 Cachet Technologies 1998 Cachet Technologies Technology Overview February 1998

ÓCachet Technologies 1998 Outline n Our Technology Focus n First Application: Caching at the Edge of the Internet n Comparison with Competing Products n Some Details of the Technology –A new hashing protocol n Other Potential Applications n Current Plans

ÓCachet Technologies 1998 Technology Focus n General: –Development of applications and infrastructure for distributed networks such as the Internet. n 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. 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 n 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 ISP Internet CNN MIT IBM Users

ÓCachet Technologies 1998 Example ISP Internet CNN MIT IBM Cache Users

ÓCachet Technologies 1998 Different Approaches n Proxy Caches (Microsoft, Cacheflow) n Monolithic Caches (Cisco, Inktomi) –Large caches made up of clusters of machines under centralized control and placed at a specific point in the network n Distributed Caches (NetCache) –Large cache made up of loosely coupled machines that are spread throughout the network

ÓCachet Technologies 1998 Monolithic vs. Distributed n Need faster response time for users –Caches should be close to the users at the edges of the network (Distributed) n Need reduced traffic out of network –Cache should have large capacity (Monolithic?) n Cachet’s Vision: Distributed caches that cooperate to form a cache with large aggregate capacity.

ÓCachet Technologies 1998 Necessary Components n Resource Location –Where do I put it and how do I find it? n Resource Discovery –Who else is out there that will cooperate with me? n Preventing Hot Spots –How do I cooperate without being overloaded by requests?

ÓCachet Technologies 1998 Our Key Technologies n Invention of Consistent Hashing to solve resource location problem n Discovery of protocols that enable caches to learn about the network n Development of a novel replication strategy to prevent hot spots –i.e. when to make more copies?

ÓCachet Technologies 1998 Our Advantages n No special purpose hardware n No centralized control –Very loosely coupled network of caches n Perfect information on status of caches is not needed n Fully scaleable and fault tolerant n Automatic load balancing n Prevents swamping and hot spots

ÓCachet Technologies 1998 Some of the Difficulties Standard Way: Hashing h(x) = ax+b mod n X Where do I put file X?

ÓCachet Technologies 1998 Standard Hashing: The Good n Balanced load n Fast to compute n Local control

ÓCachet Technologies 1998 Standard Hashing: The Bad n Perfect information is needed ax+b mod 4 = 2

ÓCachet Technologies 1998 Standard Hashing: The Bad n Perfect information is needed ax+b mod 4 = 2

ÓCachet Technologies 1998 Standard Hashing: The Bad n Perfect information is needed ax+b mod 4 = 2

ÓCachet Technologies 1998 Standard Hashing: The Bad n Perfect information is needed

ÓCachet Technologies 1998 Standard Hashing: The Ugly n Small changes in the system cause drastic changes in the cache A B C Caches Pages

ÓCachet Technologies 1998 Standard Hashing: The Ugly n Small changes in the system cause drastic changes in the cache A B C Caches Pages D

ÓCachet Technologies 1998 Standard Hashing: Summary Useless for large and/or evolving distributed networks

ÓCachet Technologies 1998 Consistent Hashing n Consistency under changing ranges A B C Caches Pages

ÓCachet Technologies 1998 Consistent Hashing n Consistency under changing ranges A B C Caches Pages D

ÓCachet Technologies 1998 Consistent Hashing: Features n Continuous balanced load n Fast to compute n Local control n Scales without any catastrophic updating n Users need only partially correct view of the network. Enables “lazy” resource discovery. n Enables resource location to take into account load balancing and geographic information.

ÓCachet Technologies 1998 Related Applications n Eliminating hot spots on the web (same technology on larger scale) n Distributed file servers n Swamping protection as a service n Distributed servers n On-line movies

ÓCachet Technologies 1998 Current Plans n 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 n Development of market strategy and business plan n Secure VC funding and identify CEO for company