Course Objectives

This course follows the top-down approach: we start at the application layer, where you already have intuition, and work down to the wire. Each chapter below names what you should be able to do once we are through it, not just what you should have read.

1. Computer Networks and the Internet

• Describe the Internet as a layered system, and name the service each layer sells to the layer above it.
• Trace a message through encapsulation on the way down and de-encapsulation on the way up.
• Break end-to-end delay into transmission, propagation, queuing, and processing, and compute each one.
• Explain why packet switching beat circuit switching for data traffic.

2. The Application Layer

• Write a client that speaks a text-based protocol over a socket.
• Explain how HTTP, SMTP, and DNS are structured, and why each one made the design choices it did.
• Compare client-server and peer-to-peer architectures for a given workload.
• Explain what a DNS resolver actually does, step by step, on a cache miss.

3. The Transport Layer

• Build a reliable data transfer protocol on top of an unreliable channel.
• Explain the difference between TCP and UDP in terms of the service each provides.
• Trace TCP connection setup, teardown, flow control, and congestion control.
• Explain why congestion control is a network-wide problem and not a per-connection one.

4. The Network Layer: Data Plane

• Describe what a router does to a packet, in order.
• Read and write IPv4 addresses in CIDR notation, and subnet an address block.
• Explain NAT, what it buys, and what it breaks.
• Explain the split between the data plane and the control plane.

5. The Network Layer: Control Plane

• Trace link-state (Dijkstra) and distance-vector (Bellman-Ford) routing by hand.
• Explain why the Internet needs both intra-AS and inter-AS routing.
• Describe what BGP advertises and why routing policy is a business decision.
• Explain what SDN changes about the control plane.

6. The Link Layer and LANs

• Explain error detection and correction, and compute a checksum and a CRC.
• Compare the multiple access protocols: channel partitioning, random access, taking turns.
• Trace a request end to end through ARP, DHCP, a switch, and a router.
• Explain how a switch learns, and how that differs from routing.

7. Wireless and Mobile Networks

• Explain what makes a wireless link harder than a wired one.
• Describe 802.11 and why it uses CSMA/CA rather than CSMA/CD.
• Explain the hidden terminal problem and how RTS/CTS addresses it.
• Describe how mobility is handled by cellular networks.

8. Security in Computer Networks

• Define confidentiality, integrity, authentication, and availability, and name the mechanism that provides each.
• Explain symmetric and public key cryptography at the level of what each is for.
• Describe what TLS protects, and what it leaves exposed.
• Identify common attack vectors and the defenses that apply to each.