Networking, Part 8: Protocols (TCP Handshaking, HTTP latency, Heart Bleed)

Protocols

How does TCP initiate a communication channel between sockets?

Which POSIX call causes the first syn packet to be sent to the server?

The first outgoing packet is sent by the client when the client calls connect

socket(...) <- A socket is created but no actual connection has been performed yet.
connect(fd,...) <- Initiate connection

Subverting protocols case study: Denial of Service

Syn flood Distributed Denial of Service Internet of Things Denial of Service

TCP Latency

Save the astronaut! The moon is 1.3 light seconds distant. The TCP client is on the Earth and a lunar console runs a TCP server. Assume a new TCP connection is required each time. How many seconds elapse between wanting to send a CLOSE-AIRLOCK message and the server receiving the data?

fd=socket(...)
connect(fd,...,...)
write(fd,"CLOSE-AIRLOCK!",14);

Answer: 3.9 seconds. TODO: Explain why. Create diagram

How many seconds elapse between requesting data from the server and receiving the result?

fd= socket(...)
connect(fd,...,...)
write(fd,"READ-TEMP!",10);
bytes= read(fd,buffer,256);

Answer: 5.2 seconds. Todo Explain why.

TCP and HTTP/1.0 performance

If the client-server round trip time is 10 milliseconds, what is the minimum time required to display a web page with an image? Assume HTTP/1.0 and the image requires a separate HTTP request.

HTTP/1.1 performance improvements

HTTP/2.0 performance improvements

QUIC protocol