VCP – Data Center Virtualization – Question 93

Exam 2V0-622 : VMware Certified Professional 6.5 – Data Center Virtualization

An administrator finds that the Microsoft Exchange virtual machines are exhibiting network latency. What two in-guest changes can help decrease latency? (Choose two.)

A. Large Segment Offload (LSO)
B. TCP Segmentation Offload (TSO)
C. SR-IOV
D. PVRDMA

Correct Answer: AB

Explanation:
Using TSO and LRO on physical and virtual machine NICs improves the performance of ESX/ESXi hosts by reducing the CPU overhead for TCP/IP network operations. The host uses more CPU cycles to run applications.

If TSO is enabled on the transmission path, the NIC divides larger data chunks into TCP segments. If TSO is disabled, the CPU performs segmentation for TCP/IP. TSO is referred to as LSO (Large Segment Offload or Large Send Offload) in the latest VMXNET3 driver attributes.

LRO reassembles incoming network packets into larger buffers and transfers the resulting larger but fewer packets to the network stack of the host or virtual
machine. The CPU has to process fewer packets than when LRO is disabled, which reduces its utilization for networking.

Reference: https://kb.vmware.com/s/article/2055140