IP Multicast is one of those technologies that most everyone loves to hate.
It’s almost the perfect example of how complicated we have made networking.
Getting IP Multicast to run depends on several protocols that are all
somewhat intertwined or dependent on each, their relationship sometimes
explicit, sometimes implicit.
Even trying to describe the basic operation is complicated.
When an application or service provides information using IP multicast, it
simply starts sending it onto a specific multicast group. The multicast
router for the subnet of the sender sees the incoming multicast packet and
will initially have no forwarding information for that stream in its
forwarding hardware. The packet is passed onto the CPU of that router, which
will encapsulate this packet and send it towards a special multicast router
designated the Rendez-vous Point (RP). When the RP... (more)
Throughout the development cycle of new features and functions for any
network platform (or probably most other products not targeted at the mass
market consumer) this one question will always come up: should we protect the
user of our product from doing this? And “this” is always something that
would allow the user of the product to really mess things up if not done
right. As a product management organization you almost have to take a
philosophical stand when it comes to these questions.
Protect the user
Sure enough, the question came up last week as part of the development of on... (more)
[This is not really about the Red Sox or pumpkins this Halloween, but how
could I not use those in the title? Go Red Sox]
I left an awful teaser at the end of my article last week. In Brent
Salisbury's original article that triggered some of these additional
virtualization thoughts, he articulated two very clear differences between
native network based L2 virtualization mechanisms and the mechanisms that are
being provided by overlay solutions based mostly in server vSwitch
infrastructure. These two fundamental functions are MAC learning and tunnel
encapsulation. In today's post... (more)
We still see quite a few eyebrows raised when we explain how we use WDM
optics in our datacenter solution. In the various descriptions of the Plexxi
solution it is often mentioned and referred to, but it is worth explaining
what that optical infrastructure actually looks like and why it is part of
One of the key attributes of the Plexxi solution is the ability to create
network topologies at L1, L2 and L3 that meet the need of the workload
offered, calculated based on the load on the network, and the Affinities
created that describe the needs of specific applicatio... (more)
We love analogies. No matter what the topic, analogies are a great way to
explain something in a different context to make a specific point with a
frame of reference that may be more familiar to those we are making a point
to. There is one that seems to come back over and over again in our industry,
the one that compares the network to the power grid, network connections to
power plugs. I had not heard it for a while but at Interop last week, I
heard it used twice in booth demonstrations as part of plug and play pitches.
And I really do not like that analogy.
The comparison to ... (more)