1.5 Content Delivery Network

Question 1

What is a content delivery network (CDN)?

Answer 1

A globally distributed network of proxy servers, serving content from locations closer to the user.

Question 2

What types of content are generally served from CDNs?

Answer 2

• HTML/CSS/JS
• Photos
• Videos
• Dynamic content (in some cases)

Question 3

How does serving content from CDNs improve performance?

Answer 3

• Users receive content from data centers close to them
• Your servers do not have to serve requests that the CDN fulfills

Question 4

What is a push CDN?

Answer 4

A CDN that receives new content whenever changes occur on your server, requiring you to upload content directly.

Question 5

When is a push CDN most effective?

Answer 5

For sites with a small amount of traffic or content that isn’t often updated.

Question 6

What is a pull CDN?

Answer 6

A CDN that grabs new content from your server when the first user requests it, caching it afterward.

Question 7

What determines how long content is cached in a pull CDN?

Answer 7

A time-to-live (TTL) setting.

Question 8

What are some disadvantages of using a CDN?

Answer 8

• Significant costs depending on traffic
• Content might be stale if updated before TTL expires
• Requires changing URLs for static content

Question 9

What is the primary goal of CDNs?

Answer 9

To provide high availability and performance by distributing services spatially relative to end users.

Question 10

What are some notable content delivery service providers?

Answer 10

• Akamai Technologies
• Edgio
• Cloudflare
• Amazon CloudFront
• Fastly
• Google Cloud CDN

Question 11

What is the role of CDN nodes?

Answer 11

To reduce bandwidth costs, improve page load times, and increase global content availability.

Question 12

How do CDNs optimize content delivery?

Answer 12

By directing requests to optimal nodes based on performance and cost.

Question 13

True or False: CDNs can serve both static and dynamic content.

Answer 13

True.

Question 14

What is server-load balancing?

Answer 14

A method to share traffic among multiple servers or web caches to improve scalability and reliability.

Question 15

What does request routing in CDNs do?

Answer 15

Directs client requests to the content source best able to serve the request.

Question 16

What is the Internet Content Adaptation Protocol (ICAP)?

Answer 16

A protocol developed to provide an open standard for connecting application servers.

Question 17

What is a peer-to-peer (P2P) content delivery network?

Answer 17

A network where clients provide resources as well as use them.

Question 18

What is a private CDN?

Answer 18

A CDN created by content owners to serve their own content, consisting of PoPs only for their use.

Question 19

What advantages do telco CDNs have over traditional CDNs?

Answer 19

• Own the last mile
• Deliver content closer to the end-user
• Built-in cost advantage
• Better control over resource utilization

Question 20

What is the Open Caching specification?

Answer 20

Defines a set of APIs allowing a Content Provider to deliver content using several CDNs consistently.

Question 21

What is EDNS0 and how does it improve CDN performance?

Answer 21

An extension that allows CDNs to utilize the requesting client’s subnet IP address, reducing round-trip latencies.

Question 22

What are virtual CDNs (vCDNs)?

Answer 22

CDNs that use virtualization technologies to reduce costs, increase elasticity, and decrease service delay.

Question 23

What is the purpose of EDNS0 in DNS?

Answer 23

To optimize trip latencies and improve performance for clients using public DNS or non-local resolvers.

EDNS0 has drawbacks including decreased caching effectiveness, increased DNS resolution traffic, and privacy concerns.

Question 24

What does vCDN stand for?

Answer 24

Virtual Content Delivery Network.

vCDNs use virtualization technologies to reduce costs, increase elasticity, and decrease service delay.

Question 25

How does a vCDN improve service delivery?

Answer 25

By deploying virtual caches dynamically based on content type and server or end-user geographic location. ## Footnote This approach helps to avoid traditional CDN limitations.

Question 26

What are Image CDNs designed to do?

Answer 26

Serve multiple versions of the same image through HTTP based on browser properties. ## Footnote The goal is to serve high-quality images while preserving download speed.

Question 27

What are the three components generally supported by an Image CDN?

Answer 27

* A Content Delivery Network for fast serving of images * Image manipulation and optimization * Device Detection ## Footnote Device Detection involves analyzing User-Agent strings, HTTP Accept headers, or Client-Hints.

Question 28

What is the main difference between Pull CDNs and Push CDNs?

Answer 28

Pull CDNs cache content upon request, while Push CDNs require uploading all content beforehand. ## Footnote Each has different benefits and costs associated with their usage.

Question 29

What are the benefits of using a Pull CDN?

Answer 29

* Easier to configure * Seamless storage and updating of content * Lower maintenance required ## Footnote Ideal for low traffic sites or those well-optimized with caching.

Question 30

What is a potential drawback of a Pull CDN?

Answer 30

Lack of control over cache duration, leading to delays in updates being reflected. ## Footnote Changes might take up to 24 hours to propagate.

Question 31

What is a benefit of using a Push CDN?

Answer 31

Content is always available on CDN servers, reducing load times for large downloads. ## Footnote More efficient for sites with videos or podcasts.

Question 32

When might a Push CDN strain your server?

Answer 32

When pushing frequent updates or if the server is underpowered for high traffic. ## Footnote It requires more server resources to sync data with the CDN.

Question 33

What should you monitor after choosing a CDN type?

Answer 33

Usage over the first 1-3 months and loading times. ## Footnote This helps determine which CDN type is best suited for your needs.