Cisco's FabricPath and HP's FlexNetwork move to fabric-based designs.
network vendor is now touting an architecture that challenges the traditional
three-tier design. Cisco and Hewlett-Packard are introducing equipment and
design changes that increase the size of the Layer 2 collision domain to enable
greater virtual workload mobility. Network managers are being offered a choice
between known, proven designs and unknown, flattened architectures. And these
new architectures require new switch chassis along with new line and supervisor
network manager will be fired for adhering to risk-avoiding orthodox networks.
The question is, in the face of sweeping changes offered by virtualization and
cloud computing, can traditional networks remain competitive?
the widely used and well-understood STP (Spanning Tree Protocol) makes switched
networks possible. At a basic level, STP enables switches to be plugged into
other switches so that redundant paths are available to prevent a single point
of failure, but loops, which are fatal to network operation, are prevented.
Creating smaller collision domains inside a larger broadcast domain worked
in networks where applications were installed on single, physical host systems.
However, when VMware vSphere was introduced, these smaller domains also limited
where virtual machines could migrate because VMs must have access to the same
subnets on the source and destination physical hosts. Thus, business-continuity
strategies are usually limited to a single physical location and are, therefore,
much more likely to fail.
architectures, one from Cisco and the other from HP, offer a range of hardware,
protocol and management changes. It's worth noting that other network-equipment
manufacturers are also offering architecture options including Brocade's
Extreme's Open Fabric
Juniper Networks' just released QFabric
in 2008, Cisco introduced the Nexus 7000 data center switch chassis, a new
operating system called NX-OS and a family of Nexus switches. The FabricPath
architecture came the following year and in 2010 OTV (Overlay Transport
, which extends Layer 2 functionality between
data centers, was released. Along with these switch and protocol changes Cisco
released its UCS (Unified Computing System)
thus setting the stage for a substantial change in network architecture and the
current competitive struggle with HP.
month at Interop, HP announced the A10500 switch
, basically a competitor to the Catalyst 6500
family, and the A12500
, which is roughly analogous to the Cisco 7000.
HP also unveiled its FlexNetwork architecture including FlexFabric for the data
center. It almost goes without saying that HP has long made data center
protocols are being jostled by emerging network concepts that could morph into
the standards that will run on networks in short order. Besides working to move
beyond STP, a research project called OpenFlow
experimental, open standard intended for future switches, routers and wireless
access points-seeks to be the basis for software-defined networks where
hardware elements support optimized traffic flows that eliminate bottlenecks
that current protocols such as OSPF (Open Shortest Path First) can introduce.
And all of these protocols will require better network-management oversight.
often chided for having too many disparate management tools while HP has a
well-established place in the enterprise operations-management field. Both
companies are using the network architecture changes as an opportunity to
recreate management as a competitive advantage, which is all to the good for IT
managers. Cisco is reducing the number of management tools by consolidating
functions while HP started shipping IMC5 release (Intelligent Management
Center, version 5) at Interop.
The Fabric and the Tree
next several years, as early adopters put the new equipment and designs into
practice, no word is likely to be more used and abused than "fabric." Both
Cisco and HP use fabric as an integral part of their network designs. In both
cases, fabric lacks the concrete, limited meaning found in the storage world. Instead,
a network fabric is a densely woven high-speed interconnect between compute and
storage in an environment where traffic flows and workloads are dynamically
relocated based on priority and available resources.
HP both recognize that moving from a tree to a fabric-based architecture will
be an evolution. Neither company sees network managers ordering a
rip-and-replace strategy. And the new network designs aren't suited for all
business needs. For example, Microsoft Exchange or SharePoint client/server
traffic will likely still be best served by current designs. Instead of taking
a rip-and-replace approach, both companies have made it clear that they will
continue to support three-tier designs that use STP. But IT managers can expect
a push from equipment makers to purchase switch line cards that enable the
gradual transition to a fabric design. The evolution from tree to fabric favors
the edge and core and deemphasizes the aggregation layer.
Cisco and FabricPath
opened the attack on STP on a variety of fronts when it launched the Nexus
product platform. In short order, OTV and FabricPath were released to deal with
the Layer 2 domain limits of STP. Around the same time, the VPC (Virtual
PortChannel) was introduced on the Nexus 7000, and that enabled all uplink
ports to be used to increase bandwidth but without introducing loops.
introduced FabricPath as a feature in the Nexus 7000 hardware platform. The
FabricPath Switching System combines NX-OS software features with the hard
capabilities of the Nexus 7000 F1 series module as the basis of its next-generation
incorporating FabricPath enable workload mobility
such as VMware vMotion in a much larger resource pool, while also gaining
significant bandwidth and N+1 redundancy and fast network convergence after a
link failure. FabricPath-enabled modules use active-active links between
devices-losing the idle ports that spanning tree required-and instead use ECMP
(equal-cost multipath) to direct traffic.
modules can support up to 16-way ECMP, which can be combined with 16-port 10G
bps PortChannels, for a total of 2.56T bps between switches. FabricPath builds
on technologies that Cisco developed to create OTV and increases performance
for enterprises moving to the Nexus 7000 and NX-OS.
HP Releases FlexNetwork
After being a Cisco partner for many years, HP became a fierce rival. Its acquisition of 3Com last year was
aimed at shoring up its position against Cisco. HP's release of the FlexNetwork
architecture last month is among its latest competitive salvos.
center heart of the architecture is FlexFabric and the HP A10500. In keeping with its
legacy, HP has placed unified management at the heart of the FlexNetwork
architecture, which is also a distinguishing characteristic of the design.
Although the much-worn "single pane of glass" metaphor is central to the IMC5
release, it is useful to know that more than 10 separate modules can be
implemented as needed. The network element manager is a basic requirement that
IT managers should place at the top of their evaluation list.
A10500 is one of the main hardware components of the FlexNetwork design but is
not expected in the United States until sometime in the third quarter, although
the chassis is shipping in China. Thus, I have not yet seen the "proof in the
pudding" as it were. Even so, HP appears to have all the basic ingredients to
support the FlexNetwork architecture with the hardware and software components
that were announced in mid-May.
it's clear that in the coming decade an evolutionary change in enterprise
networks will happen. It's easy to let the incremental changes slip by. However,
it's unmistakable that virtualization, mobility and cloud computing will soon
place stresses on networks that forward-thinking IT managers must consider