IT and Communication Engineering: Networks, Protocols, Software, Security and Telecom
IT and Communication Engineering in IESL Part III combines data networking, protocol behaviour, software and database engineering, information security, and telecommunication transmission and services.
Core rules and concepts
- Layering: OSI seven layers and the TCP/IP stack, with the mapping of functions (routing at network layer, retransmission and flow control at transport layer).
- Addressing: for a /n IPv4 prefix, host bits = 32 − n; usable hosts = 2^(32−n) − 2 after removing network and broadcast addresses.
- Performance: throughput on a path is bounded by window/RTT; the bandwidth-delay product tells you how much data can be in flight before the sender stalls.
- Routing: longest-prefix match, administrative distance, and the difference between interior (OSPF) and exterior (BGP) protocols.
- Software and data: requirements → design → implementation → testing; ACID properties in transactions; normal forms remove update, insert and delete anomalies.
- Security: confidentiality by encryption, integrity by hashing/MAC, authentication by certificates; TLS combines all three. Never store passwords with reversible encryption.
Worked example
A TCP connection has a 32 KB receive window and a 40 ms round-trip time, on a 10 Mbit/s link. Window = 32 768 bytes = 262 144 bits. Throughput limited by the window = 262 144/0.040 = 6.55 Mbit/s, below the 10 Mbit/s line rate. So the window, not the link, caps performance; enlarging the window to 64 KB would allow 13.1 Mbit/s, and the link then becomes the limit.
Traps that cost marks
Reporting 2^n hosts instead of 2^n − 2; treating the broadcast address as usable; confusing Mbit/s with MB/s; assuming throughput equals line rate without checking the window; and describing hashing as a form of encryption.