1. Network-on-Chip Network Adapter and Network Issues System-on-Chip Group, CSE-IMM, DTU

2. © System-on-Chip Group, CSE-IMM, DTU 2 NoC Overview Slide Network Adapter Routing Node

3. © System-on-Chip Group, CSE-IMM, DTU 3 Overview Network Adapter Session / Transport Layer Plug and play interface Traffic encapsulation Network Topology Protocol

4. © System-on-Chip Group, CSE-IMM, DTU 4 Network Adapter Functions Encapsulation Service Management Interface multiple IPs to a single NoC port Sockets OCP VCI

5. © System-on-Chip Group, CSE-IMM, DTU 5 Encapsulation Convert messages into packets Header to payload ratio Header is overhead  Routing information  Control information (such as services, flit number, etc)  Possible error-correction Broadcast, narrowcast services

6. © System-on-Chip Group, CSE-IMM, DTU 6 Service Management Definition: Acquire, retain, use and relinquish any service in a predictable way!! Types of Services: BE: not guarantee, only correctness and completion of transmission is guaranteed GS: provides bounded guarantees  Latency  Bandwidth  Power  etc…

7. © System-on-Chip Group, CSE-IMM, DTU 7 Sockets Point-to-point connection (abstraction) Abstract away the network details for the IP cores Examples: OCP, VCI, etc Limitations (a bus-based view): Broadcast, narrowcast, services are not supported Easy means for GS service request, retention and teardown not supported

8. © System-on-Chip Group, CSE-IMM, DTU 8 Network Two characteristics Topology Protocol Flow-Control Quality-of-Service

9. © System-on-Chip Group, CSE-IMM, DTU 9 Topology Form: relates to geometry Scalable with area and power Easy to lay out in 2D chip plane Nature of link: relates to unidirectional or bidirectional links Presence of IP core

10. © System-on-Chip Group, CSE-IMM, DTU 10 Forms of Topology preferred for easy of layout better utilization of available bandwidth K-ary 2-cube K-ary tree better hardware utilization for same bandwidth good to exploit locality of traffic

11. © System-on-Chip Group, CSE-IMM, DTU 11 Nature of Topological Link Common variations: torus and mesh Uni-directional Bi-directional

12. © System-on-Chip Group, CSE-IMM, DTU 12 IP Core of Topology Direct network Indirect network

13. © System-on-Chip Group, CSE-IMM, DTU 13 Irregular Topologies Hybrid, asymmetric and hierarchical

14. © System-on-Chip Group, CSE-IMM, DTU 14 Router Architecture

15. © System-on-Chip Group, CSE-IMM, DTU 15 Buffering Schemes Input Head-of-line blocking Output Expensive in terms of hardware Virtual-output Moderately buffer cost at very high improvement in performance

16. © System-on-Chip Group, CSE-IMM, DTU 16 Crossbar and Arbitration Unit Crossbar connects input port to output port Arbitration is used to prioritize, setup and manage crossbar connections Possibly programmable for best-effort and guaranteed service connections

17. © System-on-Chip Group, CSE-IMM, DTU 17 Protocol Many dimensions Circuit vs packet switched Connectionless or connection-oriented Adaptive or deterministic Minimal or non-minimal Delay or loss Centralized or decentralized control

18. © System-on-Chip Group, CSE-IMM, DTU 18 Common Routing Mechanisms Store-and-forward Virtual-cut through Wormhole Protocol Router Stalling LatencyStorage Store-and- forward Packet At two nodes and link between them Virtual-cut through Header At all nodes and links spanned by the packet WormholeHeaderPacketAt the local node

19. © System-on-Chip Group, CSE-IMM, DTU 19 Flow-Control Network-level: NA-to-NA In-order delivery Packet Acknowledgment Credit based injection schemes Link-Level: Node-to-Node Congestion look-ahead or stalling Virtual channel selection

20. © System-on-Chip Group, CSE-IMM, DTU 20 Quality-of-Service End-to-end Reserving virtual circuits from source to destination One-way, round-trip or just reverse-way Connection management overhead!! Node-to-Node Logically independent resource allocation (avoid contention) Division of link bandwidth!!

21. © System-on-Chip Group, CSE-IMM, DTU 21 Conclusion Each NoC level offers many parameters such as topology, packet size, buffereing, that to optimize the implementation Sockets are enable plug’n’play of IP cores, thus flexibility in placement anywhere within the network geometry Topology is influenced by placement of IP cores Many protocol choices available, with wormhole costing the least in terms of buffering Buffers are most area consuming component within the routers

22. © System-on-Chip Group, CSE-IMM, DTU 22 References BJERREGAARD, T. and MAHADEVAN, S. 2004. “NoC Survey Manuscript”, Submitted. JANTSCH, A. and TENHUNEN, H. 2003. Networks on Chip. Kluwer Academic Publishers. BHOJWANI, P. and MAHAPATRA, R. 2003. Interfacing cores with on-chip packet-switched networks. In Proceedings of the Sixteenth International Conference on VLSI Design. ANDRIAHANTENAINA, A. and GREINER, A. 2003. Micro-network for SoC : Implementation of a 32-port spin network. In The Proceedings of Design, Automation and Test in Europe Conference and Exhibition. IEEE. BANERJEE, N., VELLANKI, P., and CHATHA, K. S. 2004. A power and performance model for network-onchip architectures. In Proceedings of the 2004 Design, Automation and Test in Europe Conference (DATE’04). IEEE. DALLY, W. J. 1990. Performance analysis of k-ary n-cube interconnection networks. IEEE Transactions on Computer. DALLY, W. J. and SEITZ, C. L. 1987. Deadlock-free message routing in multiprocessor interconnection networks.IEEE Transactions on Computers. DUATO, J. 1996. A necessary and sufficient condition for deadlock-free routing in cut-through and store-and forward networks. IEEE Transactions on Parallel and Distributed Systems. KUMAR, S., JANTSCH, A., SOININEN, J.-P., FORSELL, M., MILLBERG, M., OBERG, J., TIENSYRJÄ, K., and HEMANI, A. 2002. A network on chip architecture and design methodology. In Proceedings of the Computer Society Annual Symposium on VLSI, ISVLSI 2002. IEEE Computer Society. OCPIP. 2003. Open Core Protocol Specification, Release 2.0. http://www.ocpip.org. MILLBERG, M., NILSSON, E., THID, R., and JANTSCH, A. 2004. Guaranteed bandwidth using looped containers in temporally disjoint networks within the nostrum network on chip. In Proceedings of the conference on Design, automation and test in Europe. IEEE Computer Society. RADULESCU, A., DIELISSEN, J., GOOSSENS, K., RIJPKEMA, E., and WIELAGE, P. 2004. An efficient on-chip network interface offering guaranteed services, shared-memory abstraction, and flexible network configuration. In Proceedings of the 2004 Design, Automation and Test in Europe Conference (DATE’04). IEEE. RIJPKEMA, E., GOOSSENS, K. G. W., RADULESCU, A., DIELISSEN, J., MEERBERGEN, J. V., WIELAGE, P., and WATERLANDER, E. 2003. Trade offs in the design of a router with both guaranteed and best-effort services for networks on chip. In Proceedings of the Design, Automation and Test in Europe Conference. IEEE. TAMIR, Y. and FRAZIER, G. L. 1988. High-performance multiqueue buffers for VLSI communication switches. In Proceedings of the 15th Annual International Symposium on Computer Architecture. IEEE Computer Society.