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Mapper preps SAN traffic for Sonet/SDH

Posted: 25 Mar 2004 ?? ?Print Version ?Bookmark and Share

Keywords:galazar networks? ethernet-over-sonet framer? eos framer? storage-area-networking mapper? mdx251 mapping chip?

Startup Galazar Networks Inc. is complementing its line of Ethernet-over-Sonet (EoS) framers with the release of a storage-area-networking mapper that will allow operators to carry storage streams over Sonet/SDH links.

Equipment vendors and chip makers have developed EoS devices over the past two years that allow for the efficient mapping of Ethernet streams over Sonet/SDH links, with the generic framing procedure (GFP) playing a key role in that mapping. GFP comes in two flavors: GFP-F, a frame-mapped mode optimized for standard Ethernet streams, and GFP-T, a transparent mode optimized for storage traffic. With interest in carrying SAN traffic over Sonet/SDH links on the rise, equipment manufacturers are looking to bring GFP-T support to their designs.

Galazar wants to help make that happen with its MDX251 mapping chip, which can take in Escon, Ficon, 8B/10B-encoded Ethernet or Fiber Channel storage traffic. Once the traffic is received, the MDX251 takes the 8B/10B encoded streams and maps them into a 64B/65B superblock - a process defined by the GFP-T specification. The chip then combines the superblocks and hands them off to Galazar's DSF250 or MSF250 framer devices over the SPI-3 interface. The framer, in turn, encapsulates the traffic for transport over the Sonet/SDH network.

The MDX251 can handle four channels of Escon or Ficon traffic, two channels of encoded Ethernet or Fiber Channel streams, or four subrate Fiber Channel streams.

To support the subrate operations, designers typically use a flow-control mechanism whereby credits are passed over the SAN. But the latencies associated with the Sonet network can choke this flow-control process, Galazar said.

To solve the problem, Galazar has designed the MDX251 to support locally managed flow control.

In 5,000-unit lots, the chip is expected to be priced at about $200 apiece.

- Robert Keenan

EE Times

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