> From: "Flinck, Hannu (NSN - FI/Espoo)" <[email protected]>
> I am left wondering how does the locator and identifier separation
> fit into the story line.
> ...
> They separation seems to be orthogonal to the aggregation based
> solutions.
No, because a lot of the routing-table entries which are appearing now are
'de-aggregates' caused by a number of things which separation of location
and identity will give us additional tools to provide _without_ having to
depend on the routing. (Remember Wheeler's/Lampson's famous aphorisms
about problems in computer science being solved by another layer of
indirection, i.e. binding - separation of location and identity gives us
just such a layer of binding.)
(BTW, "locator and identifier" is not really optimal terminology, because
those refer to specific kinds of names, and it's better to refer to the
generic concepts, i.e. 'identity' and 'location'.)
Here are some examples of things which are causing extra routing table
entries to appear, which can be done without those extra entries if there
is a identity/location binding layer:
- Injecting more-specifics into the external scope to cause inbound
traffic to take the optimal entry point: this can be down with I/L
separation by binding the addresses of different parts of the internal
scope to different entry routers (with others listed as lower-priority,
in case the prime router fails).
- Multi-homing, which causes what are effectively PI addresses (even if
allocated from one provider's block) to be advertized from routers
connected to other providers: again, with I/L separation, the different
entry routers can be listed in that block's binding, and only the location
of the entry routers (which can/should be given addresses from the block
of the provider to which they are attached) need be advertized -
aggregated, of course, into that provider's advertisement.
- Provider-independent addresses, which are inherently unaggregatable:
with I/L separation, the PI addresses need not be advertized in the
modified part of the network, only the location of the entry routers.
There are more, such as punch-outs (an organization changes providers, and
takes their address block with them), etc.
Do note that the exact details, and the benefits, will vary from case to
case, depending on the particulars; in some cases (e.g. the PI one), only
parts of the network which are running the location/identity separation
will benefit from reduced routing tables.
Which is, of course, not a bug, but a feature - it's an incentive to
those parts of the network to convert... :-)
Noel
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