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KembaraXtra-Computer Science-Foundational Internet Capabilities
1. Dynamic Host Configuration Protocol (DHCP)
ii.If the server has the record in its cache, it returns the IP address.
iii.If not, the server queries other DNS servers, starting at the root, to find the record.
iv.The server caches the record for future queries.
4. Networking in Context of Computing
1. Dynamic Host Configuration Protocol (DHCP)
- Purpose: Automatically assigns IP addresses and related network information to devices when they connect to a network.
- Why it's important: Simplifies network configuration for end-users by eliminating the need for manual IP address assignment.
- How it works:
- Discovery: A device broadcasts a message to discover available DHCP servers.
- Offer: The DHCP server offers an IP address from its available pool.
- Request: The device requests the offered IP address.
- Acknowledgment: The DHCP server acknowledges the request, assigning the IP address to the device.
- Lease: IP addresses are leased to devices for a limited time. The device must renew the lease to continue using the IP address.
- DHCP Server: A device on the network configured to provide DHCP services, including managing a pool of available IP addresses.
- Problem: Limited number of public IP addresses available, but many networks have multiple devices.
- Solution: Using private IP addresses for internal network communication and NAT to share a single public IP address.
- Private IP Addresses:
- IP address ranges reserved for internal networks (e.g., homes, offices).
- Ranges: 10.x.x.x, 172.16.x.x to 172.31.x.x, 192.168.x.x.
- Non-routable on the public internet.
- Can be used simultaneously on multiple private networks without conflict.
- Network Address Translation (NAT):
- Allows devices on a private network to share a single public IP address.
- The NAT router modifies the source IP address of outgoing packets to its public IP address.
- When responses return, the router translates the destination IP address back to the correct private IP address.
- Security benefit: Hides devices on the private network from direct exposure to the public internet.
- Proxy Server:
- An alternative to NAT, typically used in corporate networks.
- Operates at the application layer.
- Provides additional features: User authentication, traffic logging, and content filtering.
- Purpose: Translates human-friendly domain names (e.g., www.example.com) into IP addresses.
- Why it's important: Makes the internet easier to use by allowing users to remember names instead of IP addresses.
- Fully Qualified Domain Name (FQDN): The complete DNS name of a computer (e.g., travel.example.com).
- Consists of a hostname (travel) and a domain suffix (example.com).
- Domain: A grouping of network resources managed by an organization (e.g., example.com).
- Resolving a Hostname: The process of querying a DNS server to find the IP address associated with a hostname.
- Mapping:
- One-to-many: A single name can map to multiple IP addresses (used for load balancing and geographic distribution).
- Many-to-one: Multiple names can map to the same IP address (used for web hosting).
- DNS Records: Entries in the DNS database.
- A Record: Maps a hostname to an IP address.
- CNAME Record: Maps one hostname to another hostname (alias).
- MX Record: Used for email services.
- DNS Hierarchy:
- A distributed system with shared responsibility for managing DNS records.
- Root Domain: Top of the hierarchy, contains records for top-level domains (TLDs).
- Top-Level Domains (TLDs): (e.g., .com, .org, .edu).
- Second-Level Domains: Registered under TLDs (e.g., example.com).
- DNS Resolution Process:
ii.If the server has the record in its cache, it returns the IP address.
iii.If not, the server queries other DNS servers, starting at the root, to find the record.
iv.The server caches the record for future queries.
4. Networking in Context of Computing
- The internet is a network of hardware and software enabling communication between devices.
- Data transmission over the internet is based on binary data (0s and 1s).
- Network interfaces (e.g., Wi-Fi, Ethernet) are I/O devices.
- Operating systems use device drivers and software libraries to facilitate network communication for applications.
- Networking devices (routers, switches) are specialized computers.
- Networking extends computing beyond single devices.
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