RE: GSE

[Iljitsch van Beijnum <iljitsch@muada.com>]

On Fri, 1 Nov 2002, Tony Li wrote:

> |   - GSE doesn't provide any failover mechanisms but depends
> |   on tunnels to
> |     repair dead customer<->ISP links. This could be done just
> |   as easily
> |     with regular PA space.

> Each host needs to advertise its locator to correspondent hosts.  Whether
> this happens via DNS or via a mobile IP type solution is more detailed
> than we need to be right now, but basically, the correspondent can
> get multiple locators for any MH host.  Failover in this case is simply
> changing the locator in the packet and does not require tunneling.

Yes, switching to a different locator is what we want to do when a
failure occurs. However, the GSE draft doesn't.

Determining when to change locators isn't an altogether trivial
exercise. This is where we can use the help from TCP, since it knows
about timeouts and retransmissions, the IP layer has no idea about any
of this stuff.

> |   - The flat part of the identifier space makes locator
> |   discovery hard.

> Identifiers need not be flat.  They could be hierarchically assigned
> administrative entities.

EUI-64 identifiers don't have a hierarchy that is of use to us. Using
anything else means autoconfiguration has to be changed.

None of this is impossible, but what exactly is it about the 6+2+8 thing
that makes it worth going through all this trouble? If you simply assign
people a PI /48 you can use this address block as identifiers and
replace the first six bytes to make locators. The only "problem" with
this is that you have to replace the first six bytes in the address with
the original ones at some point, but it's much easier to make that
happen than having transport protocols only look at the bottom 64 bits.
If only because some box at the edge can do this.