Defense by Amit Saha March 25 th, 2004, Rice University ANTS : A Toolkit for Building and Dynamically Deploying Network Protocols David Wetherall, John Guttag, and David Tennenhouse

2 Outline of the talk  Motivation  Architecture  Goals  Components  Examples  Related work  Conclusion

3 Motivation  Easily build and deploy network protocols at intermediate nodes as well as end points

4  Simultaneous support for multiple network protocols  Support new protocol construction – no centralized authority  Support dynamic deployment – no down time Architecture - Goals

5  Capsules  Active nodes  Code distribution Architecture - Components

6 Architecture - Hierarchy Capsule Code group Protocol Capsule Code group Unit of message forwarding Unit of code transfer Unit of programming protection

7  A capsule is a replacement for a packet  Reference to forwarding routine  Fingerprint based identifier reduces danger of protocol spoofing Capsule Identifier (MD5) Shared header Type dependant header Payload Source Destination Resource limits

8  Exports a set of node primitives  Determines what kind of processing routines can be deployed by applications  Execution model  Optimized for packet forwarding  Can be extended to generalized computation Active node

9  Environment access  Query routing tables, state of links, etc  Capsule manipulation  Access to capsule headers and payload  Control operations  Create, copy, forward, discard capsules  Node storage  Manipulate short-lived application-defined objects Active node primitives

10  Forwarding routines  Immutable and fixed at sender  Run locally within a short time  Memory and bandwidth usage is bounded by a TTL like scheme  Only capsules belonging to the same protocol may share state  A capsule cannot create new capsule of a different protocol Active node execution model

11  Not all nodes need to be active nodes  Sandboxing and Java byte code verification used for protection Active node execution model

12  Unfeasible approaches  Carry entire program in capsule  Pre-load program into all active nodes  Couple code transfer with data transfer  Distributes code to where needed  Adapts to connectivity changes Code distribution

13 Code distribution steps Capsule Request Capsule Search cache Response Code group

14 Example – Mobile hosts  Mobile IP like protocol with two cooperating capsule types 1.Register: Sent by mobile host to register forwarding information 2.Data: Used by other hosts to send messages to mobile host

15 Example – Mobile hosts Sourc e Home agent Foreign agent Dest (home ) Dest (home ) Dest (away) Dest (away)

16 Example – Multicast Member Intermediate node Member Sender

17 Related work  Softnet (1983)  Seminal work; safety and efficiency ?  Most similar to this work  x-kernel (1991)  Dynamic composition of micro-protocols on a per packet basis  Inherently less flexible since restricted to a set of micro-protocols  Messenger paradigm (1995)  End-to-end in nature

18 Conclusion  Rapid deployment of new protocols to exactly the required nodes  No advance consensus required about protocols