North American Network Operators Group
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: who gets a /32 [Re: IPV6 renumbering painless?]

  • From: Andre Oppermann
  • Date: Mon Nov 29 15:50:56 2004 
Paul Vixie wrote:

i have long wished for and sometimes needed a way to renumber a host
w/o killing or restarting its active tcp flows.  this isn't a
layering violation.  tcp should be able to know about
endpoint-renumber events.

This is a layering violation and has endless security implications.

as i told someone in private e-mail earlier this morning, tcp's notion
of a flow-identifying tuple includes network addresses, and so, the
ability to change these on the fly will absolutely affect tcp.  when
you bind a session to an address, as tcp currently does, you cause the
community to waste ipv4 /32's or ipv6 /128's as loopback aliases just
to have something they can virtualize, manage, move around, play with.

So?


let me put that another way, in case it's not clear enough as stated:

tcp's existing reference to network addresses are a layering violation,
and so anything we do to improve the situation will also be a layering
violation, but what of it?  deciding against making tcp "less pure" is
not going to meet the needs and demands of the community -- and those
needs and demands WILL be met, and probably in even less pure ways.
google for a product or feature called "3TCP" to see what i mean.

Instead of hacking the nice and working TCP we have now you should
move on to greener grass and use SCTP instead.  It does what you
want, at least in the specification.  I don't know how many implementors
have managed to code it properly.


You can solve the renumber thingie by having all TCP connecting
to/from an official IP on the loopback interface.  Then the routing
code could do its work and route the packets through some some other
or renumbered interface.

see above.  we do that now.  however, it limits the scope of mobility to
"same autonomous system" and often "same campus" so it's not useful for
any wide area purpose.  the internet's target area is very wide indeed.

Yea, but what is a surviving TCP good if you put your laptop to sleep
and wake it up somewhere else?  It can't pre-announce the next IP address
it will use.  Instead at the new location it will have to convince somehow
the remote host that he is he indeed.  No way without cryptography.  IPSEC
will break too.

Oops, the remote end switched IP addresses too and you are lost.

The question is whether renumbering while moving active TCP sessions to
the new IP address is a problem at all other than a nice-to-have dream
of 'propellerhead' Paul? ;)

And the other, more serious, question is whether IP addresses are something
that you only use temporarily or permanently?


Try to get your TCP automatic renumbering stuff implemented from spec
by five different people in five different codebases in a compatible
way within two month time... No way.

where i come from that's called "the fallacy of the straw man" and is
not a well respected technique for debate or discussion.  the process
i'm thinking of would take years to reach deployability, and more years
to reach wide scale deployment.

Nonetheless having a simple and easily implementable spec is key to
success and compatibility.  I know you can write, hmm, interesting
and complex code...


KISS KISS KISS KISS !!!

Why is the telephone (POTS/Mobile) so popular?  Easy answer: Even the
most stupid person on earth capable of correctly reading digits is able
to punch in a number.  As simple as it gets.

i guess i was expecting smart people to write kernels and "lusers" to
just run working code.  this seems to work for apple and suse and redhat
and sun and microsoft.  or is this another straw man thing?  certainly
my kids think their mac/os/x machine is as easy to use as a telephone,
and if you asked them how the routing table worked they wouldn't care.

No, they don't mind just using the computer because you set up the internet
connection.  Have them call your favorite ADSL provider and order an ADSL
line and then have them set up some DSLWLAN thingie plus a printer connected
via ethernet.  And using the Apple offerings is cheating, take the average
cheap windooze stuff.

Because all this worked so well they want to run their own webserver on
their computer and others from the internet should be able to connect...

You see?

--
Andre