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Cachet Technologies. Technology Overview February 1998. Outline. Our Technology Focus First Application: Caching at the Edge of the Internet Comparison with Competing Products Some Details of the Technology A new hashing protocol Other Potential Applications Current Plans.
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Cachet Technologies Technology Overview February 1998 ÓCachet Technologies 1998
Outline • Our Technology Focus • First Application: Caching at the Edge of the Internet • Comparison with Competing Products • Some Details of the Technology • A new hashing protocol • Other Potential Applications • Current Plans ÓCachet Technologies 1998
Technology Focus • General: • Development of applications and infrastructure for distributed networks such as the Internet. • Current Emphasis: • A solution to the Resource Location Problem in distributed networks. ÓCachet Technologies 1998
Resource Location Problem • Where to put “it” and how to find “it” in a rapidly changing environment where there is no centralized control and information is imperfect. ÓCachet Technologies 1998
First Application • Construction of large distributed caches at the edges of the Internet • Keeps commonly accessed items close to users • Results in improved performance (e.g. latency) for users and decreased cost (e.g. bandwidth utilization) for service providers • Can be sold to service providers and/or user groups (e.g. companies) with 10-10M members ÓCachet Technologies 1998
Example CNN MIT Users ISP Internet IBM ÓCachet Technologies 1998
Example CNN MIT Users ISP Internet IBM Cache ÓCachet Technologies 1998
Different Approaches • Proxy Caches (Microsoft, Cacheflow) • Monolithic Caches (Cisco, Inktomi) • Large caches made up of clusters of machines under centralized control and placed at a specific point in the network • Distributed Caches (NetCache) • Large cache made up of loosely coupled machines that are spread throughout the network ÓCachet Technologies 1998
Monolithic vs. Distributed • Need faster response time for users • Caches should be close to the users at the edges of the network (Distributed) • Need reduced traffic out of network • Cache should have large capacity (Monolithic?) • Cachet’s Vision: Distributed caches that cooperate to form a cache with large aggregate capacity. ÓCachet Technologies 1998
Necessary Components • Resource Location • Where do I put it and how do I find it? • Resource Discovery • Who else is out there that will cooperate with me? • Preventing Hot Spots • How do I cooperate without being overloaded by requests? ÓCachet Technologies 1998
Our Key Technologies • Invention of Consistent Hashing to solve resource location problem • Discovery of protocols that enable caches to learn about the network • Development of a novel replication strategy to prevent hot spots • i.e. when to make more copies? ÓCachet Technologies 1998
Our Advantages • No special purpose hardware • No centralized control • Very loosely coupled network of caches • Perfect information on status of caches is not needed • Fully scaleable and fault tolerant • Automatic load balancing • Prevents swamping and hot spots ÓCachet Technologies 1998
Some of the Difficulties 1 Standard Way: Hashing h(x) = ax+b mod n Where do I put file X? 2 5 X 3 4 ÓCachet Technologies 1998
Standard Hashing: The Good • Balanced load • Fast to compute • Local control ÓCachet Technologies 1998
Standard Hashing: The Bad • Perfect information is needed ax+b mod 4 = 2 ÓCachet Technologies 1998
ax+b mod 4 = 2 Standard Hashing: The Bad • Perfect information is needed ÓCachet Technologies 1998
ax+b mod 4 = 2 Standard Hashing: The Bad • Perfect information is needed ÓCachet Technologies 1998
Standard Hashing: The Bad • Perfect information is needed ÓCachet Technologies 1998
Standard Hashing: The Ugly • Small changes in the system cause drastic changes in the cache Caches C B A Pages 1 2 3 4 5 6 7 8 9 10 11 ÓCachet Technologies 1998
Standard Hashing: The Ugly • Small changes in the system cause drastic changes in the cache Caches D C B A Pages 1 2 3 4 5 6 7 8 9 10 11 ÓCachet Technologies 1998
Standard Hashing: Summary Useless for large and/or evolving distributed networks ÓCachet Technologies 1998
Consistent Hashing • Consistency under changing ranges Caches C B A Pages 1 2 3 4 5 6 7 8 9 10 11 ÓCachet Technologies 1998
Consistent Hashing • Consistency under changing ranges Caches D C B A Pages 1 2 3 4 5 6 7 8 9 10 11 ÓCachet Technologies 1998
Consistent Hashing: Features • Continuous balanced load • Fast to compute • Local control • Scales without any catastrophic updating • Users need only partially correct view of the network. Enables “lazy” resource discovery. • Enables resource location to take into account load balancing and geographic information. ÓCachet Technologies 1998
Related Applications • Eliminating hot spots on the web (same technology on larger scale) • Distributed file servers • Swamping protection as a service • Distributed e-mail servers • On-line movies ÓCachet Technologies 1998
Current Plans • Implement Demo 1.0 at LCS • Software package installed by user • Program integrates automatically into loosly-coupled distributed cache • Distributed cache performs as if a large virtual cache existed between LCS and the Internet • Development of market strategy and business plan • Secure VC funding and identify CEO for company ÓCachet Technologies 1998