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Bhutan Civil Service Main Examination (ICT Category) study materials
Bhutan Civil Service Main Examination (ICT Category) study resources

Bhutan Civil Service Main Examination (ICT Category): Computer Networks and Internet Technologies

Bhutan Civil Service Main Examination (ICT Category) · Work through your exam, one topic at a time.

All guide sections

Computer Networks and Internet Technologies

Core concepts

Know the OSI seven layers and the TCP/IP model, mapping protocols to layers: application (HTTP, FTP, SMTP, DNS, DHCP), transport (TCP, UDP), network (IP, ICMP, ARP), and link layers. Understand TCP's connection setup (three-way handshake), reliability, flow control, and congestion control versus UDP's connectionless speed. Study IP addressing and subnetting (classes, CIDR, subnet masks), routing basics (static versus dynamic, RIP, OSPF, BGP), switching, and network devices (hub, switch, router, gateway).

Internet technologies include DNS resolution, URL structure, HTTP methods and status codes, cookies, NAT, firewalls, and VPNs. Know bandwidth, latency, and the difference between IPv4 and IPv6.

Traps to watch

  • Placing ARP at the network layer; it operates between link and network for address resolution.
  • Confusing TCP port numbers with IP addresses.
  • Assuming a hub filters traffic; only switches and routers do.
  • Miscounting usable hosts: a /24 gives 254 usable addresses, not 256.

Worked example

For 192.168.10.0/26, the mask borrows 2 bits, creating 4 subnets of 64 addresses each. Usable hosts per subnet = 2^6 - 2 = 62. The first subnet ranges 192.168.10.0 to .63 with usable hosts .1 to .62. Rule of thumb: usable hosts = 2^(host bits) - 2, subtracting network and broadcast addresses.