Cisco's cluster router approach reveals break with past

Articles: Cisco's cluster router approach reveals break with past

Posted by admin on Wednesday, May 26, 2004 - 07:48 AM

COLORADO SPRINGS, Colo. — Analysts and competitors alike acknowledged that Cisco Systems Inc.'s clustered-router approach, unveiled Tuesday (May 25) with its CRS-1 Carrier Routing System, could change core-router architectures as profoundly as clustered servers and storage controllers changed the client-server data center.
Chief Executive John Chambers said Cisco had considered extending its 12000 core-router family, but "we quickly determined we needed to start from scratch." That implied moving to a multi-shelf architecture with a massively-parallel, packet-forwarding ASIC at the heart of each router line card. It also entailed shifting to a microkernel-based modular operating system that would allow higher-availability processes than the traditional internetwork operating system (IOS). While the advertised high-end speed of 92 Tbits/sec for 72 clustered routers may be daunting, competitors were actually encouraged by Cisco's break from 12000 hardware, and from the original unified IOS. By telling carriers that high-end scalability requires a shift to CRS-1 hardware and IOS XR software, Cisco might have done some competitors a favor. "The specs look good, but a turn to modular software can be a Pandora's box," said G. Hudson Gilmer, senior product manager at Avici Systems Inc. "Can you prove testability without a unified software model? The other risk they run, that we'd look to take advantage of, is the announcement of new systems replacing old before the new ones are in the pipeline. Car manufacturers understand the problem of not pre-announcing before you're fully ready to ship, and our customer base tells us that HFR [the original code-name for CRS-1] ain't fully baked yet." Cisco said Sprint is already using a single-shelf CRS-1 production unit. It also said additional systems will ship in July. Mike Volpi, senior vice president and general manager of Cisco's routing technology group, said traditional core router architectures could not move to tens-of-terabits performance, nor could they offer in-service upgrading of both hardware and software — as is claimed for the CRS-1. Cisco spent close to $500 million on research for CRS-1, which sports 40-Gbit/s line-card hardware as a basic granularity level. The system features a 40-Gbit forwarding ASIC called the Silicon Packet Processor, and a 40-Gbit packet-based line interface meeting Sonet carrier levels of OC-768c/STM-256c, which Cisco claims is a first. While demonstrations featured what Cisco called the "first true 40-Gbit IP network traffic," analysts still wondered how quickly core networks will upgrade from 10 Gbits/s. Drew Lanza, principal with Morgenthaler Ventures, said 10-Gbit channels will be the "747 airliner for the transport industry, becoming a workhorse that won't be upgraded to 40 Gbits for a long time." Cisco worked with IBM Microelectronics to develop eight separate ASICs for the CRS-1. The Silicon Packet Processor implements 188 massively-parallel RISC cores in an 18-million-gate CMOS device with 8 Mbits of embedded memory. The switching fabric ASIC, dubbed Sea, implements a three-stage Benes non-blocking switch network with more than 100 2.5-Gbit/s channels. Six other ASICs are distributed between line cards and switching fabric cards. While services provided by the IOS routing software are preserved from the original real-time OS, IOS XR was developed specifically for the multi-processing SPP and the multi-shelf expandability of the CRS-1's line-card shelves and switch-fabric shelves. Volpi said XR features would be similar to those in transaction-processing systems. XR implements non-stop packet forwarding, stateful switchover and in-service upgrades. The craft interface is based on XML scripts, and network managers can use Cisco's Route Policy Language to set routing domains using a high-level interface. While IOS processes are preserved from the original routing OS, XR allows the distribution of processes and subsystems across thousands of processing resources. Chambers admitted that the core-router market had been subject to fitful growth during the recession, and now constitutes a $1.2 billion market. However, he predicted that gaming and HDTV applications, particularly in Asia, would drive upgrades to core router networks. He added that Cisco recognized the inroads made by competitors like Juniper and Avici, but said CRS-1 would change the dynamics of high-end backbone routing.

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