Data Center Ethernet (or DCB or CEE, depending on who you are) is a hot story these days and it’s no wonder that misconceptions galore. However, when I hear several CCIEs I highly respect talk about “Priority Flow Control can be used to stop all th…

Few days ago I wrote about the impact of vMotion on a Data Center network and the traffic flow issues. Now let’s walk through what happens when you move a running virtual machine (VM) between two data centers (long-distance vMotion). Imagine we’re …

The FCoE confusion spread by networking vendors has reached new heights with contradictory claims that you need TRILL to run multihop FCoE (or maybe you don’t) and that you don’t need congestion control specified in 802.1Qau standard (or maybe you …

A few weeks ago I wrote about the multihop FCoE basics and the two fundamentally different ways an FCoE network could be designed: FCoE on every switch or FCoE on the edges with DCB-extended bridging in the middle. There are two other configurations you’ll likely see in access parts of an FCoE network: FCoE VN_port proxying and FIP snooping.

Enhanced Transmission Selection (ETS) is the second part of the Data Center Bridging puzzle (I’ve already described Priority Flow Control). It specifies two different technologies, queuing mechanisms in bridges and Data Center Bridging eXchange protocol. Although some bridges from some vendors supported numerous QoS mechanisms in the past, 802.1Qaz is the first attempt to standardize a richer set of QoS behaviors than the strict priority queuing defined in 802.1p.

Yesterday I wrote that you don’t need DCB technologies to implement FCoE in your network. The FC-BB-5 standard is quite explicit that lossless Ethernet may be implemented through the use of the PAUSE mechanism. The PAUSE mechanism (802.3x) gives you lossless behavior, but results in undesired side effects when you run LAN and SAN traffic across a converged Ethernet infrastructure.

A while ago I had a chat with a fellow CCIE (working in a large enterprise network with reasonably-sized Data Center) and briefly described vMotion to him. His response: “Interesting, I didn’t know that.” … and “Ouch” a few seconds later as he realized what vMotion means from bandwidth consumption and routing perspectives. Before going into the painful details, let’s cover the basics.