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Re: [RRG] Six/One Router Design Clarifications



Hi Dino -

When two hosts in upgraded edge networks communicate, addresses are
rewritten bilaterally such that the second rewrite is the inverse of
the first.  The result is the same as with tunneling.  The difference
is that it works without an additional IP header.

Not true. The packet, when traveling in the core, doesn't contain the
original addresses. With tunneling, it does.

With "the result is the same", I was referring to what hosts see end
to end:  both tunneling and rewriting are transparent and stateless.
Yes, that was unclear, sorry.

The fact that IP addresses are not carried in packets is something I
see as an advantage because it does without extra packet overhead (no
extra bandwidth, no MTU issues).  And...

And if you have ACLs anywhere in boxes after the translator, they need
to change when the translate addresses change. With tunneling, when
the inner header addresses are EIDs that are portable, you can change
the outer header addresses and the ACLs in the core never have to
change.

...ACLs in the Internet core can use transit addresses just as well as
edge addresses because both uniquely identify a host.

A core ACL needs only a single transit address per host in the general
case, i.e., when the ACL is in an edge network's immediate provider.

- Christian



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