James Carlson wrote:
Erik Nordmark wrote:
Shim6 provides the ability for hosts to recover from IP
communication failures when the hosts have two or more IP
addresses, by the shim switching from using one pair of IP
addresses to another pair. This is done transparently to TCP,
UDP and other transport protocols.
+1, I think, but a question: I haven't been paying much attention to how
things have changed over the past few years, so could you summarize the
story for Shim6 versus PI addresses?
There has been a lot of discussion about this in the routing research
group, and still is (with many different proposals). None of them are
really trying to make Provider Independent (PI) address scale to all the
sites that might multihome in the future. But there are intersting ideas
around major changes to BGP to essentially add another layer of
indirection, to make it more scalable than today to have multiple paths.
Folks have proposed extensions based on Shim6, such as proxy shim6 and
six/one, to enable doing this in routers instead of in hosts.
There is an IETF WG on LISP, which is doing router-based encapsulation.
I personally find its approach to security lacking (some of the security
is based on folks manually configuring filters in a separate LISP BGP
overlay instance.)
There is also a recent IETF WG on multi-path TCP. That is very
interesting since it will use multiple paths at the same time, and the
fraction of the traffic sent on each path is a function of its available
bandwidth. But AFAICT MPTCP needs a security mechanism to avoid
redirection attacks. Thus some folks have talked about reusing the shim6
security mechanism (and perhaps other parts of the state machine and
messages) together with MPTCP.
It's certainly good that there's progress, but if it turns out to be
another Mobile IP ...
Folks have been complaining about the fact that an IP address is both a
locator and identifier for at least 20 years. Hence the RRG effort
around ID/Locator separation. But at the same time the Internet is so
full of inertia (due to existing technical practises, existing business
models, etc) that it isn't clear if *any* radical changes can be deployed.
The benefits of Shim6 and MPTCP is that they can be deployed at the
edge, hence they don't need approval from the operators. And they are a
very nice fit for the multihomed laptop with a WiFi plus a Cellular
interface.
The benefits of LISP is that is it deployed by the operators.
Fundamental question is whether the users at the edge or the operators
have more incentives to deploy something new. I'm slightly more
optimistic about the edge.
Erik
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