Understanding Network Fundamentals: Cables, Protocols, and Security

Posted on Aug 14, 2024 in Computers

Network Cable Characteristics

Impedance (Z)

Resistance to electron movement in AC circuits, measured in ohms (Ω).

Attenuation

Signal degradation over distance, measured in dB/m.

Capacitance (C)

Energy storage capacity, measured in picofarads (pF).

Cable Types and Materials

Twisted Pair Cable

Consists of four twisted wire pairs to reduce crosstalk and noise. Types include:

  • UTP (Unshielded Twisted Pair): Most popular, flexible, and cost-effective.
  • STP (Shielded Twisted Pair): Better noise protection, used for longer distances.

Coaxial Cable

Comprises four parts:

  • Copper Core: Transmits data.
  • Plastic Insulation: Isolates the core.
  • Woven Copper Braid Shield: Reduces interference.
  • PVC Jacket: Provides protection from external elements.

Fiber-Optic Cable

Transmits data using light through these components:

  • Core: Made of silica, transmits light signals.
  • Cladding: Reflects light back into the core.
  • Buffer Material (e.g., Kevlar): Protects the core and cladding.
  • Outer Jacket: Provides overall protection.

UTP vs. STP

STP offers better noise reduction due to shielding but is more difficult to install and more expensive than UTP.

RJ-45 Cable Types

Crossover Cable

Connects similar devices (e.g., computer to computer). Used when a network device like a router or switch is absent.

Straight-Through Cable

Connects dissimilar devices (e.g., computer to switch).

Loopback Cable

Used for testing network interfaces by redirecting output back to itself.

Single-Mode vs. Multimode Fiber

Single-mode fiber has a smaller core, allowing only one light path, resulting in higher bandwidth and longer distances. Multimode fiber has a larger core, allowing multiple light paths, suitable for shorter distances.

Network Types by Size

  • PAN (Personal Area Network): Example: Bluetooth, Range: ~10m
  • LAN (Local Area Network): Example: Office network, Range: ~100m
  • CAN (Campus Area Network): Example: University network, Range: ~2km
  • MAN (Metropolitan Area Network): Example: City network, Range: ~10km
  • WAN (Wide Area Network): Example: The Internet, Range: Global

Transmission Modes

  • Simplex: One-way communication (e.g., television broadcast).
  • Half-Duplex: Two-way communication, but only one direction at a time (e.g., walkie-talkie).
  • Full-Duplex: Simultaneous two-way communication (e.g., phone call).

Packet Structure

A packet contains:

  • Header: Contains instructions and addressing information.
  • Payload: The actual data being transmitted.
  • CRC (Cyclic Redundancy Check): Error detection code.

OSI Model Layers

  1. Application Layer: User interface and APIs.
  2. Presentation Layer: Data formatting and translation.
  3. Session Layer: Manages communication sessions.
  4. Transport Layer: Ensures reliable data delivery and segmentation.
  5. Network Layer: Routing and logical addressing (IP addresses).
  6. Data Link Layer: Error detection, framing, and MAC addresses.
  7. Physical Layer: Physical transmission of data (bits).

TCP vs. UDP

TCP (Transmission Control Protocol): Reliable, connection-oriented, suitable for large data transfers.

UDP (User Datagram Protocol): Unreliable, connectionless, faster for small data transfers where reliability is less critical.

Application Protocols in TCP/IP

  • SMTP (Simple Mail Transfer Protocol): Sending emails.
  • POP3 (Post Office Protocol 3): Receiving emails.
  • IMAP4 (Internet Message Access Protocol 4): Accessing emails on a server.
  • FTP (File Transfer Protocol): Transferring files.
  • HTTP (Hypertext Transfer Protocol): Delivering web pages.
  • HTTPS (Hypertext Transfer Protocol Secure): Securely delivering web pages.
  • DNS (Domain Name System): Resolving domain names to IP addresses.

Internet Protocols

  • ARP (Address Resolution Protocol): Maps IP addresses to MAC addresses.
  • RARP (Reverse Address Resolution Protocol): Maps MAC addresses to IP addresses.
  • ICMP (Internet Control Message Protocol): Reports network errors.
  • IGMP (Internet Group Management Protocol): Manages multicast group memberships.

IP Addresses vs. MAC Addresses

IP Address: Logical address, assigned by network administrators or DHCP servers.

MAC Address: Physical address, assigned by the manufacturer of the network interface card.

Pinging an IP Address

Ping tests network connectivity by sending ICMP echo requests to a target IP address.

Subnet Masks

Subnet masks define the network portion of an IP address. Common classes include:

  • Class A: 255.0.0.0
  • Class B: 255.255.0.0
  • Class C: 255.255.255.0

TCP 3-Way Handshake

  1. Host A sends a SYN (synchronize) message to Host B.
  2. Host B responds with a SYN-ACK (synchronize-acknowledgment) message.
  3. Host A responds with an ACK (acknowledgment) message, completing the connection.

Network Topologies

  • Bus: All devices connected to a single cable. Simple but prone to single point of failure.
  • Star: Devices connected to a central hub or switch. More resilient but requires more cabling.
  • Ring: Devices connected in a circular loop. Less common, can be slow.
  • Mesh: Devices interconnected for redundancy. Highly resilient but complex and expensive.

Ethernet CSMA/CD

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is a protocol used to manage access to the network medium and handle collisions.

Token Ring Network

In a Token Ring network, a token circulates the ring, and only the device holding the token can transmit data.

Switch Functions

  • Learning: Builds a MAC address table by associating MAC addresses with ports.
  • Flooding: Sends packets to all ports when the destination MAC address is unknown.
  • Filtering: Forwards packets only to the port associated with the destination MAC address.
  • Forwarding: Sends packets to the correct destination port based on the MAC address table.
  • Aging: Removes inactive entries from the MAC address table.

Static vs. Dynamic Routing

Static Routing: Routes are manually configured by administrators.

Dynamic Routing: Routers automatically learn and adjust routes using protocols like RIP.

Wireless Transmission Media

Infrared

Requires line of sight, shorter range, suitable for point-to-point communication.

Radio Frequency (RF)

No line of sight required, longer range, supports point-to-multipoint communication.

Wireless Network Terms

  • Extension Point: A device that extends the range of a wireless network.
  • Dead Spot: An area within the network coverage where the signal is weak or absent.
  • Roaming: Seamlessly switching between access points while maintaining a connection.

CSMA/CA in Wireless Networks

CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) is used in wireless networks to minimize collisions by sensing the channel before transmitting.

802.11 Standards

  • 802.11b: 2.4 GHz, 11 Mbps
  • 802.11g: 2.4 GHz, 54 Mbps, backward compatible with 802.11b
  • 802.11a: 5 GHz, 54 Mbps, less interference but shorter range

Configuring a WAP as an Extension Point

This involves setting the WAP’s SSID, security settings, channel, and IP address to match the main network.

Frequency Hopping Spread Spectrum (FHSS)

FHSS is a technique used by Bluetooth to avoid interference by rapidly switching between different frequencies.

ISDN vs. POTS

ISDN (Integrated Services Digital Network) uses the same wiring as POTS (Plain Old Telephone Service) but offers higher data rates by using multiple channels.

Cable Internet Challenges

Cable internet users share bandwidth with others in their area, potentially leading to slower speeds during peak usage.

Factors Affecting Internet Speed

Internal factors include computer performance and software usage. External factors include network congestion, distance from the ISP, and wiring quality.

Caesar Cipher

A simple encryption method that shifts each letter a fixed number of positions down the alphabet.

Symmetric-Key vs. Public-Key Encryption

Symmetric-Key: Uses the same key for encryption and decryption. Faster but less secure.

Public-Key: Uses a public key for encryption and a private key for decryption. More secure but slower.

SSL Encrypted Communication

SSL uses a combination of public-key and symmetric-key encryption to establish a secure connection between a client and a server.