November, 1998
By Andrew Cray
Product Leader: Edge Routers
Giving the Edge to Aggregation
Redstone’s RX family of routers can help more corporate customers get T1 access to the Internet
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Forget the crunch at the core. These days Internet service providers are just as edgy about the edge of their networks—where bandwidth bottlenecks are also putting the squeeze on performance.
Redstone Communications Inc. says its RX Internet Edge Routing Switch could be the cure to congestion. A single device can aggregate T1 access lines from thousands of customers and funnel data at wire speed to the gigabit routers in the core. The upshot? Service providers can do away with multiple boxes while deploying higher speed Internet access at a lower price—and pass the savings on to corporate customers. What’s more, the RX routers meet the latest traffic management specs, which means those customers also should eventually be able to get guaranteed quality of service.
But it may be some time before this prescription can be filled. The Redstone routers have yet to be deployed as part of a commercial service and are completely unproven. “It’s too early to know whether test results will show wire-speed performance or not,” says Jim McManus, vice president of engineering at Uunet Technologies Inc. (Fairfax, Va.), which is beta-testing the product.
Demand and Supply
Nevertheless, the RX is coming along at the right time. “We’re going to see an utter explosion in demand for bandwidth at the edge,” says Tom Nolle, president of consultancy CIMI Corp. (Voorhees, N.J.). And McManus notes that the router will “enable us to service more demand.”
How? A single chassis can handle at least 924 T1 (1.544-Mbit/s) circuits; a seven-foot rack, as many as 2,772. That’s nearly five times the ports available in the 7500 router from Cisco Systems Inc. (San Jose, Calif.), the device used by most ISPs at the edge of their networks.
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MORE INFO
Product Summary
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The RX Internet Edge Routing Switch comes in two models. The RX1400 has 14 slots for line cards, and the RX700 has space for seven. At least one slot is needed for the vendor’s SRP (switch router processor) card, which manages the peering links with other routers.
Two other line cards are available. One contains three channelized T3 (45-Mbit/s) interfaces for incoming traffic; the 84 T1 circuits that card handles typically head out to corporate sites via a local carrier’s central office. For the uplink, the vendor offers a two-port OC3 (155-Mbit/s) card for connection to a core router like the Cisco 12000 or the M40 Internet backbone router from Juni-
per Networks Inc. (Mountain View, Calif.). Redstone says that keeping physical wires separate from the line cards adds redundancy. Also, each card carries its own power supply and is hot-swappable.
As for transport protocols, RX routers support IP over ATM, IP over frame relay, and IP over Sonet for connection to the core router. The IP link to the corporate premises is made via either frame relay or PPP (point-to-point protocol).
Wired Up
On the performance front, Redstone (Westford, Mass.) says there are three ways its router achieves wire speed. First, ASICs are used to take care of packet forwarding on each line. Second, the device uses a 10-Gbit/s switching fabric to move packets quickly from the input cards to the output cards. Third, a copy of the routing table is distributed to each card, which means routing decisions are made locally and backplane use is minimized. That also frees the SRP to focus on managing the peering links.
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Prepared to Prioritize
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Quality of service is another advantage the RX router offers. It supports an early version of MPLS (multiprotocol label switching); processors on the line cards can classify incoming IP packets according to source and destination address, the status of the DS (differentiated service) byte, physical interface, and application. Packets are mapped into different queues and MPLS flows according to their throughput needs (see the figure).
But Redstone isn’t alone in the aggregation router market. The Bay Networks division of Northern Telecom Ltd. (Mississauga, Ontario), for instance, sells the Versular 15000, while Ennovate Networks Inc. (Boxborough, Mass.) offers the Envoy 1600. Both vendors say their products costs $500 per T1 port, compared with the $750 Redstone charges. For a basic chassis, prices are about $32,950 for the 7-slot version of the RX and $49,950 for the 14-slot version. Still, the vendor says that’s cheaper than using multiple routers and frame relay switches to terminate lines.
And Redstone also claims that its box terminates up to 32,000 simultaneous IP sessions, compared with Northern Telecom’s 1,024 IP interfaces. Why is that important? Nortel’s product limits the number of subscribers to just two per T1—not very useful when servicing DSL (digital subscriber line) users via channelized T3 interfaces. Service providers typically oversubscribe such users at the DSLAM (DSL access multiplexer) and therefore need plenty of IP assignments.
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