RE: Next question...

["J. Noel Chiappa" <jnc@ginger.lcs.mit.edu>]

    > From: Margaret Wasserman <mrw@windriver.com>

    > How does this differ from the GSE proposal -- routing goop inserted at
    > the edge routers?

I must confess that at this remove I've forgotten the fine details of GSE. I
do recall that it included more than just dividing the IPv6 address field
into location and identity parts, although I do vaguely recall the function
you alluded to (some of the location information being added at the border).
Could you give us a brief refresher?


    > Would these locators be considered part of the IP address by upper
    > layers?

Did you really mean to ask that exact question, or were you asking instead
"would this location information be considered part of the identity of the
far end, by upper layers?"

If the latter, then I think the answer is definitely "no" - the whole point
is to make "location" separate from identity, so that the former can change
(although the binding between the two needs to be secured to prevent
connection/etc hijacking). I said "location" since that might also include
which ISP you're currently using, for a multi-homed site, even if your actual
network connectivity hasn't changed.


If the former, however, it would depend on i) exactly what scheme you pick
for the two kinds of name (i.e. do you cram it into an IP address, or perhaps
rather into some sort of option read by the higher level), and ii) whether
you change e.g. TCPv6's checksum algorithm. Note that if you *do* make it
part of the IPv6 address, you're partly (mostly?) vitiating the whole point
of having separate location and identity, as discussed in the previous
paragraph.

At this point, it's too late for the combination of i) 8+8 and ii) not
changing TCPv6, since the TCPv6 pseudo-header already includes all 16 bytes.
So note that going with 8+8 now is not really very useful, since without ugly
TCPv6 checksum hacks, it's going to be hard to switch to a different locator
(at least, if your functional goal includes keeping open connections up).

16+16 looks attractive for that reason, plus to which applications which have
already been modified to work with 16 byte identities will continue to work,
too.

	Noel