Class of Service
Key design elements for class of service in this solution include network control (OSPF, BGP, and BFD), virtualization control (high availability, fault tolerance), storage (iSCSI and NAS), business-critical applications (Exchange, SharePoint, MediaWiki, and vMotion) and best-effort traffic. As seen in Figure 1, incoming packets are sorted, assigned to queues based on traffic type, and transmitted based on the importance of the traffic. For example, iSCSI lossless Ethernet traffic has the largest queue and highest priority, followed by critical traffic (fault tolerance and high availability), business-critical application traffic (including vMotion), and bulk best-effort traffic with the lowest priority.
Figure 1: Class of Service – Classification and Queuing
As seen in Figure 2, the following percentages are allocated for class of service in this solution: network control (5 percent), virtualization control (5 percent), storage (60 percent), business-critical applications (25 percent) and best-effort traffic (5 percent). These categories have been maximized for network-level traffic, as the network supports multiple servers and switches. As a result, storage traffic and application traffic are the most critical traffic types in the network, and these allocations have been verified by our testing.
Figure 2: Class of Service – Buffer and Transmit Design
To provide class of service in the virtualized IT data center and meet the design requirements, this solution uses:
- Lossless Ethernet for storage traffic
- Five allocations to differentiate traffic
- A queue for business-critical applications
- Best-effort traffic for data traffic
