Computer networks
Computer networks is a core paper in most CS degrees and a regular topic in campus placement interviews, where subnetting questions, the TCP handshake and “what happens when you type a URL” come up by name. This course goes down the stack one layer at a time and explains how each protocol works and why it was designed that way, with worked calculations you can repeat in an exam or an interview.
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Lessons
Layers and encapsulation: how a network is organized
Why networks are built in layers, the OSI and TCP/IP models, what each layer adds and how one packet travels down and up the stack.
The link layer: Ethernet, switches and ARP
Ethernet frames and MAC addresses, how switches learn, ARP, error detection with CRC, and VLANs and Wi-Fi.
IP addressing and subnetting
IPv4 addresses, CIDR and subnet masks with worked calculations, private ranges and NAT, DHCP and the basics of IPv6.
Routing: forwarding tables, distance vector and link state
Forwarding versus routing, longest-prefix match, Bellman-Ford and count to infinity, Dijkstra, and OSPF and BGP between autonomous systems.
UDP and reliable delivery with TCP
Ports and sockets, UDP, the three-way handshake, sequence numbers and ACKs, retransmission timeouts, sliding windows and connection teardown.
TCP congestion control
Congestion collapse, slow start, AIMD, fast retransmit and fast recovery, and what CUBIC and BBR change.
DNS and HTTP: from names to requests
How a name resolves from stub resolver to root to authoritative server, record types and TTLs, and what HTTP/1.1, HTTP/2 and HTTP/3 each fixed.
TLS and what happens when you type a URL
What TLS guarantees, the TLS 1.3 handshake, certificates and chains of trust, then a full walk from keypress to rendered page.
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