Packets of Interest 2012-06-12 — OSPF Refresher

I was recently brushing up and refreshing my OSPF knowledge and I discovered some great resources that I wanted to document for my future use and also share with others. I found these resources great for explaining/detailing area types, packet types, and neighbor states. This first document hosted at packetlife.net is one of the best explanations of packet types I've ever seen due to the visual aids that the author, Jeremy Stretch, incorporated.

How would you like to do IP Multicast without PIM or RP’s? Seriously, let’s use Shortest Path Bridging and make it easy!

 

Why do we need to do this? What’s wrong with today’s network?

Anyone who has deployed or managed a large PIM multicast environment will relate to the response to this question. PIM works on the assumption of an overlay protocol model. PIM stands for Protocol Independent Multicast, which means that it can utilize any IP routing table to establish a reverse path forwarding tree. These routes can be created with any independent unicast routing protocol such as RIP or OSPF, or even be static routes or combinations thereof. In essence, there is an overlay of the different protocols to establish a pseudo-state within the network for the forwarding of multicast data. As any network engineer who has worked with large PIM deployments will attest, they are sensitive beasts that do not lend themselves well to topology changes or expansions of the network delivery system. The key word in all of this is the term ‘state’. If it is lost, then the tree truncates and the distribution service for that length of the tree is effectively lost. Consequently, changes need to be done carefully and be well tested and planned. And this is all due to the fact that the Continue reading

Today is World IPv6 Launch Day!

After the success of last year’s World IPv6 Day, where success was measured with little to no problems reported, World IPv6 Launch Day has arrived! For a while major players like Google and Facebook had been white-listing their AAAA records to specific ISP recursive nameservers. This meant you had to query one of those in order to see IPv6 entries for their websites. Now that white-listing has been removed and all properly operating recursive nameservers will now serve up these records. They aren’t the only companies participating of course! Take a look at this list to see whom else signed up to promote their enabling of IPv6. Want some stats, take a look at the following:

But what does this mean to the non-techies out there? It is meant to be a passive change. You shouldn’t notice much in the way of interruptions. Perhaps your ISP will have a shorter route to a destination over IPv6, and you might get what you are trying to access a tiny bit quicker. If you like video/chat applications, this will soon mean that you’ll be Continue reading

The Best MPLS Lecture on the Net

The title says it all. Professor Karandikar gives two amazing lectures on MPLS and MPLS-TE that most engineers should hope to know cold. I watch it probably once every few months. Not saying much for my memory these days. It is an amazing amount of material delivered very precisely. Great stuff! I added some figures to […]

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Ethernet Switch Fabric Cards

I was working with a buddy today about switch fabric cards in the nexus 7000 and not doing a very good job at explaining it, so I figured I would draw some pictures. The conversation was around how adding more fabric cards increases the bandwidth. I think some, myself included growing up on Catalyst 6500’s […]

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Help Wanted: Cultural Change

This post is low on the nerdalert meter and more of the arts, rather than the science. Earlier this year, Level3 blogged about their new initiative of training ~%20 of their 11,000 person staff to be “change agents” in order to cross-pollinate their peers, the notion that change is healthy for the company (speculating). Change […]

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SDN and OpenFlow Quotes from some of the Best

Like anyone reading this, we are avid consumers (in my case leech) of information. I put together some quote from people regarding SDN and OpenFlow. Most of the people in the list are intrinsic in helping me shape my own views regarding technology with the outstanding content, ideas and research they generate. “Think of it as a […]

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Auto-RP and usage of "ip pim autorp listener"

After reading several forums with people arguing about what routers should be configured with the "ip pim autorp listener" command, I have decided to write this post explaining things in my own way (of course, with a lot of pictures, as usual).

MPLS VPLS configuration with Juniper JunOS.

Posting a Juniper VPLS how-to on a couple of J-series routers. Have been pretty SDN focused lately so wanted to get some real stuff in for a post. Docs on JunOS VPLS can be shaky so nothing like a couple real configs to plugin your address in the lab if having problems with L2 VPNs. […]

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The Fabric ERA

“Fabric” is a loosely used term, which today creates more confusion instead of offering direction. What exactly is a Fabric ? What is a Switch Fabric? Greg Ferro did a post here explaining how Ethernet helped the layer 2 switch fabric evolve. Sadly the use of switch fabric did not stop there. And this is […]

The Bufferbloat Bandwidth Death March

Some puzzle pieces of a picture puzzle.Latency much more than bandwidth governs actual internet “speed”, as best expressed in written form by Stuart Chesire’s It’s the Latency, Stupid rant and more formally in Latency and the Quest for Interactivity.

Speed != bandwidth despite all of what an ISP’s marketing department will tell you. This misconception is reflected up to and including FCC Commissioner Julius Genachowski, and is common even among technologists who should know better, and believed by the general public. You pick an airplane to fly across the ocean, rather than a ship, even though the capacity of the ship may be far higher.

The Internet could and should degrade gradually in the face of load; but today’s Internet does not degrade gracefully due to bufferbloat. Instead, performance falls off a cliff. We are lemmings on migration.

The Internet is designed to run as fast as it can, and so will fill any capacity network link as soon as you have any applications that asks to do so. We have more and more such applications, and the buffers get bigger each hardware generation, though usually operated at a small fraction of that possible bandwidth. As soon as a network or network link reaches100% capacity, the usually grossly Continue reading

SDN Business Cases

We have a few problems in the networking construct and as much as I dont want to say,  paradigm, ecosystem, abstraction etc. a million times there may be a couple hundred in the following writeup. The following document are some rationalizations that have come up over the past recent months/years for some new abstractions in networking that […]

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