SUMMARY of Days 1-19 of CPSC 441 L01
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<Day 1 recap:> "The Internet is built using a layered stack of communication protocols."

<Day 2 recap:>
  "The Internet consists of hosts, links, and switches."
  "The Internet uses packet-switching, and relies on statistical multiplexing."

<Day 3 recap:>
  "There are a wide range of Internet access technologies, with many different tradeoffs."
  "Routers in the core of the Internet do two main tasks: forwarding and routing."

<Day 4 recap:>
  "There are four sources of delays for packets on the Internet:
   processing delay, queueing delay, transmission delay, and propagation delay."

<Day 5 recap:>
  "The Internet is built using a five-layer protocol stack:
  Application, Transport, Network, Datalink, and Physical."

<Day 6 recap:>
  "The Web is built using HTTP as its application-layer protocol."
  "HTTP/1.0 is a simple, stateless, request-response protocol."

<Day 7 recap:>
  "HTTP is a simple yet surprisingly powerful AL protocol."
  "New features in HTTP involve the addition of protocol state information."

<Day 8 recap:>
  "SMTP is a session-oriented AL protocol that uses TCP."

<Day 9 recap:>
  "DNS is a UDP-based request-response AL protocol for
   mapping between host names and IP addresses."

<Day 10 recap:>
  "P2P apps use a mix of TCP and UDP to deliver AL services to peers."

<Day 11 recap:>
  "Video streaming apps are built using application-layer infrastructure,
  such as AL protocols, media encoding, client-side buffering, and CDNs."

<Day 12 recap:>
  "The TL provides logical end-to-end (process-to-process) communication."
  "UDP is connection-less; TCP is connection-oriented."

<Day 13 recap:>
  "Reliable Data Transfer (RDT) is a fundamental and challenging Transport Layer problem."
  "Providing RDT requires the addition of more and more protocol state information."

<Day 14 recap:>
  "RDT 3.0 can handle delay, loss, and corruption of segments by an unreliable Network Layer,
   by using checksums, sequence numbers, ACKs, timers, and retransmission at the Transport Layer."

<Day 15 recap:>
  "TCP is a connection-oriented reliable byte-stream TL protocol,
   which uses seqnums, ACKs, timers, retransmissions, and more."

<Day 16 recap:>
  "TCP is a connection-oriented protocol, with lots of state information
  kept at the TL endpoints, and also carried in the segment headers."

<Day 17 recap:>
  "TCP congestion control follows AIMD principles, using two key
  algorithms called Slow Start (SS) and Congestion Avoidance (CA),
  and two new state variables called 'cwnd' and 'ssthresh'."

<Day 18 recap:>
  "The TCP family tree includes many variants, but AIMD in
  the CA algorithm ensures fairness amongst competing flows."

<Day 19 recap:>
  "Transport-layer functionality on the Internet continues to evolve,
  with QUIC, BBR, and HTTP/3 as the most recent new innovations."