Networking Fundamentals: Caching and DNS

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Questions and Answers

What is the primary benefit of caching for a client?

Increases storage requirements on the client device

Enhances the quality of content received

Reduces response time by serving content from a closer cache (correct)

Limits the number of servers needed for content delivery

What role does the server play in caching?

It informs the cache about the object's allowable caching through headers (correct)

It manages the downloading speed of clients

It primarily stores data for future requests

It caches all content without restrictions

How does the presence of many caches on the Internet benefit content providers?

It decreases the number of users accessing content

It increases the cost of content delivery

It standardizes pricing for all content

It allows content providers to serve content more efficiently (correct)

What is the utilization of the access link in the example provided?

.97 Signup and view all the answers

What is indicated by the average request rate from browsers to origin servers?

Browsers average 15 requests per second to origin servers Signup and view all the answers

What is the purpose of coding in digital images?

To decrease the number of bits used to encode an image Signup and view all the answers

Which of the following is an example of spatial coding?

Sending color value and number of repeated values Signup and view all the answers

What does CBR stand for in video encoding?

Constant Bit Rate Signup and view all the answers

How does VBR differ from CBR in video streaming?

VBR changes encoding rate based on content complexity. Signup and view all the answers

What is a primary challenge of streaming stored video over the Internet?

Network congestion affecting bandwidth transmission Signup and view all the answers

When using temporal coding, what is sent instead of the complete frame?

Only the differences from the previous frame Signup and view all the answers

In video encoding, which of the following is NOT a common parameter for MPEG standards?

MPEG3: 50 Mbps Signup and view all the answers

Which of the following best describes how a packet loss can affect video streaming?

It will cause delays or degrade video quality. Signup and view all the answers

What is the primary purpose of DNSSEC?

Providing authentication and message integrity Signup and view all the answers

Who manages the root DNS domain?

ICANN Signup and view all the answers

What is the role of top-level domain (TLD) servers?

Responsible for top-level domains like .com and .edu Signup and view all the answers

What does a local DNS server do when it receives a DNS query?

Checks its local cache and may forward the request Signup and view all the answers

Which of the following correctly describes an authoritative DNS server?

Provides authoritative hostname to IP mappings for an organization Signup and view all the answers

What is an iterated DNS query?

A query where each server replies with the next server's location Signup and view all the answers

Which of the following is an example of a local DNS server query command in Windows?

ipconfig /all Signup and view all the answers

What happens in a recursive DNS query?

The local DNS server resolves the name on behalf of the requester Signup and view all the answers

What does it indicate when a local DNS server returns a response from its cache?

The data might be outdated Signup and view all the answers

Which organization is the authoritative registry for the .edu TLD?

Educause Signup and view all the answers

What is the role of a tracker in a P2P file distribution system like BitTorrent?

To track peers participating in the torrent Signup and view all the answers

What happens when a peer in a torrent has no chunks initially?

The peer accumulates chunks over time from other peers. Signup and view all the answers

How does a peer decide which peers to send chunks to in BitTorrent?

It uses a tit-for-tat strategy to send to peers sharing chunks at the highest rate. Signup and view all the answers

What is indicated by the term 'churn' in the context of a P2P file distribution system?

The joining and leaving of peers in the torrent. Signup and view all the answers

What is the primary purpose of the 'optimistically unchoke' strategy in BitTorrent?

To randomly select a peer for possible file exchange. Signup and view all the answers

Which of the following accurately describes how file chunks are managed in BitTorrent?

Peers may have different subsets of chunks and request the rarest ones first. Signup and view all the answers

What is a significant feature of the peer-to-peer system in BitTorrent regarding file sharing?

Peers can continuously change the selection of peers with whom they exchange chunks. Signup and view all the answers

In BitTorrent, what does it mean for a peer to be one of the 'top four providers'?

The peer consistently uploads chunks at a high rate to the other peers. Signup and view all the answers

What is the first step a peer takes when joining a torrent in BitTorrent?

Register with the tracker to obtain a list of peers. Signup and view all the answers

What are the characteristics of a client-server architecture?

Centralized and stateful Signup and view all the answers

Which protocol is used for email transmission?

SMTP Signup and view all the answers

In a typical request/reply message exchange, what does the client do?

Requests information or service Signup and view all the answers

What type of transport service does TCP provide?

Connection-oriented and reliable Signup and view all the answers

What themes are important when discussing application service requirements?

Reliability, bandwidth, delay Signup and view all the answers

What does the term 'stateless' imply in application interactions?

Each request is treated independently without stored context Signup and view all the answers

Which of the following is NOT a specific application protocol mentioned?

POP3 Signup and view all the answers

In the context of message formats, what do headers represent?

Field sections providing information about the data Signup and view all the answers

Study Notes

Caching

Caching reduces response time by storing frequently requested data closer to the client, reducing traffic on access links.
Caches are present throughout the internet, assisting even "poor" content providers to deliver content effectively.
Servers inform caches about appropriate caching behavior through response headers.

DNS (Domain Name System)

Resolves domain names to IP addresses
DNSSEC (Domain Name System Security Extensions) adds security by authenticating name servers and ensuring message integrity.
Top-Level Domain (TLD) servers handle .com, .org, .net, and country-specific domains (.cn, .uk, etc.).
Authoritative DNS servers are specific to organizations, providing hostname to IP mappings for their hosts.
Local DNS servers act as intermediaries between hosts and the DNS hierarchy, caching recent name-to-address translations, but might contain outdated information.
When a host makes a DNS query, its local DNS server either resolves it from its cache or forwards the request through the DNS hierarchy.

DNS Resolution Processes

Iterated query: The initial server contacts other servers in the hierarchy until the authoritative DNS server provides the IP address.
Recursive query: The initial server takes on the responsibility to resolve the query, contacting other servers until the authoritative DNS server is reached. This puts a heavy load on servers at the top of the hierarchy.

Peer-to-Peer (P2P) File Distribution

In P2P, peers contribute resources and act as both clients and servers, distributing files faster than traditional client-server approaches as the number of peers increases.
P2P file distribution is typically faster than client-server for large file sizes.

Bittorrent

Bittorrent protocol divides files into chunks and allows peers to exchange those chunks.
Bittorrent uses a tracker to keep track of participating peers and their available chunks.
When a peer joins a torrent, it gradually accumulates missing chunks and uploads chunks it already possesses to other peers, effectively contributing to the file distribution process.
Peers might "churn" – join and leave the network, potentially affecting the distribution rate.

Multimedia: Video Compression

Encoding reduces the number of bits required to represent images, improving storage and transmission efficiency.
Spatial coding: Exploits redundancies within an image, such as repeating color values.
Temporal coding: Leverages redundancies between consecutive frames, sending only differences in frame content.
Constant Bit Rate (CBR): Maintains a fixed encoding rate, regardless of the complexity of the video content.
Variable Bit Rate (VBR): Adjusts the encoding rate based on the complexity of the image, offering varying levels of compression.

Streaming Stored Video

Streaming video presents challenges due to varying bandwidth and potential packet loss or delays.
Techniques like buffering, adaptive streaming, and content delivery networks (CDNs) are employed to manage video quality and smooth playback.
The text provides a simplified illustration of the video streaming process, highlighting the server’s role in sending the video content to a client.

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Description

This quiz covers essential concepts in networking, focusing on Caching and the Domain Name System (DNS). You'll learn about how caching minimizes response times, the role of DNS in resolving domain names, and security enhancements through DNSSEC. Test your knowledge on these critical components of internet infrastructure.