Overlay networking has been around for a year or so now and the ideas behind it are well established. It was about 3/4 weeks ago while researching VTEP functionality in Dell and Arista switches that I realised I could build manually configured tunnels with VXLAN and get the same results as an EoMPLS x-connect with almost zero effort. More importantly, I don’t have to pay for expensive hardware that has MPLS functions or pay again for software licenses to upgrade with MPLS features.
I was going to call this article “Ethernet Switches for Virtualisation Engineers” but, really, everyone should have some understanding of the internals of an Ethernet switch. But particularly I want to focus on how multicast and broadcasts are handled in a high speed, low latency environment like a Data Centre Network.
It’s vital to understand that latency is critical to your application performance. It is common for a single transaction to take hundreds of round trips so a small increase in latency on each round trip has a large impact on the perceived performance. The client will send a chunk of data and wait for acknowledgement. Even setting up the TCP connection takes a few round trip – remember that TCP sessions are setup, and each data transfer is confirmed.
A modern network switch will have latency around 10 microseconds. The Cisco Nexus 7000 is about 8 microseconds & Brocade VDX 8770 claims less than 4 microseconds. There are many reasons why a switch can be faster or slower but I’ll look at a specific example
Remember, the latency interval is the time taken to receive a packet, decode the address, lookup the forwarding table, switch the packet (and copy it if needed) and transmit out of an Ethernet interface. That’s really fast processing. How does an Ethernet switch do this ?
Arista has announced the 7150S device. It’s low latency, 10 Gigabit and VXLAN terminating. What’s interesting to me is that Brocade and Arista are solving the same problem in different ways. Ivan has determined that Arista have decided to use the Intel chipset (I’m guessing the SM6000?) and then enable the tunnel termination features in the software.
I attended the Brocade Analyst and Tech Day last week as a guest of Brocade where I got to learn more about product, technology and strategy. In particular, the event was led by the launch of the Brocade VDX 8770.
TL:DR version: I have a better understanding of Brocade’s market strategy, insight into the technology and believe that Brocade has a a good product here. The proof will be in the delivery, and whether Brocade can let go of it’s storage legacy (FibreChannel) and properly commit to Ethernet. They will need to convince networking professionals that their product managers understand the market and requirements to get them to switch to Brocade. At this time, I think Brocade has a chance of making that happen based on the emphasis of VCS Fabric and Automation.
Where I’m less comfortable is that Brocade will rely on external parties to deliver the software automation – that’s a strategy that has NOT worked in the last 20 years. There is no reason to believe this anything has changed.
Contains pictures and words.
This is the Packet Pushers podcast recorded after the OpenFlow Symposium. We talk extensively about the possible value of OpenFlow, and the limited value of VXLAN. Note especially that VXLAN is not suitable for use as a Layer 2 Data Centre connection – it’s simply not suited to this task.