Author : David Wetherall (djw@cs.washington) Presented By : Gokul Nadathur

1. Active Networks Author : David Wetherall (djw@cs.washington.edu) Presented By : Gokul Nadathur (gokul@cs.wisc.edu)

2. Tour Guide ... • Introduction • Design of ANTS • Implementation of ANTS • Protection and resource management issues • What’s beyond active networks … Active Networks : Visions and Reality

3. What is an Active Network ? • Network architecture that allows : • Application Customized Code to be dynamically deployed in the network • Code to be Executed in a controlled framework within the network • Similar to extensible operating systems (SPIN, Synthesize etc) • Packet = Code + data Active Networks : Visions and Reality

4. Result Bid Server Client Motivation Client • Dynamic deployment of new Internet services • Online Auctions • Client submits bids • Central Server processes bids • Responds to requests for current price • During high load on server, current price may become invalid by the time it reaches the client INTERNET Schema for Auction Service Active Networks : Visions and Reality

5. Client Bid Fail Server Bid Filter Auction Service in an Active Network • Customized forwarding routine in active router • if (bid is valid) success else fail • Filters low bids in the network before they reach server • Server periodically updates current prices to active routers • Lowers load on server Active Router INTERNET Active Networks : Visions and Reality

6. Apprehensions • Security • Untrusted user code executing in core routers - Is it safe ? • Efficiency • Dynamic code distribution consumes bandwidth • Every packet now requires additional processing • Auction Service example :- • Every router has to check if ( user bid > current bid ) • Kills packet forwarding performance Active Networks : Visions and Reality

7. ANTS • Architecture designed to provide extensible network layer service • Routers are active • Extendable at packet level in the form of Capsules • A code distribution scheme Active Networks : Visions and Reality

8. Entities in ANTS • Active Nodes : • Programmable routers connected to IP routers through network channels • Maintain a cache of forwarding code (protocols) and data used by different services • Responsible for secure execution of forwarding code Active Networks : Visions and Reality

9. IP header Version Type Previous Address Dep fields Payload Capsules ANTS Header • Type • Identifier for the forwarding routine to be executed (carries code by reference) • Previous address • Where to get the forwarding routine from if it is not available in the present node (Code Distribution) • Dependent Fields • Parameters for the forwarding code • Payload • Header + data of higher layers Active Networks : Visions and Reality

10. Client Bid Code Code Request Server Previous Address field Example • Online Auction : • FILTER Capsule : Sent periodically by server to update current bids • BID Capsule : Used by client to submit bid • Forwarding Code not found ? • Code provided by end user software • Light weight Code Distribution within the network INTERNET Active Router (Caches Forwarding Code) Active Networks : Visions and Reality

11. No Capsule Capsule Extract Type Check in Cache Suspend Execution Receive Response Wake up Capsule Continue Execution Bootstrap code to cache Discard on Timeout Yes Fetch code from Previous Addr Code Distribution Active Networks : Visions and Reality

12. Code Distribution (Contd)... • Need for Bootstrap Capsules to transfer code • Well known type (System Capsules) • Directory service for selecting protocols • Advantages • Adapts to packet loss, node failures, changing routes • Disadvantages • High Latency of loading can trigger end-system timeouts Active Networks : Visions and Reality

13. IP Packet Capsule Implementation • User level process in Java • Node Runtime : • Schedules and executes capsule instances • Controlled access of soft store using restricted API • Channel Class : Creates Capsule instance from IP packet • Capsule : Execute custom forwarding routines from cache Active Node Runtime CH 1 Soft Store Cached code + data JAVA Sandbox Application Node API CH 2 Active Networks : Visions and Reality

14. Protection Schema • Type : MD5 fingerprint of forwarding routine • Prevents code spoofing • Provides authentication free foundation • Java SandBox • Prevents untrusted code from corrupting node runtime • type field is defined as constant • Impossible to create a Firewall • Very Slow ( PLANet - 3 times faster) Active Networks : Visions and Reality

15. Protection Schema ... • Code is read-only • Data is protected by hashing the store on the type of service to which it belongs Active Networks : Visions and Reality

16. Shared State Protection • R/W sharing of Cached state between related capsule types • Auction Example : • FILTER Capsule sent by server updates current bids • BID Capsule sent by client uses this data to validate its bid • Hierarchical Fingerprint for shared state : • Complex Type identifiers for shared state • Forwarding routines A and B share state • Type identifier for shared state: (A,(A, B)H )H and (B,(A, B)H )H • Identifies a single service (A, B)H to which both A and B belong Active Networks : Visions and Reality

17. Resource Management • Unbounded utilization of • Computing resources (Long forwarding routines) • Network Bandwidth ( Flooding child capsules ) • Solutions : • Watchdog timers for breaking long forwarding routines • TTL to limit number of hops • Static limit on fanouts • Application floods Network • network based resource allocation Active Networks : Visions and Reality

18. Open Issues • Administrative Issues • Who can introduce new services ? • Hackers Paradise • Open Research Area : A Killer Application ? Active Networks : Visions and Reality

19. And Beyond … • Radio Active Networks • Adaptable Wireless Network Architecture • Extend programmability to physical layer • Uses Software Radios and Active Networks • Higher layers interact with physical layer to observe changing conditions • Based on the change appropriate physical layer is selected • Example : Basestation to mobile system • Dynamically create channels according to mobile host population • Create channels of different priority and QoS Active Networks : Visions and Reality