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Internetworking perspectives by Ivan Pepelnjak
Updated: 2 hours 43 min ago

That’s It for 2014

December 18, 2014 - 11:45pm

A dozen webinars, tens of public presentations and on-site workshops, numerous highly interesting ExpertExpress sessions, three books and over 250 blog posts. That should be enough for a year; it’s time to go offline.

I hope your company has a New Year freeze (and not let’s upgrade everything over New Year policy), so you’ll be able to do the same and enjoy some time during the rest of the year with your loved ones. See you in 2015!

MPLS Tech Talks: RSVP-TE 101

December 18, 2014 - 1:22am

After discussing the basics of MPLS, MPLS-TE and LDP, and the relationship between FECs, LDP and BGP, Seamus and myself focused on another interesting topic: how MPLS protocol stack uses RSVP to implement traffic engineering.

Watch the video

VRF Lite on Nexus 5600

December 16, 2014 - 11:35pm

One of the networking engineers using my ExpertExpress to validate their network design had an interesting problem: he was building a multi-tenant VLAN-based private cloud architecture with each tenant having multiple subnets, and wanted to route within the tenant network as close to the VMs as possible (in the ToR switch).

He was using Nexus 5600 as the ToR switch, and although there’s conflicting information on the number of VRFs supported by that switch (verified topology: 25 VRFs, verified maximum: 1000 VRFs, configuration guide: 64 VRFs), he thought 25 VRFs (tenant routing domains) might be enough.

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Just Published: Scaling Overlay Virtual Networking Videos

December 16, 2014 - 12:11am

The edited videos for Scaling Overlay Virtual Networking webinar are available on Content site. Nuage Networks sponsored the webinar; the videos are thus publicly available (without registration).

Watch the videos

Webinars in 2014, and a Quick Peek Into 2015

December 15, 2014 - 6:48am

I promise engineers who renew their subscription 4-6 new webinars a year. It’s time to see whether I kept that promise in 2014.

TL&DR summary: it was a great year, but I still missed a few things.

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L2VPN over IPv6 with Snabb Switch on Software Gone Wild

December 12, 2014 - 5:23am

Highly customizable high-speed virtual switch written in Lua sounds great, but is it really that easy to use? Simon Leinen was kind enough to get me in touch with Alex Gall, his colleague at Switch, who's working on an interesting project: implementing L2VPN over IPv6 with Snabb Switch.

Alex is a quiet speaker, so I had to do plenty of massaging to make him heard in the recording, resulting in not-so-spectacular voice quality.

We warmed up discussing pretty standard questions…

  • Why would you not want MPLS in your network?
  • Why does it make sense to run L2VPN over IPv6?
  • Why is no hardware manufacturer doing it?
  • Is SDN a solution - and what is SDN anyway?
  • Can it be done on an x86-based device? At what speed?

... and then focused on implementation details of Alex’s solution riding on top of Snabb Switch:

  • How long does it take to pick up Snabb Switch and get a working prototype?
  • Doing packet forwarding in interpreted (scripting) language is an interesting problem;
  • If you run out of memory and the system starts doing garbage collection, you’re dead;
  • Using object-oriented code with plenty of inheritance might not be the best choice in high-speed real-time code;
  • Just-in-time compiler tries to optimize the code based on traces collected during the execution - you have to be somewhat lucky to get just the proper trace so your code is well-optimized;
  • Libraries help: Alex figured out how to do things fast, and wrote a library that did all the complex stuff;
  • Working on a low-level platform means you have to reinvent all the wheels… including interface counters, and ways of accessing them.

Enjoy the show, and subscribe to the podcast feed to get future episodes straight into your podcast client. For even more information, download Alex’s presentation from Terena 2014 conference (video).

Facebook Next-Generation Fabric

December 11, 2014 - 7:09am

Facebook published their next-generation data center architecture a few weeks ago, resulting in the expected “revolutionary approach to data center fabrics” echoes from the industry press and blogosphere.

In reality, they did a great engineering job using an interesting twist on pretty traditional multi-stage leaf-and-spine (or folded Clos) architecture.

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Performance Tests and Out-of-Box Performance

December 10, 2014 - 12:39am

Simonp made a perfectly valid point in a comment to my latest OVS blog post:

Obviously the page you're referring to is a quick-and-dirty benchmark. If you wanted the optimal numbers, you would have to tune quite a few parameters just like for hardware benchmarks (sysctl kernel parameters, Jumbo frames, ...).

While he’s absolutely right, this is not the performance data a typical user should be looking for.

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Last Call: Overlay Virtual Networks in Software Defined Data Centers

December 9, 2014 - 4:49am

If you want to get a free copy of my Overlay Virtual Networks in Software-Defined Data Centers book, download it now. The offer will expire by December 15th.

Just published: Enterprise IPv6 videos

December 9, 2014 - 12:51am

The edited videos for my Enterprise IPv6 webinars have been published on Enjoy!

Load Balancing in Google Network

December 8, 2014 - 12:35am

Todd Hoff (of the HighScalability fame) sent me a link to an interesting video describing load-balancing mechanisms used at Google and how they evolved over time.

If the rest of the blog post feels like Latin, you SHOULD watch the Load Balancing and Scale-Out Application Architecture webinar.

The beginning of the story resembles traditional enterprise solutions:

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Scaling Distributed Systems Is Hard

December 6, 2014 - 6:31am

Stumbled upon a hilarious description of challenges encountered when trying to scale distributed systems (cluster of controllers running centralized control plane comes to mind).

It starts with “If someone tells you that scaling out a distributed system is easy they are either lying or drunk, and possibly both,” and gets better and better. Enjoy!

Hotel California Effects of Public Clouds

December 5, 2014 - 4:24am

In his The Case for Hybrids blog post Mat Mathews described the Hotel California effect of public clouds as: “One of the most oft mentioned issues with public cloud is the difficulty in getting out.” Once you start relying on cloud provider APIs to provide DNS, load balancing, CDN, content hosting, security groups, and a plethora of other services, it’s impossible to get out.

Interestingly, the side effects of public cloud deployments extend into the realm of application programming, as I was surprised to find out during one of my Expert Express engagements.

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Should I Really Program My Network?

December 3, 2014 - 9:27am

In my presentation @ SDN Meetup in Stockholm, I tried to answer a simple question: “Should I really program my network?” and obviously had to start with an even simpler one: “What is SDN?

The video of the presentation is already available on YouTube, and you can watch the slides on my content web site.

Also, make sure you watch other presentations from that event, particularly David Barroso’s SDN Internet Router.

MPLS P-Router, Router or Layer-3 Switch?

December 1, 2014 - 9:31pm

One of my readers is struggling with the aftermath of marketing gimmicks:

We will be implementing a new network soon, and we're discussing P-routers versus regular routers versus switches. I'm looking for arguments to go one way or the other.

TL&DR: there’s no difference between router and L3 switch.

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Can You AS-Prepend a Single Host Route?

November 28, 2014 - 2:18am

Someone recently sent me this question:

Is it possible to prepend one IP address from a public IPv4 segment?

I don’t want to know what crazy stunt this engineer was forced to pull off, but just in case you land in a similar quandary here’s how you shoelace yourself out of it.

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Thanks for being there!

November 27, 2014 - 5:45am

A third of my readers are celebrating Thanksgiving today, and I’d like to use the opportunity to say what I always wanted to say but somehow never got to it. Let’s make it short: Thank you! Without you, there would be no

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Transactional Thoughts on a Stormy Night

November 26, 2014 - 4:51am

It was a dark stormy autumn night and three networking engineers had nothing better to do than ponder the heavy topics of transactional consistency in a distributed SDN environment in Episode 16 of Software Gone Wild podcast.

Here are a few of the topics that crossed our minds:

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FECs, LDP and BGP in the MPLS World

November 25, 2014 - 2:33am

After discussing the basics of MPLS and LDP in our Tech Talks chat, Seamus Gilchrist and myself focused on a concept that perplexes many networking engineers entering the MPLS world: the relationship between Forward Equivalence Classes (FEC), LDP and BGP.

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Quick Peek: Juniper vMX Router

November 24, 2014 - 2:09am

While the industry press deliberates the disaggregation of Arista and Cisco, and Juniper’s new CEO, Juniper launched a virtual version of its vMX router, which is supposed to have up to 160 Gbps of throughput (as compared to 10 Gbps offered by Vyatta 5600 and Cisco CSR). Can Juniper really deliver on that promise?

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