[nvo3] Comments on draft-dunbar-nvo3-overlay-mobility-issues

["Guyingjie (Yingjie)" <[e-mail]>]

Hi Linda,
I read your draft on NVO3-mobility.
I am okay with most of the content, just some secondary comments on your description of mechanism between NVE and TES.
In my mind, external controller assistance is a bit more complicate to implement than using a protocol between NVEs and TES.
A premise of my comments is that NVE is on external network devices, such as TOR and EOR, and TES are VMs in physical servers.


4.1.1 First paragraph: "NVEs may
   not be aware of VMs being added or deleted unless NVEs have a north
   bound interface to a controller which can communicate with VM/server
   Manager(s).

"
This is not true. In VDP, with an Association/De-association message from Hypervisor to edge bridge(i.e. NVE in NVO3, and will use NVE instead of edge bridge in below), the bridge can be timely notified about the connect and disconnect to the bridge. That means it doesn't need an northbound API for NVEs to be aware of VMs (dis)connection.  And also, VDP protocol can carry a field showing "This is a new created VM" or "This is a VM migrated from somewhere else". That is VDP can fulfill the requirement of mobility notification, which can be a trigger for NVE to timely updating the states on itself, e.g. acquiring VNID associated with the VM moving/adding to the NVE, inner-outer address mapping, deleting states associated with the VM moving/deleting from this NVE.




In the 4th paragraph of 4.1.1, If, for whatever reason, it is necessary to have local VID in the

   data frames before encapsulating outer header of EgressNVE-DA/

   IngressNVE-SA /VNID, NVE should get the specific local VID from the

   external Controller for those untagged data frames coming to each

   Virtual Access Point
For some reasons, I don't think this part is good.
First, there is other way to get the local VID except for external controller. In VDP, when NVE receives a (Pre)Association message from TES, it can acquire local VID from a Database which is managed by network administrator.

Secondly, while defining VDP, we consider of the situation you described, i.e. different local VID at different location. So the VDP can support different local VID under different NVE, by getting local VID from Database while receive the (Pre)Association message. And it can even feedback to the Hypervisor, so that the data frames from TES could have the local VID on it, but it's also okay for NVE to add the local VID to data frames.


In the 6th paragraph in 4.1.1, The IEEE802.1Qbg's VDP protocol (Virtual Station Interface (VSI)

   discovery and configuration protocol) requires hypervisor to send VM

   profile upon a new VM is instantiated. However, not all hypervisors

   support this function.
The following is the VDP TLV definition from Qbg. Each VSI (Virtual Station Interface) usually is a VM interface id(could be MAC,IPV4/V6, UUID, etc).
The NVE gets profile from Database by VSI type & instance information. I think your profile ID also means the combination of VSI type and instance information. So we are talking the same thing.   My point is it's not profile, but the IDs to get profile, that is carried in VDP message. It might be confusing to people knowing nothing about VDP. Carrying profile in message is a huge overload.

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External Controller can be very useful in NVO3, but not best suitable for each part of NVO3. I think we should think of other way for different problems.


________________________________
Best Regards
Gu Yingjie