Topics to understand in TCP/IP networking

tcp-ip-topics.md

• What is encapsulation
• Link layer
  • Link layer basics (pick something like Ethernet to get a quick overview of what the link layer entails)
  • What is a MAC address
• IP - this is a vast topic but there are several important concepts to understand here
  • IP addresses and subnet masks
  • How are IP addresses different from MAC addresses and why are they required
  • How do you discover a MAC address of a device on the same network if you only have its IP address (hint: see ARP)
  • What are routers and how IP routing works
  • Route tables
  • IP fragmentation
  • TTL
  • How ping and traceroute work
  • IPv6, why its required and why has its adoption been slow
• Transport layer
  • What is a port number and why is it required
  • UDP
  • TCP
    • Connection establishment (three way handshake)
    • Connection termination
    • Data transfer
    • Reliable transmission
    • Flow control (sliding window)
    • Congestion control
    • Error detection
    • Maximum segment size (MSS) and its relation with IP fragmentation
    • Selective acknowledgements (SACK) and how they help
    • When should you use TCP instead of UDP and vice versa?
• DNS
  • How it works - does it use UDP, TCP or something else?
  • What are root name servers and how do DNS resolvers works starting from the root
  • What is the nameserver (NS) of a domain?
  • Different types of records
    • A
    • AAAA
    • CNAME
    • MX
    • TXT
    • NS
  • DNS-over-HTTPS and why browsers have started using it
• HTTP
  • Request
    • Request line (method + path + query params + HTTP version)
    • Headers
    • Body
  • Response
    • Status line
    • Headers
    • Body
  • Safe methods v/s idempotent methods
  • When to use GET vs POST vs PUT
  • Cookies
  • Authentication
  • Content types
    • application/x-www-form-urlencoded
    • text/html
    • text/plain
    • application/json
    • Content types for images and other documents
  • Multi part requests
  • Chunked encoding
  • Compression
  • Why is the Host header required?
  • Connection re-use and request pipeline
  • Overview of HTTP/2 and HTTP/3
• TLS
  • No need to go into details of TLS but understand the basics
  • What are X509 certificates and how does a client use them and a certificate authority to authenticate the server
  • What is asymmetric encryption and how it is used in TLS
  • What is Diffie Helman key exchange
  • When does symmetric encryption (like AES) come into play in a TLS connection
  • SNI
• HTTP
  • Understand the relationship between TCP, TLS and HTTP - especially how HTTP is built on top of TCP/TLS and the guarantees that the underlying protocols provide (e.g. stream of bytes, etc.)
  • What is HTTP proxying and how it works
  • CDNs and how they reduce network latency
• HTTPS
  • Difference between HTTP and HTTPS