1.3 HTTP

request method

An HTTP _________ indicates the desired action to perform on a resource. Other request methods besides GET may also be sent in an HTTP request.

Status line, Zero or more header fields, Empty line, Optional message body

An HTTP request and an HTTP response are both composed of four parts:

Expires

Contains a date/time indicating when the requested resource is considered "stale". .

last-modified

Datetime the requested resource was last modified on the web server.

date

Datetime the response was generated by the web server.

HTTP/2

maintains most of HTTP/1.1's semantics, and this material focuses on the basic HTTP workings that both standards share.

network sniffer

software that monitors network traffic and allows users to inspect HTTP requests and responses.

status line

specifies the HTTP version being used. A request __________ includes a request type and path; a response status line includes a status code.

HTTP/1.1

the HTTP standard used for most of the web's lifetime, but many websites are adopting HTTP/2, a new HTTP standard that speeds-up the transfer of information between web browsers and web servers.

Cache-Control

used to specify a number of caching directives. Ex: "___________: no-store" tells the web browser to never cache the requested resource, and "_____________: max-age=180" tells the browser to cache the resource for 180 seconds.

If-Modified-Since

used with the Last-Modified date/time to request the web server only send the requested resource if the resource has changed since the specified date/time.

DNS lookup

web browser performs a _____________ by sending the domain name to the local DNS and getting back the IP address of the web server hosting the domain name.

browser redirect

when the web server returns a 301 or 302 status code with a Location header indicating the URL the browser should load next.

certificate authority

A website wanting to use HTTPS must acquire a digital certificate, issued by a trusted ________, that contains a public key used by TLS to encrypt data.

status code

HTTP response _______ is a three digit number that indicates the status of the requested resource.

Transport Layer Security (TLS)

HTTPS uses a protocol called _____________, which uses asymmetric public keys to encrypt data between the browser and web server.

user-agent

Identifies the browser making the request.

server

Identifies the web server software that generated the response.

example of browser cache

If a web page is accessed now and again 10 minutes from now, the browser can display the cached web page instead of re-downloading the web page.

content-type

Media type of the response's message body.

content-length

Number of bytes in the response's message body.

browser requests an HTTPS connection to a web page.

Put the steps used in an HTTPS transaction in order. Step 1:

web server sends digital certificate to the browser.

Put the steps used in an HTTPS transaction in order. Step 2:

The browser and web server initate "TLS handshake".

Put the steps used in an HTTPS transaction in order. Step 3:

The browser and web server transmit encrypted information.

Put the steps used in an HTTPS transaction in order. Step 4:

Request method: GET

Request method: Request a representation of the specified resource.

Request method: PUT

Request method: Request the web server accept the message body enclosed in the request as a modification of an existing resource.

Request method: POST

Request method: Request the web server accept the message body enclosed in the request as a new resource.

Request method: DELETE

Request method: Request the web server delete the existing resource.

Request method: HEAD

Request method:.Request a response identical to GET but without the response body.

host

The domain name for the requested path.

Status code: 403

What is this status code to status phrase Forbidden and the web browser does not have permission to access the resource.

Status code: 302

What is this status code to status phrase Found and the resource should temporarily be requested at a different URL.

Status code: 500

What is this status code to status phrase Internal Server Error and something unexpected happened on the web server.

Status code: 301

What is this status code to status phrase Moved Permanently and the resource should always be requested at a different URL.

Status code: 404

What is this status code to status phrase Not Found and the resource could not be located.

Status code: 304

What is this status code to status phrase Not Modified and the resource has not been modified since the last time the resource was requested.

Status code: 200

What is this status code to status phrase OK and standard response for successful request.

header fields

a keyword followed by a colon and a value. ______supply additional information about the request or response.

HTTP request

a message sent from the web browser to the web server. Often the request asks the web server to send back a web resource like an HTML file, image, CSS style sheet, JavaScript file, or video.

HTTP response

a message sent from the web server back to the web browser in response to an HTTP request. Often the response contains the requested web resource.

HyperText Transfer Protocol (HTTP)

a networking protocol that runs over TCP/IP and governs communication between web browsers and web servers.

Transmission Control Protocol/Internet Protocol (TCP/IP)

a protocol suite that governs how packets of data are transferred over the Internet from one machine to another.

Internet Assigned Numbers Authority (IANA)

a standards organization that manages various internet numbers and symbols, like global IP address allocation, root zone management in DNS, and media types.

browser cache

an area on the computer's disk where web content can be stored by the web browser for quick retrieval later

entity tag (ETag)

an identifier for a specific version of a web resource. Ex: 34905a3e285dd11. When the resource changes, so should the ETag associated with the resource.

Optional message body

contains data being transferred between a web browser and web server. In a request, the message body may be empty or contain submitted form data. In a response, the message body may contain the requested resource.

HTTPS

encrypts HTTP traffic between a browser and web server so a network sniffer cannot intercept sensitive information in the HTTP traffic like passwords, credit card numbers, financial transactions, etc.