1. Web Server Design Assignment #3: Transfer Encoding & Content Negotiation
Old Dominion University
Department of Computer Science
CS 495/595 Spring 2012
Michael L. Nelson

2. Grading
To be done by an automated program that will test most (all?) combinations
assignment is listed under the day it is to be demoed in class
each person will give a 3-4 minute status report the week before an assignment is due!
If you have a question:
the class list
mimic the behavior of a well known Apache server (e.g.,

3. Methods to Support
Same as assignments 1 & 2

4. Status Codes to Support
Same as assignments 1 & 2, plus:
206 Partial Content
300 Multiple Choice
use if there are > 1 possible representations
provide html list for a user to pick from
406 Not Acceptable
use if there are no possible representations that match the requested q values
416 Requested Range Not Satisfiable

5. Note: I'll be testing 403
Via sudo, I'm going to remove the read permissions on one of your files on mln-web.cs.odu.edu

6. Request Headers Same as assignments 1 & 2 Add: (note: we won't do TE:)
Accept
Accept-Charset
Accept-Encoding
Accept-Language
Negotiate
Range
User-Agent
Referer
(note: we won't do TE:)

7. Response Headers Same as assignments 1 & 2, but add: Vary
Content-Language
Content-Location
Content-Encoding
“Transfer-Encoding: chunked”
Alternates
TCN
Accept-Range
Content-Range
Modified
Content-type
add charset after type if not ISO (ASCII)
see week 8 slides for example

8. MIME Types
Same as assignment #1

9. Encoding Types compress, gzip, deflate, identity, chunked
(see week 8 lecture)
Use “chunked” transfer encoding for any dynamically generated server response
i.e., directory listings and 3xx, 4xx, 5xx html snippets
use 2 lines as the “chunk”

10. Further Guidance
Support/advertise partial GET capability for all resources for all resources/responses for which you don't use Transfer-Encoding: chunked
i.e.: representation == files on the file system
Use these language encodings
en, es, de, ja, ko, ru
Use these non-ASCII charset encodings
“.jis” -> “iso-2022-jp”
“koi8-r” -> “koi8-r”
“euc-kr” -> “euc-kr”

11. Further Guidance Build “Vary” response header as:
Vary: negotiate, header1, header2, …, headerN
use the “Vary” header only if content negotiation has been performed
No “default” q values in content negotiation
remember: content negotiation only happens if the request would have generated a 404 without content negotiation
Generate structured ETags on selected representation as per RFC-2295 (section 9.2)

12. Status Code Definition
Generate a 200:
if there is only a single representation as a result of Accept headers and q values
Generate a 300:
if there are multiple representations that “tie” in q values OR the client sends a “Negotiate: 1.0” request header
generate an HTML list showing possible options
Generate a 406:
if no representations are suitable given Accept headers and q values
generate an HTML list showing closest options

13. Redirections Delete the previous 302 redirections
Add the 301 redirections on the next page:

14. 301 Redirection # # Incoming RE 301 URI
^(.*)/dj-shadow/(.*)
^/wsdl/$
^(.*)/3/(.*) $1/4/directory3isempty

15. Combined Log Format Basically, add Referer: and User-Agent: fields:
"%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\""