1 Content Delivery Networks iBAND2 May 24, 1999 Dave Farber CTO Sandpiper Networks, Inc. [email protected].

1

Content Delivery Networks

iBAND2May 24, 1999

Dave FarberCTO

Sandpiper Networks, Inc. www.sandpiper.net

[email protected]

2

A popular web site

Browsers

Web Server

3

Congestion slows delivery

Browsers

Web Servers

Routers

Networks

4

• Reduces load on server• Avoids network congestion

Replicating content closer to users

Browsers

Web Server

Replicatedcontent

Router

5

Content Delivery Networks

• Outsourcing for web publishers– lets existing web sites scale – serves content closer to end users– uses a massive, shared infrastructure– provides reserved resources– serves all clients

6

Benefits for Web Publishers

• Improves quality of service• Scales easily as demand grows• Offers full-service management• Reduces costs

7

The Footprint Network

• Content Distributors– replicate content– manage shared resources

• Content Migrators– determine when to

migrate requests– select the best distributor– rewrite HTML– provide publisher control

8

The Footprint Network

• Improves connection to user– bandwidth is monitored for quality– distributors are located near clients– measurements identify the best distributor

• Allows capacity to scale– bandwidth can be increased quickly– new distributors can be added easily

• Works for ISPs– distributors reduce ISP peering costs– distributors cooperate with ISP caches

9

Content Distributors

• Strategy– cache HTTP and FTP resources– adjust cache-control directives– publish updates by explicit

broadcasting of invalidations,and expiration policy

– collect and merges logs

• Results– very high hit rates– avoids control problems

created by traditional caches

Origin Server

ContentDistributor

Content Migrator

10

Rendezvous: Migrator

• Strategy– operator specifies which

resources should “migrate”– migrator makes selection

as resources are served– URLs in HTML are rewritten

• Results– easy to deploy– most resources migrate

to distributor network– rewriting HTML reduces

visits to origin server and allows FTP redirection

Content Migrator

OriginServer

RuleBase

HTMLRewriter

HTTPRequest

HTTPReply

11

Rendezvous: DNS

• Strategy– URLs in HTML are

modified before serving to use “supernames”

– browser uses DNS to resolve the supernameto a content distributor

– Sandpiper custom DNS servers resolve the nameto the best distributor

• Results– high scalability for very

busy web servers

OriginServer

HTMLRewriter

Browser

FootprintDNS server

ContentDistributor

12

• Adapts to traffic conditions

• Supports a wide variety of content– static files - images, downloads, HTML – authenticated content– dynamic (custom) content– audio/video streaming

• Provides publisher controls– access to logs– complete control of content freshness

– coupled with client-side caches

Unique Footprint Services

13

Selecting Best Distributor

• Strategy– group client IP addresses – measure network

congestion regularly– measure load frequently– use load and congestion data

to select best distributor

• Results– reduces delays

when net is congested– wide area load balancing– high availability of servers

Client IP address

Network map

Distributor load

Best Distributor Selection

Network status

Specific Content

Distributor

14

Commercial Web Server Site

Ave

rag

e re

sp

on

se

tim

e (

se

con

ds)

Origin Server

With Footprint

Footprint Performance

15

Serving HTMLfrom content distributors

• Many sites serve 50% or more HTML• Benefits

– increases scalability– improves performance

• Challenges– bookmarks on resources– cookies and authenticated content– customized dynamic content

16

Custom domain names

• Distributor aliases for web publishers– http://38.200.111.132 /www.hotstuff.com/products– http://www41.hotstuff.com /products

• Benefits– name recognition value in each URL– bookmarks remain under publisher’s control– browsers send cookies and passwords to distributors– Java sandbox can talk to content distributors

17

Cookies and Authentication

• Cookie support– custom domain names make cookies available– cookies are logged on receipt– cookies are forwarded when

custom content is required

• Authentication support– custom domain names make passwords available– requests are forwarded for authorization– content is cached & served by content distributor

18

Custom content

• Dynamic content is customized per user• Many custom pages built from common elements

– ad insertions– custom home pages– product status updates

• Distributor-Side Include– origin server provides minimal custom content– Content Distributor assembles elements

OriginServer

ContentDistributor

Browser

19

Streaming in Footprint

• Scales to vast numbers of viewers– without requiring changes to server

• Rendezvous clients with best server– using Sandpiper’s proprietary technology

• Replicates streams on demand– live via Real proxy (splitter)– on-demand via Inktomi’s Media Cache Option

• Uses existing shared infrastructure

20

Footprint StreamingArchitecture

Browser Content Migrator Real G2

Server

Content Distributor

Origin Server

Inktomi TS/MCO

RealProxy

FootprintRequest Processor

rendezvous

cache fills &live streams

Browser

21

Footprint offerspublisher-friendly caching

• Content distributors:– provide activity logs– keep resources “fresh”– guarantee local bandwidth– guarantee local disk space– handle more than HTTP traffic– give publishers control

22

Coupling Footprintwith ISP caches

• Used by caching ISPs – for example, AOL

• Gives Footprint customers– access to logs– control of freshness

Browser

ISP Caches

ContentDistributor

OriginServer

ISP Network

23

Working for ISPs

• For Demand-side ISPs, Footprint– reduces bandwidth costs– improves end user performance– couples with traditional caches– provides publisher-friendly caching– can serve browsers located anywhere

• For Supply-side ISPs, Footprint– extends ISP hosting services– offers differentiated services– increases the “reach” of your web publishers– provides additional source of revenue

24

Conclusion

• Scaling Internet servers requires serving content closer to users

• Content Delivery Networks give publishers a way to scale

• Sandpiper’s Footprint provides a comprehensive set of benefits today

• Content Delivery Networks will become a natural part of the Internet infrastructure