[rrg] RANGER-06

[Robin Whittle]

Hi Fred,

Thanks for these clarifications.  I am surprised, based on what I
read in the I that RANGER I-D:

  http://tools.ietf.org/html/draft-templin-ranger-06

that RANGER resembles LISP, APT or Ivip in that it has xTRs (ITRs and
ETRs) and a mapping system.  There is no mention of xTRs in the I-D.

I hope you will explain this more clearly, on the RRG list and/or in
a revised I-D - including by giving detailed examples and
explanations of many things, such as:

 0 - The major architectural differences between RANGER and other
     comparable schemes, such as LISP-ALT - and what benefits and
     problems arise from RANGER compared to some alternatives.

 1 - How the mapping system works from the point of view of the
     ITR.  This includes what actual data is in the mapping for
     each EID or whatever it is which is a unit of address space
     ("inner" address space, I think, in your terminology) which
     has a common treatment at ITRs.

 2 - Who controls the mapping - from an administrative point of view
     - and in a technical sense: what are the query servers which
     respond to mapping queries.   I gather it is a global query
     server system as with LISP-ALT or TRRP and that ITRs are all
     caching ITRs.

     Are the mapping queries and the query servers which send back
     the reply all operating on the "outer" address space, the
     "inner" or both?

 3 - How ITRs do reachability testing to ETRs, and make decisions
     about which ETR to use.  Ivip doesn't do it this way, but LISP
     and APT do - so as far as I know, so does RANGER.

 4 - One or two concrete examples of site multihoming.

 5 - Likewise RANGER's "site mobility" and an explanation of how this
     differs in principle and practice from "end system mobility".

 6 - What "reuse of outer address space" means, with some examples.
     I gather that, for instance, IPv4 space would be "outer" in the
     way you are depicting RANGER - analogous to LISP's RLOC space.
     "Inner space" I think is analogous to LISP's EID space - and
     in your preferred example is IPv6 space.

 7 - I understand a "legacy" host, such as an IPv4 host would keep
     working normally, and wouldn't be able to access anything in the
     inner address space (IPv6).  But what about existing IPv6
     hosts in networks which don't implement RANGER?  Will they
     still be able to communicate with any IPv6 host in any of the
     RANGER equipped networks?

 8 - I understand, in your preferred example, that IPv4 acts like
     RLOC space and IPv6 like EID space.  I guess that means that
     each network somehow only needs to have a routing system which
     handles a subset of the IPv6 space, with the rest accessible
     via ITRs and the mapping system.

     If you could explain clearly how RANGER achieves a reduction in
     DFZ size, while providing multihoming, TE and portability, that
     would be great.  I guess this means the IPv4 DFZ, where
     all the VET tunnels occur.  Is there anything like an IPv6 DFZ
     in RANGER?


It is always difficult explaining something new to people you you
don't know, via a unidirectional link such as a written document.  It
is hard to avoid using terms which mean something detailed and
specific to the author, but mean little - or something different - to
the reader.

Your response has definitely helped me understand what you are trying
to achieve, but I probably won't be diving into VET or SEAL soon.  My
overall experience is that you describe things in such high-level
terms, quite a few of which I don't understand in the specific way
you do, and that I have a very hard time constructing a nuts and
bolts model in my head of what RANGER would be like.

It helps to know the goals of RANGER - as I think you have described
more clearly in this reply than I in the I-D.  However, in order for
me to I feel I understand something I need to imagine a number of
building blocks which I understand very clearly, and then imagine
them strung together and interacting.

Then I can start to consider whether I think the whole thing will work!

I probably won't have time to build such an understanding of RANGER
in the foreseeable future, but I am keen to read anything more you
can say about it on the list, and I am sure other people would be
interested too.

  - Robin