Computer Systems
HTTP & HTML
HTTP & HTML
Table of Contents
1.1
1.2
1.3
1.4
-
meaning of HTTP headers
-
how many bytes to implement this page?
- how many requests are there? 23!
- what is each request for?
- GET requests to get HTML, images, ad services, javascript
- POST request to beacon
- response status codes
200: successful302: resource temporarily moved (redirects)204: no content
- which ones are cacheable?
- GET, HEAD, and POST can be cached (in general)
Cache-Controlheader holds instructions for caching, and can be in both requests and responses. Some examples from the page:Cache-Control: private: response is for a single user and mustn’t be stored by a shared cache, but can be stored by private cache e.g. browser cacheCache-Control: no-store: don’t store anything
- how many different domain names are used to build the page
1.5
- Javascript executes code in browser to provide dynamic content
- in this case, the JS is making requests for images that then get embedded webpage
1.6
http://info.cern.ch/hypertext/WWW/TheProject.html
<HEADER></HEADER>: header<TITLE></TITLE>: page title (shown in the tab description)<NEXTID>: used to generate automatic NAME identifiers for anchors; obsolete<BODY></BODY>: main body of the page<A></A>: anchor; hyperlink<DL></DL>: description list<DT></DT>: description term (in description list)
2.1
2.2
- ARC: Authenticated Received Chain:
email authentication to allow intermediate
mail server e.g. mailing list to sign an email’s original authentication results
- allows receiving service to validate an email
- ARC-Seal: instance number + signature of previous headers + validity of prior ARC entries
- ARC-Message-Signature: instance number + signature of entire message except seal headers
- ARC-Authentication-Results: instance number + validation results