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TCP Congestion Avoidance on Satellite Links

While some people spread misinformation others work hard to figure out how to make TCP work on exotic links with low bandwidth and one second RTT.

Ulrich Speidel published a highly interesting article on APNIC blog describing the challenges of satellite Internet access and the approach (network coded TCP) they took to avoid them.

Ethernet-over-VPN: What Could Possibly Go Wrong?

One of my readers sent me a link to SoftEther, a VPN solution that

[…] penetrates your network admin's troublesome firewall for overprotection. […] Any deep-packet inspection firewalls cannot detect SoftEther VPN's transport packets as a VPN tunnel, because SoftEther VPN uses Ethernet over HTTPS for camouflage.

What could possibly go wrong with such a great solution?

OpenFlow and Firewalls Don’t Mix Well

In one of my ExpertExpress engagements the customer expressed the desire to manage their firewall with OpenFlow (using OpenDaylight) and I said, “That doesn’t make much sense”. Here’s why:

Obviously if you can't imagine your life without OpenDaylight, or if your yearly objectives include "deploying OpenDaylight-based SDN solution", you can use it as a REST-to-NETCONF translator assuming your firewall supports NETCONF.

Automate the Exceptions

Every time I have a network automation presentation (be it a 2-day workshop or a 45 minute keynote) I get the same question afterwards: “How do we deal with exceptions?

The correct answer is obvious: “there should be no exceptions, because one-offs usually cost you more than you earn with them,” but as always the reality tends to intervene.

Optimize Your Data Center: Use Distributed File System

Let’s continue our journey toward two-switch data center. What can we do after virtualizing the workload, getting rid of legacy technologies, and reducing the number of server uplinks to two?

How about replacing dedicated storage boxes with distributed file system?

In late September, Howard Marks will talk about software-defined storage in my Building Next Generation Data Center course. The course is sold out, but if you register for the spring 2017 session, you’ll get access to recording of Howard’s talk.

New Open-Source IPAM + DCIM Tool

My friend Jeremy Stretch wrote an IPAM+DCIM tool for Digital Ocean and open-sourced it. As the tool was designed by networking engineers to manage data center networks (more in Jeremy’s blog post), it might be a better fit than other tools out there. In any case, check it out and let me know how it works.

Why Is Every SDN Vendor Bashing the Networking Engineers?

This blog post was written almost two years ago (and sat half-forgotten in a Word file somewhere in my Dropbox), but as it seems not much has changed in the meantime, it’s time to publish it anyway.

I was listening to the fantastic SDN Trinity podcast while biking around Slovenian hills and almost fell off the bike while furiously nodding to a statement along the lines of “I hate how every SDN vendor loves to bash networking engineers.”

Cutting through the IPv6 Requirements Red Tape

Few years ago a bunch of engineers agreed that the customers need a comprehensive “IPv6 Buyer’s Guide” and thus RIPE-554 was born. There are also IPv6 certification labs, US Government IPv6 profile and other initiatives. The common problem: all these things are complex.

However, it’s extremely easy to get what you want as Ron Broersma explained during his presentation at recent Slovenian IPv6 meeting. All it takes is a single paragraph in the RFP saying something along these lines:

The equipment must have the required functionality and performance in IPv6-only environment.

Problem solved (the proof is left as an exercise for the reader… or you could cheat and watch Ron’s presentation, which you should do anyway ;).

Typical SDN Architectures

Now that we know which definitions of SDN make no sense (and which one might) let’s see what a typical architecture of an SDN solution might look like.

I described some of them in the SDN 101 webinar, for more details watch the SDN Architectures and Deployment Guidelines webinar.

Does It Make Sense to Build Your Own Networking Solutions?

One of my readers was listening to the Snabb Switch podcast and started wondering “whether it’s possible to leverage and adopt these bleeding-edge technologies without a substantial staff of savvy programmers?

Short answer: No. Someone has to do the heavy lifting, regardless of whether you have programmers on-site, outsource the work to contractors, or pay vendors to do it.

Awesome Response: Complexity Sells

Russ White wrote an awesome response to my Complexity Sells post:

[…] What we cannot do is forget that complexity is real, and we need to learn to manage it. What we must not do is continue to think we can play in the land of dragons forever, and not get burnt. […]

Now go and read the whole blog post ;)

Build Your Own Service Provider Gear on Software Gone Wild

A few days after I published a blog post arguing that most service providers cannot possibly copy Google’s ideas Giacomo Bernardi wrote a comment saying “well, we managed to build our own gear.

Initially I thought they built their own Linux distribution on top of x86 server, but what Giacomo Bernardi described in Episode 59 of Software Gone Wild goes way beyond that:

Optimize Your Data Center: Reduce the Number of Uplinks

Remember our journey toward two-switch data center? So far we:

Time for the next step: read a recent design guide from your favorite hypervisor vendor and reduce the number of server uplinks to two.

Not good enough? Building a bigger data center? There’s exactly one seat left in the Building Next Generation Data Center online course.

Directed ARP Saga Continues

Reading my Directed ARP and ICMP Redirects blog post you might have wondered “how did Directed ARP ever get into ***redacted***?”

I searched for “directed ARP cisco” and found this gem, which really talks about unicast ARP behavior, an ancient mechanism documented in RFC 1122 (it’s not my Google-Fu, I got the reference to RFC 1122 in this blog post).

On the Lossiness of TCP

When someone tells you that “TCP is a lossy protocol” during a job interview, don’t throw him out immediately – he was just trusting the Internet a bit too much (click to enlarge).

Everyone has a bad hair day, and it really doesn’t matter who published that text… but if you’re publishing technical information, at least try to do no harm.

Where Is the Explosion of Overlay Virtual Networks

Three years ago I was speaking with one of the attendees of my overlay virtual networking workshop @ Interop Las Vegas and he asked me how soon I thought the overlay virtual networking technologies would be accepted in the enterprise networks.

My response: “you might be surprised at the speed of the uptake.” Turns out, I was wrong (again). Today I’m surprised at the lack of that speed.