Standards

Chapter 1: Introduction to Data Communication -​ Standards = accepted rules and guidelines for ensuring compatible data transfer.
-​ Two types:
-​ Data = processed and stored information (usually in digital form). -​ Proprietary (Closed): Made and controlled by one company.
-​ Data communication = transferring digital information between two or more -​ Open: Any company can use or make compatible products (sometimes
points. with a fee).
-​ The main goal is to transmit, receive, and process digital data. -​ Example: IBM’s PC is an open system standard.​

2. History of Data Communications

-​ Early methods: Smoke signals and drums (not digital or binary)

-​ 1753: Idea of 26 parallel wires
-​ 1832: Samuel Morse ( the telegraph and Morse Code.) ​
-​ 1874: Emile Baudot made a multiplexer (sent multiple signals over one wire).
-​ 1875: Alexander Graham Bell invented the telephone.
-​ 1899: Marconi sent wireless telegraph messages via radio.
-​ 1920: First commercial voice radio stations.
-​ Modern era: Internet, intranets, and the WWW have created huge demand for
faster and better data communication.

3. Data Communications Network Architecture, Protocols, and Standards

Network Architecture

-​ A data communications network = system of computers/devices that send and

receive information.
-​ Architecture defines how the network is arranged and how components interact.
-​ Includes layers (electrical, hardware, software responsibilities).
-​ Two basic types:
-​ Broadcast: One message is shared with all devices (with options like
broadcasting or multicasting).
-​ Point-to-point: Direct connection between two devices.

Protocols

-​ Protocols = rules for how data is exchanged.

-​ Define communication processes (like customs or formal rules).
-​ A protocol stack = list of protocols used (one per layer).
-​ Two main types:
-​ Connection-oriented: A logical connection is made before data transfer
(like a virtual circuit)
-​ Connectionless: Data is sent without prior setup (like a datagram).
CHAPTER 2 REVIEWER: Organizations, OSI & Data Circuits 1 Physical (PHY) Raw bit transmission (cables, signals)

Standard Organizations for Data Communication

Data Communication Circuit Components
●​ ISO – International Organization for Standardization: Global IT standard
●​ Source – Where data originates (PC, terminal).
○​ Creates international standards (e.g., OSI model).
●​ Transmitter – Converts data to signal form.
●​ ITU-T – International Telecommunication Union – Telecom Sector
●​ Transmission Medium – Carries the signal (e.g., copper wire, fiber, air).
○​ UN body for telecom standards (e.g., signaling, TV, network
●​ Receiver – Converts signal back to data.
performance).
●​ Destination – Final target of data (PC, server).
●​ IEEE – Institute of Electrical and Electronics Engineers:
●​ Station/Node – Any endpoint device in the network.
○​ Tech standards (e.g., LAN, Wi-Fi).
●​ ANSI – American National Standards Institute: U.S. official rep to ISO;
○​ sets national standards.
●​ EIA – Electronics Industries Association:
○​ Hardware interface standards (e.g., RS-232).
●​ TIA – Telecommunications Industry Association:
○​ Develops telecom & IT standards.
●​ IAB – Internet Architecture Board:
○​ Oversees Internet protocols & architecture.
●​ IETF – Internet Engineering Task Force:
○​ Builds Internet protocols (e.g., TCP/IP).
●​ IRTF – Internet Research Task Force:
○​ Researches future Internet technologies.

OSI Model

-​ Mnemonic (Top to Bottom): All People Seem To Need Data Processing

Layer Name Function

7 Application (APL) User-level services (HTTP, FTP, email)

6 Presentation (PRS) Data format, encryption, translation

5 Session (SES) Manages sessions (logins, connections)

4 Transport (TRN) Reliable delivery (TCP/UDP)

3 Network (NET) Routing and addressing (IP, routers)

2 Data Link (DLL) Framing, error detection (MAC, switches)

CHAPTER 3 Network Basics, Topologies, and Models ●​ NIC (Network Interface Card):
○​ Sends/receives data
○​ Controls network data flow
Key Network Considerations
●​ LOS (Local OS):
○​ Manages local files/devices on a personal PC
1.​ Network goals (set by management)
●​ NOS (Network OS):
2.​ Security
○​ Allows networked devices to communicate
3.​ Uptime
○​ Manages file sharing, printing, security​
4.​ Response time
5.​ Cost (network + resources)
Network Models

🔹Peer-to-Peer:
Servers & Clients
-​ All computers share their resources equally
🔹Servers: -​ No dedicated server

●​ Store files, programs, and NOS (Network Operating System 🔹Client/Server:

●​ Provide shared resources (virtual disks, files, printers)
●​ File servers manage user access & rights ●​ Server provides services; clients request them
●​
●​
Use file mapping to simulate local access
Security systems protect access 🔹Dedicated Client/Server:
🔹Clients: ●​
●​
One or more devices are assigned as full-time servers
Clients do not act as servers
●​ User computers that request and use network services
●​ Rely on servers for files, printers, and other resources
Network Topologies

Transmission Media 🔹Point-to-Point - Connects exactly two devices directly

●​ Connects computers in a network 🔹Multipoint - Connects 3 or more devices on one medium
●​
●​
Examples: Twisted-pair, coaxial, fiber optics, wireless
Also called: channels, links, or lines
🔹Star - All devices connected to a central hub
Shared Resources
🔹But - One communication line shared by all devices
🔹Ring - Devices connected in a closed loop
●​ Shared Data: Files, email, printer access
●​ Peripherals: Printers, storage, software 🔹Mesh-Every device connects directly to every other device
●​ Provided by servers, used by clients
🔹Hybrid - Combination of two or more topologies
NIC & Operating Systems
Types of Networks

🔹LAN (Local Area Network):

●​ Covers: small area (room/building)
●​ Speed: 10–100 Mbps

🔹MAN (Metropolitan Area Network):

●​ Covers: city-sized area
●​ Speed: 1.5–10 Mbps

🔹WAN (Wide Area Network):

●​ Covers: nationwide or continental
●​ Speed: 1.5 Mbps–2.4 Gbps

🔹GAN (Global Area Network):

●​ Covers: entire globe
●​ Speed: 1.5 Mbps–100 Gbps
CHAPTER 5: 🔹 FEC
●​ Adds redundant bits before sending
Error Detection ●​ Corrects error without needing retransmission​

-​ Detects when errors occur during data transmission (does not correct or locate
the error).
🔹 Hamming Code (a type of FEC)
-​ Redundancy Checking – Duplicates data to detect errors (costly with long
●​ Corrects single-bit errors only
messages)
●​ Requires extra overhead (error bits)​

🔹 VRC (Vertical Redundancy Check / Parity) Hamming bits inserted at agreed locations between sender and receiver​
Combines data + error bits = Hamming code

●​ Adds a parity bit per character

●​ Detects single-bit errors per character

🔹 Checksum
●​ Assigns numeric values to characters
●​ Adds them to form a simple checksum

🔹 LRC (Longitudinal Redundancy Check)

●​ Adds parity bits across multiple characters
●​ Also called message parity

🔹 CRC (Cyclic Redundancy Check)

●​ Uses polynomial division (convolutional code)
●​ Highly reliable (99.999% detection rate)

Error Correction

Two methods:

1.​ ARQ (Automatic Repeat Request) – Retransmits on error

2.​ FEC (Forward Error Correction) – Corrects error on the spot using extra bits

🔹 ARQ Types
●​ Discrete ARQ – Uses positive/negative acknowledgments
●​ Continuous ARQ – Sends blocks of data without waiting, uses sequential
numbering