Web caches are being rapidly deployed in the Internet.

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• Web caches are being rapidly deployed in the
  Internet.
• Hierarchical Web caching provides an
  infrastructure for asynchronous reliable
  multicast.
• There isnt a need for reliable multicast at the
  network/transport layers.

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Web Caches are Being Rapidly Deployed

• NLANR Backbone caches
• 6 caches 5 supercomputer sites and one NAP.
• Sites communicate over vBNS.
• Each cache is a parent to 125-200 client caches.

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NLANR Caching Hierarchy
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NLANR Caching Hierarchy
Provided by NLANR
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Hierarchical Caching Provides an Infrastructure
for Asynchronous Reliable Multicasting
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Asynchronous Reliable Multicast
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Latency in Cache Hierarchy
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Multicast Latency
Receivers
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Comparison of Continuous Multicast Push Caching

• Caching latency is typically less than
  multicast.
• For multicast, transmission rate is bottleneck
  rate between server and receiver.
• For caching, transmission rate is bottleneck
  rate between nearest cache with object and
  receiver.

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Do we need reliable multicast infrastructure at
network/transport layers?

• Unreliable multicast targets live information.
• Reliable multicast targets stored information.
• Stored information can be distributed through a
  cache hierarchy.
• Cache hierarchy is easier to deploy than reliable
  multicast.
• Cache hierarchy typically provides lower latency
  than continuous multicast push.