Computer Networks is one of the most high-yielding subjects in the technical segment of the Wireless PSI exam. Historically, networking concepts contribute to nearly 15-20% of the technical questions.
By analyzing past papers, we have grouped the most repeated questions into three primary themes. Master these concepts to guarantee high marks in this section.
1. The OSI Model and TCP/IP Protocol Stack
Almost every exam contains questions asking you to match a specific protocol to its layer or function.
- Transport Layer: Understand the key differences between TCP (connection-oriented, reliable, windowing) and UDP (connectionless, fast, unreliable).
- Network Layer: Study IP routing, ICMP error reporting, and Address Resolution Protocol (ARP) mapping.
- Application Layer: Memorize the default port numbers for HTTP (80), HTTPS (443), FTP (20/21), DNS (53), SMTP (25), and DHCP (67/68).
2. IP Addressing and Subnetting Calculations
Numerical questions on subnetting are standard. You must be able to calculate subnet masks, host ranges, and network IDs quickly.
Be prepared for questions like: "What is the network address of a host with IP 192.168.1.45/26?" or calculations involving CIDR notations. Know the classes of IP addresses (Class A, B, C, D, E) and their corresponding default subnet masks.
Number of usable hosts in a subnet = 2^n - 2 (where n is the number of host bits, and 2 is subtracted for the network address and broadcast address).
3. Routing Algorithms and Network Devices
Make sure you understand the difference between Distance Vector Routing (RIP) and Link State Routing (OSPF).
Also, know the layer at which network devices operate: switches operate at Data Link Layer (Layer 2), hubs at Physical Layer (Layer 1), and routers at Network Layer (Layer 3).