IPng ADs Wish to Gauge Consensus on Address Length Requirements

[IPng Area Directors <[e-mail]>]

Hi, TUBA, SIPP, CATNIP, BIG-INTERNET, and IETF:

This message is one last pre-Toronto recommendation 
attempt to gauge the extent of consensus on one
of the IPng issues.  We apologize for duplications.  We wanted
to reach a wide audience.

Steve Deering's message "Chicago Meeting -- Possible Changes
to SIPP" to the SIPP list a while back elicited quite a bit
of discussion on various lists (both SIPP and big-internet and
in other venues) about the length of "address" required for an IPng. 
We have also had considerable discussion within the directorate.

At this time it would appear to us that there is considerable consensus
that a fixed length, topologically structured, hierarchical
address 16 bytes in length is reasonable for an IPng (that is
meets the needs of the very very large-scale Internet).
We understand that we are being a bit vague in using the term "address" in
light of the question we asked two weeks ago.  For the purposes of this
request, please assume that the transport level and internet level names
are the same.  

Some hold the view that 16 bytes is larger than would be required
for any imaginable Internet structure in the future and that an 
8 byte address is all that is required.

There seems to be a stronger, but still minority, view that, for various
reasons, a variable length address, one that could be smaller or larger
than 16 bytes, would meet the needs better for the future of the 
Internet.

Much of the discussion on the lists has revolved around the relative
efficiency of processing fixed and variable length addresses.  We would
like to assess the consensus just on the length for the future Internet,
instead of discussing efficiency any more at this time.  We want  
to make sure that we have understood consensus on meeting the needs
of the very very large Internet.  Therefore, this message is to
ask people what present or future rationale they see for one of:

  8 byte fixed length address.

  16 byte fixed length address.

  longer than 16 byte fixed length address now.

  only 16 byte length addresses now but ability 
  to lengthen the address later.

To amplify a bit more, we are especially interested in your views
on the address length's ability to offer:

   routing aggregation power

   topological flexibility 

   adminstrative manageability

At this point the consensus among the IPng directorate
and on several of the mailing lists seems fairly clear
(a 16 byte length address is good for those things).   
This is a good time to bring forward your remaining views 
about the requirements for address length for IPng.

Thank you,

Scott and Allison