Is Shortest Path Bridging (SPB) winning the data center fabric standards battle? One could have walked away from Interop 2012 with that impression, given the level of interest in it during a conference session and the production implementations that were discussed at the show.
SPB is IEEE 802.1aq and is based on the same MAC-in-MAC technique used in IEEE 802.1ah, Provider Backbone Bridging. SPB uses a link state routing protocol to allow switches to learn the shortest paths through an Ethernet fabric and dynamically adjust to topology changes.
SPB also allows Ethernet networks to deploy multiple active paths to overcome the traditional active-passive redundancy of Spanning Tree, in which half of all ports could be in a non-forwarding mode.
Jim Metzler's "Alternatives to Spanning Tree" panel discussion on Tuesday morning at this week's trade show generated a lot of questions for an Avaya engineer after his presentation advocating SPB as a replacement for Ethernet's Spanning Tree Protocol. Other panelists included Extreme Networks, Juniper and Cisco, each promoting their respective MLAG, QFabric and FabricPath implementations.
Some in the session remarked that MLAG is a non-interoperable standard, while QFabric and FabricPath are considered proprietary. No one spoke specifically on behalf of TRILL, the IETF fabric specification, though Cisco did mention that FabricPath was a pre-standard version of TRILL and that Cisco switches could be configured in "TRILL mode" if FabricPath was not desired.
Of all the presentations, Avaya's SPB talk was the only one to provide an example of a production deployment. It mentioned a hospital deploying SPB to support a multitenant environment.
The Avaya presenter fielded most of the questions after the talks were done. Attendees wanted to know how Ethernet and IP-like SPB was, since the presenter said "the only things that matter" when deploying SPB are IP and Ethernet.
"If you know OSPF, you know more than half of SPB," the presenter, Avaya engineer Paul Unbehagen, said. He also mentioend that Avaya, Alcatel-Lucent and Huawei have demonstrated SPB interoperability.
Does it scale? "This was designed to go into carriers," Unbehagen said, referring to SPB's MAC-in-MAC Provider Backbone Bridging characteristics.
Do you other vendors on the panel plan to support it?
"It depends on what you're trying to do," said Shehzad Merchant, senior director of strategy at Extreme Networks. "MLAG works just fine. What's the problem you're trying to solve?"
Cisco? Cisco has no plans to support SPB, said Francois Tallet, Nexus 7000 product manager.
"We're doing TRILL," Tallet said.
Curiously, Tallet was replaced on the speaker's list of the "Alternatives to Spanning Tree" session with Shashi Kiran, senior director of Data Center/Virtualization and Enterprise Switching at Cisco. His session presentation has also been removed as a downloadable PDF file from the Interop site.
Tallet does appear here though.
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