cdn: content distribution networks

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CDN: Content Distribution Networks References: CS613 textbook, “Computer Networking – A Top-Down Approach”, 6 th edition. Chapter 7.2.4. The text of 7.2.4 offers several references, including study on Google. Selected a couple from these references. Multmedia Networking 7-1

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CDN: Content Distribution Networks. References: CS613 textbook, “Computer N etworking – A Top-Down Approach”, 6 th edition. Chapter 7.2.4. The text of 7.2.4 offers several references, including study on G oogle. Selected a couple from these references. Content distribution networks. - PowerPoint PPT Presentation

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Page 1: CDN: Content Distribution Networks

CDN: Content Distribution Networks References:

CS613 textbook, “Computer Networking – A Top-Down Approach”, 6th edition. Chapter 7.2.4.

The text of 7.2.4 offers several references, including study on Google. Selected a couple from these references.

Multmedia Networking 7-1

Page 2: CDN: Content Distribution Networks

Content distribution networks

challenge: how to stream content (selected from millions of videos) to hundreds of thousands of simultaneous users?

option 1: single, large “mega-server” single point of failure point of network congestion long path to distant clients multiple copies of video sent over outgoing

link….quite simply: this solution doesn’t scale

Multmedia Networking 7-2

Page 3: CDN: Content Distribution Networks

Content distribution networks

challenge: how to stream content (selected from millions of videos) to hundreds of thousands of simultaneous users?

option 2: store/serve multiple copies of videos at multiple geographically distributed sites (CDN) enter deep: push CDN servers deep into many

access networks • close to users• used by Akamai, 1700 locations

bring home: smaller number (10’s) of larger clusters in POPs near (but not within) access networks

• used by LimelightMultmedia Networking 7-3

Page 4: CDN: Content Distribution Networks

CDN: “simple” content access scenario

Multmedia Networking 7-4

Bob (client) requests video http://netcinema.com/6Y7B23Vvideo stored in CDN at http://KingCDN.com/NetC6y&B23V

netcinema.com

KingCDN.com

1

1. Bob gets URL for for video http://netcinema.com/6Y7B23Vfrom netcinema.com web page 2

2. resolve http://netcinema.com/6Y7B23Vvia Bob’s local DNS

netcinema’sauthorative DNS

3

3. netcinema’s DNS returns URL http://KingCDN.com/NetC6y&B23V

4

4&5. Resolve http://KingCDN.com/NetC6y&B23via KingCDN’s authoritative DNS, which returns IP address of KIingCDN server with video

56. request video fromKINGCDN server,streamed via HTTP

KingCDNauthoritative DNS

Page 5: CDN: Content Distribution Networks

CDN cluster selection strategy

challenge: how does CDN DNS select “good” CDN node to stream to client pick CDN node geographically closest to

client pick CDN node with shortest delay (or min #

hops) to client (CDN nodes periodically ping access ISPs, reporting results to CDN DNS)

IP anycast

alternative: let client decide - give client a list of several CDN servers client pings servers, picks “best” Netflix approach

Multmedia Networking 7-5

Page 6: CDN: Content Distribution Networks

Case study: Netflix 30% downstream US traffic in 2011 owns very little infrastructure, uses 3rd party

services: own registration, payment servers Amazon (3rd party) cloud services:

• Netflix uploads studio master to Amazon cloud• create multiple version of movie (different

endodings) in cloud• upload versions from cloud to CDNs• Cloud hosts Netflix web pages for user

browsing three 3rd party CDNs host/stream Netflix

content: Akamai, Limelight, Level-3Multmedia Networking 7-6

Page 7: CDN: Content Distribution Networks

Case study: Netflix

Multmedia Networking 7-7

1

1. Bob manages Netflix account

Netflix registration,accounting servers

Amazon cloudAkamai CDN

Limelight CDN

Level-3 CDN

22. Bob browsesNetflix video

3

3. Manifest filereturned for requested video

4. DASH streaming

upload copies of multiple versions of video to CDNs