Category: data center

Nicolas Vermandé sent me a really interesting question: “I've been looking for answers to a simple question that even different people at Cisco don't seem to agree on: Is it a good idea to class IP traffic (iSCSI or NFS over TCP) in pause no-drop class? What is the impact of having both pauses and TCP sliding windows at the same time?”

During the recent Data Center Fabrics Update webinar Dan Backman from Plexxi explained how their innovative use of CWDM technology and controller-assisted forwarding simplifies deployment and growth of reasonably-sized data center fabrics.

I would highly recommend that you watch the video – the start is a bit short on details, but he does cover all the juicy aspects later on.

In the Optimal L3 Forwarding with VARP and Active/Active VRRP blog post I made a remark along the lines of “Things might get nasty [in Arista EOS Virtual ARP world] if you have configuration mismatches”, resulting in a lengthy and amazingly insightful email exchange with Lincoln Dale during which we ventured deeper and deeper down the Virtual ARP (VARP) rabbit hole. Here’s what I learned during out trip:

The true OpenFlow zealots would love you to believe that you can drop whatever you’ve been doing before and replace it with a clean-slate solution using dumbest (and cheapest) possible switches and OpenFlow controllers.

In real world, your shiny new network has to communicate with the outside world … or you could take the approach most controller vendors did, decide to pretend STP is irrelevant, and ask people to configure static LAGs because you’re also not supporting LACP.

I was reading What Network Virtualization Isn’t¹ from Jon Onisick the other day and started experiencing all sorts of unpleasant flashbacks caused by my overly long exposure to networking industry missteps and dead ends touted as the best possible solutions or architectures in the days of their glory:

Meeting Brad Hedlund in person was definitely one of the highlights of my Interop 2013 week. We had an awesome conversation and quickly realized how closely aligned our views of VLANs, overlay networks and virtual appliances are.

Not surprisingly, Brad quickly improved my ideas with a radical proposal: running BGP between the virtual and the physical world.

One of my blogger friends sent me an interesting observation:

After talking to networking vendors I'm inclined to think they are going to focus on a mesh of overlays from the TOR, with possible use of overlays between vswitch and TOR too if desired - drawing analogies to MPLS with ToR a PE and vSwitch a CE. Aside from selling more hardware for this, I'm not drawn towards a solution like this bc it doesn't help with full network virtualization and a network abstraction for VMs.

The whole situation reminds me of the good old SNA and APPN days with networking vendors playing the IBM part of the comedy.

The Optimal L3 Forwarding with VARP/VRRP post generated numerous comments, ranging from technical questions about VARP (more about that in a few days) to remarks along the lines of “you can do that with X” or “vendor Y supports Z, which does the same thing.” It seems I’ve opened yet another can of worms, let’s try to tame and sort them.

Brad Hedlund wrote another great article, this one explaining the fundamentals of network virtualization. As you'll see, VMware (and everyone else) aims way higher than replacing VLANs with overlay networks. Highly recommended!

Regardless of what the vendors are telling you, it’s hard to get data center disaster recovery right (unless you’re running regular fire drills), and your job usually gets harder due to the intricate (sometimes undocumented) intertwining of physical and virtual worlds. For example, do you know how to get the firewall and load balancer configurations from the failed site implemented in the equipment currently used at disaster recovery site?

Imagine a simple application stack with a few web servers, app servers and two database servers. There’s a firewall in front of the web servers and a load balancer tying all the segments together.

I’ve blogged about the need for optimal L3 forwarding across the whole data center in 2012 when I introduced it as one of the interesting requirements in Data Center Fabrics webinar. Years later, the concept became one of the cornerstones of modern EVPN fabrics, but there are still only a few companies that can deliver this functionality in a more traditional environment.

A while ago, while listening to an interesting CloudCast podcast (my second favorite podcast - the best one out there is still the Packet Pushers), I stumbled upon an interesting idea “Data has gravity”. The podcast guest used that idea to explain how data agglomerates in larger and larger chunks and how it makes sense to move the data processing (application) closer to the data.

In one of his Open Networking Summit blog posts Jason Edelman summarized the presentation in which Goldman Sachs described its plans to replace stateful firewalls with packet filters (see also a similar post by Nick Buraglio).

These ideas are obviously not new – as Merike Kaeo succinctly said in her NANOG presentation over three years ago “stateful firewalls make absolutely no sense in front of servers, given that by definition every packet coming into the server is unsolicited.” Real life is usually a bit more complex than that.

A few days after I published the Interop Product Launch Craze post, Jason Edelman told me HP claims they have running TRILL implementation. Time to read their release notes.

Results: No mention of TRILL in latest release notes for 12500, 9500 or 58xx. 5900 switches support TRILL, EVB and FCoE since release 2207 (January 2013).

More about changes in the data center switching market in the Data Center Fabrics Update webinar. Now I have to catch the next plane on the way home.

In the last part of Clos Fabrics Explained webinar Brad Hedlund described how you can use Dell Fabric Manager to plan, design, configure and operate leaf-and-spine Clos fabric built with Dell Force10 switches. Should we call Dell Fabric Manager an SDN solution? Who cares, it sure is useful ;)