Last Call Review of draft-ietf-core-observe-14
review-ietf-core-observe-14-secdir-lc-gellert-2014-08-28-00

I have reviewed this document as part of the security directorate's

ongoing effort to review all IETF documents being processed by the IESG.

These comments were written primarily for the benefit of the security

area directors. Document editors and WG chairs should treat these

comments just like any other last call comments.

This Standards Track draft is a best effort protocol extension to CoAP to
enable clients to retrieve a representation of a resource and keep this
representation updated by its server for a period of time.

The security considerations section does exist and discloses the following
threats and suggests ways to mitigate these attacks.

- an increase in amplification attacks, and requires the server to limit
notifications without client authentication.

- acknowledgements may be spoofed if confirmable messages are predictable.

- server may want access control to prevent resource exhaustion attacks,

- intermediaries may create loops..

Section 1.3, describes 2 issues where a client might be assuming an old state.
This issue could be considered a security threat depending on the sensitivity
of that resource.  You might
 want to flag this also in the security considerations section.

This protocol is intended to be best effort only, as noted in the abstract
section.    This should be also emphasized in the security section.

In general, very nice thorough analysis of all the race conditions inherent in
a best effort only protocol syncing state between client and server.

As an editorial comment, please expand the first occurrence of CoAP

Best Regards,

Dorothy Gellert

Silver Spring Networks

Director, Standards and Technology

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dgellert at silverspringnet.com

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+1 650 839 4378

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 650 556-5994