Protocols and Standards

Protocols and Standards

• Protocols are sets of rules governing data communication
• Standards provide models for product development, regardless of the manufacturer

Protocol Architecture

• Protocol architecture consists of layered hardware and software to support data exchange between systems
• It facilitates distributed applications like E-Mail and File Transfer
• Each layer in protocol architecture has a specific set of rules
• TCP/IP and OSI are two widely used protocol architectures

Protocol Key Elements

• Protocols govern data communication by defining: what, when and how data is communicated
• Key elements include: Syntax, Semantics, and Timing

Syntax

• Syntax represents data structure and the order of its presentation
• Data commonly includes sender/receiver addresses, and the message stream

Semantics

• Semantics refers to the meaning of each section within a bit

Timing

• Timing defines when data is sent and its transmission speed such as 100Mbps

Protocol Standards Categories

• De Facto standards are not officially adopted, but are widely used
• De Facto standards are of two types: Proprietary or Non-Proprietary
• Proprietary standards are wholly owned by a company
• Non-Proprietary standards are developed for public use by a group or community
• De Jure standards are legislated by an officially recognized body such as: International Standard Organization, ANSI, and IEEE

The OSI Model

• The Open Systems Interconnection (OSI) model is managed by the International Organization for Standardization (ISO)
• The OSI model covers all aspects of network communications
• An open system allows different systems to communicate, despite their different underlying architectures (hardware or software)
• The OSI model facilitates interoperability, flexibility, and robustness as a network architecture design model, not a protocol
• The OSI model is a seven-layer framework facilitating communication across computer systems

OSI Model Layers

• The seven ordered layers of OSI model are:
  • Layer 1: Physical
  • Layer 2: Data link
  • Layer 3: Network
  • Layer 4: Transport
  • Layer 5: Session
  • Layer 6: Presentation
  • Layer 7: Application

Peer-to-Peer Process

• Within a single machine, each layer uses services from the layer below
• Between machines, corresponding layers (x) communicate using specific protocols, engaging in a peer-to-peer process
• Communication between machines involves peer-to-peer processes with layer-specific protocols

Interfaces between Layers

• Interfaces exist between adjacent layers
• They define which services and information a layer provides to the one above

Functions of Layers: Physical Layer

• The physical layer transmits individual bits from one node to another

The Physical Layer

• The physical layer specifies media characteristics and defines the type of transmission
• It specifies Physical characteristics of interfaces and media
• The physical layer involves representation of bits (stream of 0s and 1s)
• It defines the type of encoding, electrical or optical
• The physical layer defines the data rate
• The physical layer addresses line configuration, connecting devices to the medium
• It specifies physical topology examples: Ring, star etc
• It defines the Transmission Mode, such as: Simplex, Half duplex Full Duplex

Data Link Layer

• The data link layer handles node-to-node delivery of data

Data Link Layer Functions

• Framing: The data link layer divides bit streams from the network layer into frames
• The Physical Addressing function facilitates frame distribution via headers, defining sender/receiver addresses
• For outside-network frames, the receiver address points to the connecting network device
• Flow Control feature manages transmission rates by preventing the receiver from being overwhelmed
• Error Control provides reliability by detecting/retransmitting damaged frames, usually via a trailer
• Access Control protocols determine link control when multiple devices share a link

OSI Model: Postal Mail Analogy

• Sending a letter via postal mail serves as a real-world analogy for the concept of layers in network models
• Higher layers involved with writing the letter, putting it in an envelope, and reading it upon arrival
• Middle layers correspond to the letter being transported between the mailbox and the post office
• Lower layers represent the physical delivery of the letter by a postal carrier

OSI Model History

• Established in 1947, The International Standards Organization (ISO) developed the Open Systems Interconnection (OSI) model
• The OSI model was developed in the late 1970s

OSI Model Notes

• ISO is the organization
• OSI is the model

Physical Layer Note

• The physical layer facilitates the movement of individual bits from one hop (node) to the next

Data Link Layer Note

• The data link layer is responsible for moving frames from one hop (node) to the next

Network Layer Note

• The network layer handles delivery of individual packets from source to destination host

Transport Layer Note

• The transport layer manages delivery of a message from one process to another through Service-point addressing

TCP/IP Protocol Suite

• The TCP/IP protocol suite does not precisely align with the OSI model's layers
• The original TCP/IP suite had four layers: host-to-network, internet, transport, application.
• Compared to OSI, TCP/IP has five layers: physical, data link, network, transport, application

Addressing

• Four address levels using TCP/IP protocols on the internet: physical, logical, port, and specific

Physical Addresses Example

• A node that has physical address 10 sends a frame to node 87
• The two nodes are connected by LAN with a bus topology
• Computer with the physical address 10 is the sender and 87 is the receiver

Local-Area Networks Example

• Most local-area networks use a 48-bit physical address displayed as 12 hexadecimal digits
• Format for each byte (2 hexadecimal digits) is separated by a colon, such as: 07:01:02:01:2C:4B

Paired Addresses Example

• Devices on the internet have many types of addresses
• Figure 2.20 shows a partial internet that has two routers which connect three LANs
• Routers have three pairs of addresses for each connection, while computers have one pair

Port Addresses Example

• Figure of two computers on the Internet shows port addresses a, b, and c. for the sending computer
• Addresses j and k shows the receiving computer
• Process (a) shows the sending computer process that is communicating with process (j)
• Physical addresses change from hop to hop, but the computer logical and port numbers stay the same

Port Address Note

• Addresses change from one hop to another, though ports and logical addresses remain the same

Example 16-bit Port Adress

• A port is address is a 16 bit number represented as decimal
• Example: 753