Hypertext Transfer Protocol

Question 1

Functionalities of HTTP protocol.

Answer 1

• client initiates TCP connection (creates socket) to server, port 80
• server accepts TCP connection from client
• HTTP messages (application-layer protocol messages) exchanged between browser (HTTP client) and WWW server (HTTP server)
• TCP connection closed

Question 2

Operations of HTTP protocol.

Answer 2

GET - requests data from specified resource

HEAD- almost identical to GET, but without the response body (useful for checking what a GET request will return before actually making a GET request)

POST - sends data to a server to create/update a resource; no restrictions on data type or data length

PUT- sends data to a server to create/update a resource + idempotent characteristic (calling the same PUT request multiple times will always produce the same result)

DELETE- deletes the specified resource

CONNECT- requests that the recipient establish a tunnel to the destination origin server identified by the request target; intended only for use in request to a proxy

TRACE - performs a message loop-back test along the path to the target resource, providing an useful debugging mechanism

OPTIONS - requests info about the communication options available for the target resource

Question 3

HTTP Intermediate Systems - GATEWAY.

Answer 3

Gateway - server to client (acts on behalf of servers);
Security intermediary: server part on a firewall.
Non-HTTP server: allows for accessing servers running other protocols than HTTP (FTP, Gopher servers).

Question 4

HTTP Intermediate Systems - PROXY.

Answer 4

Proxy - acting on behalf of clients, forwarding their request;
Security intermediary:
- server interacting with client & client vs server
- client side within a firewall
- presents clients’ requests to server over an authenticated connection
Different versions of HTTP implemented: if the client and server are running different versions of HTTP.

Question 5

HTTP Intermediate Systems - TUNNEL.

Answer 5

Tunnel:
- relays between TCP connections
- no extra info check
- firewall in which a client and a server maintains a secure connection for purpose of HTTP transactions.

Cache - facility that may store previous requests and responses for handling new requests.