fundamental scalability of data centres
that’s under question from this perfect
storm in networking. Will it be possible
to build data centre networks to the size
needed in the future?
Re-Inventing The Network
To enable future data centres, we need
to significantly simplify the network.
Fortunately, the industry is already
migrating towards simpler and more
efficient network architectures. One
example is the move from classical
single-rooted tree topologies with
bandwidth bottlenecks and single
points of failure, to folded Clos-based
topologies that increase the capacity of
the network by providing redundancy
with multiple paths through the
network.
Software-defined networks allow
architects to separate the application,
control, and physical transport layers
and move them from proprietary
hardware to open software. This
approach allows the control plane
processing, which guides packets to their
destination, to be performed on a set of
commodity servers, thus simplifying the
design of the switches.
These are both examples of
important, but fundamentally
incremental improvements. To enable
real scalability, we need much more. We
need to deploy innovative, disruptive
technologies in key areas of the network.
Simplified Switching
We need three basic functions to
create a data centre network: packet
processing, switching and transport.
Today, the packet processing and
switching functions are implemented
in electronics, typically conventional
CMOS technology, while the transport
function is migrating towards the
higher bandwidth capability of optical
(photonics) technology.
As we have seen, the current reliance
on relatively small radix switches created
in CMOS severely constrains both
the throughput and scalability of an
economical mega data centre network.
However, simplifying the work that
the sw itch has to do by changing the
network architecture gives us a unique
www.netcommseurope.com
opportunity and we can now introduce
optical technology into areas of the
system that have previously been out
of bounds for photonics. This ‘smart
integration’ of electronics and photonics
will enable each technology to play to its
strengths: CMOS’s density and ability
to perform complex processing, and
photonics’ outright speed and capacity
of transmission.
Relaxing the constraints on switch
size by dramatically increasing port
density is fundamental to being able
to scale data centre capacity, simplify
the network and increase throughput.
A combination of electronics and
photonics will enable packet switching
to be performed in the optical domain
to support scalable switch functionality
that is not possible in the electronic
domain.
For example, high-speed data signals
can travel much further over
single-mode fiber optics than copper
wire and at much lower power and cost.
This capability gives network designers
more options to partition a large optical
switch over multiple locations in a
data centre. In addition, we can easily
mix multiple signals over the same
optical fiber using wavelength division
multiplexing, which reduces cable
complexity and cost.
Radix Switches
By integrating advanced optical
switching features with the packet
processing capabilities of CMOS we
are able to achieve a larger radix for the
basic switch building block. Taking a
modular approach to large, multi-stage
switches simplifies their design and
enables easier and cheaper connectivity
for data centres.
This solution will benefit from
Moore’s Law scaling in CMOS
technology, as well as advances in the
optical domain. These two factors
will help redirect the cost trajectory
of networking to better align with the
compute function and alleviate data
centre operators’ concerns about how
to increase data centre capacity while
keeping cost and power in check.
Combining CMOS and photonics
in switching has the potential to reduce
networking cost and power by a factor
To enable future data centres, we need to simplify the network
of 10. Bringing the switch function into
the optical domain means that it will
not only scale with the growing size of
the basic building block, but also, and
uniquely, through the modular switch
architecture. This allows unprecedented
scalability in the network and the means
to deliver the data centre bandwidth
capacity required for the next
generation.
Still, developing this technology will
take a system-level, multi-disciplinary
approach, which is why we are
bringing together world-class experts
in photonics, electronics, software,
system architecture and semiconductor/
photonics manufacturing.
Data centre networking is a $10
billion (and growing) market.
Silicon-photonics is the key to fulfilling
this market potential and enabling the
factor of 1,000 increase in compute
capacity that we will need to fuel the
next 10 years of Internet growth.
NETCOMMS europe Volume V Issue 6 2015 35