Deep-dive

TCP/IP – Deep-dive

Detailed overview of each layer in the TCP/IP model, including types of data, protocols, ports, headers, encapsulation, and interactions between layers.

Animation to explain the initial connection and then data encapsulation

  1. Application Layer: This is the highest layer and it interfaces directly with the applications we use to communicate over the network. This is where high-level protocols like HTTP, FTP, SMTP, DNS, DHCP, etc., operate. In terms of data, this layer deals with application-specific data. For instance, HTTP deals with web page data, SMTP deals with email data, etc.  This layer is responsible for establishing the initial connection with the destination, hence providing source/destination IP address (Via DNS) and ports (using preassigned ports number based on specific application or protocol type) for the next transport layer to start the data transfer using TCP or UDP. For a deeper understanding, you can refer to the following sources:
  2. Transport Layer: This layer is responsible for end-to-end communication over the network. The two most common protocols at this layer are TCP and UDP. This layer deals with segments (TCP) or datagrams (UDP), which are chunks of data packaged for transmission. TCP and UDP use port numbers to distinguish between different services or applications. TCP is connection-oriented and provides reliable transmission with error checking and correction, and flow control. UDP is connectionless, providing faster but less reliable transmission. For a deep dive:
  3. Internet Layer: Also known as the network layer, its main function is to organise and route packets across network boundaries, enabling data to be transmitted across networks from source to destination. The most important protocol at this layer is the Internet Protocol (IP), and data at this layer is referred to as packets. This layer handles the IP addressing and routing of packets based on their destination IP address. For a detailed exploration:
  4. Network Access Layer: This is the lowest layer, also known as the link layer or network interface layer. It’s responsible for data transmission of a packet between two devices on the same network. It covers protocols like Ethernet for wired connections and Wi-Fi for wireless connections. The data at this layer is called frames. For more information, consider:

Encapsulation: When data moves from the higher layers to the lower layers, it is encapsulated, meaning that each layer adds its own headers (and in some cases trailers) to the data. For example, the application layer’s HTTP data is encapsulated in a TCP segment, which is then encapsulated in an IP packet, which is finally encapsulated in a link layer frame.

Headers: Each layer adds its own header information to the data unit during the encapsulation process, such as source and destination IP addresses at the Internet Layer, source and destination ports at the Transport Layer, etc.

Layers interaction: Each layer in the model communicates with its peer layer on the receiving end. For example, the Transport Layer at the source communicates with the Transport Layer at the destination. In terms of communication with each other, typically, each layer in the TCP/IP model interacts directly only with the layer above it and the layer below it. However, this can vary based on the specific implementation and system design.

OSI Model – Deep-dive

Layer 7 – Application 

Protocols and Services:

The Application layer encompasses protocols and services like HTTP (Hypertext Transfer Protocol), which defines the rules and procedures for communication between web browsers and web servers. You can refer to the HTTP specification provided by the World Wide Web Consortium (W3C) for more details: W3C – HTTP Specification

Data Formatting:

The Application layer handles data formatting and presentation, such as encryption. An example is the Transport Layer Security (TLS) protocol, which provides secure communication over the internet. The TLS specification can be found in RFC 8446: IETF – TLS 1.3 Specification

Application-Specific Functionality:

An example of application-specific functionality is the Simple Mail Transfer Protocol (SMTP), which enables the transmission of emails between mail servers. The SMTP protocol is defined in RFC 5321: IETF – SMTP Specification

User Interface:

The Application layer provides user interfaces like the Graphical User Interface (GUI) of a web browser. For example, you can refer to the documentation and specifications of popular web browsers like Mozilla Firefox: Mozilla Developer Network

Network Virtual Terminal:

Telnet is an example of a protocol used to create a Network Virtual Terminal (NVT). Telnet allows a user to establish a virtual terminal session with a remote host over a network. You can find more information about Telnet in RFC 854: IETF – Telnet Specification

Network Services:

An example of a network service is the Lightweight Directory Access Protocol (LDAP), which provides directory services for organizing and accessing distributed information. The LDAP protocol is defined in RFC 4511: IETF – LDAP Specification

Interoperability:

The Hypertext Transfer Protocol (HTTP) is an example of a protocol that ensures interoperability by allowing web browsers and web servers developed by different vendors to communicate. The HTTP specification can be found in RFC 7230: IETF – HTTP/1.1 Specification

Application Layer Gateways:

An example of an Application Layer Gateway (ALG) is the Network Address Translation (NAT) ALG, which performs address translation for applications using protocols like FTP (File Transfer Protocol). For more information on NAT ALG, you can refer to the Cisco documentation: https://technebo.com/application-layer-protocols-deep-dive/‎

Layer 6 – Presentation

“Computer Networks: A Systems Approach” – This comprehensive textbook by Larry Peterson and Bruce Davie provides in-depth coverage of networking concepts, including the Presentation Layer. You can find more information on the book here: Computer Networks: A Systems Approach

“ISO/IEC 8822: Open Systems Interconnection – Connection-Oriented Presentation Protocol Specification” – This ISO/IEC standard document provides detailed information about the Connection-Oriented Presentation Protocol at the Presentation Layer. You can access it through your institutional library or ISO’s official website.

“RFC 2045: Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies” – This RFC specification defines the MIME standard, which is widely used for email data formatting at the Presentation Layer. You can read the document here: RFC 2045

“RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2” – This RFC document explains the TLS protocol, which operates at the Presentation Layer and provides encryption and data integrity for secure communication. You can access the document here: RFC 5246

Exploring these resources will provide you with a deeper understanding of the technical aspects, protocols, and mechanisms associated with the Presentation Layer in the OSI model.

Layer 5 – Session

“Computer Networks: A Systems Approach” – This comprehensive textbook by Larry Peterson and Bruce Davie covers networking concepts, including the Session Layer. It provides detailed explanations and examples related to session management, synchronisation, and recovery. You can find more information on the book here: Computer Networks: A Systems Approach

“RFC 1001: Protocol Standard for a NetBIOS Service on a TCP/UDP Transport: Concepts and Methods” – This RFC specification explains the NetBIOS Session Protocol, which operates at the Session Layer. It covers the concepts and methods for establishing and managing sessions using NetBIOS. You can access the document here: RFC 1001

“RFC 1002: Protocol Standard for a NetBIOS Service on a TCP/UDP Transport: Detailed Specifications” – This RFC document provides detailed specifications for the NetBIOS Session Protocol at the Session Layer. It delves into the message formats and procedures used in NetBIOS sessions. You can access the document here: RFC 1002

Exploring these resources will provide you with a deeper understanding of the technical aspects, protocols, and mechanisms associated with the Session Layer in the OSI model.

Layer 4 – Transport

Computer Networking: A Top-Down Approach” – This widely used textbook by James F. Kurose and Keith W. Ross provides detailed coverage of networking concepts, including the Transport Layer. It offers explanations, examples, and illustrations to understand the mechanisms and protocols used at this layer. You can find more information on the book here: Computer Networking: A Top-Down Approach

“RFC 793: Transmission Control Protocol” – This RFC specification defines the TCP protocol, which operates at the Transport Layer. It covers the reliable, connection-oriented delivery of data, including concepts like sliding window flow control and error detection and recovery. You can access the document here: RFC 793

“RFC 768: User Datagram Protocol” – This RFC document explains the UDP protocol, which operates at the Transport Layer and provides a connectionless, unreliable data transfer mechanism. It describes the format and behavior of UDP packets. You can access the document.

here: RFC 768

“RFC 4960: Stream Control Transmission Protocol” – This RFC specification introduces the SCTP protocol, which provides reliable, message-oriented transport with support for multihoming and fault tolerance. It details the features and behavior of SCTP at the Transport Layer. You can access the document here: RFC 4960

Exploring these resources will provide you with a deeper understanding of the technical aspects, protocols, and mechanisms associated with the Transport Layer in the OSI model.

Layer 3 – Network

“Computer Networks: A Systems Approach” – This comprehensive textbook by Larry Peterson and Bruce Davie covers networking concepts, including the Network Layer. It provides detailed explanations and examples related to addressing, routing algorithms, and protocols at this layer. You can find more information on the book here: Computer Networks: A Systems Approach

“RFC 791: Internet Protocol” – This RFC specification defines the Internet Protocol (IP), which is a fundamental protocol of the Network Layer. It covers the format of IP packets, addressing schemes, and packet forwarding. You can access the document here: RFC 791

“RFC 792: Internet Control Message Protocol” – This RFC document explains the Internet Control Message Protocol (ICMP), which operates at the Network Layer. It defines the messages used for network troubleshooting, error reporting, and other control functions. You can access the document here: RFC 792

“RFC 2328: OSPF Version 2” – This RFC specification describes the OSPF (Open Shortest Path First) routing protocol, which operates at the Network Layer. It provides a link-state routing algorithm used in many large-scale networks. You can access the document here: RFC 2328

Exploring these resources will provide you with a deeper understanding of the technical aspects, protocols, and mechanisms associated with the Network Layer in the OSI model.

Layer 2 –  Data Link

For further study on the Data Link Layer, you can refer to the following reliable sources:

“Computer Networks: A Systems Approach” – This widely used textbook by Larry Peterson and Bruce Davie covers networking concepts, including the Data Link Layer. It provides detailed explanations and examples related to framing, error detection, and protocols at this layer. You can find more information on the book here: Computer Networks: A Systems Approach

“IEEE 802 Standards” – The Institute of Electrical and Electronics Engineers (IEEE) maintains a series of standards for various network technologies. This link provides access to the IEEE 802 standards, including those related to Ethernet (IEEE 802.3) and Wi-Fi (IEEE 802.11): IEEE 802 Standards

“RFC 1662: PPP in HDLC-like Framing” – This RFC specification describes the Point-to-Point Protocol (PPP), which operates at the Data Link Layer. It outlines the framing, encapsulation, and control procedures used in PPP for point-to-point connections. You can access the document here: RFC 1662

“802.11 Wireless Networks: The Definitive Guide” – This book by Matthew Gast provides in-depth coverage of the Wi-Fi technology and the IEEE 802.11 standards, which operate at the Data Link Layer. It covers various aspects of wireless networks, including frame formats, access methods, and security mechanisms. You can find more information on the book here: 802.11 Wireless Networks: The Definitive Guide

Exploring these resources will provide you with a deeper understanding of the technical aspects, protocols, and mechanisms associated with the Data Link Layer in the OSI model.

Layer 1 – Physical Layer

“Computer Networks: A Systems Approach” – This widely-used textbook by Larry Peterson and Bruce Davie covers networking concepts, including the Physical Layer. It provides detailed explanations and examples related to various aspects of physical media, signaling, and transmission techniques. You can find more information on the book here: Computer Networks: A Systems Approach

“IEEE 802 Standards” – The Institute of Electrical and Electronics Engineers (IEEE) maintains a series of standards for various network technologies. This link provides access to the IEEE 802 standards, including those related to Ethernet physical standards: IEEE 802 Standards

“Optical Fiber Communication” – This book by Gerd Keiser provides in-depth coverage of optical fiber communication, which is a significant aspect of the Physical Layer. It covers topics such as fiber types, propagation, and modulation techniques used in optical communication systems. You can find more information on the book here: Optical Fiber Communication

“Physical Layer Protocols” – This page from the GeeksforGeeks website provides an overview of physical layer protocols, including their functions and examples. It can be a useful starting point for understanding the protocols used at the Physical Layer: Physical Layer Protocols