Few applications really need a direct connection to a switch backplane, something Cisco tacitly admits in its own product line. The company hasn't yet ported some less network-centric products, such as its Call Manager PBX software or Wireless Location Appliance, to the 6500. IP telephony and queries on Wi-Fi users' whereabouts run happily over standard Ethernet, so plugging them directly into the switch would waste a Catalyst slot.
This equation should change as virtualization goes mainstream. While a single application or appliance may not need enough bandwidth to justify a switch slot, multiple applications or virtual appliances aggregated together are another matter. While a traditional architecture might use a 16-port Gigabit Ethernet module to connect one switch to 16 servers, the virtual data center would put 16 virtual machines right on the module. These VMs will have little relation to what we now think of as servers. For maximum flexibility, workloads must be able to move among servers--or switches--without necessarily dragging data with them, so they won't contain hard disks, relying instead on storage area networks. Cisco thinks the same will happen to memory: It will migrate outside the server or VM, requiring a new type of network to link memory and CPU.
The network really will become the computer.
How realistic is this vision? Cisco hasn't yet released a module for the Cat 6500, or any other switch, that can run third-party applications, and it won't say when (or if) it will. However, it describes the vision as spanning 10 years; there are still technical and physical barriers to overcome. Running applications at switch backplane speed will generate a lot of heat, which, according to Cisco, is one reason it won't initially release Catalyst-style service modules for the faster Nexus. The new switch is aimed only at network aggregation, virtualizing SANs and LANs over the same physical cable.
Competing vendors are grabbing onto this trend. In January 2007, 3Com launched its Open Services Network product line, aimed at moving server functions to networking devices. The most important is the OSN Module, a blade server that plugs in to its 6000 series enterprise routers and multiservice routers, or MSRs, for branch offices. Running a customized version of Linux, the blade has a direct connection to the router's backplane and a link to its control channel via a 3Com API. This lets applications on the blade route traffic to a particular destination, prioritize some packets over others, or select some for deeper processing.
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