Subject: efficient-nd NOT a wholesale change

From: Erik Nordmark <[email-masked]>
Date: Thu, 13 Mar 2014 14:51:30 -0700

There seems to be some confusion about the intent in the efficient-nd 
draft, and given the discussion on the list a clarification is in order.

The draft provides for an optional address registration option (ARO) but 
ensures that this is compatible with existing hosts and routers 
implementing RFC 4861 (and current extensions to that spec). This is 
called "mixed mode" in the draft. The intent is that hosts which want 
more efficient behavior, in particular be able to sleep without always 
have to redo DAD when they wake up, can get benefits as long as there is 
a router supporting ARO on the link.

Note that draft-chakrabarti-nordmark-6man-efficient-nd-05 uses the term 
"legacy" to refer to RFC 4861 without the new and optional behavior - I 
don't know if a different term would  make a difference.

Previous versions talked about a transition to efficient-nd, which might 
partly explain any misunderstanding. That statement was intended to be 
for cases when there is a need to transition all hosts and routers on a 
particular link for maximal efficiency. Based on what we've realized 
since 04 was written it is possible can handle mixed mode efficiently as 
part of normal operations.

Version 05 of the draft has substantial editorial changes to more 
clearly specify the protocol mechanisms, and also close some technical 
gaps for router state loss and VRRP that the WG identified in -04. Thus 
those that have read earlier versions might benefit from reading the 05 
version.

Last but not least, as part of the design team we are exploring the 
tradeoffs between current DAD, implicit registrations (as in the 
proxy-dad draft), explicit registrations (such as ARO), and other 
alternatives (such as contiguous DAD based on the ideas in RFC 5227).

Regards,
    Erik