I spent the first half of the Introduction to SDN webinar explaining various attempts at defining SDN, and the obvious place to start was the centralized control plane mantra.
This part of the webinar is now public; to access the rest of the webinar, register on my web site.
Daniel Dib wrote a great series of BGP-related blog posts well worth reading.
Daniel is looking at BGP from the WAN/ISP perspective; if you want to know more about running BGP in the data center, watch the videos I recorded with Dinesh Dutt a few days ago.
The featured webinar in March 2016 is the Leaf-and-Spine Designs update to the Leaf-and-Spine Fabrics webinar, and in the featured videos (the ones marked with a star) you'll find in-depth explanation of BGP features available in Cumulus Linux, including a cool trick that allows you to run EBGP sessions across unnumbered interfaces.
Read more ...My latest spanning tree protocol (STP) posts generated numerous comments, some of them so relevant that I decided to summarize them into another blog post.
The unidirectional link scenario mentioned by Antonio is pretty well known:
Read more ...A while ago I guestimated that most private clouds don’t have more than a few thousand VMs, and that they don’t need more bandwidth than what two ToR switches could provide.
Last autumn Iwan Rahabok published a blog post describing the compute- and storage parts of it, and I had a presentation describing the networking aspects of high-density consolidation. However…
Read more ...After explaining the basics of BGP-LS and PCEP, and a quick deep dive into BGP-LS, Julian Lucek focused on the second topic of his excellent webinar and described the details of Path Computation Element Protocol (PCEP).
A few days ago Inside-IT published an interview Christoph Jaggi did with me. In case you don’t understand German, here’s the English version of it.
There is a lot of talk about data center fabrics. What problem do they try to solve?
The data center fabrics are supposed to solve a simple-to-define problem: building a unified data center infrastructure that seamlessly supports data and storage communications. As always, the devil hides in the details.
Read more ...This article was initially sent to my SDN mailing list. To register for SDN tips, updates, and special offers, click here.
During one of my SDN workshops one of the attendees working for a mid-sized European ISP asked me this question:
Our management tells us we should build our network like Google does, including building our own switches. Where should we start?
The only answer I could give him was “You don’t have a chance.”
Read more ...Continuing our bridging loops discussion Christoph Jaggi sent me another question:
Theoretically STP should avoid bridging loops, and yet you claim they cause data center meltdowns. What am I missing?
In theory, STP avoids bridging loops. In practice, there are numerous reasons STP got a bad name.
Read more ...Everyone talks about public or hybrid clouds, whitebox switching with home-grown networking operating system, or SDN nirvana, but whenever I talk with enterprise-focused architects, consultants or vendor SEs, I see a totally different story.
Here's a typical response I'm getting from engineers in this group: “I work with multinational financial customers, and in this group hybrid cloud is not even a topic. They do private cloud projects, with some of them looking into public cloud deployments of isolated projects on base AWS functionality.”
Read more ...Imagine you get a routing outage in your network resulting in three minutes of traffic blackholing. After a few tense minutes it goes away and life is good, but you desperately want to know what went wrong. Can you figure it out? Well, you could if you were using PacketDesign tools, as Cengiz Alaettinoglu explained on Episode 51 of Software Gone Wild.
I somewhat expected that the leaf-and-spine fabrics designs webinar won’t be as short as I initially planned it to be, but when I started developing the scenarios and talking with guest speakers the whole thing exploded into a four-session saga (or maybe we’ll end up with the fifth session of a four-part trilogy).
Here’s a short update on what’s planned and where we are at the moment:
Read more ...My friend Christoph Jaggi, the author of fantastic Metro Ethernet and Carrier Ethernet Encryptors documents, sent me this question when we were discussing the Data Center Fabrics Overview workshop I’ll run in Zurich in a few weeks:
When you are talking about large-scale VLAN-based fabrics I assume that you are pointing towards highly populated VLANs, such as VLANs containing 1000+ Ethernet addresses. Could you provide a tipping point between reasonably-sized VLANs and large-scale VLANs?
It's not the number of hosts in the VLAN but the span of a bridging domain (VLAN or otherwise).
Read more ...One of the engineers watching the vSphere 6 Networking Deep Dive found it particularly useful:
There were pearls of knowledge in there which expanded my understanding of ESX and gave me more than a few "aha!" moments […] The course is worth the money and time for sections "uplink redundancy & load balancing" and "VLAN based virtual networks" alone.
Not convinced? Check out other reviews and survey results.
My good friend Tiziano Tofoni (the organizer of wonderful autumn seminars in Rome) sent me these questions after attending the BGP-LS and PCEP Deep Dive webinar, starting with:
Are there real use cases for BGP-LS and PCEP? Are they really useful? Personally I do not think they will ever be used by ISP in their (large) networks.
There are some ISPs that actually care about the network utilization on their expensive long-distance links.
Read more ...After explaining why you’d want to use BGP-LS and PCEP in your network, Julian Lucek did a quick deep dive into the intricacies of BGP-LS, including printouts relating BGP-LS updates to IS-IS topology database.
This part of the PCEP/BGP-LS webinar is already public, to watch the rest of it fill in a short form on the webinar description page.
A lot of people love to talk about ASICs and merchant silicon, but very few really understand the basics. Now there’s a quick way to fix that: watch the excellent Tech Field Day video with Dave Zacks from Cisco Systems.
Read more ...Mr. A. Anonymous left this comment on my BGP in the data centers blog post:
BGP is starting to penetrate into servers as well. What are your thoughts on having BGP running from the servers themselves?
Finally some people got it. Also, welcome back to the '90s (see also RFC 1925 section 2.11).
Read more ...Here’s another interesting coincidence:
Homework for today: listen to the podcast, read the article, and start exploring some new technology (network automation immediately comes to mind).
A while ago someone posted a link to an article that links to LinkedIn’s blog post describing their switch-building efforts to the LinkedIn SDN group (how’s that for a circular reference?), and a consultant from Brocade felt compelled to share his wisdom with the world. Unfortunately he got most of the facts wrong.
Read more ...