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[RRG] Re: Not separate namespaces: Loc-ID-separation, map-encap etc.
Hi Dino,
In a recent message in the "Long term clean-slate only for the RRG?"
thread, you wrote, in part:
The sort of management issues I see what LISP are:
1) There is a new namespace.
2) There is encapsulation.
3) There is a mapping database.
Map-encap (map and encapsulate) schemes including LISP, APT, Ivip
and TRRP are often referred to as "Loc-ID-Split" or "Locator -
Identifier Separation" schemes or similar.
I think that "Split" and "separate" on their own are valid terms for
the concept of having a subset of the IPv4/6 addresses managed by
the map-encap scheme as Identifier space ("EID" - Endpoint
IDentifier in LISP).
But I am sure there is no new namespace in LISP or any other
map-encap system.
I think there is. You can have a host assigned an address out of EID
space and the locator for the ETR *could* use the same bit-value. And
a site might do this if it has PA addresses and can't or won't change
to PI when they want to deploy LISP. But I think in practice, it
should be suggested that if locator addresses for the ETRs should not
also be assigned to any devices at the site (but both could come out
of the same subnet).
Since, at any given hop in the network, you look at one DA versus the
outer DA, you do a lookup in a single RIB/FIB.
In a map-encap system, some IP addresses refer to address space
which is managed conventionally by BGP. LISP terminology for this
is "RLOC" space. ETRs and ITRs need to have RLOC addresses.
Other IP addresses are within the subset of the address space which
ITRs and ETRs manage. These are "EID prefixes" in LISP, or
"micronets" in Ivip.
Right, and each are in their own routing table. That is, for IGP
routers the EID-prefixes are in a single routing table the router
maintains. For core routers, the RLOC-prefixes are in a single routing
table the router maintains. In the LISP prototype, the ITR keeps the
site EID-prefixes (the site's subnets) in the default VRF routing
table but the external EID-prefixes learned and advertised by LISP-ALT
in a "lisp" non-default VRF. And the ITR also keeps external RLOCs in
the default VRF routing table.
However, "RLOC" and "EID" are not separate namespaces.
I view they are since they are allocated from different allocation
entities.
If they were separate namespaces, then the address 12.34.56.78 would
mean one thing when used in the RLOC namespace and another thing
entirely when used in the the EID space.
And I believe it does.
But that is not the case. 12.34.56.78 may be an EID address or an
RLOC address - but it can't be both.
But 12.34.56.78/24 could be the host address and 12.34.56.79/24 could
be the ETR's address. But the point is that they clash only when PA
addresses are assigned to the site. I think there will be a trend
(which already exists) to keep or obtain PI addresses for it's
advantages.
I believe that all public IPv4 addresses - those outside 10.0.0.0/8,
172.16.0.0/12, 192.168.0.0/16 and 127.0.0.0/8 - are in the one
namespace, with or without LISP etc.
Without LISP they all, including the private addresses, are in one
address space. The reason that private addresses don't clash is
because the clouds that use them don't overlap and when they merge you
have to fix the address conflicts.
Dino
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