Computer Networks · free preview
Traditional Applications
The Internet's oldest applications are still its most instructive, electronic mail splitting into a message format, headers and body in ASCII extended by MIME to carry encoded binary, a transfer protocol, SMTP, that pushes mail between servers, and a retrieval protocol, IMAP, that lets readers manage mailboxes on the server, while the web pairs a document language with a request-response protocol, URLs naming resources so documents can link, HTTP carrying text-oriented requests and responses over TCP, stateless by design, with methods, status codes, persistent connections, and caching proxies making the whole thing scale, two designs that show how application protocols turn the transport layer's byte streams and datagrams into something people use.
1. Mail in Three Pieces
Mail in Three Pieces
2. Naming Things So They Can Link
Naming Things So They Can Link
3. Stateless Requests, Scalable Web
Stateless Requests, Scalable Web
4. From Documents to Services
From Documents to Services
5. Three agreements
What are the three separable pieces of Internet email architecture?
6. The ASCII costume
How does MIME carry a photograph through a system designed for ASCII text?
7. Why retrieval is separate
Why does IMAP keep the mailbox on the server rather than downloading everything to one machine?
8. The name before the protocol
What makes URLs the web's foundational invention?
9. The stateless bet
Why is HTTP designed stateless, and what follows?
10. The caching multiplier
How do caching proxies multiply the web's capacity?
11. The format's name
Which standard defines email messages as an ASCII header of structured lines plus a body?
12. The push protocol
Which protocol transfers mail from the sender's server toward the receiver's in a store-and-forward conversation?
13. The three-digit verdict
In an HTTP response, what does the three-digit status code convey?
14. The standing channel
What HTTP feature amortizes TCP connection setup across the many objects of one page?
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