Computer Networking Lecture 25-the web
Computer Networking Lecture 25 – The Web
Outline Http review and details(more in notes Persistenthttpreview Http caching Content distribution networks Lecture19:2006-11-02
Lecture 19: 2006-11-02 2 Outline • HTTP review and details (more in notes) • Persistent HTTP review • HTTP caching • Content distribution networks
Http Basics(review) Http layered over bidirectional byte stream Almost always TCP ·| nteraction Client sends request to server, followed by response from server to client Requests/responses are encoded in text Stateless Server maintains no information about past client requests Lecture19:2006-11-02 3
Lecture 19: 2006-11-02 3 HTTP Basics (Review) • HTTP layered over bidirectional byte stream • Almost always TCP • Interaction • Client sends request to server, followed by response from server to client • Requests/responses are encoded in text • Stateless • Server maintains no information about past client requests
How to Mark End of Message?(Review) Size of message Content-Length Must know size of transfer in advance Delimiter> MIME-style Content-Type Server must escape" delimiter in content Close connection Only server can do this Lecture19:2006-11-02
Lecture 19: 2006-11-02 4 How to Mark End of Message? (Review) • Size of message → Content-Length • Must know size of transfer in advance • Delimiter → MIME-style Content-Type • Server must “escape” delimiter in content • Close connection • Only server can do this
Http Request(review) equest line R Method GET- return URi HEAD-return headers only of Get response POST-send data to the server(forms, etc.) URL (relative) °Eg., index html Http Version Lecture19:2006-11-02 5
Lecture 19: 2006-11-02 5 HTTP Request (review) • Request line • Method • GET – return URI • HEAD – return headers only of GET response • POST – send data to the server (forms, etc.) • URL (relative) • E.g., /index.html • HTTP version