The DECNIS 500/600 Multiprotocol Bridge/Router and Gateway

1 Abstract The DECNIS 500/600 high-performance multiprotocol bridge/router and gateway are described. The issues affecting the design of routers with this class of performance are outlined, along with a description of the architecture and implementation. The system described uses a distributed forwarding algorithm and a distributed buffer management algorithm executed on plug-in linecards to achieve scalable performance. An overview of the currently available linecards is provided, along with performance results achieved during system test. The DEC Network Integration Server 500 and 600 (DECNIS 500/600) products are general-purpose communications servers integrating multiprotocol routing, bridging, and gateway functions over an evolving set of local and wide area interfaces. The product family is designed to be flexible, offering a wide range of performance and functionality. The basic system consists of a Futurebus+ based backplane, a management processor card (MPC), and a packet random-access memory (PRAM) card with a centralized address recognition engine (ARE) for forwarding routed and bridged traffic. Network interface cards or linecards are added to provide network attachment. The DECNIS 500 provides two linecard slots, and the DECNIS 600 provides seven linecard slots. The applications run from local memory on the MPC and linecards. PRAM is used to buffer packets in transit or destined to the system, itself. The system was developed around distributed forwarding on the linecards to maximize performance. Software provides forwarding on the linecard for internet protocol (IP), DECnet, and open systems interconnection (OSI) traffic using integrated IS-IS (intermediate system to intermediate system) routing, along with bridging functionality for other traffic. The management processor controls the system, including loading and dumping of the linecards, administering the routing and bridging databases, generating routing and bridging control traffic, and network management. X.25 functionality, both for routing data and as an X.25 gateway, and routing for AppleTalk and IPX are supported on the management processor. Performance measurements on a system configured with 14 Ethernets have demonstrated a forwarding performance of 80,000 packets per second as a router or a bridge. This paper discusses the issues involved in the design of a fast bridge /router. It presents the processing considerations that led us to design the distributed forwarding system used in the DECNIS 500/600 products. The paper then details the hardware and software design and concludes with a