Broadband, Internet and Data Communication
This section covers Broadband, Internet and Data Communication. The exam tests IP addressing, TCP/IP protocols, broadband access technologies, and basic troubleshooting of data links.
Core rules and concepts
- TCP/IP model: application, transport, internet, link. IP delivers packets; TCP provides reliable, ordered delivery; UDP is connectionless and low overhead.
- IPv4 is 32-bit, written as four octets. IPv6 is 128-bit. Private IPv4 ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. NAT translates private addresses to a public address.
- A subnet mask separates network and host bits. /24 = 255.255.255.0, 256 addresses. DHCP issues addresses; DNS resolves names; the default gateway is the router for off-subnet traffic.
- Broadband access: DSL over copper, cable, FTTH/GPON, and wireless. Bandwidth is capacity; throughput is achieved rate; latency is delay. Congestion, Wi-Fi interference, and distance reduce real throughput.
- Common tools: ping, traceroute, ipconfig/ifconfig, nslookup, speed test, and modem/ONT status LEDs.
Worked example
Divide 192.168.1.0/24 into four equal subnets. Borrow 2 host bits: new prefix /26. Each subnet has 2^(32-26) = 64 addresses, 62 usable. Mask = 255.255.255.192. Subnets: .0, .64, .128, .192. The first usable in the second subnet is 192.168.1.65; broadcast is 192.168.1.127.
Traps that cost marks
Confusing MAC and IP addresses; borrowing too few bits and then double-counting network/broadcast; saying NAT is a security feature; confusing DNS with DHCP; and treating advertised bandwidth as guaranteed throughput.