1. Capsule-based Active Networks: What have we learned? David Wetherall (djw@cs.washington.edu) University of Washington

2. djw // OpenSig’99 // 10/99 2 State of Active Networks So when can I use it? Vision 96 99989700 The Active Internet ANTS PLAN ACTIVE IP MØMØ PAN Plugins AS1 Are we there yet? ?? Softnet 0x…

3. djw // OpenSig’99 // 10/99 3 Context: Styles of Extensibility SystemUser Middlewaretranscoding proxies (AS1) mobile agents (Active Names) Packetcongestion gateway (Plugins) routing w/ nack suppression (PLAN / ANTS) Getting beyond “One size fits all”

4. djw // OpenSig’99 // 10/99 4 This is ANTS Aim: Each user controls the handling of their own packets in the network How well does this work? User 1 User 2 capsules active nodes

5. djw // OpenSig’99 // 10/99 5 ICMP as a Minimal System ICMP –Runs at all IP routers, can be used by all users Programs –Traceroute, path MTU discovery flexibility performance security ICMPANTS?

6. djw // OpenSig’99 // 10/99 6 ANTS Tradeoffs Mobile code for flexibility Simple forwarding model for performance / security –Depend on caching; target experimentation data IP #7 #23 #7 RUNTIME

7. djw // OpenSig’99 // 10/99 7 Accepting Heterogeneity Can’t make forwarding simpler, so processing ultimately depends on node’s abilities /position –E.g. 1GHz, 1Gbps, 1000b, 100%  1000 cycles –Or if 100Mbps, 10%  100,000 cycles –Wide variation  heterogeneity is fundamental Build into programming model –Can query node to determine what’s appropriate –Non-active nodes (IP routers) at bottom

8. djw // OpenSig’99 // 10/99 8 A Minor Matter of Security Vision: unprivileged users have unrestricted access Requires Protection –My program can’t corrupt your program  We know how to do this Requires Resource Management –My program can’t starve your program  The harder problem

9. djw // OpenSig’99 // 10/99 9 Resource Management Tasks InternetANTS Per Packet At One Router Yes, by design of IP Yes, for a simple model Per PacketYes, by design of protocols Woops … big hole here Per UserNeed FQ or penalty boxes Same as Internet

10. djw // OpenSig’99 // 10/99 10 The “Per Packet” Problem TTLs are a weak solution; not related to topology Fairness mechanisms mitigate, but arguably not enough Restricted program forms may help … Want to Stop this!

11. djw // OpenSig’99 // 10/99 11 Programming with ANTS Examples –Multicast (single source and PIM) –Mobility –Reliable Multicast support –Path MTU discovery –Auctions –Web cache diversion routing –“TCP-SYN” filtering

12. djw // OpenSig’99 // 10/99 12 Lessons / Discoveries How to program mixed networks: A complication Code as flexible “glue”: Many variations A clean way to query the network: Heterogeneity The set of unchangeable things: Shared assumptions More Application Experience is Needed!

13. djw // OpenSig’99 // 10/99 13 More Details See paper in SOSP’99: Active Network Vision and Reality: Lessons from a Capsule-based System, D. Wetherall.