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16 Cards in this Set
- Front
- Back
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What is the difference between network architecture and application architecture? |
1 |
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A popular social networking site can quickly become overwhelmed if it has onlyone server handling all of its requests. How is this tackled in practice? |
2 |
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Suppose you want to do transmission from a remote client to a server as fast as possible. Would you use TCP or UDP? Justify your choice. |
3
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Recall that TCP can be enhanced with SSL to provide process-to-process security services,including encryption. Does SSL operate at the transport layer or the application layer? If the application developer wants TCP to be enhanced with SSL, what doesthe developer have to do? |
4
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What is the main purpose of DNS? What other services does it provide? Name at leasttwo. |
5
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Name two record types of DNS and briefly explain the meaning of their fields. |
6
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How is the reliability and scalability of DNS guaranteed? |
7
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Which transport protocol is used by DNS? Why? |
8 |
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App-layer protocol defines: |
Types of messages exchanged - request, response Message syntax - What fields in messages & how fields are delineated Message semantics - Meaning of information in fields Rules for when and how processes send & respond to messages Open protocols - e.g. HTTP, SMTP Proprietary protocols - e.g. Skype |
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What transport service does an application need? |
Data integrity - Some apps require 100% reliable data transfer. Timing - Some apps require low delay to be effective Throughput - Some apps require minimum amount throughput to be effective. Security - Encryption, data integrity . . |
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TCP service : |
Reliable transport between sending and receiving process Flow control: Sender won't overwhelm receiver Congestion control: throttle sender when network overloaded Does not provide: Timing, minimum throughput guarantee, security Connection-oriented: Setup required between client and server processes |
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UDP Service: |
Unreliable data transfer between sending and receiving process Does not provide: reliability, flow control, congestion control, timing, throughput guarantee, security, connection setup |
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HTTP |
Web application protocol Uses TCP HTTP is Stateless non-persistent HTTP -- at most one object sent over TCP connection -- downloading multiple objects require multiple connections persistent HTTP --Multiple objects can be sent over single TCP connection |
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RTT |
Time for a small packet to travel from client to server and back |
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HTTP response status codes |
200 OK 301 Moved permanently 400 Bad request 404 Not found 505 HTTP Version not supported |
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Cookies |
Four components: 1) cookie header line of HTTP response message 2) cookie header line in next HTTP message 3) cookie file kept on user's host, managed by browser 4) back-end database at Web site |
