Last Call Review of draft-ietf-hip-native-nat-traversal-27
review-ietf-hip-native-nat-traversal-27-tsvart-lc-perkins-2018-02-26-00

Hi,

I've reviewed this document as part of the transport area review team's ongoing
effort to review key IETF documents. These comments were written primarily for
the transport area directors, but are copied to the document's authors for
their information and to allow them to address any issues raised. When done at
the time of IETF Last Call, the authors should consider this review together
with any other last-call comments they receive. Please always CC tsv-art@… if
you reply to or forward this review.

Summary:
This draft is basically ready for publication, but has nits that should be
fixed before publication.

Comments:
This draft describes how the ICE algorithm can be applied for NAT traversal
with the Host Identity Protocol (HIP). The classical ICE algorithm is tied to
STUN and TURN for connectivity checks, encapsulation, and tunnelling. This
draft recasts ICE to work with HiP-specific mechanisms. The proposed mechanism
looks to be a straight-forward reworking of ICE into this new context, and
there do not look to be any significant new transport issues raised compared to
classic ICE.

The draft could perhaps better explain the rationale for recasting the ICE
protocol to use HIP specific mechanisms rather than reusing STUN and TURN. In
addition, the reference to Appendix B (which explains the differences from
classical ICE) at the end of the Introduction could perhaps be highlighted.
Both would be useful to show why this mechanism is needed, and to clearly
document the differences to classical ICE.

The draft doesn’t mention the impact on the MTU of encapsulating HIP messages
for NAT traversal. It probably should discuss the implications of this MTU
reduction.

Section 4.1, page 11, suggests the use of UDP port 10500. The IANA
considerations do not register this port. The draft should either register this
port, or clearly cite the draft/RFC that does register it.

Regards,
Colin

--
Colin Perkins
https://csperkins.org/