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Telechat Review of draft-ietf-intarea-ipv4-id-update-

Request Review of draft-ietf-intarea-ipv4-id-update
Requested revision No specific revision (document currently at 07)
Type Telechat Review
Team Security Area Directorate (secdir)
Deadline 2012-07-03
Requested 2012-06-28
Authors Dr. Joseph D. Touch
I-D last updated 2012-07-05
Completed reviews Secdir Telechat review of -?? by Stephen Kent
Assignment Reviewer Stephen Kent
State Completed
Request Telechat review on draft-ietf-intarea-ipv4-id-update by Security Area Directorate Assigned
Result Ready
Completed 2012-07-05
I 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 document, "Updated Specification of the IPv4 ID Field" is a 

update of RFCs 791, 1122 and 2003. The primary motivation for the 

update is a recognition that the uniqueness requirement imposed on 

the field values (on a per host pair and protocol basis) would limit 

"connections" to about 6.4 Mb/s (for typical 1500 byte packets), an 

unrealistically low data rate today. This document updates the cited 

RFCs to reflect current practice and to more closely match IPv6. 

Specifically, the field value is defined only when a datagram is 


The Security Considerations section is very brief, only three 

paragraphs.  It notes that removing the prior constraints on ID field 

generation (MSL uniqueness) make it easier to use this field as a 

covert channel. It suggests that rewriting the field is a possible 

countermeasure. This advice is presented with the context of 

datagrams not protected using AH. Because AH is no longer a mandatory 

to implement element of the IPsec suite, I suggested an edit to avoid 

suggesting that AH use if common.

The text goes on to discuss how removing the MSL uniqueness 

requirement reduces the entropy associated with the IPv4 header. It 

fails to explain why this might be significant. There is no 

indication that modern encryption algorithms used IETF security 

protocols are harmed by this reduction in entropy. Thus the paragraph 

devoted to this issue seems extraneous, possibly confusing to 


The final paragraph in this section notes that the proposed ID field 

conventions may make it more difficult to count the number of 

distinct devices behind a NAT or similar device. I agree with the 

author's observation that this side effect of the current ID field 

requirements is not a security feature per se and thus not a concern.

Earlier sections of this document do a good job explaining how this 

change may impact various forms of middleboxes. The author should 

note in the SCC whether the change proposed in this document may 

adversely affect availability, if these devices are not updated to 

account for this change.




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