1/25/2000 Active Names: Flexible Location and Transport of Wide-Area Resources Luis Rivera

1/25/2000 Luis Rivera Outline Motivation Active Names »Definition »Goals »Architecture Conclusions Related Work Discussion »In case something had not been discussed yet!

1/25/2000 Luis Rivera Motivation Problem »Mobile computing and modern web applications does not fit well into the static DNS scheme »Need for rapid deployment and extensibility of Internet services Solutions »Active Networks »Active Services »Active Cache »Smart Clients »Active Routing »Active Names!!!

1/25/2000 Luis Rivera Active Names Name »Chain of programs to resolve and reply »The name is ACTIVE: “There is not second step to request the service after name resolution”. R RR R RR R R CS

1/25/2000 Luis Rivera Architecture Goals Namespace should be »Customizable –Clients and services customize their namespaces »Extensible –Add functionality without modifying the architecture »Composible Efficient use of network resources Location independence resolution »The chain of programs should not be linked to fixed locations Discussion »Efficiency through extensibility! »Extensibility through naming!

1/25/2000 Luis Rivera Resolution Active chain mechanisms »Delegation »CPS  Continuation Passing Style Resolvers »Located in strategic points in the network R R R CS Name Namespace program Partially Solved Name Next Namespace program After Method Service Reply After Method list Solved Name Service Request Service Reply

1/25/2000 Luis Rivera Active Name Programs Microkernel approach Resolvers must provide »A loader to fetch namespace programs »Security for untrusted code (Java-2) »Local soft state »Communication interfaces Bootstrap »Some initial programs are loaded onto each Active Name machine Discussion »This works at the service level, we still need DNS right? »With different services in the same machine, who dictates security and resource access policies?

1/25/2000 Luis Rivera Namespace A namespace is a program Locates data and resources Hierarchically organized »Root interprets all names »Each namespace can interpret a name according to its own rules »Those rules are set by the owner of that portion of the namespace Discussion »Namespace boundaries are fuzzy! »How scalable is this architecture?

1/25/2000 Luis Rivera After Methods and API After methods »Multi-way RPC based on distributed CPS »The remaining work of the namespace is prepended to the After Method list »The list represents the way to follow back to the client API »Partially resolved name »Reference to the data stream »List of after methods The framework support legacy applications

1/25/2000 Luis Rivera Active Names Principles Extensibility »Functionality can be added as needed »Example: Replicated Service Access Location Independence »A name does not reveal the location of the service »Example: Image Distiller Composibility »Combination of client and server extensions to improve service performance »Example: Web caching

1/25/2000 Luis Rivera Performance Replicated Service »DNS Round Robin: Best performance at low load. »Distributed Director: Best performance high load. »Active Names –Technique: Selection is biased by the number of hops and a decaying histogram of previous performance. –Best performance overall Distiller »Server: Worse performance when server is loaded »Proxy: Overall good performance in both cases »Active Names: –Technique: Selection biased by end-to-end distillation cost. –Best performance in most of the cases

1/25/2000 Luis Rivera Performance (cont…) Data on Table 1 is interesting »Justify composibility? Test »Analysis of server-initiated and client-initiated customizations »Distillation implements client-initiated customizations »Combination of server and client customizations –Better than distillation only by 50% –Better than server-only by 104% Discussion »In all these examples, the client is mobile and the service is static »Does this represents a solution the applications of tomorrow?

1/25/2000 Luis Rivera Related Work TP monitors (Transaction Processing monitors) »“A Swiss Army knife of tools reflecting the particular holes in the surrounding system” Intentional Naming System (INS) »Applications specify what they are looking for, not where to locate them. Ninja project Smart Clients Active Caches

1/25/2000 Luis Rivera Conclusions Active names »Programs that resolve the name and retrieve the reply from the requested service The Active names framework support »Extensibility »Location-independence »Composibility The experiments showed a significant performance gain using the Active Name extensions »Even with the use of Java to code the programs.

1/25/2000 Luis Rivera Discussion Good or bad? »I think is a cool idea !!! Where these experiments enough? What could happened with a very long chain of active names? Is this a solution for a really mobile environment where services are not fixed? How scalable is this framework? »They say that several thousands, but where are they justifying it?