This document summarizes research on using peer-assisted content delivery to improve streaming of BBC iPlayer content. There are three key obstacles to peer-assisted delivery: 1) Increased traffic outside an ISP's network increases bandwidth costs, 2) Content is streamed in different bitrates which stratifies sharing, and 3) Low participation rates in peer-to-peer networks limit swarm sizes. Despite these obstacles, simulations show that traffic savings can still be high for popular content due to large swarm sizes. Caching recently viewed content can further boost savings. While peer assistance is most effective for top content, it has limited benefits for unpopular or long-tail content due to small swarm sizes.

1. ISP-friendly Peer-assisted On-demand Streaming of Long
Duration Content in BBC iPlayer
Dmytro Karamshuk1, Nishanth Sastry1, Jigna Chandaria2, Andy Secker2
1King's College London, 2BBC R&D
CD-GAIN: EPSRC project in collaboration with BBC R&D, http://bit.ly/cd-gain

2. This talk is about BBC iPlayer

3. iPlayer is popular and growing
Total monthly BBC iPlayer requests across all platforms, since 2009
Introduced in 2005 for 5K users,
now covers 50% of the UK population
“iPlayer Usage Effect - A Bandwidth Explosion”
http://community.plus.net/blog/2008/02/08/iplayer-usage-effect-a-bandwidth-explosion/

4. Content Delivery: traditional approach
Install more distributed caches Requires investments
Any alternatives?

5. Peer-assisted Content Delivery
Content Delivery
Network
user
user user
user
user
user
average of 5K users online every sec in the first day after release
5K duplicates
every second!!!
Ask users for assistance

6. CDNs are interested in traffic savings
Content Delivery
Network
user
user user
user
user
user
Traffic gain
- volume of traffic downloaded from content delivery nodes
- total volume of traffic watched by the userss
u
T
T
-1=G

7. Intuition: bigger P2P swarm yields higher gain
CDN user
1
user
2
user
3
P2P is self-scaling Bigger swarms yield higher savings

8. Analytical Model based on M/M/ Queues
ci
= ui
riAverage number of peers online
How much we can offload to peers
Traffic gain is an exponential function of swarm’s capacity
content popularitycontent duration
G c 1 e
c
- by Little`s law

9. How peer-assistance works in real life
… there is a number of obstacle factors they do not address
Huang, Cheng et al. [NOSSDAV’2008] Zhao, Mingchen, et al. [IMC’2013]
Balachandran et al. [IMC’2013]

10. Obstacle N1: ISP Friendliness
Content Delivery
Network
P2P increases egress traffic, impacting bandwidth
cost for ISPs, Karagiannis et al. [USENIX’2005]
Traffic savings drop from 87% to 13% if swarms are
localized within ISP and city, Balachandran et al.
[IMC’2013]

11. Obstacle N1: ISP Friendliness
Content Delivery
Network
ISP1
ISP2
P2P increase egress traffic, impacting bandwidth cost
for ISPs, Karagiannis et al. [USENIX’2005]
Traffic savings drop to 13% if swarms are localized
within ISP and city, Balachandran et al. [IMC’2013]

12. Obstacle N2: Bitrate Stratification
Content Delivery
Network
ISP1
ISP2
1080p
720p
480p

13. Obstacle N2: Bitrate Stratification
Content Delivery
Network ISP2
ISP1 -768Kbps
ISP1 -1.5Mbps
1080p 720p
480p

14. Obstacle N3: Partial Participation
Content Delivery
Network ISP2
ISP1 -768Kbps
ISP1 -1.5Mbps
Obstacle factors decrease size of swarms
Only 31% signed up for sharing in
Akamai NetSession
Zhao, Mingchen, et al. [IMC’2013]

15. Users - 2.2 M
IP address – 1.3 M
Sessions - 15.9 M
London, Sep. 2013
Understanding Obstacles with Data-driven Analysis

16. Dealing with ISP Friendliness
Five biggest ISPs account for over 80% of traffic

17. Two main bitrate formats dominate in over 70% of sessions
1080p
720p
480p
Dealing with Bitrates
AverageBroadbandSpeed

18. Results of the Simulations
1080p
720p
480p
G c 1 e
c
An episode of Bad Education series, 100K views

19. Results of the Simulations
potential traffic gains for popular content are high despite obstacles
G c 1 e
c
An episode of Bad Education series, 100K views

20. How about Unpopular Content?
BECAUSE swarms are small  availability is less
An episode of What You Can Eat show, 1K views
G c 1 e
c

21. Increasing Availability #1: Content Bundling
Content Bundling is not effective

22. Increasing Availability #2: Client Caching
Simple caching can boost savings by 23%

23. Savings across Content Corpus
Top-5% of the content
corpus accounts for 80% of traffic
Most of accesses happen in the
first day after release
Yes, it’s all about very popular content

24. Savings across Content Corpus
https://vimeo.com/99054874

25. Conclusions
• with peer-assisted delivery savings grow with the
demand and size of the content despite obstacles
• we give a closed form solution for traffic gains
• up to 88% of traffic can be saved
• content bundling does not work but caching can
boost savings by 23%
G c 1 e
c

26. Dmytro Karamshuk
King's College London
follow me on Twitter: @karamshuk
Come to our second talk tomorrow:
Room: Ballroom C
Time: 4/29/2015 8:30 — 4/29/2015 10:00
Geography Devices PricingOperators
Measurement study on 50% of the UK’s population