This chapter explains DNS name resolution as a procedure that walks from a resolver through root, TLD, and authoritative servers. It covers the mechanism of zones and delegation, the relationship between TTL and caching, and what "DNS propagation" actually refers to.
This chapter starts from the structure of HTTP requests and responses and then covers the nine standard methods with their safety and idempotency, and the classification of status codes. It covers how to choose between PUT, PATCH, and POST by what the body means, explains that methods appear only on the request line, and why UPDATE and REMOVE are not the ones to use.
This chapter explains TCP/IP's layered model from the division of labor where IP decides where to deliver and TCP guarantees how it is delivered. It covers the three ranges of port numbers, why the server port is fixed and the client port is variable, and that IANA registration is optional.
This chapter explains that among the three properties TLS guarantees, what the certificate covers is the other side's identity. It covers certificate chain verification, that intermediate certificate delivery is the server's responsibility, what changes with the location of TLS termination, and reading certificate errors.