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Re: And Now for Something Completely Different (was Re: IPv6 news)

  • From: Joe Maimon
  • Date: Sun Oct 16 05:35:10 2005 

Mike Leber wrote:

On Sun, 16 Oct 2005, Joe Maimon wrote:


For example, if your goal was to have TCP-like sessions between
identifiers survive network events without globally propagating full
network topology information about your site (the gripe against classic
IPv4 BGP) you could have multiple locators associated with any single
identifier sort of like the same way you can have multiple A records for a
domain name.
Real world shows that that doesnt work very well. Multiple A records is not usuable practicaly speaking for anything other than load balancing, today.

If the location layer session times out then it would try
the other locators listed (pick a method of selection) and if it suceeded
would resume the session transparent to the identifier layer. Design the
timeout and retransmit algorithm and parameters to achieve the convergence
times of your choice.
DNS is a good example of something that was designed that way, but few people rely on common implementations actualy performing it properly.

You would need a new protocol stack on the hosts at both ends of
connections.  By common convention classic TCP hosts could be told to use
one of the locators (a transition hack, or just run the protocols in
parallel).  No change would be required to the network, and existing TCP
could continue to be supported (no flag day).

Appears to me thats what shim6 is (cursory reading + nanog discussions)


Of course support of this new protocol would be limited to the clients and
servers that chose to implement it, however this is no less than the
change required for IPv6 which some hoped would solve the multihoming
problem (possibly defined as scalably supporting network topology change
without sessions being interrupted).
Long story short, seperating endpoint/locator does nothing to allow multiple paths to a single IP6 address/prefix to scale.