Cisco Systems Inc, Menlo Park, California has announced a new high-end router, the Cisco 7000, based on a new architecture. The company says that it is its fastest product to date. The architecture is also rather different from anything it has done to date: while sticking with a bus-based system, rather than the more radical […]
Cisco Systems Inc, Menlo Park, California has announced a new high-end router, the Cisco 7000, based on a new architecture. The company says that it is its fastest product to date. The architecture is also rather different from anything it has done to date: while sticking with a bus-based system, rather than the more radical crosspoint approach, the company has plumped for multiple buses, three of them, with distinct functions. The main data bus is a 533Mbps synchronous affair, and is dedicated, as the name implies, just to carrying user data. All the housekeeping traffic – system overhead and interprocessor communication – is shunted onto one of the other two buses. The multi-bus approach is mirrored by multiple processors. Each of the interface boards has its own on-board processor and in addition there is a central routing processor and a switch processor. The last is an Advanced Micro Devices Inc 2901-class bit slice processor optimised for switching. Bit-slice processors are building block slices through a full arithmetic-logic unit – the Am2901 is four bits wide – and can be ganged together to create a CPU with any desired word length. The instruction set is undefined, so that the designer can write the desired set, which is stored in microcode. Cisco has written an instruction set of 96-bit words. The practical upshot is that almost any operation can be carried out with one instruction potentially speedy. The switch processor handles real time forwarding of traffic between the interface processors. The Routing processor, meanwhile (a Motorola Inc 68040) deals with the non-real time operations such as routing protocol updates and routing calculation. The company quotes the Harvard Network Device Lab as measuring an aggregate Internet Protocol forwarding rate of more than 110,000 64-byte packets per second using a 10-Ethernet to 10-Ethernet test set-up. However the switching speed of any particular protocol depends on whether it is handled completely by the switch processor or whether the routing processor needs to intervene.
Both IP and NetWare’s IPX protocol fall into the former category, as does FDDI-to-FDDI bridging, Switched Multi-megabit Data Service access and quite a few others. The rest, such as the Open Systems Interconnection routing protocols, need the routing processor and are consequently slower, but by how much is not stated. Those fast-switched protocols are expected be switched around twice as fast some time in 1994 when the company is aimimg to replace the programmable bit-slice processor switching processor with a hard-wired custom chip. The chassis itself is a seven slot affair, two of which are filled by the route and switch processor boards. The interface boards, which are available straight away, will be: Ethernet interface processor with two, four or six ports; Token Ring interface processor – two or four port, using the IBM chip set; FDDI Interface processor: a one port board that supports routing, multiple methods; Fast Serial interface processor – four or eight running at T1 speeds of 8Mbps; and a selection of RS-232, V.35, X.21 or RS-449 physical interfaces. Promised enhancements over the next couple of years include an ISDN primary rate interface, an IBM channel connection and an Asynchronous Transfer Mode interface. Initially this will be in the form of an external Data Sswitching Unit, but a native, internal interface is promised later. The new device is to cost $20,000 for the chassis with route and switch processors. The interface processors cost between $6,500 to $22,000. At the same time the company has cut the price of its previous top-range AGS+ to $9,900 from $13,800 for the chassis. FDDI interface board costs have also been cut by 15% and the Ciscobus controller board halved in price to $2,200. The AGS+ price cuts should ensure that the older product does not become a dead duck. In fact the company is at pains to explain that development work will continue on th AGS+ and cites proposed improvements in a number of protocol switching speeds, a doublin
g in number of Token Ring ports, Advanced Peer-to-Peer Interworking support and an Asynchronous Transfer Mode interface as reasons to believe that this may be a new product that is here to stay.