Subject: [nvo3] Comments to draft-narten-nvo3-overlay-problem-statement

From: Linda Dunbar <[email-masked]>
Date: Fri, 29 Jun 2012 15:50:40 +0000

Thomas, Murari, David, Dinesh, and Lawrence,

I think the NVo3 problem statement draft has done a good job in capturing problems facing modern data centers with massive number of VMs and requirement to make them scale.

However, the "nvo3 problem statement draft" hasn't covered the problems introduced by VMs mobility in overlay environment.

To support tens of thousands of virtual networks, the local VID associated with client payload under each NVE has to be locally significant. When some VMs associated with Virtual Network X using VID 120 under NVE1 are moved to NVE2, VID#120 might be used by other virtual networks under NVE2.

"nvo3 problem statement" hasn't addressed the scenario when  data frames from VMs already have VID encoded, which is not uncommon in data centers, e.g. applications on different subnets. The VIDs encoded in the VMs will move with the VMs, making the VIDs encoded in the VMs global.

If ingress NVE simply encapsulates an outer header to data frames received from VMs and forward the encapsulated data frames to egress NVE via underlay network, the egress NVE can't simply decapsulate the outer header and send the decapsulated data frames to attached VMs as done by TRILL.

When a VM communicate with peers in different subnets, all the egress NVEs will be at the gateway router. It is tremendous amount of load at Gateway router's NVE. Plus all the local VIDs will be terminated by the gateway routers.  If using multiple gateway routers, with each handling a subset of tenants in data centers,  then each tenant's VMs are only reachable by their designated routers or router ports, which limit the range of VM mobility.

Therefore, I think that the problems identified by http://www.ietf.org/id/draft-dunbar-nvo3-overlay-mobility-issues-00.txt should be merged to the "nvo3 problem statement" draft.

Thanks, Linda Dunbar