Transcript ppt

Content Delivery
Networks
iBAND2
May 24, 1999
Dave Farber
CTO
Sandpiper Networks, Inc.
www.sandpiper.net
[email protected]
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A popular web site
Browsers
Web Server
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Congestion slows delivery
Networks
Browsers
Routers
Web Servers
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Replicating content
closer to users
• Reduces load on server
• Avoids network congestion
Browsers
Replicated
content
Router
Web Server
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Content Delivery Networks
• Outsourcing for web publishers
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lets existing web sites scale
serves content closer to end users
uses a massive, shared infrastructure
provides reserved resources
serves all clients
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Benefits for
Web Publishers
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Improves quality of service
Scales easily as demand grows
Offers full-service management
Reduces costs
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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
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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
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Content Distributors
• Strategy
Content
Distributor
– 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
Content Migrator
Origin Server
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Rendezvous: Migrator
• Strategy
– operator specifies which
resources should “migrate”
– migrator makes selection
as resources are served
– URLs in HTML are rewritten
HTTP
Request
HTTP
Reply
Rule
Base
HTML
Rewriter
Content
Migrator
• Results
– easy to deploy
– most resources migrate
to distributor network
– rewriting HTML reduces
visits to origin server and
allows FTP redirection
Origin
Server
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Rendezvous: DNS
• Strategy
– URLs in HTML are
modified before serving
to use “supernames”
– browser uses DNS to
resolve the supername
to a content distributor
– Sandpiper custom DNS
servers resolve the name
to the best distributor
• Results
– high scalability for very
busy web servers
Browser
Content
Distributor
Footprint
DNS server
Origin
Server
HTML
Rewriter
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Unique Footprint Services
• Adapts to traffic conditions
• Supports a wide variety of content
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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
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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
Network
status
Best
Distributor
Selection
Distributor
load
Specific
Content
Distributor
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Footprint Performance
Average response time (seconds)
Commercial Web Server Site
Origin Server
With Footprint
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Serving HTML
from 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
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Custom domain names
• Distributor aliases for web publishers
– http://38.200.111.132 /www.hotstuff.com/products
– http://www41.hotstuff.com /products
• Benefits
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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
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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
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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
Origin
Server
Content
Distributor
Browser
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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
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Footprint Streaming
Architecture
Origin Server
Browser
rendezvous
Content
Migrator
Real G2
Server
Content Distributor
Browser
Footprint
Request Processor
Real
Proxy
cache fills &
live streams
Inktomi
TS/MCO
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Footprint offers
publisher-friendly caching
• Content distributors:
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provide activity logs
keep resources “fresh”
guarantee local bandwidth
guarantee local disk space
handle more than HTTP traffic
give publishers control
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Coupling Footprint
with ISP caches
• Used by caching ISPs
ISP
Caches
Content
Distributor
– for example, AOL
• Gives Footprint customers
– access to logs
– control of freshness
ISP
Network
Browser
Origin
Server
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Working for ISPs
• For Demand-side ISPs, Footprint
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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
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extends ISP hosting services
offers differentiated services
increases the “reach” of your web publishers
provides additional source of revenue
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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
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