Category: workshop

Every data center network has a mixture of bridging (layer-2 or MAC-based forwarding, aka switching) and routing (layer-3 or IP-based forwarding); the exact mix, the size of L2 domains, and the position of L2/L3 boundary depend heavily on the workload ... and I would really like to understand what works for you in your data center, so please leave as much feedback as you can in the comments.

Fernando made a very valid comment to my Monkey Design Still Doesn’t Work Well post: if we would add a few more links between edge and core (fabric) switches to that network, we might get optimal bandwidth utilization in the core. As it turns out, that’s not the case.

Virtual (soft) switches present in almost every hypervisor significantly reduce the performance of high-bandwidth virtual machines (measurements done by Cisco a while ago indicate you could get up to 38% more throughput if you tie VMs directly to hardware NICs), but as I argued in my “Soft Switching Might Not Scale, But We Need It” post, we need hypervisor switches to isolate the virtual machines from the vagaries of the physical NICs.

Engineering gurus from Cisco and VMware have yet again proven me wrong – you can combine VMDirectPath and vMotion if you use VM-FEX.

One of the challenges of designing data center networks that support cloud service is agreeing on what exactly each one of those services should be doing. This video (part of the Cloud Computing Networking webinar) explains what various categories of cloud services actually do and where they could be used in a typical web application stack.

A long while ago I got a very interesting e-mail from Dmitriy Samovskiy, the author of VPN-Cubed, in which he politely asked me why the networking engineers find the stretched layer-2 subnets so important. As we might get lucky and spot a few unicorns merrily dancing over stretched layer-2 rainbows while attending the Networking Tech Field Day, I decided share the e-mail contents with you (obviously after getting an OK from Dmitriy).

You’re probably sick and tired of me writing and talking about networking requirements for VM mobility (large VLAN segments that some people want to extend across the globe), but just in case you have to show someone a brief summary, here’s a video taken from the Data Center Fabric Architectures webinar.

You’ll also find VM mobility challenges described to various degrees in Introduction to Virtual Networking, VMware Networking Deep Dive and Data Center Interconnects webinars

A while ago I wrote that the hypervisor vendors should consider turning the virtual switches into PE-routers. We all know that’s never going to happen due to religious objections from everyone who thinks VLANs are the greatest thing ever invented and MP-BGP is pure evil, but there are at least two good technical reasons why putting MPLS/VPN (as we know it today) in the hypervisors might not be the best idea in very large data centers.

The first question everyone asked after Nicira had published yet another MAC-over-IP tunneling draft was probably “do we really need yet another encapsulation scheme? Aren’t VXLAN or NVGRE enough?” Bruce Davie tried to answer that question in his blog post (and provided more details in another one), and I’ll try to make the answer a bit more graphical.

Wim (@fracske) De Smet sent me a whole set of very good VXLAN- and EVB-related questions that might be relevant to a wider audience.

If I understand you correctly, you think that VXLAN will win over EVB?

I wouldn’t say they are competing directly from the technology perspective. There are two ways you can design your virtual networks: (a) smart core with simple edge (see also: voice and Frame Relay switches) or (b) smart edge with simple core (see also: Internet). EVB makes option (a) more viable, VXLAN is an early attempt at implementing option (b).

When I was writing about the NEC+IBM OpenFlow trials, I figured out a perfect use case for OpenFlow-controlled network forwarding: SMB data centers that need less than a few hundred physical servers – be it bare-metal servers or hypervisor hosts (hat tip to Brad Hedlund for nudging me in the right direction a while ago)

Instead of drinking beer and lab-testing vodka during the PLNOG party I enjoyed DHCPv6 discussions with Tomasz Mrugalski, the “master-of-last-resort” for the ISC’s DHCPv6 server. I mentioned my favorite DHCPv6 relay problem (relay redundancy) and while we immediately agreed I’m right (from the academic perspective), he brought up an interesting question – is this really an operational problem?

I didn’t expect we’d see multi-vendor OpenFlow deployment any time soon. NEC and IBM decided to change that and Tervela, a company specialized in building messaging-based data fabrics, decided to verify their interoperability claims. Janice Roberts who works with NEC Corporation of America helped me get in touch with them and I was pleasantly surprised by their optimistic view of OpenFlow deployment in typical enterprise networks.

Three days ago IBM launched Distributed Virtual Switch 5000V, its own distributed vSwitch for VMware ESX platform. On one hand, it proves Cisco has been going the right way with Nexus 1000v (just in case you wondered), on the other hand, things just got way more interesting – IBM is obviously returning to networking.

I figured out I wrote a lot about Microsoft Network Load Balancing (NLB) without ever explaining how that marvel of engineering works. To fix that omission, here’s a short video taken from the Data Center 3.0 webinar.

Numerous articles published in the last few days describing how Nicira clashes heads-on with Cisco and Juniper just proved that you should never let facts interfere with a good story (let alone eye-catching headline). Just in case you got swayed away by those catchy stories, here’s the real McCoy (as I see it):