1. Content Delivery: Extending to the Edge through the IX
March 2018 | Ivan Sanz
Introduction:
Ivan Sanz
Infrastructure Acquisition Manager for Fastly. Fastly is a content delivery network based in the US and we have physical presence in nearly 50 POPs across 6 continents.
I’m responsible for Fastly’s expansion strategy in newer markets - this includes South America, Africa, India and the Middle East.
Before I get started, I want to take a quick poll of the audience:
How many of you are familiar with what a CDN is ?
How many of you use a CDN for your operations?

2. Agenda What’s a CDN? Pursuit of the Edge How IXs Extend the Edge
The Fastly Network
I’ll introduce CDN
Characteristics
Functionality
Compare sites with / without CDNs
Next, I’ll explain why CDNs are pushing to get closer to end Users
Elaborate on the role latency plays in this
I will also discuss how pursuing the edge is challenging and presents its own problems
Then, I’ll talk about how IXs enable better connectivity at the edge.
Last, I’ll finish with the Fastly approach to edge delivery and how we are building a better Internet.

3. What’s a CDN?
So, first, What’s a CDN?

4. Content Delivery Network
Network of caching servers
Geographically dispersed; each location a POP
Intermediary between Users and Origin
Users are served from closest edge server
Network of “edge” servers that hold temporary copies of content (think videos, songs, HTML, any type of file your browser or application might request from a host)
Installed in data centers all around the world
Act as intermediary (all requests go to them first)
If content is on an edge server, content is served from closest machine
So, we now some of the defining characteristics, but how does this look in practice?
Let’s start with a site that does not have a CDN
Part 1 – What’s a CDN?

5. A site without a CDN... ...is slow
This request takes at minimum 200ms before content flows
Request
São Paulo
Concepción
Content
Part 1 – What’s a CDN?

6. A site without a CDN... ...is not redundant
If Origin is unavailable, User receives an error
Request
São Paulo
Concepción
503 Error
User in Concepcion requests content. Hits edge node in Santiago first. If content is there, content is returned quickly. If not, edge node in Santiago fetches content from origin in Sao Paulo over preexisting connection
Subsequent users will receive the file from cache in Santiago and no additional requests to the origin will be made.
Multiple by thousands and you’ll still be fine. Your origin will only see one request.
Part 1 – What’s a CDN?

7. A site without a CDN... ...is not scalable 100,000 Request São Paulo
Here you might have a slight demand in traffic but the origin is fine.
Now, a DDoS attack comes and multiplies your requests by 100K, killing your origin.
Part 1 – What’s a CDN?

8. A site with a CDN...
...is fast
Instead of São Paulo, request goes to Santiago. Content flows in less than 10ms
São Paulo
Santiago
Concepción
Buenos Aires
User in Concepcion requests content. Hits edge node in Santiago first. If content is there, content is returned quickly. If not, edge node in Santiago fetches content from origin in Sao Paulo over preexisting connection
Subsequent users will receive the file from cache in Santiago and no additional requests to the origin will be made.
Multiple by thousands and you’ll still be fine. Your origin will only see one request.
Part 1 – What’s a CDN?

9. A site with a CDN...
...is fast
If content is not in cache (cache-miss), existing keep-alive connections enable fast origin pull
São Paulo
Santiago
Concepción
Buenos Aires
If not, edge node in Santiago fetches content from origin in Sao Paulo over preexisting connection
Subsequent users will receive the file from cache in Santiago and no additional requests to the origin will be made.
Part 1 – What’s a CDN?

10. A site with a CDN... ...is redundant
If Santiago is unavailable, User is routed to another site
São Paulo
Santiago
Concepción
Buenos Aires
User will be served from Sao Paulo or Buenos Aires - before origin
Part 1 – What’s a CDN?

11. A site with a CDN... ...is scalable
Edge nodes absorb traffic and keep your services and origin running
São Paulo
Santiago
Buenos Aires
Part 1 – What’s a CDN?

12. Why Use a CDN?
Fast
Content moves closer to end users. Reduces latency.
Redundant
If a POP is offline, others serve traffic. If Origin is offline, CDN continues serving from cache.
Scalable:
Entire network can absorb traffic spikes and DDoS attacks.
To summarize, these are some of the reasons to use a CDN.
Fast -
Redundant
Scalable
However, if all of these features are inherent in a distributed systems model? How do CDNs differentiate themselves?
Part 1 – What’s a CDN?

13. Pursuit of the Edge: Getting Closer to End Users
One big way is by getting closer to end users!

14. Why Get Closer to Users?
Although redundancy and scalability are important… being Fast is one of the most impactful and measurable aspects of User experience
In fact, studies time and time again show that users will abandon a website or application if load time is too long.
So, CDNs push to get closer to Users to improve user experience even more.
The power to say “I am faster than that provider”
Part 2 – Pursuit of the Edge

15. CDN Response Times for Dynamic Delivery (Chile)
<<CDNs use this as a differentiator and start to compete on speed - Cedexis ratings>>
I’m serious - We’re all competing on it whether we like it or not.
In fact, Cedexis is a metrics company that measures CDNs and many other types of providers.
Look - Fastly is fastest for Dynamic Delivery in Chile!
13 March 2018, Country: Chile
Part 2 – Pursuit of the Edge

16. So We Should Build More POPs?
It really depends. The key to a great user experience is more complex than simply building a POP closer to end users to reduce latency...
Part 2 – Pursuit of the Edge

17. It Is A Complex Trade Off
Expanding a network introduces new infrastructure risks...
Power required for dense POPs is hard to find outside of big cities
Data centers of high security and reliability are limited
Connectivity for communication with origin may be less reliable
All of these jeopardize a CDN’s ability to run a network with the high standard of service and quality you would expect.
Part 2 – Pursuit of the Edge

18. It Is A Complex Trade Off
And expanding the server pool introduces software risks...
Cache-Hit Ratio will decrease and traffic to origin will increase
Purging old content becomes more challenging because more servers must successfully evict content
As you continue to distribute load across a higher denominator, cache hit ratio will necessarily fall.
Purging gets more difficult as you increase the pool of servers that need to be notified of new content
So, I just said that everyone is reaching for the edge, but
Part 2 – Pursuit of the Edge

19. It Is A Complex Trade Off
So everyone is reaching for the edge but doing so is difficult and can present its own risks to the User experience...
As you continue to distribute load across a higher denominator, cache hit ratio will necessarily fall.
Purging gets more difficult as you increase the pool of servers that need to be notified of new content
So, I just said that everyone is reaching for the edge, but
Part 2 – Pursuit of the Edge

20. So Who Is Going to Save Us?
Nuestros amigos de PITChile
Part 2 – Pursuit of the Edge

21. How IXs Extend the Edge

22. IXs Bring Networks Together
Internet Exchanges provide a shared fabric and a direct path for bits to move from one network to another.
Part 3 – How IXs Extend the Edge

23. IXs Improve Operations
Internet Exchanges improve routing and latency, and reduce costs for network operators in a region.
Part 3 – How IXs Extend the Edge

24. Traffic Flow Without an IX ISP 1 ISP 3 ISP 4 ISP 2 TRANSIT
In this example, without an IX,
ISPs with users accessing Fastly content might have to hop across multiple networks before connecting to content served by the Fastly CDN - might even leave the country - depending on routing
Congestion on a neighboring network
Paying transit to carry bits
Part 3 – How IXs Extend the Edge

25. Traffic Flow With an IX ISP 1 ISP 3 PITChile ISP 2 ISP 4
In the CDN example, because of PITChile any ISP connected to PITChile has a direct path to all content delivered by Fastly.
Either using the route server or bilateral sessions, traffic should move seamlessly to / from Fastly across this infrastructure
Part 3 – How IXs Extend the Edge

26. With PITChile, we are BGP neighbors and less than ~10ms apart - even if we are physically far from one another
ISP 2
Arica
PITChile
ISP 1
Santiago
Concepción
Part 3 – How IXs Extend the Edge

27. Provides reliable connectivity to CDN POP in metro market without infrastructure and software risks
ISP 2
Arica
PITChile
ISP 1
Santiago
In other words, IX provide reliable connectivity to a CDN POP in major metro market with the CDN
Concepción
Part 3 – How IXs Extend the Edge

28. The Best of Both Worlds
Very reliable access to powerful CDN POPs in major metro markets, with very limited additional latency for regional Users
Part 3 – How IXs Extend the Edge

29. The Fastly Network

30. Real-Time with Real Control
At Fastly we...
build very powerful, cache-dense POPs
enable our Customers to control delivery
provide real-time analytics
… and much more...
Part 3 – How IXs Extend the Edge

31. Santiago Now Live!

33. Summary

34. Summary Use a CDN to improve speed, redundancy and scalability
Part 3 – How IXs Extend the Edge

35. Summary
CDNs can efficiently localize content from anywhere in the world to a major metro region
Part 3 – How IXs Extend the Edge

36. Summary
CDNs could extend out to the edge to further localize content but this comes with limitations and risks to User experience
Part 3 – How IXs Extend the Edge

37. Summary
IXs unlock wider access to content by providing reliable, cost-effective paths for edge Users to connect to powerful CDN POPs
Part 3 – How IXs Extend the Edge

38. Summary Fastly is now on the PITChile Santiago exchange.
We would love to make the Internet faster for everyone. Peer with us!
Part 3 – How IXs Extend the Edge

39. Thank you.