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Move Over Cloud – Fabric is the New Buzz Word
Oct 31, 2011

Move Over Cloud – Fabric is the New Buzz Word


I have been in this industry for almost 30 years. In the pantheon of words that have been abused by marketing folks during that time, the term “cloud” has to rate near the very top.  Today everything is a cloud. Too bad. “Cloud” is a great metaphor to describe shared, virtualized resource pools. A good friend of mine recently pulled out a slide from 1997 where I used the term and a pictorial depiction of a cloud to describe dynamic pools of compute and storage resources. It got me to thinking: am I to blame?


In a case of history repeating itself, about two and a half years ago I started talking publicly about the benefits of fabrics in the data center. Fabrics represent a faster, simpler, more efficient topology to interconnect the infrastructure of the modern data center. Since then, I have noticed that our competitors have also started talking about fabrics and, as is typically the case when marketing folks get hold of a term they do not fully understand, the term “fabric” has begun its ascent up the list of abused terms. When I cut through all the chatter, I find three types of architectures being marketed as data center “fabrics”:


1.    The first, which I call a Marketing Fabric, is not really a fabric at all. It is merely a collection of switches arrayed in a traditional hierarchical network. It appears that marketing types, who were feeling left out of the fabric conversation, started referring to their current offerings as a fabric and stamped that moniker on the pictures in their brochures. Either they do not get it, or they are trying to confuse you.  Shame on them (and they know who they are).




2.    The second type I call a Protocol Overlay Fabric, which is built on top of a non-blocking network topology commonly known as a "spine and leaf" design constructed with standard Ethernet switches. The “leaves” act as the access tier of the network while the “spine” acts as the backbone or core.  Each node in the spine is connected to every leaf; the number of nodes in the spine is a function of the bandwidth required to achieve a non-blocking network according to the principles first laid out by Charles Clos while he was at Bell Labs in 1953.




This design commonly used in the WAN, presents problems when applied to an L2 environment. While Ethernet is great at providing plug-and-play access, it unfortunately struggles with multi-switch topologies that present multiple paths or loops. Applying Spanning Tree Protocol could solve the problem, but that would unfortunately disable most of the bandwidth.  As a result, we have seen the evolution of two new multi-link protocols, TRILL and SPB (Shortest Path Bridging), to address the problem. Done properly, this architecture provides three benefits:


  1. A simpler, flatter two-tier network topology 
  2. All access ports are equal, eliminating the effects of network locality
  3. No Spanning Tree


  1. The third type of fabric I call a Switch Fabric. A switch fabric preserves the operational construct, performance and simplicity of a single switch, but it delivers the scalability and resiliency you expect from a data center network—the best of both worlds. It eliminates the need to run any multi-link protocol inside the fabric by utilizing a hardware-based transport mechanism and enables the fabric to be managed as a single "device". This is the path that we have taken with QFabric, and one I have discussed in previous blogs. Juniper is the only vendor to have taken this path, and the benefits are many.


  1. It is the simplest network topology, flattening the network to a single tier
  2. All access ports are equal, eliminating the effects of network locality
  3. This design eliminates the need to run any multi-link protocols such as Spanning Tree, TRILL or SPB
  4. It improves efficiency by reducing the number of hardware components, thus reducing the power, space and cooling requirements
  5. It reduces network latency, improving the behavior of every application
  6. The design simplifies operations by reducing the number of devices to be managed from many to one
  7. It provides the lowest capital and operating costs.



So even though the marketing types will continue to misuse the term fabric the characteristics and benefits of a true fabric remain clear.


Related Resources:

ACG QFabric TCO Whitepaper for download here. Listen to the video interview with Mike Marcellin and Ray Mota on You Tube here.

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