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Questions and Answers
What is a primary characteristic of a Peer-to-Peer (P2P) architecture?
What is a primary characteristic of a Peer-to-Peer (P2P) architecture?
Which DNS record type is responsible for mapping a domain name to an IP address?
Which DNS record type is responsible for mapping a domain name to an IP address?
What happens to DNS cache entries after they timeout?
What happens to DNS cache entries after they timeout?
Which of the following describes a CNAME DNS record?
Which of the following describes a CNAME DNS record?
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What is a potential security threat to DNS outlined in the content?
What is a potential security threat to DNS outlined in the content?
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What is one disadvantage of cached DNS entries?
What is one disadvantage of cached DNS entries?
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In DNS, which type of record indicates the authoritative server for a domain?
In DNS, which type of record indicates the authoritative server for a domain?
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What is the main purpose of DNSSEC?
What is the main purpose of DNSSEC?
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Which of the following is a benefit of a Content Distribution Network (CDN)?
Which of the following is a benefit of a Content Distribution Network (CDN)?
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What is a challenge specifically associated with P2P file sharing?
What is a challenge specifically associated with P2P file sharing?
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Study Notes
Mega-Server vs. CDN
- A single large "mega-server" can be a single point of failure, leading to network congestion and inefficient long-distance routing.
- Cannot scale effectively to serve millions of video streams to numerous users simultaneously.
Content Distribution Networks (CDNs)
- CDNs are used to stream content from multiple servers in geographically distributed sites, enhancing scalability.
- Akamai is a major CDN provider with around 240,000 servers across 120 countries as of 2015.
- Content is stored in CDN nodes, allowing subscribers to request and receive videos from copies located close to them, improving retrieval times.
Over-The-Top (OTT) Streaming
- OTT enables Internet host-host communication, facing challenges such as dealing with network congestion and optimizing content placement across CDN nodes.
Streaming Stored Video Challenges
- Continuous playout requirements mean clients must match playback timing with variable network delays, necessitating buffering.
- Interactivity features like pause, fast-forward, and rewind can affect streaming performance, as video packets might be lost and need retransmission.
Playout Buffering
- Client-side buffering is crucial for managing network delays and jitter during video playback.
- Ensures a smooth viewing experience by buffering and adjusting to network conditions.
DASH (Dynamic Adaptive Streaming over HTTP)
- DASH divides video files into chunks encoded at various rates, with a manifest file linking to these chunks.
- Clients request video chunks based on real-time assessments of available bandwidth, allowing for adaptive streaming quality.
Client Intelligence in DASH
- Clients determine when to request new chunks and select encoding rates based on current network conditions to prevent buffer starvation or overflow.
DNS Caching and Management
- DNS entries cache mappings of names to IP addresses, with a time-to-live (TTL) after which they may expire.
- Updates on DNS mappings could lead to outdated entries until TTLs expire globally.
DNS Records
- DNS operates as a distributed database with various resource record (RR) types, including A (address), CNAME (canonical name), NS (name server), and MX (mail server).
DNS Protocol Messages
- Both DNS queries and replies share the same general format, including fields for identification, flags, questions, answers, authority records, and additional information.
Inserting Records into DNS
- New domain registrations require authoritative name server details, with NS and A records inserted into TLD servers appropriately to establish domain mappings.
DNS Security Concerns
- DNS is vulnerable to DDoS attacks, redirect attacks, and DNS poisoning, where false responses are sent to disrupt service.
- DNSSEC offers a layer of security to prevent certain types of attacks by validating responses.
Overview of Application Layer
- The application layer encompasses various services including P2P applications, video streaming, web services (HTTP), and email protocols (SMTP, IMAP), addressing fundamental network principles.
Peer-to-Peer (P2P) Architecture
- P2P networks lack centralized servers, allowing arbitrary end systems to communicate directly.
- P2P systems are self-scaling; new peers enhance capacity and demand simultaneously, supporting applications like file sharing (BitTorrent) and streaming (KanKan).
Client-Server vs. P2P File Distribution
- The efficiency of file distribution from a server to multiple peers (N) involves consideration of the file size (F) and network conditions impacting distribution time.
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Description
Explore the challenges and solutions of streaming content using content distribution networks (CDNs). This quiz highlights the issues with a single 'mega-server' approach and discusses scalable alternatives. Test your understanding of how CDNs support simultaneous users efficiently.
