FreeBSD is used in virtualization environment widely as OS for web servers, virtual appliances, etc. The network performance for such workloads is critical. This talk will introduce how to achieve network performance improvement through collaboration between the host and the guest and the implementation of TSO (TCP Segmentation Offload) and vRSS (virtual Receive Side Scaling). TSO is used to reduce the CPU overhead of TCP/IP on fast networks. By offloading the TCP segmentation to the NIC which would split large (up to 64K) TCP segments into small frames honoring the MTU size, CPU cycles can be saved to handle more workloads. In multi-core virtual machines, the single virtual processor which handles all the interrupts from the virtual network adapter typically becomes the bottleneck for receive-side network processing. vRSS removes this bottleneck by enabling a network adapter to distribute its network processing load across multiple virtual processors. With vRSS support in FreeBSD guest, the network performance is improved dramatically. Lastly we will also share the tuning practices of optimizing host/guest signaling and implementing scalable interrupt delivery architecture in the FreeBSD guest.