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WBCHSE HS Vocational Telecom study materials
WBCHSE HS Vocational Telecom study resources

WBCHSE HS Vocational Telecom: Data Communication, Networking and Internet

WBCHSE HS Vocational Telecom · Work through your exam, one topic at a time.

All guide sections

Data Communication, Networking and Internet

Data Communication, Networking and Internet

This domain tests how data moves across networks. Expect questions on the OSI and TCP/IP models, IP addressing and subnetting, switching and routing, common protocols and internet services.

Core rules

  • The TCP/IP model has application, transport, internet and network-access layers; OSI has seven layers. Encapsulation adds headers at each layer.
  • IPv4 addresses are 32-bit; a prefix length gives the network mask. The network and broadcast addresses cannot be assigned to hosts.
  • Switches forward frames by MAC address within a LAN; routers forward packets by IP address between networks.
  • TCP is connection-oriented and reliable; UDP is connectionless and suited to real-time traffic where low delay matters.
  • DNS resolves names to IP addresses; DHCP assigns addresses automatically; HTTP/HTTPS carries web traffic.

Worked example

For 192.168.10.0/26, the mask is 255.255.255.192 because 26 bits are network bits. The block size is 64, so subnets begin at .0, .64, .128 and .192. The host 192.168.10.70 lies in the .64 subnet; its range is .65–.126, and its broadcast address is .127. Each subnet has 2^6 − 2 = 62 usable hosts. The subtraction removes the network and broadcast addresses.

Traps that cost marks

Assigning a broadcast address to a PC; confusing a switch with a router; using public addresses inside a private LAN without NAT; mixing TCP and UDP requirements; and forgetting that /26 is not the same as /24. Always check the prefix before calculating hosts.