Hi, IPv4 packets are allowed to have a zero checksum, but IPv6 packets are not. The problem of tunnelling zero checksum IPv4 packets through IPv6 tunnels is described in RFC 6935.
Currently RFC 7599 doesn't address this issue, and as a result we've found that some existing BR and CE implementations don't handle zero checksum UDP IPv4 packets correctly. I think it would be helpful to add RFC 6935 as a normative reference and add a new section 8.5 to discuss the issue. Something like the following would help: 8.5. UDP Checksum Considerations IPv4 UDP packets arriving at the BR or CE are can have a checksum value of zero, indicating no checksum was calculated. Historically, a zero checksum value is not permitted in IPv6 UDP datagrams, and some implementations will discard these packets. The MAP-T CE and BR MUST translate and forward zero checksum UDP datagrams in both the IPv4 and IPv6 domains as described in [RFC6935]. The text above could use some wordsmithing, but hopefully you get the idea. Michael Overcash Principal Architect, Premises Technology C 678.637.5649 [cid:[email protected]]
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