Last Call Review of draft-ietf-ipsecme-ikev2-fragmentation-05

Request Review of draft-ietf-ipsecme-ikev2-fragmentation
Requested rev. no specific revision (document currently at 10)
Type Last Call Review
Team General Area Review Team (Gen-ART) (genart)
Deadline 2014-04-22
Requested 2014-02-27
Draft last updated 2014-05-08
Completed reviews Genart Last Call review of -05 by Suresh Krishnan (diff)
Secdir Last Call review of -05 by Derek Atkins (diff)
Assignment Reviewer Suresh Krishnan
State Completed
Review review-ietf-ipsecme-ikev2-fragmentation-05-genart-lc-krishnan-2014-05-08
Reviewed rev. 05 (document currently at 10)
Review result Almost Ready
Review completed: 2014-05-08


I am the assigned Gen-ART reviewer for draft-ietf-ipsecme-ikev2-fragmentation-05


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Please resolve these comments along with any other Last Call comments you may receive.


Summary: This draft is almost ready for publication as a Proposed Standard but I have some suggestions that the authors may like to consider.


* Retransmission and duplication


It is unclear how the receiver of the message deals with lost fragments that are retransmitted. If I understand correctly, the sender only knows that all the fragments did not get to the receiver, and has no knowledge about which fragments
 were not received. So it ends up retransmitting all the fragments. This means that the receiver needs to do some form of de-duplication. Are the duplicate fragments discarded on the receiver (without verification) or are they blindly written into a reassembly
 buffer (after verification)? The difference is pretty significant because there is a authentication step involved for each fragment.


* IPv6 payload length


I find this text to be a bit handwavy 


“   For IPv6 this estimation is difficult as there may be varying IPv6

   Extension headers included.”


I think it would be preferable to at least estimate for the case where there are no extension headers. Suggest adding some text like this (Feel free to modify/ignore)




   For IPv6 Encrypted Payload content size is less than IP Datagram size

   by the sum of the following values in the case where there are no

   extension :


   o  IPv6 header size (40 bytes)


   o  UDP header size (8 bytes)


   o  non-ESP marker size (4 bytes if present)


   o  IKE Header size (28 bytes)


   o  Encrypted Payload header size (4 bytes)


   o  IV size (varying)


   o  padding and its size (at least 1 byte)


   o  ICV size (varying)


   The sum may be estimated as 81..85 bytes + IV + ICV + padding.


   If extension headers are present, the payload content size is further

   reduced by the sum of the size of the extension headers. The length of

   each extension header can be calculated as 8 * (Hdr Ext Len) bytes

   except for the fragment header which is always 8 bytes in length.


* Editorial


Appendix A: 


s/ reassempling/reassembly/