After describing MTU basics and drawbacks of IP fragmentation, it’s time for more details: Path MTU Discovery (PMTUD) and network implications of using ICMP for PMTUD.
Interested in similar topics? Check out How Networks Really Work webinar.
This blog post was initially sent to subscribers of my SDN and Network Automation mailing list. Subscribe here.
Have you ever seen a presentation in which a startup is telling you how awesome their product is because it allows you to simulate your whole network in a virtual environment? Not only that, you can use that capability to build a test suite and a full-blown CI/CD pipeline and test whether your network works every time you make a change to any one box in the network.
Sounds awesome, right? It’s also dead wrong. Let me explain why that’s the case.
Read more ...Last year when I was creating the first version of VMware NSX Deep Dive content, NSX-V was mainstream and NSX-T was the new kid on the block. A year later NSX-V is mostly sidelined, and all the development efforts are going into NSX-T. Time to adapt the webinar to new reality… taking the usual staged approach:
After discussing the challenges one encounters even in the simplest networking scenario connecting two computers with a cable we took a short diversion into an interesting complication: what if the two computers are far apart and we can’t pull a cable between them?
Trying to answer that question we entered the wondrous world of transmission technologies. It’s a topic one can spent a whole life exploring and mastering, so we were not able to do more than cover the fundamentals of modulations and multiplexing technologies.
You need free ipSpace.net subscription to watch the video, or a paid ipSpace.net subscriptions to watch the rest of the webinar.
We’re back from the summer break for real - the first autumn 2019 ipSpace.net event takes place today: I’ll talk about the fallacies of distributed computing.
September will be an intensive month:
Of course, we’ll keep going… our event calendar is fully packed till mid-November. More about that in a month.
In mid 2000s I wrote a number of articles describing various TCP/IP features. Most of them are a bit outdated, so I decided to clean up, update and repost the most interesting ones on ipSpace.net, starting with Never-Ending Story of IP Fragmentation.
The first part of that article is already online, covering MTU basics and drawbacks of IP fragmentation.
Andrea Dainese decided to describe a series of mechanisms and protocols you can use in network automation. He started with Zero-Touch Provisioning and continued with screen scraping. Next one on his list: NETCONF and RESTCONF
Remember my rant about the glacial speed of Azure orchestration system? I decided I won’t allow it to derail yet another event and recorded the demos in advance of the first live session. The final videos are just over an hour long; it probably took me at least three hours to record them.
If you plan to attend the live webinar session on September 12th, you might want to watch at least the first few videos before the live session - I will not waste everyone’s time repeating the demos during the live session.
Whenever you’re discussing a complex topic it’s worth adhering to two principles: (A) identify the challenges you’re trying to solve and (B) start as simple as you can and add complexity later.
We did exactly that in the Introducing Networking Challenges part of How Networks Really Work webinar. We started with the simplest possible case of two computers connected with a cable… and even there identified a plethora of challenges that had to be solved more than half a century ago (and still have to be solved today no matter what magic software-defined technology someone pulls out of their wizard hat).
You need free ipSpace.net subscription to watch the video, or a paid ipSpace.net subscriptions to watch the rest of the webinar.
Stumbled upon an excellent redundancy-focused blog post (HT: High Scalability). Here are just a few important points:
I’m guessing that people promoting stretched VLANs, vSphere and/or NSX clusters running across multiple sites, weird combination of EVPN and OTV, and a dozen similar shenanigans never considered any one of these points.
I spent a lot of time during this summer figuring out the details of NSX-T, resulting in significantly updated and expanded VMware NSX Technical Deep Dive material… but before going into those details let’s do a brief walk down the memory lane ;)
You might remember a startup called Nicira that was acquired by VMware in mid-2012… supposedly resulting in the ever-continuing spat between Cisco and VMware (and maybe even triggering the creation of Cisco ACI).
Read more ...In mid-June I started another pet project - a series of webinars focused on networking fundamentals. In the first live session on June 18th we focused on identifying the challenges one has to solve when building an end-to-end networking solution, and the role of layered approach to networking.
Not surprisingly, we quickly went down the rabbit holes of computer networking history, including SCSI cables, serial connections and modems… but that’s where it all started, and some of the concepts developed at that time are still used today… oftentimes heavily morphed by recursive application of RFC 1925 Rule 11.
Read more ...I’m too stupid to unwind and relax over summer - there’s always some janitorial task to be done, and I simply cannot leave it alone. This summer, I decided to migrate our server infrastructure to AWS.
TL&DR: It went smoother than I expected, and figuring out how AWS virtual networks, public IP addresses, and security groups work while creating AWS Networking webinar definitely helped, but it also took way longer than I expected.
Read more ...One of my readers sent me a link to an interesting L2-over-IP "design". Someone tried to connect two data centers with redundant etherip links using home-brewed redundancy mechanism and (surprise, surprise) managed to bring both of them down. The obvious fix: patch the etherip device driver.
I don't know enough about OpenBSD to figure out whether (A) it doesn't have STP at all, (B) STP doesn't work over EtherIP, (C) host routing based on ARP entries would be too much of a hassle, (D) some people don't understand the networking fundamentals, (E) everything looks like a nail once you found a hammer, or (F) all of the above. Insightful comments would be highly appreciated.
Stumbled upon an interesting article describing numerous examples of how it's impossible to fix a system from the inside because the good guys always lose to the more aggressive (and less scrupulous) individuals.
It's amazing how well the same ideas apply to TCP-versus-UDP, P2P traffic versus everything else (this one has been fixed after a lot of pressure from the outside), latency- versus drop-based TCP congestion management and $vendor marketing.
I was saying “you’ll get the best network automation (or SDN) results if you pair network engineers with software engineers” for ages, but there’s always someone else saying it more eloquently, in this case Jeremy Schulman in his recent blog post.
Jeremy will talk about ChatOps in Autumn 2019 Building Network Automation Solutions online course, but of course you’re more than welcome to ask him other questions as well.
I was listening to a nice podcast with Nick Buraglio discussing the recent BGP hijack SNAFU impacting Cloudflare (and their reaction) and while I usually totally agree with Nick, I think that he tried to be way too nice when saying (paraphrasing) “I think Cloudflare was a bit harsh - I would prefer a more community-oriented approach along the lines of how could we help you do your job better”
Read more ...It’s high time for another summer break (I get closer and closer to burnout every year - either I’m working too hard or I’m getting older ;).
Of course we’ll do our best to reply to support (and sales ;) requests, but it might take us a bit longer than usual. I will publish an occasional worth reading or watch out blog post, but don’t expect anything deeply technical for the new two months.
We’ll be back (hopefully refreshed and with tons of new content) in early September, starting with network automation course on September 3rd and VMware NSX workshop on September 10th.
In the meantime, try to get away from work (hint: automating stuff sometimes helps ;), turn off the Internet, and enjoy a few days in your favorite spot with your loved ones!
Daniel Teycheney attended the Spring 2019 Building Network Automation Solutions online course and sent me this feedback after completing it (and creating some interesting real-life solutions on the way):
I spent a bit of time the other day reflecting on how much I’ve learn’t from the course in terms of technical skills and the amount I’ve learned has been great. I literally no idea about things like Git, Jinja2, CI testing, reading YAML files and had only briefly seen Ansible before.
I’m not an expert now, but I understand these things and have real practical experience on these subjects which has given me great confidence to push on and keep getting better.
Read more ...When I was still at university the fourth-generation programming languages were all the hype, prompting us to make jokes along the lines “fifth generation will implement do what I don’t know how”
The research team working in Networked Systems Group at ETH Zurich headed by prof. Laurent Vanbever got pretty close. The description of their tool says:
Read more ...