Application Layer - Kap 2- Uke 4-5

Authoritative DNS server

Provides authoritative hostname to IP mappings for organization's named hosts.

Why is video buffering important in streaming?

To ensure smooth playback by preloading video data to handle potential network inconsistencies.

What is the purpose of web caching?

To reduce response time for client requests and reduce traffic on an institution's access link.

What is the format of a DNS resource record (RR)?

(name, value, type, TTL)

DASH

An approach that allows a client to adapt the ecoding rate of retrived video to network congestion conditions

What are Top-Level Domain (TLD) servers responsible for?

Managing top-level domains such as .com, .org, .net, .edu, and country-specific domains.

What does the HTTP status code 404 indicate?

Not Found: The requested resource could not be found on the server.

What does the HTTP status code 200 indicate?

OK: The request succeeded, and the requested resource is in the response.

What percentage of residential ISP traffic was video streaming in 2020?

80% (from services like Netflix, YouTube, Amazon Prime).

Enter Deep

A CDN approach that stores content in access networks, close to clients.

Manifest

A file containing the location and encoding rate of files corresponding to video segments in a video

What information does the type "A" resource record hold in the DNS database?

A hostname and an IP address

What is an iterated DNS query?

A process where the queried server replies with the address of another server to ask, continuing until the correct server is reached.

What is HTTP?

A protocol to exchange hypertext documents

What is a Uniform Resource Locator (URL)?

A reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it.

What does a client-server architecture entail?

A server is always on and has a permanent address, while clients are intermittently connected and communicate with the server.

local DNS server

A server that handles DNS queries for clients within a specific local network, either answering from its cache or forwarding to higher hierarchy servers.

HyperText Markup Language (HTML)

A textual format to represent hypertext documents

chunk

A unit of video, each of which may be encoded at multiple different rates, stored in different files.

Name the types of DNS resource records and their purpose.

A: maps a hostname to an IP address. NS: points to a name server. CNAME: maps an alias to a canonical name. MX: directs to a mail server.

What are the three main components of a URL?

Protocol, Host Name, Path Name

What is HTTP/3 built on, and what issue does it address?

Built on QUIC protocol over UDP, addressing the problem of head-of-line blocking in HTTP/2.

How does video streaming adapt to network conditions?

By offering multiple quality levels and switching between them based on current network performance.

Why is caching important in DNS?

Caching improves response times by storing recent query results, reducing the need for repeated resolutions.

Where can web caching occur?

Client browsers, proxies, and content delivery networks (CDNs).

Peer-to-Peer (P2P) architecture.

Clients directly communicate with each other without a server, providing services to each other.

What mechanism is used by websites and browsers to maintain state between transactions?

Cookies.

Explain the purpose of DNS.

DNS translates human-readable domain names to IP addresses, enabling the location of devices on the Internet.

DNS

Domain Name System

What is DASH in video streaming?

Dynamic Adaptive Streaming over HTTP, a protocol that allows adaptive streaming of multimedia content over the Internet by segmenting video into small chunks.

What are the common HTTP methods and their functions?

GET: Requests data from a specified source. HEAD: Similar to GET but without the response body. POST: Sends data to the server. PUT: Updates or creates a resource on the server. DELETE: Deletes a specified resource.

DNS root services

Highest level of the DNS hierarchy, knows how to reach servers responsible for a givendomain (e.g., .com, .edu)

What are the main services provided by DNS?

Hostname to IP address translation, host aliasing, mail server aliasing, and load distribution.

What are the four building blocks of the WWW?

HyperText Markup Language (HTML) HyperText Transfer Protocol (HTTP) A client (first web browser) A server to provide access to the pages

Who manages the root DNS domain?

ICANN (Internet Corporation for Assigned Names and Numbers).

What is the function of an authoritative DNS server?

It provides authoritative responses to queries about domain names within its scope.

What is the role of an authoritative name server in the DNS?

It provides the definitive answer to the query with respect to a name in the authoritative name server's domain

What is the main advantage of HTTP/2 over HTTP/1.1?

It uses multiplexing to improve latency by allowing multiple requests and responses to be sent in parallel over a single TCP connection.

Local DNS server

Replies to DNS query by local host, by contacting other DNS servers to answer the query.

Top Level Domain (TLD) servers

Responsible for a domain (e.g., *.com, *.edu); knows how to contact authoritative name servers.

Why is DNS not centralized?

Single point of failure, jigh traffic volume, distant centralized database issues, difficult maintenance. It doesn't scale

What is a recursive DNS query?

The DNS server contacted will resolve the query completely by querying other servers on behalf of the client.

Describe the HTTP request-response process

The client initiates a TCP connection to the server, sends an HTTP request, and the server responds with the requested content.

What is a root DNS server?

The highest level in the DNS hierarchy, it helps resolve requests by directing them to appropriate TLD servers.

Define Round-Trip Time (RTT) in the context of HTTP performance.

The time it takes for a small packet to travel from the client to the server and back.

What is the significance of persistent connections in HTTP/1.1?

They maintain the same TCP connection for multiple requests, reducing connection setup and teardown time.

Who first implemented the WWW and in what decade?

Tim Berners-Lee in the 1990s.

Why do video services use Content Distribution Networks (CDNs)?

To distribute content closer to users, reducing latency and improving load times and reliability.

Explain HTTP streaming.

Video is stored on an HTTP server and delivered to clients who request the URL, allowing buffering to minimize interruptions.

What is the World Wide Web (WWW)?

a collection of websites that are hosted on web servers and accessed through the http protocol