Bay Networks` new Accelar routing switch family uses new technologies and processing techniques to deliver the high performance of a switch, coupled with the flexibility of a router: gigabit performance with Layer Three control. The Accelar products use a combination of a high speed switch fabric and ASIC (Application Specific Integrated Circuit) technology instead of a shared CPU. This distributed approach eliminates performance drop-offs and maintains features such as VLANs and prioritisation to run at a high level. The main switching fabric holds the central processing resource (a RISC PowerPC CPU), which performs standard routing functions such as spanning tree, bridge learning and protocol handling such as RIP and OSPF. Packet forwarding decisions are made by ASICs on the I/O modules, however, reducing the central load. The I/O modules perform interface and buffering tasks and maintains its own information base for routed and bridged traffic, which means that local traffic can be resolved and forwarded independently of the CPU. Each I/O port is equipped with dual queues for different priority traffic. Because the switching fabric is capable of faster packet throughput than the I/O port, no latency is introduced during policy checking and prioritisation while the advance packets are queued. The Accelar throughput runs at 7 Gbps on the 1200, with a packet forwarding capability of 7 million pps and a typical latency of less than 10 microseconds. This low latency allows high quality data streams even across a multiple hop connection. Where traditional routers introduce latency which leads to jitter or broken connections, the Accelar`s throughput and facilities for multiple qualities of service, as well as separate queues for multicast traffic, allows streamed broadcasts such as video to be introduced with no network brownout. Unlike traditional switches, the Accelar examines each packet for both Layer 2 and Layer 3 policies, which allows the creation of much more secure and robust VLANs. VLANs can be created logically, rather than by user location, and then easily configured and maintained through the evolution of the network. The Accelar 1000 family allows 127 port or police-based VLANs to be created. The Accelar management software includes support for drag-and-drop VLAN creation. The Accelar can be deployed in different configurations in many different network locations depending on the need. The wire-speed routing capability allows widespread subnets and VLANs; power workgroups need not hang off the same device but can be distributed. Flexible configurations of Gigabit Ethernet can support central backbone applications, network riser connectivity or bursty campus backbones with policy based VLAN and prioritisation.
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