Podcast
Questions and Answers
What is the primary requirement for file transfer applications in terms of data loss?
What is the primary requirement for file transfer applications in terms of data loss?
No loss
Which type of applications can tolerate some loss of data?
Which type of applications can tolerate some loss of data?
Real-time audio/video and stored audio/video
What is the primary advantage of using UDP over TCP?
What is the primary advantage of using UDP over TCP?
Faster transmission due to lack of reliability checks
What is the purpose of flow control in TCP?
What is the purpose of flow control in TCP?
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What is the primary requirement for interactive games in terms of time sensitivity?
What is the primary requirement for interactive games in terms of time sensitivity?
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What is the main difference between TCP and UDP in terms of congestion control?
What is the main difference between TCP and UDP in terms of congestion control?
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What is the requirement for web documents in terms of throughput?
What is the requirement for web documents in terms of throughput?
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What is the primary requirement for real-time audio/video applications in terms of throughput?
What is the primary requirement for real-time audio/video applications in terms of throughput?
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What is the primary purpose of the transport layer in terms of application requirements?
What is the primary purpose of the transport layer in terms of application requirements?
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What is the main advantage of using TCP over UDP in terms of reliability?
What is the main advantage of using TCP over UDP in terms of reliability?
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Study Notes
Caching
- Caching reduces response time and traffic on an institution's access link.
- Typically, cache is installed by an ISP (university, company, residential ISP).
- Caching enables "poor" content providers to effectively deliver content.
Caching Example
- Assumptions: average object size is 100K bits, average request rate from browsers to origin servers is 15/sec, average data rate to browsers is 1.50 Mbps, RTT from institutional router to any origin server is 2 sec, and access link rate is 1.54 Mbps.
- Consequences:
- LAN utilization is 15%.
- Access link utilization is 99%.
- Total delay includes Internet delay, access delay, and LAN delay.
Fatter Access Link
- Assumptions: average object size is 100K bits, average request rate from browsers to origin servers is 15/sec, average data rate to browsers is 1.50 Mbps, RTT from institutional router to any origin server is 2 sec, and access link rate is increased to 154 Mbps.
- Consequences:
- LAN utilization is 15%.
- Access link utilization is 9.9%.
- Total delay is reduced.
Local Cache
- Assumptions: cache hit rate is 0.4, or 40% of requests are satisfied at the cache.
- Calculating access link utilization and delay with cache:
- Access link utilization is 0.58.
- Total delay is approximately 1.2 secs.
Network Applications
- Principles of network applications
- Web and HTTP
- Electronic mail (SMTP, POP3, IMAP)
- DNS
- P2P applications
- Video streaming and content distribution networks
- Socket programming with UDP and TCP
Electronic Mail
- Three major components:
- User agents
- Mail servers
- Simple mail transfer protocol (SMTP)
- User Agent:
- Data integrity and throughput
- Some apps require 100% reliable data transfer
- Other apps can tolerate some loss
Transport Service Requirements
- Common applications and their requirements:
- File transfer: no loss, elastic, and no time sensitivity
- E-mail: no loss, elastic, and no time sensitivity
- Web documents: no loss, elastic, and no time sensitivity
- Real-time audio/video: loss-tolerant, specific throughput, and time-sensitive
- Stored audio/video: loss-tolerant, specific throughput, and time-sensitive
- Interactive games: loss-tolerant, specific throughput, and time-sensitive
- Text messaging: no loss, elastic, and no time sensitivity
Internet Transport Protocols
- TCP service:
- Reliable transport between sending and receiving process
- Flow control: sender won't overwhelm receiver
- Congestion control: throttle sender when network is overloaded
- Does not provide: timing, minimum throughput guarantee, security, or connection setup
- UDP service:
- Unreliable data transfer between sending and receiving process
- Does not provide: reliability, flow control, congestion control, timing, throughput guarantee, security, or connection setup
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Description
This quiz covers the concept of client-server architecture, the role of caching in reducing response time and traffic, and its importance in content delivery.
