Subject: [lisp] Telling EIDs, RLOCs, and 'old' IPv4 addresses apart

From: [email-masked] (Noel Chiappa)
Date: Fri, 20 Mar 2009 17:11:49 -0400 (EDT)

On 3/18/09 12:36 PM, Sam Hartman wrote:

    > EIDs are IP addresses and that there will definitely be cases where an
    > end-system cannot tell whether an address is an EID or an RLOC.

Running back over some old email I ran across this, and had a thought. Is it
possible to allocation RLOCs from the Class-E space (technically, I mean - I
am somewhat aware of the the politics around allocation of IPv4 space).

I seem to recall a prior discussion that concluded that we can't allocate
EIDs from that space, because too many hosts barf on class E addresses.
However, the set of xTRs and LISP backbone routers is much smaller - perhaps
they all handle class E OK?

	Noel

---

From: Vince Fuller <[email-masked]>
Date: Fri, 20 Mar 2009 23:20:09 -0700

> they all handle class E OK?

The problem is that it isn't only the LISP-speaking routers that need to
handle 240/4 ("class E") addressing; all transit routers between LISP sites
will need to handle them as well. Remember that LISP RLOCs, assigned out of
topologically-significant, and thus, provider-assigned space, are visible
as source and destination IP addresses for packets switched through the
Internet routing system.

To use 240/4 as EID space, the hosts have to not choke on them. To use
240/4 as RLOC space, the entire routing "core" needs to accept them. Which
can be upgraded more readily? Kind of a Catch-22...

	--Vince

P.S. FWIW, draft-fuller-240space-02.txt, published almost exactly a year ago
     (and no doubt expired because the it is too contentious for the IETF to
     take any action), recommended that the trivial changes needed to allow
     240/4 addresses be made to as many implementations as soon as possible.
     Yes, it will be years, if ever, before such changes would enable 240/4
     to be used in a widespread manner but if the changes (which take about
     20 minutes to implement; I performed them on two different Linux
     implementations and I haven't done any real programming in close to 20
     years) are never made, then the space will obviously never be used.
     Typical "can't do" attitude by the IETF...