Content Delivery Network - CDN Mojtaba HOUSHMAND mojtaba.houshmand@gmail.com

1. Mojtaba HOUSHMAND
IT‐VAS Solutions Telecommunication – Consultant
Mojtaba.houshmand@gmail.com
Dec – 2017
Version 1.0
Content Delivery Network
“CDN”

2. Content Outline
• Content Delivery Network Overview ---------------------------------> 3
• Content Delivery Network Architecture -----------------------------> 21
• Content Delivery Management ----------------------------------------> 30
• CDN Services & Functionalities ----------------------------------------> 34
• CDN Schemes ---------------------------------------------------------------> 52
• CDN Protocols --------------------------------------------------------------> 59
• CDNs vs. Caches ------------------------------------------------------------> 61
• CDN Revenue Sharing Model -------------------------------------------> 62
• Future Of CDN --------------------------------------------------------------> 64
• Known CDN Platforms ----------------------------------------------------> 65
• Case Study: Akamai Technology ---------------------------------------> 66
• References -------------------------------------------------------------------> 68

3. Content Delivery Network Overview
• Online Video Business Models
• Distance Matters and Network Terminology
• Static & Dynamic CDN
• Content Delivery Network
• CDN Terminology
• Suitable Content for CDN

4. Online Video Business Models
OVP, CMS, MVP, CDN
Online Video Platform (OVP):
• Come from website video services into the multiscreen arena
• Publish video to the internet by offering an 'ingest once, publish
anywhere' approach
Have comprehensive offerings including:
• Content Management System (CMS) that helps to:
• Manage videos
• Publish videos to social media
• Advertising plug-ins that helps to:
• Monetize content
• Integration APIs for mid-large scale video distributors
• Easily deliver videos to all devices
• Famous Companies: Brightcove, Ooyala, and Kaltura

5. Online Video Business Models
OVP, CMS, MVP, CDN
Content Management System (CMS):
• Handle the metadata required to ingest, manage and publish
content as part of a Pay TV offering
• Providing better support for rights that vary by geography and
device-type
• Focus on TV Everywhere services
• Handle multiple assets based on codec or packaging format.
• Famous Companies: thePlatform and KIT Digital

6. Online Video Business Models
OVP, CMS, MVP, CDN
Managed Video Platform (MVP):
• Used by mobile operators and/or traditional Pay TV distributors
• Can generally be integrated in-house by the operators
• Can be used on a hosted basis by the operator from the vendor
using a:
• Software as a Service (SaaS)
• Platform as a Service (PaaS) model.
• Famous Companies: MobiTV and Quickplay

7. Online Video Business Models
OVP, CMS, MVP, CDN
Content Delivery Network (CDN):
• Responsible for getting bits from place to face in an efficient, low-
latency fashion
• Standalone CDNs are facing competition from two directions:
• Telcos and MSOs are building their own CDNs to minimize their
bandwidth cost
• backbone carriers such as Level3 and Tata are also looking at
CDN as a value added service to their customers.
• Famous Companies: Akamai and Limelight

8. Distance Matters
Greater Distance = Slower Communication
• Bits travel at a limited speed
• Laws of physics – apply to all connections
Greater Distance = More Routing Hops
• Greater chance of losing packets
• Slowest router in pat dictates speed
• Routing path isn’t optimal

9. Some Network Terminology
Latency
• Upload: Time to get bit from client to server
• Download: Time to get bit from server to client
Round-Trip Time (RTT)
• Upload Latency + Download Latency
Packet Loss Ratio (PLR)
• Average Percentage of Lost Packets
Effective Bandwidth
• Real Upload/Download Speed, after RTT & PLR

10. CDNs bring the data closer
Move data closer to users
• Improve RTT & Effective Bandwidth
Keep many Edge Servers
Sample Scenario
1. User requests (http://cdn.any.ir/image.gif)
2. cdn.any.ir resolves to closest Edge Server
3. if not in cache, Edge fetches and caches file
4. Edge returns data from local cache
5. Closer Copy = Faster Download

11. Static vs. Dynamic Content
Cache means Static Data
• Page Resources: Images, CSS, Javascript...
• Larger Download
For Dynamic Data, some CDNs offer:
• Routing Optimization
• Extremely short-term cache

12. Common Mistakes
Stale Cache
• Outdated copy on edge server
Solution: Versioning
Double Payments
• Pay Hosting & CDN Bandwidth cost
Solution: Separate domain for static, cache-able files
CDN-Specific Frequently Check
• Test your CDN
• Look for cache-hit header
• Check CDN cache-hit dashboards

13. Content Delivery Network
• Is a collaborative collection of network element spanning the
Internet.
• Content are replicated over several mirrored Web Server.
Why it is done?
• To perform transparent and effective delivery of content to the end-
user.
• To over come the inherent limitations of the Internet in terms of
QoS.
• Improving the performance by maximizing the bandwidth, improving
the accessibility.

14. Content Delivery Network
Generation of CDN
1st Generation:
Focused on Static or Dynamic Web Document
2nd Generation:
Focused on Video and Audio Streaming such as Video-on-Demand
(VoD) and Audio-on-Demand (AoD).
Mechanism for:
• Replicating content on multiple servers in the Internet.
• Providing clients with a means to determine the servers that can
deliver the content fastest.

15. Content Delivery Network
Model of Content Delivery Network
It contains 2 parts:
1. Encoded media
2. Meta data
Main entities in CDN systems are:
1. Content Provider
2. CDN provider
3. End-User

16. CDN: Basic Idea
congested
Not congested
original content
Replica
Replica
Client

17. CDN Terminology
• Content
Any publicly accessible combination of text, images, applets, frames,
MP3, video, flash, virtual reality objects, etc.
• Content Provider
Any individual, organization, or company that has content that it
wishes to make available to users.
• Origin Server
Content providers server , where the content is first uploaded.
• Surrogate Server
Content distributor’s server, where the replicated content is kept.

18. Players of the game in CDN
Content Provider
H/W and S/W
Vendor
Content
Distributor
Hosting
Provider
Yahoo,
MSNBC,
CNN
Cisco,
Lucent,
Inktomi,
CacheFlow
Akamai,
Digital Island,
AT&T
Exodus

19. Main drivers of CDN

20. Suitable Content for CDNs
Content Suitable for CDNs
• Images
• High-volume e-commerce transactions (thanksgiving sale)
• Streaming media (audio and video) (media events)
• Java Applets
• Virtual Reality Objects
• Flash content
Content NOT Suitable for CDNs
• Personalized content (my.yahoo.com,…)
• Dynamic Content
• Secure Content

21. Content Delivery Network Architecture
• Architectural Component of CDN
• Content Distribution Internet-working: CDI
• Request Routing
• Metrics

22. Architectural Component of CDN
4 Main Component:
1. Original Server
2. Distribution System
3. Request Routing System
4. Account System

23. Architectural Component of CDN
Request Routing in CDN Environment

24. Content Distribution Internet-working: CDI
• Interconnection of Content Networks – collaboration between
caching proxies and CDNs, as well as between individual CDNs
• Greater reach, larger scale, higher capacity, increased fault tolerance
• Basic architecture involves gateways between various content
networks

25. CDI: Architecture
A Model for Content Inter-networking (CDI)
RFC3466
Content Inter-networking (CDI) Scenarios
RFC3570

26. Request Routing Mechanisms
Best surrogate selected based on some metrics.
Techniques
• DNS based request routing
• Content Modification (URL rewriting)
• Anycast based
• Transport-Layer Request-Routing
• Application-Layer Request-Routing
• TTP Redirection
• CDN peering
• Combination of multiple mechanisms

27. CDN: DNS based Request Routing
Akamai DNS
Local DNS Server
128.4.4.12
www.cnn.com
63.251.132.22
www.cnn.com
Session
63.251.132.22
63.210.135.39surrogate
surrogate
www.cnn.com

28. Content Modification
...
<img
src="http://www.cdn.com
/cnn/images/1.gif”>
...
Index.html
GETwww.cnn.com/index.html
Index.html
DNS query: cdn.com ?
64.236.24.28
Authoritative DNS server for cdn.com
Local DNS serverClient
CNN.com
64.236.24.28

29. Metrics
Network Proximity (Surrogate to Client):
• Network hops (traceroute)
• Round Trip Time (RTT)
• Internet mapping services (NetGeo, IDMaps)
…
Surrogate Load:
• Number of active TCP connections
• HTTP request arrival rate
• Other OS metrics
…
Bandwidth Availability

30. Content Delivery Management
• Site Delivery
• Content Delivery Network Pricing/Billing

31. Content Delivery Management
Site Delivery
Full site delivery vs. Partial Site Delivery
Full Site Delivery:
All the contents are delivered by the CDN (including HTML, images,
and other objects).
Partial Site delivery:
Only images, streaming media and other bandwidth intensive objects
delivered by the CDN.

32. Content Delivery Management
Content Delivery Network Pricing/Billing
• Charging to the customer depend upon the content delivered to the
end-user by their surrogate servers.
• It support an account mechanism that collect and track client usage
information.
• The average cost of charging of CDN services is high
• Important factor which influence in revenue generation are:
1. Bandwidth cost
2. Variation of traffic distribution
3. Size of content replicated over surrogate servers
4. Number of surrogate server
5. Reliability and Stability of the whole system

33. Content Delivery Management
Pricing Model Of CDN
• Pricing Based On Aggregate Usage
• Charging on Monthly basis that is 50TB/month
• Percentile – Based Pricing
• Pricing based on the 95th percentile of traffic CDN periodically
samples the bandwidth usage of a subscribing content provider.
It then computes the 95th percentile of usage at the end of the
month and charges a price per Mbps based on the 95th
percentile of usage.

34. CDN Services & Functionalities
• Web Accelerator
• Video Delivery
• Media Streaming
• Live Streaming
• OTT
• IPTV
• Time Shifting
• VoD
• TV Catch-up
• Video Transcoding
• Load Balancing
• Reporting & Analytics

35. CDN Services & Functionalities

36. CDN Services & Functionalities
CDN services generally covered these aspects:
• Storage and Management of Content
• Distribution of Content among Edge Servers
• Cache Management
• Delivery of Encoded Media
• Backup and Disaster Recovery Solutions
• Monitoring and Performance

37. Website Accelerator
• Most web publishers start serving their site with a hosting service.
• With increase in traffic and geographically variance, don’t face
difficulty in scaling and delivering satisfactory user experiences
CDN will:
• Speed the delivery of assets to visitors
• Reduce the need to scale web infrastructure
• Improve user experiences

38. Website Accelerator
• Deliver HTML, CSS, Javascript, Ajax, images, video, and more
• Rich proxy capabilities, including query string handling and custom
header processing
• Control over HTTP header responses
• Rapid cache purging within the CDN
• Customers retain full control of their content and have the ability to
add, delete, rename, and update their own content
• Supported Devices: Support for browsers on PCs, tablets, mobile
devices, and set-top boxes
• Supported Protocols: HTTP
• Multi-format video delivery: HTTP, RTMP, RTSP
• Support for authentication with customer origin
• Support for reverting to a secondary origin in case the primary origin
server is unavailable
• Support for geo-blocking with directory-level control over

39. Video Delivery
Content owners can deliver best possible video experience on
websites and in applications
• Start instantly
• Play smoothly
• Flexible configuration options
• Advanced video features
• Reporting & Analytics
• Delivery of multiple bit-rates
• Delivery control by region
• Device supported
• Flexible configurations for storage and delivery of videos

40. Media Streaming
Streaming media is multimedia that is constantly received by and
presented to an end-user while being delivered by a provider.
Streaming Situations:
• Watch Digital Video Content
• Listen to Digital Audio Content
• No need to download before start to play
Media Streaming Applications:
• Flash: Adobe
• SilverLight: Microsoft
• HLS: Apple
Popular Streaming Services:
• Video Sharing Website: YouTube, Twitch and Mixer (Games)
• Movie & TV Shows: Netflix
• Music: Spotify and Apple Music

41. Live Streaming
Live Streaming refers to online streaming media simultaneously recorded
and broadcast in real time to the viewer.
Live stream services encompass a wide variety of topics, from social media
to video games.
With broad protocol, platform and device support, Live Broadcast
enables you to reach your viewers worldwide and on a variety of
platforms.
Lifecasting or lifestreaming is a real-life activity facilitated by live streaming.
Application:
Instagram Live, Facebook Live, Periscope
Video Game:
XboxLive, PSLive, Twitch

42. Live Streaming
Video Support Features
• DVR-Like Controls: pause, rewind, restart and jump to any point
within a live broadcast
• Configuration: Customer configurable CNAMEs
• Multiple Bit-Rate Support
• Secure
Streaming
• Encoders Supported
• Output Protocols: HTTP, HLS, RTMP, RTMPE, RTMPTE, RTSP, and
Silverlight.
• Supported Devices: laptops, tablets, mobile devices, and set-top
boxes
• iOS devices, Android devices, Windows devices,
• Resolutions: Support for up to 4K
• Reporting & Analytic

43. Over The Top (OTT)
Over the top (OTT) is an application or service that is able to provide a product over
the Internet. This method bypasses traditional methods of distribution.
Over the top services are mostly related to media and communication and are lower
in cost when compared to traditional delivery methods.
Hulu and Netflix that replaced regular TV providers and Skype that replaced long
distance communication providers are examples of OTT.
OTT Video
• Access is controlled by the video distributor, through either an app or a separate
OTT dongle or box, connected to a phone, PC or television set.
• Remains the most popular OTT content.
OTT Messaging
• Is defined as instant messaging services
• Alternative to text messaging services provided by a mobile network operator
• OTT messaging Application: WhatsApp, Viber, WeChat, Skype and Facebook msg.
OTT Voice Calling
• Use open Internet communication protocols
• For instance, as provided by Skype, WeChat, Viber, and WhatsApp

44. Internet Protocol TV (IPTV)
Internet Protocol television (IPTV):
• Deliver television content over Internet Protocol (IP) networks.
• Offers the ability to stream the source media continuously.
• Play almost immediately the content by client media player (such as a TV
channel).
• Widely deploy in subscriber-based telecommunications networks with
high-speed access channels into end-user premises via set-top boxes
• Use for media delivery around corporate and private networks.
IPTV services may be classified into three main groups:
• Live Television and Live Media
• Time-Shifted Media:
• Catch-up TV (replays a TV show that was broadcast hours or days ago)
• Start-over TV (replays the current TV show from its beginning);
• Video on Demand (VoD):
• browse and view items in a stored media catalog.

45. Video on Demand
Video on Demand (Display) (VoD)
• Allow users to select and watch/listen to video or audio content
• IPTV technology is often used to bring VoD to televisions and
personal computers.
Development of Video on Demand services:
• The video that was selected is transmitted through real-time
streaming protocol.
• While TV uses traditional broadcast technology, VoD uses unicast
transmission.
• Development of file sharing software.
Catch-up TV
• Watch TV shows though their VoD service hours or even days after
the original television broadcast.
• Watch a program in free time

46. Video on Demand
VoD vs. OTT
Service:
OTT: OTT can be related to a product or service
VoD: VoD is only related to videos and presentations
Channels:
OTT: A range of channels are available to be viewed.
VoD: The user can only view selected videos and this service is
premium in nature.
Quality:
OTT: OTT is more professional in managing, monetizing and distributing
video content.
VoD : VoD provides an uncompromised video experience.

47. Video Transcoding
Video Transcoding, also called video encoding, is the process that converts a
video file from one format to another, to make videos viewable across
different platforms and devices.
• Direct digital-to-digital conversion of one encoding to another
• such as for movie data files (e.g., PAL, SECAM, NTSC)
• audio files (e.g., MP3, WAV)
• character encoding (e.g., UTF-8, ISO/IEC 8859).
Done in cases where a target device (or workflow):
• Does not support the format
• Has limited storage capacity that mandates a reduced file size
• Convert incompatible or obsolete data to a better-supported or modern format.
One may also re-encode data in the same format, for a number of reasons:
• Editing
• Lower Bit Rate
• Image Scaling

48. Multiple video formats
Push once publish many

49. Load Balancing
Server Load Balancing (SLB):
• A Device between the customers and multiple instances of your
hardware (Real Server)
• A single, virtual server front-end to the customers of the service
• Allows to give your customers a single name or IP address for your
service (Virtual Server IP address: VIP)
• Uses the real servers' load and health check information

50. Load Balancing
Global Server Load Balancer (GSLB):
• Is a wide-area load balancer also known as a Global Server Load
Balancer (GSLB)
• Uses DNS as the traffic management mechanism
• Puts intelligence into the DNS resolution process
• Monitors site availability and performance
Static load balancing methods Dynamic load balancing methods
Drop Packet Completion Rate
Fallback IP CPU
Global Availability Hops
Round Robin Kilobytes/Second
Ratio Round Trip Time
Static Persist Packet Rate
Topology Quality of Service

51. Reporting & Analytics

52. CDN Schemes
• Web Caching
• Content Distribution Networks of Cache

53. CDN Schemes
Server Farm
L4-L7 Switch
Does load balancing
Internet
Server-1 Server-2 Server-n
Requests = R
Requests = R/n

54. CDN Schemes
Client Network without a Web Cache
1.5 Mbps access link
100 Mbps
LAN
Internet delay=2 sec
15 requests/sec
Avg. object size = 100 Kbits
Access delay =
ΔLAN = 15x100 Kb/100 Mbps = 0.015
Δaccess link = 15x100 Kb/1.5 Mbps = 1
Δ – traffic intensity
HUGE
Total delay =
Internet delay +
Access delay

55. CDN Schemes
Web Cache: Basic operation
GET
Object present ?
No-> Fetch Object
Yes-> Send Object
GET
RESPONSE
Cache
RESPONSE
GET
RESPONSE
Client 1
Web server

56. CDN Schemes
Web Cache
1.5 Mbps access link
100 Mbps LAN
Internet delay=2 Sec
delay = tens of milliseconds
ΔAL = 0.6
Δ – traffic intensity
Institutional
cache
Hit rate = 0.4
Total delay =
(2 + .01) x 0.6 = 1.2 Sec

57. CDN Schemes
Content Distribution Network of Caches
Web serverWeb server
Proactive replication
Parent
Child 1 Child 2

58. CDN Schemes
Problems with discussed approaches:
Server farms and Caching proxies
• Server farms do nothing about problems due to network congestion,
or to improve latency issues due to the network
• Caching proxies serve only their clients, not all users on the Internet
• Content providers (say, Web servers) cannot rely on existence and
correct implementation of caching proxies
• Accounting issues with caching proxies.
For instance, www.cnn.com needs to know the number of hits to the
advertisements displayed on the webpage.

59. CDN Protocols
Relating to content delivery and CDNs, HTTP/1.1 includes cache control mechanisms
In the case of a CDN, the use of HTTPS is generally accompanied by a redirection to a secure
server from a surrogate
Common famous applications are Windows Media Player, RealPlayer and QuickTime using
plugins for the web browser in order to embed the streaming inside HTML.
Timestamps for synchronization are introduced via RTP, and add-on features such as Video-on-
Demand is provided by RTSP
Cache Management Protocols:
• Internet Cache Protocol (ICP): Squid, Microsoft Proxy, Volera, Cisco Cache Engine
• HyperText Caching Protocol (HTCP)
• Cache Array Routing Protocol (CARP) and Cache Digests.
UniCast Streams:
for a small number of surrogates the origin site sends data directly to all of them.
Application Layer Multicast (ALM) protocols:
can be classified as tree-first or mesh-first approach.

60. CDN Protocols
Media Streaming common Protocols:
Audio Streaming:
audio coding format such as MP3, Vorbis, AAC or Opus.
Video Streaming:
Video coding formats include H.264, HEVC, VP8 or VP9.
Encoded audio and video streams are assembled in a container "bitstream" such as MP4, FLV,
WebM, ASF or ISMA.
The bitstream is using a transport protocol to enable adaptive bitrate streaming over HTTP:
• Adobe's RTMP or RTP, Adobe's HDS
• Apple's HLS
• Microsoft's Smooth Streaming
• MPEG-DASH
Stream Media over networks:
• Real-time Streaming Protocol (RTSP)
• Real-time Transport Protocol (RTP)
• Real-time Transport Control Protocol (RTCP)

61. CDN vs. Caching Proxies
Caching Proxies CDN
Used by ISP to reduce bandwidth
consumption
Used by Content Providers to increase
QoS
Operate Reactively Operate Proactively
Caching proxies cater to their users
(web clients) and not to content
providers (web servers)
CDNs cater to the content providers
(web servers) and clients
Caching proxies do not give control of
the content to the content providers
CDNs do

62. CDN Revenue Sharing Model
Buy Model
Network operator pays $1.8 billion in CDN fees over the six-year period.

63. Model of Revenue Sharing
Build Model
Network operator has a total capital expenditure of $51 million over a six-year
period.

64. Future OF Content Delivery Network
Global Content Delivery Network revenue
Video:- $3.8 billion US

65. Known CDN Platforms

66. Case Study: Akamai Technologies
• Leader in providing a secure, outsourced e-business infrastructure
services and software.
• Covers 85% of the market. 20,000 servers in nearly 1,000 networks
in 71 countries. It handles 20% of total Internet traffic today.
• Developed a set of breakthrough algorithms for intelligently routing
and replicating content over a large network of distributed servers.

67. Akamai Services
Core Features:
• Alerts
• Property Manager
• Luna Control Center
• Content Control Interfaces
Media Delivery:
• Adaptive Media Delivery
• Media Services Live
• Media Security Policy
• Download Delivery
• Media Analytics
• Object Delivery
• Media Services On Demand
• Infinite Media Products

68. References
Content Delivery Networks
Wikipedia: The Free Encyclopedia
https://www.wikipedia.org/
TATA
www.tatadocomo.com/business
Akamai
https://www.akamai.com/
Blaze: Intelligent & Optimization
Front-End Optimization Series
University of Delaware
Girish Borkar: Department of Computer and Information Sciences
MIT School Of Telecom
Shiv Kumar Pandey: Telecom Technologies Courses

69. Thanks