HIP%20Checksum%20Coverage%20draft-dawkins-hip-checksum-coverage-00

1
HIP Checksum Coveragedraft-dawkins-hip-checksum-
coverage-00

• XingFeng Jiang, Philip Matthews, Spencer Dawkins
• IETF 70 December 2007
• Vancouver, British Columbia

2
How we got here

• P2PSIP HIPHOP proposes HIP-layer forwarding
• Other proposals also have this concept
• Draft-ietf-hip-rvs and draft-ietf-hip-nat-traversa
  l
• Looking at HIP 16-bit checksum
• Includes transport pseudo-header
• Pseudo header updated when packet forwarded, thus
  checksum must be updated at each hop.

3
Proposal

• Remove transport pseudo-header from HIP checksum
  calculation
• No need to update checksum when forwarding
• Pseudo-header no longer needed for HIP
• Draft also proposed to change checksum to CRC32c
  dropping this idea after feedback
• This change requires larger checksum field
• Would change common HIP/SHIM6 header format
• Breaks incremental checksum update

4
Discussion

• Is proposed HIP checksum redundant?
• Signature and HMAC also cover HIP header HIP
  parameters. 
• When we run HIP over UDP, UDP checksum also
  covers HIP packet.
• Always set HIP checksum to zero?
• HIP-HOP thinking about HIP msgs with bodies
• i.e. NextHeader field ltgt NoNext Header
• Not the first to propose this, either
• Should HIP checksum cover body?