JB

Network Protocols and Models

Communication Fundamentals

  • Basic Structure: All communication involves a source (sender), a destination (receiver), and a channel or media for the communication path.

  • Essential Elements: Sender, receiver, and communication channel/media are the three most important elements.

Rules and Protocols

  • Governing Rules: Communication is governed by rules, referred to as protocols.

  • Protocol Definition: Protocols are the rules that communication will follow; these rules vary depending on the type of protocol.

  • Human Communication Examples: Nonverbal protocols (e.g., looking at each other, not talking over one another), verbal protocols (e.g., speaking the same language).

  • Message Formatting:- Unformatted: Difficult to read or understand due to lack of punctuation or multiple languages.

    • Formatted: Understandable due to specific structure and punctuation.

  • Formatting Types: De facto rules and structured rules.

  • Protocol Establishment Requirements: A protocol must account for:- Identifying sender and receiver.

    • Establishing a common language and grammar.

    • Defining the speed and timing of delivery.

    • Specifying confirmation or acknowledgment requirements.

    • Including error correction mechanisms, if necessary.

Network Protocol Requirements

  • Common computer protocols must include agreement on:- Message Encoding: The process of converting information into an acceptable format for transmission (sender) and converting it back (decoding) at the receiver.

    • Message Formatting and Encapsulation: Messages must adhere to a specific format or structure, which depends on the media and message type.

    • Message Size: Information is converted to bits (patterns of light, sound, or electric impulses). Large messages can be segmented (divided into chunks) and sent in sequence if the entire message cannot be sent at once.

    • Message Timing:- Flow Control: Manages data transmission rate (how much and at what speed).

      • Response Timeout: Manages how long a device waits for a reply.

      • Access Method: Determines when a device can send a message.

      • Collision Handling: Rules to prevent (proactive) or recover from (reactive) collisions where multiple devices send traffic simultaneously, corrupting messages.

    • Message Delivery Options:- Unicast (1:1): One source to one destination.

      • Multicast (1:Many, not all): One source to a select group of destinations.

      • Broadcast (1:All): One source to all destinations on the network (used in IPv4, not IPv6).

Network Protocols

  • Definition: Defines a common set of rules implemented in hardware, software, or both. Each protocol has its own connection format and rules.

  • Types of Protocols:- Network Communication: Allows devices to communicate over a shared network.

    • Network Security: Secures data, providing authentication (verifying identity), integrity (ensuring data isn't modified), and confidentiality (keeping data secure).

    • Routing: Enables routers to exchange information for path selection.

    • Service Discovery: Automatically detects devices or services on the network.

  • Protocol Functions (Examples):- Addressing: Identifies sender and receiver.

    • Reliability: Provides guaranteed delivery.

    • Flow Control: Ensures data flows at an efficient rate.

    • Sequencing: Uniquely labels each transmitted segment of data.

    • Error Detection: Determines if data is corrupted during transmission.

    • Application Interface: Facilitates process-to-process communication between network applications.

  • Protocol Interaction: Networks use multiple protocols, each with its own function and format.

  • Main Protocols Examples:- HTTP (Hypertext Transfer Protocol): Governs web server/client interaction, defines content format.

    • TCP (Transmission Control Protocol): Manages individual conversations, provides guaranteed delivery, manages flow control.

    • IP (Internet Protocol): Delivers messages globally from sender to receiver.

    • Ethernet: Delivers messages between NICs on the same Ethernet LAN.

Protocol Suites

  • Definition: A group of identified and interrelated protocols necessary for communication functions. Protocols can work independently or as a group.

  • Layered View: Protocols are viewed in terms of layers, such as higher-layer protocols (providing services to upper layers) and lower-layer protocols (concerned with moving data).

  • Several Protocol Suites:- TCP/IP (Internet Protocol Suite): Most common, maintained by IETF (Internet Engineering Task Force).- TCP/IP Layers: Application (HTTP, DNS, DHCP, FTP), Transport (TCP, UDP), Internet (IPv4, IPv6), Network Access (Ethernet, WLAN).

    • OSI (Open Systems Interconnection): Developed by ISO and ITU.

    • AppleTalk: Proprietary suite by Apple Inc.

    • Novell NetWare: Proprietary suite by Novell Inc.

  • TCP/IP Communication Process: Involves encapsulation at the sender (e.g., web server encapsulating a web page) and de-encapsulation at the receiver (e.g., client de-encapsulating for a web browser).

Standard Organizations

  • Open Standards: Encourage interoperability.

  • Internet Standards Organizations:- Internet Society (ISOC): Promotes open development and evolution of the Internet.

    • Internet Architecture Board (IAB): Responsible for managing and developing Internet standards; divides into IETF and IRTF.

    • Internet Engineering Task Force (IETF): Develops, updates, and maintains Internet and TCP/IP technologies.

    • Internet Research Task Force (IRTF): Focuses on long-term research related to the Internet and TCP/IP protocols.

    • ICANN (Internet Corporation for Assigned Names and Numbers): Coordinates IP address allocation, domain name management, and other information assignments.

    • IANA (Internet Assigned Numbers Authority): Oversees IP address allocation, domain name management, and protocol identifiers for ICANN.

  • Electronics and Communication Standards Organizations:- IEEE (Institute of Electrical and Electronics Engineers): Dedicated to creating standards in power, engineering, healthcare, telecommunications, and networking.

    • EIA (Electronic Industries Alliance): Develops standards for electrical wiring, connectors, and network equipment mounting racks.

    • TIA (Telecommunications Industry Association): Develops communication standards in radio equipment, VoIP devices, satellite communication, etc.

    • ITU-T (International Telecommunication Union - Telecommunication Standardization Sector): Defines standards for video compression, IPTV, and broadband communication (e.g., DSL).

Reference Models

  • Benefit of Layered Models: Simplify complex network operations by breaking them down into manageable layers, fostering understanding and collaboration.

  • Two Major Models:- OSI Reference Model: Seven layers (Application, Presentation, Session, Transport, Network, Data Link, Physical).

    • TCP/IP Reference Model: Four layers (Application, Transport, Internet, Network Access).

  • Comparison (OSI vs. TCP/IP):- OSI Application, Presentation, Session Layers map to TCP/IP Application Layer.

    • OSI Transport Layer map to TCP/IP Transport Layer.

    • OSI Network Layer map to TCP/IP Internet Layer.

    • OSI Data Link and Physical Layers map to TCP/IP Network Access Layer.

  • Benefits of Layered Models:- Facilitates protocol design at specific layers with defined interfaces.

    • Enables faster competition by allowing products from different vendors to work together.

    • Prevents technology changes in one layer from affecting others.

    • Provides a common language to describe network connections and capabilities.

  • OSI Model Layer Descriptions:- Application (Layer 7): Protocols for process-to-process communication.

    • Presentation (Layer 6): Provides common data representation between applications.

    • Session (Layer 5): Provides services to the Presentation layer to manage data exchange.

    • Transport (Layer 4): Defines services to segment and transfer data for individual communications.

    • Network (Layer 3): Provides services to exchange individual pieces of data over the network.

    • Data Link (Layer 2): Describes methods for exchanging data frames over common media.

    • Physical (Layer 1): Describes means to activate, maintain, and deactivate physical connections.

  • TCP/IP Model Layer Descriptions:- Application: Represents data to the user, including direct control (corresponds to OSI Layers 5, 6, 7).

    • Transport: Supports communication between various devices across the network (corresponds to OSI Layer 4).

    • Internet: Determines the best path through the network (corresponds to OSI Layer 3).

    • Network Access: Controls hardware devices and media that make up the network (corresponds to OSI Layers 1, 2).

  • Model Differences: OSI model subdivides the Network Access and Application layers of the TCP/IP model. TCP/IP does not specify protocols for physical media, while OSI Layers 1 and 2 detail media access procedures.

Data Encapsulation

  • Segmenting a Message: Process of breaking a message into smaller units.- Benefits: Increased speed (large data sent without tying up a lane), increased efficiency (only failed segments retransmitted).

    • Multiplexing: Interleaving multiple streams of segmented data together.

  • Sequencing: Process of numbering segments so the message can be reassembled correctly at the destination (e.g., TCP handles this).

  • Protocol Data Units (PDUs):- Encapsulation: Process where protocols add their information (headers/trailers) to the data.

    • PDU Naming: At each stage, a PDU has a different name, typically according to the TCP/IP suite:- Data (Application layer)

      • Segment (Transport layer)

      • Packet (Internet layer)

      • Frame (Data Link layer)

      • Bits (Physical layer)

    • Encapsulation Example (Top-Down): Data \rightarrow TCP \rightarrow IP \rightarrow Ethernet (each adds a header).

    • De-encapsulation Example (Bottom-Up): Bits \rightarrow Frame \rightarrow Packet \rightarrow Segment \rightarrow Data (each layer removes its header).

Addressing

  • Layer 3 (Network Layer) Logical Address: IP addresses (source and destination) are responsible for delivering the IP packet from the original source to the final destination.- IP Address Components:- Network Portion (IPv4) / Prefix (IPv6): Leftmost part, indicates network group. All devices on the same LAN/WAN have the same network portion.
    - Host Portion (IPv4) / Interface ID (IPv6): Remaining part, identifies a specific device within the group, unique per device on the network.

    • Example: 192.168.1.10 (network part: 192.168.1, host part: 10).

    • Same Network Devices: Source and destination have the same network portion (e.g., 192.168.1.10 and 192.168.1.9).

  • Layer 2 (Data Link Layer) Physical Address: MAC addresses are physically embedded into the NIC and are local addressing.- Same IP Network: When devices are on the same Ethernet network, the data link frame uses the actual MAC address of the destination NIC.- Source MAC is the originator's NIC.
    - Destination MAC is always on the same link as the source.

    • Remote Network (Different IP Network):- Layer 3 provides Layer 2 with the local default gateway IP address (router's interface IP for the LAN).

      • The default gateway acts as the