Category: virtualization

It seems that most networking vendors consider the Flat Earth architectures the new bonanza. Everyone is running to join the gold rush, from Cisco’s FabricPath and Brocade’s VCS to HP’s IRF and Juniper’s upcoming QFabric. As always, the standardization bodies are following the industry with a large buffet of standards to choose from: TRILL, 802.1ag (SPB), 802.1Qbg (EVB) and 802.1bh (Port extenders).

The following design challenge landed in my Inbox not too long ago:

My organization is the in the process of building a completely new data center from the ground up (new hardware, software, protocols ...). We will currently start with one site but may move to two for DR purposes. What DC technologies should we be looking at implementing to build a stable infrastructure that will scale and support technologies you feel will play a big role in the future?

In an ideal world, my answer would begin with “Start with the applications.”

I was sort of upset that my vacations were making me miss the VMware vSphere 5.0 launch event (on the other hand, being limited to half hour Internet access served with early morning cappuccino is not necessarily a bad thing), but after I managed to get home, I realized I hadn’t really missed much. Let me rephrase that – VMware launched a major release of vSphere and the networking features are barely worth mentioning (or maybe they’ll launch them when the vTax brouhaha subsides).

Chris Marget sent me the following interesting observation:

One of the things we learned back at the beginning of Ethernet is no longer true: hardware filtering of incoming Ethernet frames by the NICs in Ethernet hosts is gone. VMware runs its NICs in promiscuous mode. The fact that this Networking 101 level detail is no longer true kind of blows my mind.

So what exactly is going on and does it matter?

You probably know the old saying – if the mountain doesn’t want to come to you, you have to go out there and climb it. vCider, a brand-new startup launching their product at Gigaom Structure Launchpad, decided to do something similar in the server virtualization (Infrastructure-as-a-Service; IaaS) space – its software allows IaaS customers to build their own virtual layer-2 networks (let’s call then vSubnets) on top of IaaS provider’s IP infrastructure; you can even build a vSubnets between VMs running within your enterprise network (private cloud in the cloudy lingo) and those running within Amazon EC2 or Rackspace.

Full disclosure: Chris Marino from vCider got in touch with me in early June. I found the idea interesting, he helped me understand their product (even offered a test run, but I chose to trust the technical information available on their web site and passed to me in e-mails and phone calls), and I decided to write about it. That’s it.

One of the implications of Virtual Machine (VM) mobility (as implemented by VMware’s vMotion or Microsoft’s Live Migration) is the need to have the same VLAN configured on the access ports connected to the source and the target hypervisor hosts. EVB (802.1Qbg) provides a perfect solution, but it’s questionable when it will leave the dreamland domain. In the meantime, most environments have to deploy stretched VLANs ... or you might be able to use hypervisor-aware features of your edge switches, for example VM Tracer implemented in Arista EOS.

Two vSwitch portgroup-related questions:

• Can you configure the same VLAN on two portgroups in the same vSwitch? How about vDS?
• Can VMs attached to two different portgroups in the same ESX host talk to each other directly or do they have to go communicate through an external switch (or L3 device)?

Got your answers? Now click the Read more ... link.

A few years ago Cisco introduced an interesting concept to the data center networking: fabric extenders, devices acting like remote linecards of a central switch (Juniper’s “revolutionary” QFabric looks very similar from a distance; the only major difference seems to be local switching in the QF/Nodes). Cisco’s proprietary technology used in its FEX products became the basis for 802.1Qbh, an IEEE draft that is supposed to standardize the port extender architecture.

If you’re not familiar with the FEX products, read my “Port or Fabric Extenders?” article before continuing ... and disregard most of what it says about 802.1Qbh.

The Edge Virtual Bridging (EVB; 802.1Qbg) standard solves two important layer-2-based virtualization issues:

• Automatic provisioning of access switches based on hypervisor-signaled information (discussed in the EVB eases VLAN configuration pains article)
• Multiplexing of multiple logical 802.1Q links over a single physical link.

Logical link multiplexing might seem a solution in search of a problem until you discover that VMware-related design documents usually recommend using 6 to 10 NICs per server – an approach that either wastes switch ports or is hard to implement with blade servers’ mezzanine cards (due to limited number of backplane connections).

Jason sent me an interesting question a few days ago: “assuming a vSwitch *did* support MPLS/VPN PE router functionality, what type of protocol support would be needed on the access layer switches?”

While the MPLS/VPN support in hypervisor switches remains in the realm of science fiction, it’s worth knowing that there are at least five different transport options you can use between PE-routers. Here they are, from the most decoupled to the most tightly coupled ones:

I got totally fed up with the currently popular “flat-earth with long-distance bridging” architecture paradigm while developing the Data Center Interconnects webinar. It all started with the layer-2 hypervisor switches and lack of decent L3 network-side solutions; promoting non-scalable cloudy solutions doesn’t help either.

The network infrastructure would scale better if the hypervisors would work as MPLS/VPN PE-routers, but even MPLS would hit scalability limits when the number of servers grows into tens of thousands. The only truly scalable solution is IP-over-IP or MAC-over-IP implemented in the hypervisor switches.

I tried to organize all these thoughts in the “How to build a scalable IaaS cloud network infrastructure” article that was recently published by SearchTelecom ... and just a few days after the article was published, Brad Hedlund pointed me to Infrastructure as a Service Builder’s Guide document, which is saying almost the same thing (and coming to flawed conclusions because they had to promote OpenFlow and NEC).

Whenever I write about vCloud Director Networking Infrastructure (vCDNI), be it a rant or a more technical post, I get comments along the lines of “What are the network guys going to do once the infrastructure has been provisioned? With vCDNI there is no need to keep network admins full time.”

Once we have a scalable solution that will be able to stand on its own in a large data center, most smart network admins will be more than happy to get away from provisioning VLANs and focus on other problems. After all, most companies have other networking problems beyond data center switching.

Challenge: If you want to deploy virtual machines belonging to different security zones within the same physical host, you have to isolate them. VLANs are the most common approach. If you want to migrate a running VM from one host to another while preserving its user sessions, you usually have to rely on bridging. The set of VLANs needed on a trunk link between the hypervisor host and access switch is thus unpredictable (more information in my VMware Networking Deep Dive webinar)

Solution#1 (painful): Configure all possible VLANs on the trunk link. Stretched VLANs spanning the whole data center are an ideal ingredient of a major meltdown.

A while ago I decided to figure out how well various vendors support virtualized networking (one of the answers: some of the solutions don’t scale) and what can be done with virtual network appliances (I was pleasantly surprised by F5’s BIG-IP LTM VE and Vyatta). You’ll find some of my other thoughts on this subject in the Virtual network appliances: Benefits and drawbacks article published by SearchNetworking.

Duncan Epping, the author of fantastic Yellow Bricks virtualization blog tweeted a very valid question following my vCDNI scalability (or lack thereof) post: “What you feel would be suitable alternative to vCD-NI as clearly VLANs will not scale well?”

Let’s start with the very basics: modern data center switches support anywhere between 1K and 4K (the theoretical limit based on 802.1q framing) VLANs. If you need more than 1K VLANs, you’ve either totally messed up your network design or you’re a service provider offering multi-tenant services (recently relabeled by your marketing department as IaaS cloud). Service Providers had to cope with multi-tenant networks for decades ... only they haven’t realized those were multi-tenant networks and called them VPNs. Maybe, just maybe, there’s a technology out there that’s been field-proven, known to scale, and works over switched Ethernet.