Question

Indicate the order in which the following events take place in web caches: 1. Browser-X requests object A. II. Browser-Y requests object A. III. Cache does not have the object, request forwarded to web server. IV. Web server sends response with requested object. V. Cache forwards the object to req ing browser and caches the object. VI. Cache responds with its cached copy.

Answer 1

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Solution -

Since all of the events should take place in an logical order, and all of the events should be included in the final answer, they will occur in the following order -

1. Browser X requests object A (Since we aren't given any options, Browser Y can also request object A in this step).
2. Next the cache will see if the object is present in the web cache. Therefore the correct option is "Cache doesn't have the object, request forwarded to web server"
3. Next the web server will respond with the requested object, Therefore the correct option is "Web server sends response with requested object"
4. Now, the cache will send the object to the browser and since it doesn't have the object cached, it will cache it. Therefore the correct option is "Cache forwards the object to requesting browser and caches the object"
5. Now the other browser Y will make it's request( or X depending upon who made the first request) therefore the correct option in the sequence is "Browser Y requests object A"
6. Now since the object A is already loaded, it will respond with it's cached copy. Therefore, the correct option is "Cache responds with its cached copy"

In short the process occurs as > browser makes request-> cache checks its storage and if the object is not there, makes request from the server -> server responds -> cache stores the object and responds to the requesting browser -> next time any browser makes the same request, the cached copy is provided.

Therefore the correct final sequence is '1-> 3 -> 4 -> 5-> 2 -> 6' or '2-> 3 -> 4 -> 5-> 1 -> 6' depending upon which browser makes the first request.