Will Enhanced Servers Do Away With Need For Switches?

Some functions will likely be subsumed, but disaggregation not likely to replace ToR switches

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Optical interconnects and backplanes have also been evaluated before but never took off due to cost and complexity, Rivers says. Intel’s RackScale architecture, which disaggregates and pools compute, networking and storage to make an IT rack more flexible and agile through software, proposes a photonic interconnect as a fabric weaving together those pooled resources.

intel rackscale infog

But this may prove too complex to be practical, Rivers suggests.

“Optical backplanes are too complex, and that’s why it hasn’t played out,” he says. “RackScale is too tightly coupled for today’s data center environments and too much of a highly engineered system, as opposed to a loosely coupled system able to move at network scale and speeds. RackScale looks like a one type fits all, which inevitably it doesn’t, and oftentimes customers don’t get the benefit out of it.”

He likens it to efforts to embed blade switches in blade servers, which users virtually ignored. Instead, they used pass thru modules to Cisco switch ports.

In the same vein, Rivers is skeptical of the idea of using optical technology in the data center to directly connect servers and bypass a ToR switch.

“A large file takes less than a second to transfer, so it’s hard to get leverage out of that technology,” Rivers says. “It’s hard to see optical crosspoint switches being the fundamental technology element that changes networking forever. They’ve existed for quite some time.”

As will ToR switches, according to Intel. Even though servers will take on more switching intelligence and local function, the horsepower will remain with a physically separate and distinct switch.

“The ToR will still be relevant in the data center,” says Steve Price, general manager of Intel’s Communications Infrastructure Division. “The trend is that network intelligence is also increasing in the server shelf. Policy enforcement and multi-tenant tunneling capability today occurs in either the vSwitch or the ToR, for example. With increased compute density within the rack and the emergence of SDN and NFV on servers, there will be an increase in east-west traffic at the shelf level across both virtual and physical switching. The server will become a hybrid platform able to process packets through software on Intel Architecture and use a shelf-level switch to aggregate and manage traffic workloads across multiple servers.”  

Shelf-level switching in the server can provide low latency connectivity to multiple server sleds within the shelf, along with traffic aggregation through 100G Ethernet uplinks to the ToR, Price says. Besides, providing high port count switching within each server shelf increases cabling costs, he says, so Intel proposes the aggregation of all server shelf traffic through 100G uplinks to a ToR.

Intel’s strategy is to increase investment in Open vSwitch community projects with a focus on a data plane development kit (DPDK) to advance both virtual switching performance on Intel Architecture, as well as enable hardware offloading to the NIC and/or physical switch when needed. DPDK is currently planned for inclusion in Open vSwitch 2.4, Price says.

As for the RackScale architecture initiative, that’s focused on hyperscale data centers where administrators want to reduce total cost of ownership, and increase resource flexibility and agility, Price says.

Intel and Cisco have had discussions on the RackScale architecture, and generally on server/switch disaggregation and distributed memory, according to Dan Hanson, technical marketing director from Cisco’s Computing Systems Product Group. Cisco’s views on switch disaggregation are complementary with Intel’s, Hanson says, but they diverge on how best to achieve it.

“The idea holds a lot of promise. A lot of people have been driving towards something like that,” Hanson says. “We’re just trying to figure out the best way to do it.”

Intel’s DPDK is an enabler, Hanson says, as are some of the hardware assist capabilities of Cisco’s UCS servers in Network Functions Virtualization applications where general purpose x86 platforms lack adequate horsepower. But how best to achieve distributed, disaggregated switching and memory management and when the industry is ready for it is still open for debate, he says.

“The reasons we’re having these discussions with Intel around RackScale is as a complementary architecture, where we’re looking at expanding more sections of that server, distributed and disaggregated, across a rack of servers,” Hanson says. “We have that right now within a rack of UCS to share some of these components, but maybe not down to the memory channels that Intel is looking at.”

Hanson pointed to Cisco’s System Link technology in its UCS M-Series servers, unveiled three months ago, as a capability that could map into RackScale. System Link is silicon that gives M-Series the ability to connect disaggregated subsystems into a fabric with software-defined, policy-based provisioning, deployment and management of resources per application.

But like Dell’Oro’s Weckel, Hanson believes the rate at which customers adopt System Link, RackScale or server/switch disaggregation will ultimately determine if or when servers become the ToR switch of the future.

“The question is, how fast some of this might happen and the depth at which that will come together,” Hanson says. “There will be underlying technical hurdles that need to be addressed. Depending on the customer ability to consume that kind of change in technology will be the primary driving factor. We’re always looking at new and better technology than what we can bring, but a lot depends on the rate of absorption of technology that customers are willing to accept.”

This story, "Will Enhanced Servers Do Away With Need For Switches?" was originally published by Network World.

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Copyright © 2015 IDG Communications, Inc.

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