1. 1 Improving the Performance of Distributed Applications Using Active Networks Mohamed M. Hefeeda 4/28/1999

2. 2 Agenda 4 Active Networks –Limitations of the current Networking System –Definitions and motivations –Approaches programmable switches capsules –Programming Models (capsules) 4 Distributed Applications –Online auctions, stock quotes, distributed caching,... –Performance comparisons 4 Summary and Conclusions

3. 3 Current Networking System 4 Computation within the network –Very limited: –Only packet’s header processing, no payload change –Independent of the user and the application 4 Limitations –Difficulty of integrating new technologies and standards into the existing structure (e.g. IP6,...) –Difficulty to accommodate new services (multicast, …) –Poor performance due to redundant operations at several protocol layers

4. 4 Active Networks: Definitions 4 Emerged to solve those problems (DARPA, 94) 4 The Network is Active in two ways: –Nodes perform computations on the packets flowing through them. The packets can, for example: invoke some compression/decompression routines compute next hop to the destination send zero or more copies of the packet on selected links authenticate themselves modify themselves, …. –Users can inject programs into the network, thereby tailoring the node processing to be user_and application_specific

5. 5 Active Networks

6. 6 Active Networks: Motivations 4 Recent applications such as: –Firewalls, Web proxies, Multicast routers, Nomadic routers, …. –Go beyond the traditional network structure by doing some computations but in ad hoc approaches. 4 Active Networks objective is to: –Provide a generic approach that allows users to program their networks

7. 7 Active Networks: Rate of innovations 4 IP networks (Internet): –Standard packet format –Standard processing on almost all packets –Thus, changing the protocol means changing everything –Very low rate of innovations 4 Active Networks –Nodes will provide sets of virtual instructions –Therefore, nodes can execute many different protocols –This allows a very wide range of new user-invented services that are not limited by the network structure or the vendors’ products –Very high rate of innovations

8. 8 Active Networks: Approaches 4 Programmable Switches: Discrete approach –Programs and data are carried discretely; i.e., within separate messages –Users inject their programs into the required nodes –Then, they send the data packets –When a packet arrives, its header is examined and the suitable routine is executed –This separation is useful when programs are relatively large program loading must be carefully controlled

9. 9 Active Networks: Approaches (contd.) 4 Capsules: Integrated approach –Every message is a program that contains at least one instruction and embedded data –When a capsule arrives at a node, the program will be executed and affect the data. – In the same way as a PS printer interprets the contents of a PS file.

10. 10 Active Networks: Programming Models 4 Standardized models for programming the nodes and allocate their resources 4 The Models should provide: –Mobility executing codes on various platforms –Safety restrict the access to the resources –Efficiency achieve mobility and safety without sacrificing the network performance

11. 11 Programming Models Services (Instruction Set) 4 Common primitives –Packet manipulation changing header, payload, length,… –Access to the node’s environment node address, time of the day, link status, … –Controlling packet flow forwarding, copying, discarding, …. 4 Resource allocation (How to allocate resources?) –Physical resources transmission BW, storage, processing capacity,... –Logical resources routing tables, management information base,...

12. 12 Program Encoding Approaches 4 Source Code –Uses scripting languages (e.g. Safe-Tcl) –Programs can be composed quickly –Safe, mobile, and human readable –But Not efficient because source code interpretation relatively large size 4 Intermediate Code –Uses intermediate instruction set (e.g. Java byte-code) –Safe, mobile, and compact size –More efficient

13. 13 Program Encoding Approaches (contd.) 4 Binary code –Platform-dependent –Safe and very efficient –But Not mobile

14. 14 Distributed Applications 4 Mixing Sensor Data

15. 15 Distributed Applications (contd.) 4 Online Auctions –The server collects and processes client bids for each item –It responds to requests for the current prices –The information may be out of date by the time it reached to the user (auctioneer) because of the network delay –In an Active Network, the server may activate some routines on the routers and update them frequently –These routers can filter out the low bids and respond with current prices –So, they reduce the load on server and the network delay

16. 16 Distributed Applications (contd.) 4 Active Reliable Multicast –Provides point-to-group communication facility –NACK may overload the server and consume the BW –Active Nodes solve this problem: a limited amount of multicast data is cached and retransmitted downstream when a NACK is received, reduces latency and BW Duplicate NACKs are suppressed by checking the sequence number; reduces the server load and BW usage Missing data packets are detected by checking for gaps in the sequence numbers. If a gap found the node generates a NACK and sends it towards the server for retransmission; reduces latency

17. 17 Distributed Applications (contd.) 4 Stock quotes –The server should supply changing up-to-date info. (quotes) to users as fast as possible –Traditional whole web page caching is not suitable –Active nodes used to reduce server load and latency they cache quotes (with their time stamp) then they receive the subsequent requests and check the cache. If they are available, they are assembled into a web page and sent to the client. This greatly reduces the load on the server and latency

18. 18 Performance comparisons 4 Load on Servers

19. 19 Performance comparisons (contd.) 4 Latency at Clients

20. 20 Summary and Conclusions 4 Active Networks allow users to program the network 4 Wide range of new services and applications can easily and rapidly be realized 4 Performance of the distributed application can be enhanced by using active networks