Week 13

Question 1

Non-Persistent HTTP

Answer 1

One TCP request per file (vs multiple files per connection). In modern day, we use multiple files per connection, even when reloading a webpage, because this reduces overhead over the short term. This explains why I didn’t see a new SYN, SYN ACK, ACK.

Non persistent takes 2RTT per resource
Persistent takes 1RTT + 1RTT(NUM_RESOURCES)

Question 2

RTT

Answer 2

Round Trip Time

Question 3

Pipelining

Answer 3

Sending multiple requests and receiving multiple resources at once. Works over persistent and non-persistent HTTP and requires the base HTML to get started.

Question 4

HTTP 1.0

Answer 4

GET, POST, and HEAD (testing if server exists)

Question 5

HTTP 1.1

Answer 5

GET, POST, HEAD, PUT (upload files), DELETE (delete files)

Question 6

200

Answer 6

OK

Question 7

301

Answer 7

Moved

Question 8

400

Answer 8

Bad request

Question 9

404

Answer 9

Not found

Question 10

505

Answer 10

Unsupported HTTP version

Question 11

Parts of working with cookies

Answer 11

1. Cookie Header line in HTTP response
2. Cookie Header line in HTTP request
3. Cookie files on user’s filesystem
4. Backend database

Question 12

Uses of Cookies

Answer 12

1. Memorize user state
2. Server can learn about a user
3. Targeted adds
4. Sell data

Question 13

Web Caching Proxy

Answer 13

Original request is sent to a closer proxy server instead of the original base server. Checks to see if it has the cache of the object to see if it doesn’t need to access the original. Uncashed requests are forwarded to the original server.

Question 14

Nodal Delay

Answer 14

Processing, queueing, transmission, and propogation

Question 15

CDN

Answer 15

Geographically distributed cache
Main shared CDNS are akami and limelight.

Dedicated CDNS are Google and Microsoft as examples

Question 16

Web Cacheing problems

Answer 16

Stale data - severing an old version
Cache invalidation - marking data as old
Cache coherence - different versions served
Cache warming - initial cache must be started up
Cache eviction - removing unpopular content
Cache DOS - denial of service on a cache server.