Hi Pat, Technology evolution does not stop because of many technologies existence. It continues because existing technologies let people see the better technologies.
The NVGRE/VXLAN overlay technology principle is about the separation of virtual networks from the physical transport network, i.e. virtual network traffic encapsulated in IP data grams and just likes another IP application. Using UDP src port for flow entropy is clear way to support underlying ECMP without breaking this principle and requests no change to underlying network (ECMP becomes the common underlying network capability). Yes, VXLAN encapsulation adopts this mechanism at first. IMO: current NVGRE encapsulation does not align with this principle well. It is a particular IP application (GRE), not like another IP application (TCP/UDP); it requests the underlying ECMP LB to use GRE header, which ties overlay network and underlying network together in some degree. This is why we propose gre-in-udp encapsulation to improve gre as of a generic encapsulation for an overlay technology. The semantics has the key components for an overlay technology. NVGRE is designed for virtual network overlay and uses gre header. Thus, IMO, it is merit for NVGRE to use gre-in-udp format. Although VXLAN is good to specify the use of UDP initially, but VXLAN header does not have protocol type field and only allow carrying Ethernet payload. It is designed for one purpose only as its name. So it can't apply to other overlay application without enhancement. NVGRE uses GRE header that has a protocol type field so it can easily extend for other overlay applications. If you think that gre-in-udp for NVGRE or adding a protocol type field in VXLAN is new format and strongly against them. You soon will see a new encapsulation proposal to enable other overlay application such as service function chaining. I don't see you have a way to get around that. We should be able to specify one generic overlay encapsulation format that can support an overlay application. The nvgre and vxlan enhancements we proposed makes them to be equally good to serve this purpose because both will contain the key components required for an overlay application and align with the overlay principle . It would be great if IETF can standardize just one, but given existing deployment situation, this may not be practical. We leave the choice to the community. Regards, Lucy From: Pat Thaler [mailto:[email protected]] Sent: Wednesday, September 18, 2013 6:42 PM To: Lucy yong; Pankaj Garg; [email protected]<mailto:[email protected]> Cc: [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]> Subject: RE: comments on draft-sridharan-virtualization-nvgre-03 Dear Lucy, I'm responding to your question to chip vendors about using NVGRE with your UDP encap draft. It isn't that supporting any one packet format in hardware is a problem. The issue is the number of formats that need to be supported by a chip - each may be small but the number adds up. Adding another packet format variant isn't justified and would be burdensome for the chips. [Lucy] My suggestion is not about adding a new format. It is to enhance existing NVGRE protocol. >From the point of view of hardware handling of the frames, putting the UDP >header in between the IP and NVGRE headers makes it a new format for us. The VXLAN packet format already provides for use cases where a flow field in the UDP header is desired. There is no need to duplicate that capability by adding an NVGRE in UDP format. We would be strongly against udp encapsulation of NVGRE. [Lucy] This is not about duplicate that capability, it is about use of a common way in supporting underlying ECMP. Do you support both NVGRE and VXLAN encapsulation, or only VXLAN encapsulation? There are Broadcom authors on both the VXLAN and NVGRE I-Ds. We support both formats going forward. Regards, Lucy Regards, Pat [Lucy] If NIC hardware support VxLAN which use UDP port for the flow entropy, it should be easy to support gre-in-udp encaps as well. Will be great to see chip vendor comment on this. Please take a look at the gre-in-udp encapsulation proposal (below), welcome comment on it. Regards, Lucy Here is the draft. The TSVWG will adopt it as WG draft soon. http://datatracker.ietf.org/doc/draft-yong-tsvwg-gre-in-udp-encap/ Regards, Lucy
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