Source: Cisco Licensed Test to Spirent

Cisco Systems Inc. (Nasdaq: CSCO) last year developed a storage routing tool to test the scaleability of its Fibre Channel switches -- and the company subsequently licensed the test to Spirent Communications knowing that Cisco's SAN equipment would return favorable results, an industry source tells Byte and Switch.

Cisco and Spirent representatives declined to comment for this article.

The test, which Spirent calls the Storage Routing Test (SRT), is designed to emulate as many as 239 Fibre Channel switches. That's the theoretical maximum number of FC switches allowed by the industry's Fibre Channel specification, which is maintained by the InterNational Committee for Information Technology Standards (INCITS). The SRT runs as a software module on Spirent's SmartBits testing platform.

Spirent officially launched the SRT on Wednesday and expects to make it available to customers later this month. In an interview earlier this week, Brian Mason, product manager for storage solutions at Spirent, said that, based on the company's testing using SRT, it has found "major scaleability concerns with all of the NEMs," or network equipment manufacturers. Mason told Byte and Switch that none of the vendors could actually support SAN fabrics with 239 switches (see Spirent: FC Switches Fail to Scale).

The company later clarified its statements to say certain manufacturers could, in fact, support SAN fabrics with more than 200 switches, though it wouldn't name them.It turns out that Cisco is apparently the mysterious vendor with the ability to scale into the 200-plus switch range. What's more, Cisco knew all along that it would outshine its competitors on the SRT because the company developed the test itself, according to an industry source who did not want to be identified.

"There is no way that Cisco would have licensed [the storage routing test] to Spirent if [Cisco] did not know that their switch would not work to the limits," says the source.

It's not clear how exactly how many Fibre Channel switches other vendors, such as Brocade Communications Systems Inc. (Nasdaq: BRCD) and McData Corp. (Nasdaq: MCDTA), are able to support in a single SAN. Brocade claims its SilkWorm 12000 handles the theoretical maximum of 239; McData makes the more conservative claim of supporting 24 switches per fabric.

But is there more at stake here than empty bragging rights? After all, it's worth noting that even the largest SANs today don't comprise more than a dozen or so switches in a single fabric.

Cisco, according to our source, does indeed believe that the high-scale test shows significant differentiation between its MDS switches and those from Brocade and McData.One of the main gating factors in the scaleability of a switch is the power of its management processor. When many switches are added to a SAN fabric, route calculations and other control-plane traffic can overwhelm individual devices -- and Cisco's results on the SRT supposedly demonstrate that its Fibre Channel switches can scale far beyond the competition.

On the other hand, Brocade, McData, and others can now point out that because Spirent's SRT test was developed by Cisco, it may favor the idiosyncrasies of Cisco's own switches. How many points Cisco ultimately gets out of this home-field advantage remains to be seen.

Todd Spangler, US Editor, Byte and Switch