Hi Authors, I read this new version and have a major concern on the ECMP support.
* The new version adds ECMP support section (4.1) and require switches and routers SHOULD provide ECMP on the NVGRE packet using the outer frame fields and entire Key field (32-bit). This means that the solution not only requires the change on the endpoint devices but also the change on the intermediate switches and routers, which put the high bar for the network. Rare switches and routers today support GRE key based load balance. * To support GRE Key based load balancing, the hardware has to check the GRE Key presence and the protocol type to avoid a mis-operation on other GRE usages, which is bad. * Using 8 bits in the Key field for flow entropy is not sufficient for all the applications. * Directly disclosing VSID to underlying network can be a security concern in some cases. * The draft further suggests the interim solution for ECMP support (without any hardware upgrade). It is to assign multiple physical addresses (PA, outer address) to NVGRE end point and use policy controlling the choice of PA to be used. This makes operation complex. We can have a better solution to support ECMP. Most switches and routers today support 5 tuple based load balance. Five tuple are IP src/dst addr, tcp|udp src/dst ports, and IP protocol type. draft-yong-tsvwg-gre-in-udp-encap-01 proposes the gre-in-udp encapsulation for GRE encapsulated protocols to be tunneled over IP networks where ECMP exists. This solution supports 16 bits flow entropy, does not require any change on intermediate switches and routers, and applies to any GRE encapsulated protocol. It also gives the ingress end point flexibility to generate the flow entropy without explicitly exposing VSID. I highly recommend NVGRE proposal to adopt this method for ECMP support. 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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