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What’s Coming in Hyper-V Network Virtualization (Windows Server 2012 R2)

Right after Microsoft’s TechEd event CJ Williams kindly sent me links to videos describing new features in upcoming Windows Server (and Hyper-V) release. I would strongly recommend you watch What’s New in Windows Server 2012 R2 Networking and Deep Dive on Hyper-V Network Virtualization in Windows Server 2012 R2, and here’s a short(er) summary.

This blog post is describing futures that will ship in 2H2013. However, as all the videos mentioned above included live demos, and the preview release shipped on June 24th, it’s obvious they’re past the “it works so great in PowerPoint” stage.

Hyper-V Network Virtualization

Support for dynamically learned customer IP addresses. Initial release of HNV relied exclusively on PowerShell scripts to supply MAC, ARP and IP forwarding information. Next release of HNV will support dynamic IP addresses used in environments with customer-owned DHCP servers or HA solutions with IP address failover.

Unicast-based flooding. First HNV release did not need flooding – all the necessary information was provided by the orchestration system through HNV policies. Support of dynamic address learning and customer-owned DHCP servers obviously requires flooding of DHCP requests and ARP requests/replies.

HNV in Windows Server 2012 R2 will use provider network IP multicast to emulate flooding (similar to initial VXLAN implementation) or unicast IP with replication at the source host (similar to current VXLAN implementation). The process is further optimized – once the hypervisor hosts learn the IP addresses of customer VMs, they can use the orchestration system (SC VMM) to propagate the ARP and IP forwarding information to other hosts participating in the same virtual subnet (similar to what Cisco’s Nexus 1000V does in MAC distribution mode).

Performance improvements. Lack of TCP offload is the biggest hurdle in overlay network deployments (that’s why Nicira decided to use STT). HNV already has NVGRE Task Offload and Emulex and Mellanox have announced NVGRE-capable NICs. Mellanox performance numbers mentioned in the Deep Dive video claim 10GE linerate forwarding (2 x improvement) while reducing CPU overhead by a factor of 6.

HNV will also be able to do smarter NIC teaming and load balancing, resulting in better utilization of all server NICs.

Built-in gateways. WS 2012 R2 distribution will include simple NVGRE-to-VLAN gateway similar to early vShield Edge (VPN concentrator, NAT, basic L3 forwarding). F5 has announced NVGRE gateways support, but as always I’ll believe it when the product documentation appears on their web site.

Improved diagnostics. Next release of HNV will include several interesting troubleshooting tools: Ability to ping provider network IP address from customer VM, ability to insert or intercept traffic in customer network (example: emulate pings to external destinations), and cloud administrator access to customer VM traffic statistics.

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