GSE

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

There has been some talk about GSE in the past few days. Before anyone
gets too excited about this, let me point out some of the numerous
prolems with this approach:

- 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.
- It is very unclear how GSE is supposed to work in a single host
  environment. Do hosts that don't sit behind a GSE-capable border
  router the GSE processing themselves or is this done by the ISP?
- It needs changes to transport protocols and possibly to intra-site
  routing and address discovery.
- The flat part of the identifier space makes locator discovery hard.

That being said, I think GSE could be a subset of a more general
approach. If you're going to map identifiers to locators one form of
these identifiers could have the first 48 bits set to 0, if the
identifier to locator discovery service is willing to go the extra mile
and provide mappings for individual 128 bit identifiers. Or you could
have 127 bit hashes as required by HIP. Or use an IPv4 or OSI NET
identifier with an IPv6 locator...

Being agnostic about the structure of the identifier is a good thing for
future extensibility. However, using identifiers with regular IPv6
unicast semantics will make the transition a lot easier as it allows
interoperability between multihoming-aware and non-multihoming aware
systems and/or providing the multihoming support in separate boxes.