024 Network and Service Security - 024.1 Networks, Network Services and the Internet (weight: 4)

Network Components

• Computer networks consist of various components utilizing different technologies and transmission media.
• Common data transmission media include:
  • Wired networks
  • Wireless networks (WiFi)
  • Cellular networks
  • Optical networks

Standards and Protocols

• Devices from different manufacturers can interact in a network.
• Protocols establish communication standards, enabling standard-compliant devices to communicate.
• Typical devices found in networks include switches, access points, and routers.

MAC Addresses / Link-Layer Addresses

• Direct data exchange is possible among devices connected in a physical network.
• Each network interface has a unique identifier known as a MAC address, which is only valid within the directly connected network.

Switches

• Switches facilitate data exchange among multiple devices connected via cables.
• Typically, a switch features 4 to 48 ports, allowing connection to various network-capable devices.
• Switches manage information about which devices are connected to which ports, forwarding data packets appropriately.

Access Points

• Access points coordinate communication within a WLAN, acting as intermediaries for devices sending packets.
• They often serve as bridges to wired networks, managing data encryption within the WLAN.

Routers

• Routers connect multiple networks, facilitating data exchange between them.
• They often have multiple network interfaces for connecting to different networks, sending packets from one network to another.
• A default router directs all outbound packets to the appropriate internet provider, while data may pass through several routers.

Internet Service Provider (ISP)

• An ISP grants end-users access to the internet, providing a default router for data transmission.
• ISPs connect to various other providers and central exchange points to route customer data traffic.

Network Protocols

• IP addresses identify specific computers within a network, ensuring that data packets reach the correct destination.
• IPv4 consists of four decimal numbers ranging from 0 to 255 (e.g., 192.168.122.1) and is nearing exhaustion, leading to the adoption of IPv6.

IPv6

• IPv6 offers a vastly larger address space than IPv4, utilizing eight blocks of hexadecimal numbers (e.g., 2001:db8::1).
• IPv6 addresses can be abbreviated for convenience.

Network Ports

• TCP and UDP protocols allow multiple applications to communicate using the same IP address by facilitating ports numbered 1 to 65536.
• Standard ports include 80 for HTTP and 443 for HTTPS, while ports below 1024 require administrative permissions.

Transmission Control Protocol (TCP)

• TCP ensures reliable data exchange between applications through continuous connection management.
• It guarantees no data loss, correct sequence delivery, and controls data flow, though at the expense of additional network traffic.

User Datagram Protocol (UDP)

• UDP allows faster, uncoordinated data exchange where packet loss is tolerated and order is not guaranteed.
• It is commonly employed in real-time applications like voice communication due to its lower overhead.

Internet Control Message Protocol (ICMP)

• ICMP conveys error messages and network status information.
• Used by commands like ping, it helps diagnose and manage network issues.

Dynamic Host Configuration Protocol (DHCP)

• DHCP automatically assigns IP addresses and configuration data to devices in a network.
• It enables devices to operate without manual configuration and manages temporary IP assignments.

Domain Name System (DNS)

• DNS acts as the "telephone book of the internet," translating human-readable names into IP addresses.
• Names are hierarchically structured, with the Root Zone and Top Level Domains (e.g., .com, .de).

DNS Records

• A-records and AAAA-records link names to IPv4 and IPv6 addresses, respectively, while MX records specify mail servers for email addresses.
• Forward DNS maps readable names to IP addresses, while Reverse DNS maps IP addresses back to names.

Cloud Computing

• Refers to on-demand access and delivery of IT services via the internet.
• Cloud providers manage infrastructure and services with automated, pay-per-use pricing.

Advantages of Cloud Computing

• Eliminates high initial costs for IT infrastructure.
• Services can scale according to demand without significant upfront investment.
• Allows clients to focus on applications rather than infrastructure.

Disadvantages of Cloud Computing

• Ongoing usage may exceed costs of maintaining in-house services.
• Pricing must be transparent and manageable.
• Potential vendor lock-in and security responsibility shift to the provider.

Cloud Computing Models

• Infrastructure as a Service (IaaS): Clients manage their servers in the cloud provider’s data centers with technical knowledge required.
• Platform as a Service (PaaS): Clients run applications on an infrastructure managed by the provider, focusing on development.
• Software as a Service (SaaS): Clients use applications provided and maintained by the provider, benefiting from automatic updates but facing potential migration challenges.

Test your knowledge on the various components and protocols used in computer networks. This quiz covers topics such as data transmission media, MAC addresses, and the function of switches in a network. Perfect for students studying network technology.