Explain three techniques used by the Web (HTTP) to reduce latency
Try an answer before revealing the guidance below.
Key Concepts
- Persistent connections
- Pipelining
- Web caching / proxy
- Conditional GET
- Compression
Answer Approach
- Think about the cost of TCP connection setup per object.
- Think about waiting one RTT per request.
- Think about avoiding the transfer altogether or making it smaller.
Full Answer
Answer status: Draft answer (unofficial). Revision notes, not an official marking scheme.
(1) Persistent connections: several objects are fetched over one TCP connection, avoiding a handshake RTT and slow-start restart per object. (2) Pipelining: the client sends several requests back-to-back without waiting for each response, so multiple objects arrive in about one RTT. (3) Caching: browser caches and web proxy caches close to the client serve objects locally; a conditional GET (If-Modified-Since) only transfers the object if it has changed. Compression of responses also reduces transfer time.
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