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)
Some people believe good or bad things always happen in threes. I believe you
will always be able to find three (and probably more) things that are good or
bad and somewhat related, but sometimes I get surprised by the apparent
coincidental appearance of several closely related “things”. Last week
the folks at networkheresy.com posted a second installment of their “policy
in the datacenter” discussion, Cisco announced the acquisition of tail-f
and internal to Plexxi we had several intense architectural discussions
around Configuration, Provisioning and Policy management. Maybe we... (more)
Over the past few weeks I have had several conversations related to
calculating network topologies and how packet forwarding is done based on
those topologies. I wrote this post about a year ago explaining some of these
details, but after a conversation with a customer earlier this week, I wanted
to explain in a little more detail and relate it not only to Shortest Path
First methods, but also to more traditional L1 traffic engineering and path
Any network can be represented as a graph. The switches in the network are
the vertices or nodes in the praph, the link... (more)
Much has been published about the Open Compute Project. Initiated by
Facebook, it has become an industry effort focused on standardization of many
parts and components in the datacenter. Initially focused on racks, power and
server design, it has also added storage and now networking to its fold. Its
goal is fairly straightforward: “how can we design the most efficient
compute infrastructure possible”, a direct quote from its web site.
The focus of OCP has been mostly around hardware designs and specifications.
If you look at the networking arm of OCP, you find several Top of Rack... (more)
Last week Greg Ferro (@etherealmind) wrote this article about his experience
with scripting as a method for network automation, with the ultimate
conclusion that scripting does not scale.
Early in my career I managed a small network that grew to be a IP over X.25
hub of Europe for a few years providing many countries with their first
Internet connectivity. Scripts were everywhere, small ones to grab stats and
create pretty graphs, others that continuously checked the status of links
and would send emails when things went wrong.
While it is hard to argue with Greg’s complaints per... (more)