A day of reckoning is coming for data center network architecture. When exactly that day will arrive and what the network will look like when it gets here remain unclear. But change is coming.
In an ambitious session at Interop entitled "How the Network Must Fundamentally Change," a broad panel of vendors reached a shaky consensus. Data center network architecture should flatten. The days of the three- and four-tiered data center networks with Layer 2 and Layer 3 are entering their twilight years as enterprises begin to adopt data center network architectures based on Layer 2 with just edge and core switches.
Vendors see a few key drivers of this change. First on the list is virtualization. Enterprises want the ability to migrate virtual machines across networks and across data centers in order to enable dynamic resource allocation and disaster recovery, but leading virtual machine migration technologies like vMotion restrict migration to Layer 2 environments within a common VLAN. With restrictions like those, it is difficult to migrate virtual machines without adding a lot of complexity.
There are plenty of other reasons for flattening the network, according to the vendors on the Interop panel. The explosion of mobility is putting stresses on the scalability of networks. Networks are also extremely complex, which keeps operational costs high.
But mostly, moving packets up from the edge to the aggregation layer to the core and back down again is not the most efficient data center network architecture. Each hop on the network is costly and adds complexity.
"I started my career in ASIC engineering, and the most expensive operation for a chip to perform is to open up a packet and decide what to do with it -- look at the MAC address, the IP addresses, apply security, etc.," said Dhritiman Dasgupta, senior product marketing manager at Juniper Networks. "[In a multi-tiered data center network], you see how many times that operation is done from the access layer up to the core and back down again, repeating the operation every step of the way. Why do that? With all this repeatability and redundancy of operations, I'm not going to get the performance I want unless I can get rid of that."
Data center network architecture must be application aware
With this flattening of the network, networks also need to be more aligned with the applications that run across them, according to Paul Congdon, CTO of HP Networking.
"We spend way too much time in network devices trying to figure out what the application is trying to do," Congdon said. "We have to crack the packet open and figure out, 'Is this voice over IP? What is it?' Then we have to apply security settings, etc. It's incredibly inefficient to reverse engineer the packet like that. We need to get the application on the on-ramp of the network as early as possible and make the network as simple as a freeway system so we're not doing all this work on the fabric of the network."
This might mean, for instance, putting each application on its own virtual network interface card (NIC), Congdon said.
As vendors try to push a flatter data center network architecture, they will also deliver faster networks that are more converged. New standards will roll out in the coming year to deliver on both of these requirements, including 40/100 Gigabit Ethernet and converged enhanced Ethernet and data center bridging.
One set of standards for the new data center network architecture?One IT pro at the Interop session said he is planning to expand his data center, but he's hesitant about whether he should move forward with flattened data center network architecture. After hearing the competing visions of network vendors, he fears that each of them is going in a different direction. To him, it sounds as if heterogeneous networks with multiple networking vendors won't be feasible in the future.
However, when panel moderator Jim Metzler, of consultancy Ashton, Metzler and Associates, asked the vendors on the panel if this were the case, they nearly all said that, despite their competing visions, they are building upon existing and future standards.
"Sometimes you have to clear the smoke to see what's behind the curtain," HP's Congdon said. "Behind a lot of these vendors' solutions, there are a lot of standards."
In fact, standards are already emerging, according to Thomas Scheibe, director of Cisco Systems' data center switching and services group. "In the long term, I think all the major players will adopt standards. It's a question of who is driving it and where standardization is being done," Scheibe said.
But standards-based technology doesn't always guarantee interoperability. And it certainly doesn't guarantee that an enterprise which wants to mix and match different vendors' products won't get bogged down in complexity.
Enterprises will need to strive for openness from their networking vendors, according to Doug Gourlay, vice president of marketing for Arista Networks.
"What I've seen happen is many incumbent vendors have used core switching and routing technologies as cash cows to fund other technology acquisitions like Flip cameras," Gourlay said. "They're milking these technologies. Some will try to lock you in with proprietary fabric, and some will bring you technologies that will add layers to your network. Keep an open mind. There is no one answer to anything. Any vendor who says this is the only way to do something, they're wrong."Where's the product and plan for a flat Layer 2 network?
Despite all the talk of a flat data center network architecture, product roadmaps from the leading vendors are in short supply, and even those vendors that have articulated some of their vision on flattened data center networks haven't said much about product specifics or availability.
For instance, in February, Juniper outlined Project Stratus, its vision for a flattened data center network architecture and cloud computing networks. What shape these products will take and when they will arrive on the market remains rather clouded, although during the panel discussion Dasgupta shed a little light on what Stratus will eventually look like.
"The best network is the network that connects ports inside a switch," he said. "It's completely flat. Any port can talk to any other port. The ports share a consistent state. You can add line cards and it just scales seamlessly. If I could extend that to my data center network, that would be the best network to solve the challenges that virtualization brings."
"Project Stratus gives you a network that is built like the inside of a switch. It extends that out to the entire data center network," Dasgupta continued. "You can have hundreds of thousands of ports with tens of thousands of virtual machines at the end of each of these ports, all working together in harmony in one flat Layer 2 network. You process the packet once, and you have all the information you need to take it from point A to point B."