Early Review of draft-ietf-tictoc-multi-path-synchronization-04
review-ietf-tictoc-multi-path-synchronization-04-intdir-early-cao-2016-08-12-00

I am an assigned INT directorate reviewer for this draft. These

comments were written primarily for the benefit of the Internet

Area Directors. Document editors and shepherds should treat these

comments just like they would treat comments from any other IETF

contributors and resolve them along with any other Last Call comments

that have been received. For more details of the INT directorate,

see <

http://www.ietf.org/iesg/

directorate.html

>.

Summary

I do not see any strong reason to delay the publication of this document as it
is.  I do have some questions/comments below for discussion.

Comments:

(I am not experts of NTP/PTP exchanges, but I worked on some MIF (multiple
interface, a concluding wg) technology for a while. So the comments./questions
stem there)

1. What's the impact of NAT on the MP-NTP/PTP exchanges.  The packet from the
client will bear with an IP address that collude with some one else, how does
the server handle this solution?  If this is relevant, I would like to see some
discussion in the document.

2. What's the impact of the delay variance of multiple paths on the combining
algorithm?  Should the server wait for a while before abandoning the message
from a certain path?   Generally speaking, UDP traffic from multiple paths have
big variance.

3. The default route on the host may block the transmission of traffic along a
certain IP address that is not within the default interface.  This is
identified by RFC 6418.  A well-known problem is that a multiple-interface host
can only send packets through the one with a better route metric.  This may
have some impact to the operation of MP-NTP/PTP.  Some discussion or pointer to
the this problem would help implementer to save their digging time.

Thanks,

Zhen