- Lori MacVittie, senior technical marketing manager at F5
Networks (www.f5.com), says:
Whether bees or
Martians, science or science-fiction, the notion of a hive mind is one that pops
up frequently within the realm of psychology, philosophy, theology, science
and, last but not least, technology. A hive mind is one that has a collective
memory, sharing information from the past and present with every other member
of the hive.
This capability (if it really exists) enables incredible
resiliency on the population as a whole, because every member of the population
has the information necessary to replace another at any moment. This concept
has been applied to scaling applications since scaling applications because a
necessity. If applications share session state information – usually by sharing
a session data base – then any instance can immediately take over for another
without disrupting a user session. Like bees, there is no need for
on-the-job-training, it just "knows" – as though it tapped into a
shared database full of not only standard hive knowledge but of the current
state of the hive.
This concept is partially included in many SDN implementations,
with varying degrees of success. In the most common, centralized-controller
model of SDN a singular entity (the controller) maintains this vault of
knowledge but disseminates only partial views of that state to relevant pieces
of the infrastructure. Thus it is not a fully participative hive mind, but a
partial one. This leads to over-reliance on the controller, which is
responsible not just for management of the shared knowledge but of
dissemination. Like the queen bee, loss of the controller is devastating to the
ability of the controller-focused SDN to function.
Midokura, offers a new model with a more complete collective
"hive mind" that inherently supports resilient software-defined
networks and alleviates the potential risk of relying on a singular entity
through which to disseminate state of the network.
MidoNet
Midokura is a global startup focused on network virtualization.
It officially entered the US market in mid-October 2012 with the introduction
of its primary solution: MidoNet.
MidoNet virtualizes
the network stack for popular cloud platforms such as OpenStack®. Midokura’s
approach not only adds automation that significantly reduces the human cost
(OPEX) of managing the network, but also impacts the overall economics of cloud
computing (CAPEX)
by simplifying network requirements.
MidoNet is a distributed, de-centralized, multi-layer software
defined virtual network solution for IaaS. By taking an overlay-based approach
to network virtualization, MidoNet sits on top of any IP-connected network, and
pushes the network intelligence to the edge of the network, in software.
Cutting through the marketing speak, MidoNet is a fabric of
distributed, software-defined networking services. It requires no specialized
hardware infrastructure, but rather turns any Linux-based host running the Open
vSwitch kernel module and the MidoNet agent into a node on a fully-meshed, L2-4
virtual network fabric.The network executes on a role-based networking
principle, with each node able to execute on a broad set of L2-4 policies based
on its assigned role in the flow. By taking an overlay-based approach to
network virtualization, MidoNet can be deployed atop any existing network,
using traditional L2/L3 connectivity as the means to create and utilize its
peer-to-peer virtualized tunnels.
MidoNet applies faithfully the idea of
centralized management coupled with de-centralized execution.Traditional edge
services are applied at the perimeter of the network using virtual policy
execution, and then packets are routed via a tunnel to the designated
end-point. Policies are not so much deployed as they are simply applied
at the appropriate ingress node. Each node may play multiple roles, guided by
the process governing specific flows.
Failure, then, is inherently managed by the ability of any edge
node to apply the appropriate policies based on the role being executed. There
is no reliance on a controller - commonly associated with SDN implementations –
because local agents manage the application of appropriate policies on ingress
and egress traffic. It's a "shared session" approach to networking,
in which the entire state of the network is stored in scalable database systems
and distributed throughout the network. Just as is the case with "shared
session" applications, failure in any given node simply means flows are
directed through a different node – which has complete knowledge of all the
information previously known to the failed node by virtue of sharing the
network state database.
Like a hive mind, every node knows what every other node knows –
and has known – and it is only the roles assigned to any given node that
indicates a difference in how that node executes on traffic.
The difference between MidoNet's architecture and the
centralized architecture of a controller-based SDN is in the execution. While
both models "share" state and configuration, ostensibly, a
controller-based SDN relies on centralized execution. MidoNet does not,
leveraging shared state and configuration as a means to enable resiliency.
MidoNet does not come without questions. Any agent-based system
brings with it overhead, and MidoNet is no exception. The question becomes how much overhead
and does it significantly impact performance of the host system. Similarly, how
many roles can a single node assume before it becomes overwhelmed? How well
does MidoNet react to failures in the underlying L2/L3 physical network?
And while MidoNet
offers a mix of stateless and stateful services, the higher up the stack one
traverses, the less robust such services become. Layer 4 load
balancing as currently
offered by MidoNet is acceptable for simple load balancing, but depending on
the application and demand may result in uneven distribution that can make
capacity planning and elasticity less efficient and more difficult to perform.
Also problematic with any simple L4 load balancing service are
issues with application dependencies on persistence and topological
architecture and the resulting impact on load balancing algorithms. Midokura
does not refute the unique challenges associated with moving up the stack – nor
with the rudimentary nature of its existing L4 services – but believes these
challenges can eventually be addressed.
All in all, MidoNet is an impressive adaption of SDN principles
into a more resilient, flexible model. The application of a shared session
architecture combined with role-based networking is a fascinating twist on the
more common centralized control and command model put forth by competing SDN
players.
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