IT Essentials Lecture 6: Networking Concepts (Part II)
Networking Protocols, Standards, and Services
Reference Models
Reference models, such as the OSI and TCP/IP models, describe data communication processes.
Open Standards:
- Developed by organizations like IEEE, IETF, and ISO.
- Ensure compatibility across systems and platforms.
Encapsulation:
- As application data moves down through layers, protocol information is added (headers, footers, etc.).
TCP/IP Model
TCP/IP stands for Transmission Control Protocol/Internet Protocol.
- Purpose:
- Framework for the Internet's protocols.
- Organizes networking tasks into layers.
- Layers prepare data for network transmission.
Layers:
| Layer | Description | Protocols |
|---|---|---|
| Application | Provides network services to user applications | HTTP, HTML, Telnet, FTP, TFTP, SMTP, DNS |
| Transport | End-to-end data management and segmentation | TCP, UDP |
| Internet | Provides host connectivity, routing, and IP addressing | IP, ICMP, RIP, ARP |
| Network Access | Handles MAC addressing and physical transmission | Ethernet, Wi-Fi, PPP |
OSI Model
OSI Stand for Open Systems Interconnection.
Purpose:
- Divides network communications into seven layers.
- Used as a standard framework by most network vendors.
- Combines hardware (lower layers) and software (higher layers) implementations.
Protocol Stack:
- Can be implemented in hardware, software, or both.
- Lower layers often in hardware; higher layers in software.
Real-World Example (Email Transmission)
- Application Layer: Email client uses SMTP to send an email.
- Presentation Layer: Formats email data to be usable by the Application layer and ensures proper encryption, and compression of data.
- Session Layer: Establishes a session between sender and recipient.
- Transport Layer: Divides data into segments; ensures reliability via TCP.
- Network Layer: Routes data across networks using IP.
- Data Link Layer: Frames data with MAC addresses for local delivery.
- Physical Layer: Transmits data as electrical signals or Wi-Fi.
Layers:
| No. | Layer | Description | Protocols |
|---|---|---|---|
| 7 | Application | Provides network services to users or applications. | HTTP, FTP, SMTP, DNS, POP3, IMAP |
| 6 | Presentation | Translates data into a format usable by the Application layer (e.g., encryption, compression). | SSL/TLS, JPEG, MPEG, ASCII, EBCDIC |
| 5 | Session | Manages communication sessions between applications. | NetBIOS, RPC, PPTP |
| 4 | Transport | Ensures reliable data transfer with error correction and flow control. | TCP, UDP |
| 3 | Network | Handles logical addressing and routing of data packets across networks. | IP, ICMP, OSPF, RIP, ARP |
| 2 | Data Link | Manages physical addressing (MAC), error detection and prepares data for transmission. | Ethernet, Wi-Fi (802.11), PPP, MAC |
| 1 | Physical | Defines physical transmission medium and data encoding. | Cables, hubs, repeaters, voltage levels |
Comparison: OSI vs. TCP/IP Models
| Feature | OSI Model | TCP/IP Model |
|---|---|---|
| Layers | 7 Layers | 4 Layers |
| Application Layer Mapping | Separate Presentation and Session | Combined in Application layer |
| Use in Networking | Theoretical framework | Practical model |
Encapsulation Process
Definition:
Encapsulation involves wrapping data with protocol-specific headers and footers to prepare it for transmission.
- Steps:
- Data: Original information from the application.
- Segments: Data divided and prepared by Transport layer.
- Packets: Segments are assigned IP addressing by Network layer.
- Frames: Packets framed with MAC addresses by Data Link layer.
- Bits: Data transmitted as raw signals (binary) via Physical layer.
TCP vs. UDP Protocols
TCP (Transmission Control Protocol)
- Features:
- Reliable, ensures data integrity.
- Acknowledges received data.
- Resends unacknowledged data.
- Maintains data sequencing.
UDP (User Datagram Protocol)
- Features:
- Unreliable, best-effort delivery.
- No acknowledgments or retransmissions.
- Fast, low overhead.
- Delivers data as it arrives.
| Feature | TCP | UDP |
|---|---|---|
| Reliability | Reliable; acknowledges data. | Unreliable; no acknowledgments. |
| Overhead | Higher; ensures data integrity. | Lower; fast, lightweight. |
| Use Case | Email, file transfer, web browsing. | Streaming, gaming, voice calls. |
| Data Sequencing | Data delivered in order. | No guarantee of order. |
Application Port Numbers
PCs use source port numbers to track the data flow of different applications. Ports classify communication for specific protocols and services.
World Wide Web Protocols
| Port | Transport Protocol | Application Protocol | Description |
|---|---|---|---|
| 53 | TCP, UDP | DNS | Finds IP addresses associated with Internet domains. UDP is used for requests; TCP handles responses if required. |
| 80 | TCP | HTTP | Provides rules for exchanging text, images, videos, and multimedia files on the web. |
| 443 | TCP, UDP | HTTPS | Secure version of HTTP, using encryption and authentication for browser-server communication. |
Email and Identity Management Protocols
| Port | Transport Protocol | Application Protocol | Description |
|---|---|---|---|
| 25 | TCP | SMTP | Sends emails from clients to servers or relays messages between servers. |
| 110 | TCP | POP3 | Retrieves emails from servers, downloading them to the client. |
| 143 | TCP | IMAP | Retrieves emails from servers, with advanced features like folder management and synchronization. |
| 389 | TCP, UDP | LDAP | Maintains directory information for user identities and authenticates users across systems. |
Remote Access Protocols
| Port | Transport Protocol | Application Protocol | Description |
|---|---|---|---|
| 22 | TCP | SSH | Securely accesses remote systems, encrypting data and authentication. Preferred over Telnet for security. |
| 23 | TCP | Telnet | Provides an insecure command-line interface on remote systems. Use SSH instead. |
| 3389 | TCP, UDP | RDP | Enables graphical remote desktop access, primarily for Windows systems. Requires caution due to full remote control. |
File Transport and Management Protocols
| Port | Transport Protocol | Application Protocol | Description |
|---|---|---|---|
| 20 | TCP | FTP | Transfers files between computers. SFTP (port 22) is preferred for secure transfers. |
| 21 | TCP | FTP | Establishes connections for FTP sessions. |
| 69 | UDP | TFTP | A lightweight protocol with less overhead than FTP, for simpler file transfers. |
| 445 | TCP | SMB/CIFS | Allows sharing files, printers, and resources on a network. |
| 548 | TCP, UDP | AFP | A proprietary protocol by Apple for file services in macOS and classic Mac OS environments. |
Network Operations Protocols
| Port | Transport Protocol | Application Protocol | Description |
|---|---|---|---|
| 67/68 | UDP | DHCP | Dynamically assigns IP addresses. The server uses port 67, and the client uses port 68. |
| 137-139 | UDP, TCP | NetBIOS (NetBT) | Facilitates communication for older applications over TCP/IP. Each function within NetBIOS uses a specific port in this range. |
| 161/162 | UDP | SNMP | Monitors network devices and operations using centralized management stations. |
| 427 | UDP, TCP | SLP | Discovers services on a local network without manual configuration. |
Standards Organizations
Several organizations develop and maintain standards for networking and communication technologies.
| Organization | Name | Type | Standards | Established |
|---|---|---|---|---|
| ITU-T | ITU Telecommunication Standardization Sector (formerly CCITT) | Sector of the International Telecommunication Union | Standards covering all fields of telecommunications | 1992 |
| IEEE | Institute of Electrical and Electronics Engineers | Non-profit technical professional association | Standards for the computer and electronics industry | 1884 |
| ISO | International Organization for Standardization | Network of national standards institutes | Promotes international standards agreements | 1947 |
| IAB | Internet Architecture Board | Committee and advisory body | Oversees the technical and engineering development of the Internet | 1979 (formerly ICCB) |
| IEC | International Electrotechnical Commission | Global organization | Standards for electrical, electronic, and related technologies | 1906 |
| ANSI | American National Standards Institute | Private non-profit organization | Seeks to establish consensus among groups | 1918 |
| TIA/EIA | Telecommunications Industry Association / Electronic Industries Alliance | Trade associations | Standards for voice and data wiring for LANs | Post-1984 deregulation of the U.S. telephone industry |
Ethernet Standards
Ethernet Protocols
- IEEE 802.3 specifies that networks implement Carrier Sense Multiple Access with Collision Detection (CSMA/CD).
- End stations "listen" to the wire and transmit data when the network is clear.
- Collisions may occur during simultaneous transmissions.
Media Types and Transfer Rates
| Ethernet Standard | Media | Transfer Rates |
|---|---|---|
| 10BASE-T | Category 3 | Transfers data at 10 Mb/s. |
| 100BASE-TX | Category 5 | Ten times faster than 10BASE-T with 100 Mb/s transfer rates. |
| 1000BASE-T | Category 5e, 6 | Supports data transfer rates of 1 Gb/s. |
| 10GBASE-T | Category 6a, 7 | Achieves transfer rates of 10 Gb/s. |
Wireless Standards
WLAN Standards (IEEE 802.11)
- CSMA/CA is used to prevent collisions on wireless LANs.
- Encryption is critical; WPA2 has been the strongest encryption since 2006.
Wireless Ethernet Standards:
| Standard | Bandwidth | Frequency | Range | Compatibility |
|---|---|---|---|---|
| 802.11a | Up to 54 Mbps | 5 GHz band | 100 feet (30 meters) | Not compatible with 802.11b, 802.11g, or 802.11n. |
| 802.11b | Up to 11 Mbps | 2.4 GHz band | 100 feet (30 meters) | Compatible with 802.11g. |
| 802.11g | Up to 54 Mbps | 2.4 GHz band | 100 feet (30 meters) | Compatible with 802.11b. |
| 802.11n | Up to 540 Mbps | 5 GHz, 2.4 GHz | 164 feet (50 meters) | Compatible with 802.11b and 802.11g. |
| 802.11ac | Up to 1.3 Gbps | 5 GHz band | 115 feet (35 meters) | Compatible with 802.11a and 802.11n. |
| 802.15.1 Bluetooth | Up to 2 Mbps | 2.4 GHz or 5 GHz | 30 feet (10 meters) | Not compatible with any other 802.11 |
Bluetooth, NFC, RFID, Zigbee, and Z-Wave
- Bluetooth (802.15.1): Used for PANs, operating in the 2.4-2.485 GHz range with up to 7 devices.
- RFID:
- Tags can be passive (activated by readers) or active (battery-powered, range up to 100 meters).
- Operates at 125 MHz to 960 MHz.
- NFC: Close-range communication for payments, printing, and parking.
- Zigbee (802.15.4): Mesh networks, supporting up to 65,000 devices with speeds up to 250 kb/s.
- Z-Wave: Proprietary but widely used for smart homes, supporting 232 devices with speeds up to 100 kb/s.
Cellular Generations
| Generation | Features | Speeds |
|---|---|---|
| 1G/2G | Analog calls (1G); digital voice, caller ID, conference calls (2G). | <9.6 Kb/s |
| 2.5G | Supports web browsing, audio, and video clips. | Up to 237 Kb/s |
| 3G | Streaming music and video. | Up to 2 Mb/s |
| 4G | IPv6, gaming, and high-quality multimedia. | Up to 672 Mb/s |
| LTE | Enhanced 4G connectivity; mobile speeds up to 100 Mb/s, stationary up to 1 Gb/s. | 100 Mb/s (mobile); 1 Gb/s (static) |
| 5G | AR/VR support, IoT, smart homes, and cars. | Up to 3 Gb/s (download), 1.5 Gb/s (upload) |
Server Types and Roles
| Server Type | Description |
|---|---|
| DHCP Server | Provides IP addressing information to network hosts. |
| DNS Server | Translates domain names (e.g., example.com) to IP addresses. |
| Print Server | Manages printers and print jobs for multiple clients. |
| File Server | Stores and shares files using protocols like FTP, SFTP, and SCP. |
| Web Server | Serves web pages using HTTP (port 80) and HTTPS (port 443). |
| Mail Server | Handles email storage and communication using SMTP, POP, and IMAP. |
| Proxy Server | Acts on behalf of clients, caching frequently accessed web pages. |
| Authentication Server | Provides Authentication, Authorization, and Accounting (AAA) for network access. |
| Syslog Server | Collects and stores log messages from network devices for monitoring and analysis. |
Network Topologies
Types of LAN Topologies
Physical Topology
- Defines the physical layout of network components.
Logical Topology
- Determines how hosts access the medium for communication.
Logical Topologies
- Broadcast Topology:
- Hosts broadcast messages to all hosts on the same network segment.
- No specific transmission order; messages sent on a FIFO basis.
- Used in Ethernet networks.
- Token Passing:
- Network access controlled by sequentially passing a token.
- Only the host with the token can transmit data.
LAN Physical Topologies
- Bus:
- A single central cable connects all devices.
- Only one device transmits at a time; collisions destroy frames.
- Ring:
- Hosts connected in a circular pattern; uses tokens for data transmission.
- Each device connects to two others
- Variants: Single-ring and Dual-ring.
- Star:
- Central connection point (hub, switch, or router).
- Simplifies troubleshooting; independent connections for each device.
- Hierarchical (Extended Star):
- Additional devices extend a star topology to support larger networks.
- Mesh:
- Every device is connected to all (full) or to multiple devices (partial)
- High reliability; used in WANs and high-availability systems.
- Hybrid:
- Combines two or more topologies, such as star-bus or star-ring.
Comparison Table: LAN Physical Topologies
| Topology Type | Structure | Reliability | Scalability | Cost | Use Cases |
|---|---|---|---|---|---|
| Bus | Single central cable for all devices | Low; cable break disrupts all | Limited; degrades easily | Low | Small/temporary networks |
| Star | Central hub/switch for all nodes | High; central device failure | Easy to expand | Moderate | Home, office LANs |
| Ring | Circular sequence | Moderate; dual-ring improves | Moderate; complex changes | Moderate | Older LANs, token ring networks |
| Mesh | Fully/partially connected devices | Very high; redundant paths | High | High | Military, hospitals, critical WANs |
| Hybrid | Combination of topologies | Depends on design | Flexible | Varies | Diverse environments |
Types of Networks
- LAN (Local Area Network): Connects devices in a limited area (home/office).
- WLAN (Wireless LAN): Wireless connection via access points; copper cabling connects access points.
- VLAN (Virtual LAN): Logical network segmentation for management, security, and performance.
- PAN (Personal Area Network): Connects personal devices (e.g., Bluetooth for keyboards, phones, etc.).
- MAN (Metropolitan Area Network): Covers a campus or city, using wireless or fiber backbones.
- WAN (Wide Area Network): Interconnects smaller networks (e.g., the Internet).
Network Architectures
Peer-to-Peer (P2P) Networks
- Decentralized; each device acts as both client and server.
- No centralized administration; all peers manage their own resources.
- Limited scalability; performance decreases as peers increase.
- Low setup cost; no need for expensive servers.
- Less secure; each device is responsible for its own security.
- Less reliable; if a peer goes offline, its resources are unavailable.
- Slower as the network grows; depends on peer resources.
- Easier maintainance; no central device to manage.
- Used in file-sharing networks (e.g., BitTorrent).
- Data storage is distributed across peers.
Client-Server Networks
- Centralized server manages resources and security.
- Centralized control by the server.
- Higher setup cost due to the need for dedicated servers.
- Highly scalable; servers can handle many clients.
- More secure; centralized measures can be implemented.
- More reliable; servers provide consistent availability.
- Faster; optimized server hardware ensures efficiency.
- Data storage is centralized on the server; clients access shared data.
- Requires skilled admins to manage servers.
- Used in large networks (e.g., corporate systems, web apps).
- Examples include: Websites, enterprise systems (e.g., Google Drive).
Peer-to-Peer vs. Client-Server Comparison
| Feature | Peer-to-Peer | Client-Server |
|---|---|---|
| Architecture | Decentralized | Centralized |
| Control | No central control | Centralized |
| Cost | Low setup cost | High setup cost |
| Scalability | Limited | Highly scalable |
| Security | Less secure | More secure |
| Reliability | Less reliable | More reliable |
| Performance | Slower as peers grow | Faster with optimized hardware |
| Use Case | Small networks (file-sharing) | Large corporate networks |
Bandwidth and Latency
Bandwidth: Data transmitted per second, measured in:
- bps: Bits per second.
- Kbps: Kilobits per second.
- Mbps: Megabits per second.
- Gbps: Gigabits per second.
Latency: Time for data to travel from source to destination.
Transmission Modes
| Mode | Description | Example |
|---|---|---|
| Simplex | One-way transmission only | Radio broadcast |
| Half-Duplex | Bidirectional, one direction at a time | Walkie-talkies |
| Full-Duplex | Simultaneous bidirectional data flow | Telephone call |