

The Four TCP/IP Layers1. Application Layer

The Application Layer is where users and applications interact with the network.

This layer combines the functions of the top three OSI layers:

  • Application

  • Presentation

  • Session

Common responsibilities include:

  • Web browsing

  • Email

  • File transfers

  • Name resolution

Common Protocols

  • HTTP

  • HTTPS

  • FTP

  • SMTP

  • POP3

  • IMAP

  • DNS

  • DHCP

  • SSH

Think:

Everything the user interacts with.

2. Transport Layer

The Transport Layer provides end-to-end communication between devices.

It is responsible for:

  • Segmenting data

  • Reassembling data

  • Reliability

  • Error recovery

  • Port numbers

  • Flow control

The two major protocols are:

TCP

  • Reliable

  • Connection-oriented

  • Error checking

  • Guarantees delivery

UDP

  • Fast

  • Connectionless

  • No delivery guarantee

Think:

TCP = Reliable

UDP = Fast

3. Internet Layer

The Internet Layer is responsible for moving packets between different networks.

Its responsibilities include:

  • Logical addressing (IP addresses)

  • Routing

  • Packet forwarding

Common protocols:

  • IPv4

  • IPv6

  • ICMP

  • IGMP

Think:

IP lives here.

4. Network Access Layer

The Network Access Layer combines the bottom two OSI layers:

  • Data Link

  • Physical

It is responsible for sending data across the physical network.

Responsibilities include:

  • MAC addresses

  • Frames

  • Ethernet

  • Wi-Fi

  • Cables

  • NICs

Common technologies:

  • Ethernet (802.3)

  • Wi-Fi (802.11)

Think:

Actually moves the bits across the wire (or air).

TCP/IP vs OSI Mapping

TCP/IP Layer

OSI Layer(s)

Application

7, 6, 5

Transport

4

Internet

3

Network Access

2, 1

Visual

TCP/IP                     OSI

Application        ←→   7 Application
                        6 Presentation
                        5 Session

Transport          ←→   4 Transport

Internet           ←→   3 Network

Network Access     ←→   2 Data Link
                        1 Physical

Why Do We Have Two Models?

The OSI Model was created as a reference model to standardize networking concepts and make troubleshooting easier.

The TCP/IP Model was developed alongside the Internet protocols and became the model used in real-world networking.

Think:

  • OSI = Learning

  • TCP/IP = Doing

⭐ Network+ Summary

Remember these key facts:

  • ✅ TCP/IP has 4 layers

  • ✅ OSI has 7 layers

  • ✅ TCP/IP is the model used by the Internet

  • ✅ Application = OSI Layers 7–5

  • ✅ Transport = OSI Layer 4

  • ✅ Internet = OSI Layer 3

  • ✅ Network Access = OSI Layers 2–1

  • ✅ TCP = Reliable

  • ✅ UDP = Fast

  • ✅ IP addresses and routing happen at the Internet Layer

  • ✅ Ethernet, Wi-Fi, and MAC addresses are part of the Network Access Layer