Computer Networking Basics

• Computer networking refers to interconnected computing devices that can exchange data.
• The purpose of a network is resource sharing, including files, folders, printers, and disk drives.

Communication Protocols

• Computer networks rely on protocols and standards for seamless communication between devices and systems.
• Successful communication requires agreed-upon rules and procedures at both sending and receiving ends, such as Ethernet and HTTP.
• Network protocols ensure compatibility, reliability, and functionality among different technologies and network components.
• Transmission Control Protocol (TCP) is for wired/guided media.
• User Datagram Protocol (UDP) is for wireless/unguided media.

Network Hardware

• Hubs are unintelligent devices that send one signal to all connected stations and reside on Layer 1 of the OSI model.

• Switches split large networks into smaller segments, reducing user congestion.

• Switches understand device communication needs and provide switched connections and reside on Layer 2 of the OSI model.

• Bridges connect two LANs, forwarding or filtering data packets and reside on Layer 2 of the OSI model.

• Bridges operates transparently to protocols and higher-level devices like routers, basing data forwarding on the MAC address.

• Repeaters boost signals between cable segments or wireless access points and reside on Layer 1 of the OSI model..

• Repeaters do not amplify signals; they regenerate and retime packets.

• Routers connect any number of LANs and reside on Layer 3 of the OSI model.

• Routers use standardized protocols for efficient packet movement and share single IP addresses among multiple network clients.

• Routers forward data based on the Network address (IP), and not the Hardware (MAC) address.

• Network Interface Cards (NICs) put data into packets and transmit the packet onto the network, and may be wired or wireless.

• Gateways connect networks with different protocols such as TCP/IP and IPX/SPX.

• Routers and gateways are often the same thing.

• Proxy servers isolate internal network computers from the Internet.

Network Classification

• Networks are often classified by geographical boundaries, with LAN, WAN, and MAN being common types.
• LANs and WANs are frequently used.

OSI Reference Model

• The OSI Reference Model is an internationally standardized network architecture, specified in ISO 7498.
• The OSI model has 7 layers

OSI Model Layers

• Layer 7 (Application): Network process to application.
• Layer 6 (Presentation): Data representation and encryption.
• Layer 5 (Session): Interhost communication.
• Layer 4 (Transport): End-to-End connections and reliability.
• Layer 3 (Network): Path determination and IP (Logical Addressing).
• Layer 2 (Data Link): MAC and LLC (Physical Addressing).
• Layer 1 (Physical): Media, signal, and digital transmission.

More About Each Layer

• Physical Layer: Transmits bits over a medium with mechanical and electrical specifications, defining voltage, data rates, and converting digital bits to electrical signals.
• Data Link Layer: Synchronizes, controls errors, organizes bits into frames for hop-to-hop delivery and examines device addresses.
• Network Layer: Moves data packets from source to destination for inter-networking, routing signals, and determining the network path.
• Transport Layer: Ensures reliable packet transmission, monitors for errors, and manages data transfer across apps using TCP and UDP.
• Session Layer: Initiates communication links, manages logging, user identification, and billing.
• Presentation Layer: Performs data encryption, compression, and ensures data is in a format that can be understood by the receiving node.
• Application Layer: Provides access to network resources, shares drives and printers, and provides file transfer and management services using protocols like HTTP, FTP, and SMTP.

Network Types

• LAN (Local Area Network): Covers a small local area, is inexpensive, and has higher speeds.

• MAN (Metropolitan Area Network): Spans a city, is more expensive than LANs, and uses high-speed fiber optic connections.

• WAN (Wide Area Network): Connects computers over long distances and relies on telecommunication networks, making it more costly. The Internet is a WAN.

Transmission Media

• The three main types of media used to connect computers in a network: copper cable, fiber optic cable, and wireless.
• Common network media refers to physical and wireless pathways for data transmission. Types of network media impact the speed, distance, cost and reliability of the network.

Twisted Pair Cable

• Twisted Pair Cable consists of pairs of insulated copper wires.
• Unshielded Twisted Pair (UTP) is common in Ethernet networks.
• Shielded Twisted Pair (STP) has additional shielding to reduce interference.

UTP Category

• CAT1: Up to 1Mbps, Twisted Pair, Old Telephone Cable.
• CAT2: Up to 4Mbps, Twisted Pair, Token Ring Networks.
• CAT3: Up to 10Mbps, 100m Twisted Pair, Token Rink & 10BASE-T Ethernet.
• CAT4: Up to 16Mbps, 100m Twisted Pair, Token Ring Networks.
• CAT5: Up to 100Mbps, 100m Twisted Pair, Ethernet, FastEthernet, Token Ring.
• CAT5e: Up to 1 Gbps, 100m Twisted Pair, Ethernet, FastEthernet, Gigabit Ethernet.
• CAT6: Up to 10Gbps, 100m Twisted Pair, GigabitEthernet, 10G Ethernet (55 meters).
• CAT6a: Up to 10Gbps, 100m Twisted Pair, GigabitEthernet, 10G Ethernet (55 meters).
• CAT7: Up to 10Gbps, 100m Twisted Pair, GigabitEthernet, 10G Ethernet (100 meters).

Coaxial Cable

-Coaxial cable is an electrical cable featuring a central conductor, insulation, metallic shield, and an outer insulating layer.

• Coaxial cable is common for transmitting radio frequency (RF), video, and data signals.
• Coaxial cables are tradionally used in cable TV and older Ethernet (e.g., 10BASE2, 10BASE5).

Fiber Optic Cable

• Fiber optic cables use light signals to transmit data through glass or plastic fibers.
• Single-mode fiber (SMF) transmits data over long distances at high speeds.
• Multi-mode fiber (MMF) is used for shorter distances.
• High-speed, long-distance communications, backbones of large networks use fiber optic cables.

Wireless Media

• Wireless Media transmits data over radio waves, microwaves, or infrared signals without physical cables.
• Wi-Fi is used for common wireless technology for LANs.
• Bluetooth is used for short-range wireless communication for devices.
• Cellular networks are used for mobile data transmission (e.g., 4G, 5G).
• Infrared (IR) is used for short-range communication.
• Wireless LANs and personal area networks (PANs) use wireless media.

Satellite Communication

• Satellite communication uses satellites in orbit to transmit signals over long distances.
• Types of satellite communication include internet access in remote locations, broadcasting, and GPS services.
• Network media is chosen by distance, speed, environment.