Blog Posts in September 2013
Published on , commented on March 10, 2023
To ULA or Not to ULA, That’s the Question
Ed Horley, an awesome IPv6 geek I had the privilege to meet at NFD6, wrote an interesting blog post arguing against IPv6 ULA usage (particularly when combined with NPT66). We would all love to get rid of NAT, however ...
IPv6-Only Data Center: Q&A Time
Not surprisingly, the unorthodox ideas of Tore Anderson generated plenty of questions, so he spent ~20 minutes answering them.
OpenFlow and Fermi Estimates
Fast advances in networking technologies (and the pixie dust sprinkled on them) blinded us – we lost our gut feeling and rule-of-thumb. Guess what, contrary to what we love to believe, networking isn’t unique. Physicists faced the same challenge for a long time; one of them was so good that they named the whole problem category after him.
Every time someone tries to tell you what your problem is, and how their wonderful new gizmo will solve it, it’s time for another Fermi estimate.
Know Thy Boundaries
Every mid-sized company usually has legal counsel on staff (we have two lawyers for ~100 employees, but we might be a bit specific), that will escalate to an external law firm as necessary. Usually this would be when dealing with extraordinary events such as lawsuits or negotiation of a complex agreement.
Configure physical firewalls based on VM groups? Sure, use DSE from Plexxi
Plexxi has an interesting problem. They have a shiny new solution that requires unorthodox approaches to network forwarding and allows them to implement potentially cool concepts like affinities (traffic engineering in disguise). They also need to sell these new concepts to the customers, and the first question I would ask after recovering from a hefty dose of cool-aid is "and how do I configure these affinities?"
Net::Beer @ PLNOG 11
I'll be talking about overlay virtual networks and clouds @ PLNOG 11 (September 30th - October 1st in Krakow) - if you're there and would like to chat with me, send me an email or a tweet.
Also, the organizers sent me this great promotional picture - I simply have to publish it ;)
Do You REALLY Want to Program Your Network?
The primary benefit of SDN (as claimed by its promoters) is a geek’s dream: the ability to program the network (or, more precisely, control network’s behavior through programmable tools).
Sounds great – we’ll finally be able to fix that pesky detail the vendor never wanted to implement (probably for a good reason). But should we REALLY do that?
SIIT – The Magic Behind IPv6-only Data Center
Remember Tore Anderson’s IPv6-only data center design he described in last June’s webinar? Wondered how he got it done? The secret sauce he used is SIIT – the stateless IPv6-to-IPv4 translation technology. His trick: turning it around.
Layer-2 Extension (OTV) Use Cases
I was listening to the fantastic OTV Deep Dive PQ Packet Pushers podcast while biking around the wonderful Slovenian forests. They started the podcast by discussing OTV use cases, Ethan throwing in long-distance vMotion (the usual long-distance L2 extension selling point), but refreshingly some of the engineers said “well, that’s not really the use case we see in real life.”
So what were the use cases they were mentioning?
Plexxi PSI: MAU at Gigabit Speed
Regardless of the advantages of photonic switching (David Husak claims it’s 20.000 times more effective than electronic switching), the programmable optical components remain ludicrously expensive, prompting Plexxi to launch a cost-optimized fixed-topology version of their data center products.
Monitor Public SaaS Providers with ThousandEyes
If you’ve ever tried to troubleshoot web application performance issues, you’ve probably seen it all – browser waterfall diagrams, visual traceroute tools, network topologies produced by network management systems … but I haven’t seen them packaged in a comprehensive, easy-to-use and visually compelling package before. Welcome to ThousandEyes.
Test Virtual Appliance Throughput with Spirent Avalanche NEXT
During the Networking Tech Field Day 6 Spirent showed us Avalanche NEXT – another great testing tool that generates up to 10Gbps of perfectly valid application-level traffic that you can push through your network devices to test their performance, stability or impact of feature mix on maximum throughput.
Not surprisingly, as soon as they told us that you could use Avalanche NEXT to replay captured traffic we started getting creative ideas.
Dizzy from the Kool-Aid
I spent most of the last week in day-long geek parties better known as Networking Tech Field Day. Talking with startups doing cool things or vendors launching cool products, and bouncing barely-feasible ideas off fellow geeks is intoxicating. No wonder I was so excited after the previous events.
Migrating a cold VM into a foreign subnet
Moving a running VM into a foreign subnet is Mission Impossible due to stale ARP entries (anyone telling you otherwise is handwaving over a detail or two - maybe their VM doesn't communicate with other VMs in the same subnet), but it's entirely feasible to migrate a cold VM into a foreign subnet if you can fix IP routing. Here's how you can do the trick with Enterasys switches.
Overlay Networks and QoS FUD
One of the usual complaints I hear whenever I mention overlay virtual networks is “with overlay networks we lose all application visibility and QoS functionality” ... that worked so phenomenally in the physical networks, right?
How Much Data Center Bandwidth Do You Really Need?
Networking vendors are quick to point out how the opaqueness (read: we don’t have the HW to look into it) of overlay networks presents visibility problems and how their favorite shiny gizmo (whatever it is) gives you better results (they usually forget to mention the lock-in that it creates).
Now let’s step back and ask a fundamental question: how much bandwidth do we need?
Why Is Network Virtualization So Hard?
We’ve been hearing how the networking is the last bastion of rigidity in the wonderful unicorn-flavored virtual world for the last few years. Let’s see why it’s so much harder to virtualize the networks as opposed to compute or storage capacities (side note: it didn’t help that virtualization vendors had no clue about networking, but things are changing).
OpenFlow Fabric Controllers Are Light-years Away from Wireless Ones
When talking about OpenFlow and the whole idea of controller-based networking, people usually say “well, it’s nothing radically new, we’ve been using wireless controllers for years and they work well, so the OpenFlow ones will work as well.”
Unfortunately, the comparison is totally misleading.
DF bit explained
Finally a good explanation of what DF bit does ;)
Layer-2 DCI with Enterasys Switches
The second half of the Enterasys DCI Solutions webinar focused on real-life case studies. First the less interesting one: long-distance live VM migration (you know my feelings about the whole concept, but sometimes you just have to do it) and the role of fabric routing and host routing in the process.
Sooner or Later, Someone Will Pay for the Complexity of the Kludges You Use
I loved listening to OTV/FabricPath/LISP Packet Pushers podcast. Ron Fuller and Russ White did a great job explaining the role of OTV, FabricPath and LISP in a stretched (inter-DC) subnet deployment scenario and how the three pieces fit together … but I couldn't stop wondering whether there is a better method to solve the underlying business need than throwing three new pretty complex technologies and associated equipment (or VDC contexts or line cards) into the mix.
Extending Layer-2 Connection into a Cloud
Carlos Asensio was facing an “interesting” challenge: someone has sold a layer-2 extension into their public cloud to one of the customers. Being a good engineer, he wanted to limit the damage the customer could do to the cloud infrastructure and thus immediately rejected the idea to connect the customer straight into the layer-2 network core ... but what could he do?
The Plexxi Challenge (or: Don’t Blame the Tools)
Plexxi has an incredibly creative data center fabric solution: they paired data center switching with CWDM optics, programmable ROADMs and controller-based traffic engineering to get something that looks almost like distributed switched version of FDDI (or Token Ring for the FCoTR fans). Not surprisingly, the tools we use to build traditional networks don’t work well with their architecture.
In a recent blog post Marten Terpstra hinted at shortcomings of Shortest Path First (SPF) approach used by every single modern routing algorithm. Let’s take a closer look at why Plexxi’s engineers couldn’t use SPF.
Combining DMVPN with Existing MPLS/VPN Network
One of the Expert Express sessions focused on an MPLS/VPN-based WAN network using OSPF as the routing protocol. The customer wanted to add DMVPN-based backup links and planned to retain OSPF as the routing protocol. Not surprisingly, the initial design had all sorts of unexpectedly complex kludges (see the case study for more details).
Having a really smart engineer on the other end of the WebEx call, I had to ask a single question: “Why don’t you use BGP everywhere” and after a short pause got back the expected reply “wow… now it all makes sense.”