Blog Posts in September 2016
In March 2016 my friend Matt Oswalt announced a distributed network testing framework that he used for validation in his network automation / continuous integration projects. Initial tests included ping and DNS probes, and he added HTTP testing in May 2016.
I proposed a third option: go with simple VXLAN encapsulation on Nexus 9000 switches. Here’s why:
One of my readers watched my TCP, HTTP and SPDY webinar and disagreed with my assertion that shaping sometimes works better than policing.
TL&DR summary: policing = dropping excess packets, shaping = delaying excess packets.
I find the topic area of SDN and NFV a bit overwhelming in terms of information, particularly the NFV bit.
NFV is a really simple concept (network services packaged in VM format), what makes it complex is all the infrastructure you need around it.
How many VM moves do you see in a medium and how many in a large data center environment per second and per minute? What would be a reasonable maximum?
Obviously the answer to the first part is it depends (please share your experience in the comments), so we’ll focus on the second one. It’s time for another Fermi estimate.
You categorically reject the use of OSPF, but we have a couple of customers using it quite happily. I'm sure you have good reasons and the reasons you list [in the presentation] are ones I agree with. OTOH, why not use totally stubby areas with the hosts being in such an area?
I was wondering if you have had any interest in putting together an SD-WAN overview/update similar to what you do with data center fabrics where you cover the different product offerings, differentiators, solution scorecard…
That would be a good idea. Unfortunately the SD-WAN vendors aren’t exactly helping.
When people started talking about OpenConfig YANG data models, my first thought (being a grumpy old XML/XSLT developer) was “that should be really easy to implement for someone with XML-based software and built-in XSLT support” (read: Junos with SLAX).
Here’s how my simplistic implementation would look like:
One of the common taglines parroted by SDN aficionados goes along the lines of “The cost to acquire and manage server and storage architectures has declined over time while networking stays stubbornly expensive.” (I took it straight from an anonymous blog comment).
Let’s see how well it matches reality.
Got this challenge from one of my readers:
I've recently changed jobs and I am currently working for a telco. The problem is that I have no idea of what they are talking about when they mention SGSN, GGSN, Gi, Gn, etc... I only know routing and switching stuff :(.
Obviously he tried to search for information and failed.
It took us a long while (and then the summer break intervened) but I finally got it published: Episode 62 is waiting for you.
Here are the outlines of an interesting ExpertExpress discussion:
- A global organization wanted to connect data centers across the globe with a new transport backbone.
- All the traffic has to be encrypted.
Should they buy L2VPN and use MACsec on it or L3VPN and use GETVPN on it (considering they already have large DMVPN deployments in each region)?
One of the oft-repeated messages of the Software-Defined Pundits is “Standard bodies are broken, (open) source code is king”… and I’d guess that anyone who was too idealistic before being exposed to how the sausage is being made within IETF has no problems agreeing with them. However…
- Automation should be a strategy. You need management buy-in;
- You should have at least one person with strong software development experience in your automation team.
However, life is not always rosy, so @stupidengineer asked:
While most readers, commenters, and Twitterati agreed with my take on the uselessness of OSPF areas and inter-area summarization in 21st century, a few of them pointed out that in practice, the theory and practice are not the same. Unfortunately, most of those counterexamples failed due to broken implementations or vendor “optimizations”.
Does it make sense to run OpenStack on top of VMware infrastructure? How well does NSX work as a Neutron plug-in? Marcos Hernandez answered these questions (and a lot of others) in the Episode 61 of Software Gone Wild (admittedly after a short marketing pitch in the first 10 minutes).
One of my readers left this question on the blog post resurfacing the idea of running BGP between servers and ToR switches:
When using BGP on a VM for mobility, what is the best way to establish a peer relationship with a new TOR switch after a live migration? The VM won't inherently know the peer address or the ASN.
As always, the correct answer is it depends.
We have a lab with virtual IOS-XE, IOS-XR and Junos (vMX) router. I would like to learn how to provisioning the Lab router.
Covered in the workshop. I’m focusing on vIOS (which is pretty close to IOS Classic and IOS-XE) and Nexus OS because that’s what I can get up and running quickly in VIRL.
One of my ExpertExpress design discussions focused on WAN network design and the need for OSPF areas and summarization (the customer had random addressing and the engineers wondered whether it makes sense to renumber the network to get better summarization).
I was struggling with the question of whether we still need OSPF areas and summarization in 2016 for a long time. Here are my thoughts on the topic; please share yours in the comments.
In the Leaf-and-Spine Fabric Designs webinar series we started with the simplest possible design: non-redundant server connectivity with bridging within a ToR switch and routing across the fabric.
After I explained the basics (including routing protocol selection, route summarization, link aggregation and addressing guidelines), Dinesh Dutt described how network architects use BGP when building leaf-and-spine fabrics.
Eluehike Chedu asked an interesting question after my explanation of why stretched ACI fabric (or alternatives, see below) is the least horrible way of stretching a subnet: What about OTV?
Time to go back to the basics. As Dinesh Dutt explained in our Routing on Hosts webinar, there are (at least) three reasons why people want to see stretched subnets: