The World is Flat – And the Data Center Network?

Thomas Friedman in his book “The World is Flat: A brief History of the Twenty-First Century” analyzes how the world (in terms of commerce) became a level playing field as a result of globalization.

Is the Data center Network becoming flat?

Businesses reliance on IT to achieve more with less has never been greater. Flexibility and scalability of a fully virtualized or cloud data center will play a key role for the IT organization in their quest to keep up with the demand placed on them by the CXO.

Achieving a fully scaled out dynamic virtual data center (where applications and virtual servers can move seamlessly to other hosts) and a converged network (where all data center traffic, be it storage, messaging, or voice move onto a single network) is not possible with the current multi-tiered network.

The data centre network is the critical enabler of all services delivered from the data centre.  Many data centre networks in operation today were designed and architected to support a multi-tier network.

These setups were designed for traffic patterns that predate virtualization. They are not optimal for today’s brave new world of server consolidation, virtual machines, and cloud computing and 10 Gigabit switches.

The multi-tier network was created as a work around for the limitations of Spanning Tree Protocol (STP).

The main goal of STP was to give us a loop-free network. To achieve this, STP makes sure that there is only a single active path to each network device.  STP did manage to achieve its goals, but not without introducing limitations. Some of these limitations (listed below) contribute to the road blocks that needs to be addressed in order to achieve a fully scaled out and dynamic data centre.

  • Wasted bandwidth – by blocking some network paths in order to avoid loops, all the available bandwidth is not being used
  • Active path is not always the most cost effective – This impacts virtual machine and application portability
  • Fail over time – when a device fails, STP reconfigures the network and sets up new pathways, but it does so relatively slowly. This is not acceptable in today’s network

The workaround for STP limitations has been to keep Layer 2 networks relatively small and join them together via Layer 3 segments. – Welcome to 3-Tier Network.

Then came virtualization and unified network. It soon became obvious that the 3-Tier network is not ideally suited to support this new technology

For example, in order to do a non-disruptive VMotion, the source host and target host as well as their storage needs to be on the same Layer 2 network. In other words, live migration can only happen on a single subnet.

All of this (and host of other issues) leads to a requirement to make the data centre network more intelligent. The buzz word for this is FLATENNING THE NETWORK.

According to estimates by some analyst firm, if all businesses eliminated a single layer from their networks, they could collectively save $1billion in IT spending.

So what is the way forward and how are the vendors responding?

The way forward is to come up with technology that can address the STP issues at the same time flatten the network down to two tiers, and if possible one tier.

Transparent Interconnection of Lots of Links (TRILL) is a proposed standard from IETF that is aimed at eliminating the aggregation/distribution layer and creates a switch fabric. TRILL goal is to make the network more intelligent and eliminate all of the shortcomings of STP.

Radia Perlman (the creator of STP) is a member of the IETF working group developing TRILL.

TRILL is an emerging standard and some analysts believe that we are at least 2 years away from a matured standard-compliant implementation of technology such as TRILL. However vendors such as Brocade, Cisco, Extreme, HP/3com and Juniper have all come out with approaches that flatten the network down to two tiers, and in some cases one tier.

Westcon have over 25 years of experience in the networking business and our focus is to work with our customers and help them with the transition. The skills we have acquired over the years and the fact that we carry majority of these vendors mean we are well placed to educate and help our customers to negotiate the new world of a FLAT network.


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