Subject: (IPng 7506) general question

From: Vitaly Chipitsyn <[email-masked]>
Date: Tue, 11 May 1999 17:03:19 -0400 (EDT)

Hello,

I am looking into one problem of routing in IPv6, and I would like to ask
if anyone knows of any kind of research that has been done in this
area?

The problem that I am worried about relates to provider-based routing
in IPv6. Imagine a site that has 3 connectiont to the Internet, which
means there are three border routers. Assume that those three
connection points belong to different sTLAs, for the sake of argument.
As far as I know, IPv6 numbering of local hosts can be either
global or site-local. Global numbering is not interesting in this
situation. In the latter case, packets leaving the site through border
routers will have site-local prefixes of their addresses replaced with
the prefix of the corresponding connection point. There is no problem
with this.

Now that there are active TCP connections from the outside through _one_
of the three connection points, imagine _that_ corresponding link (or
router) go down.

1) It would be nice to have those active TCP connections change their
network path and use another connection point to get packets to the
destination inside the site. However, it is hard because TCP uses
destination IP address in its notion of virtual connection, while
destination IP address would definatly change in this situation.

2) However, because (1) seems hard to accomplish, has anyone thought
of somehow telling the node which originates TCP connection to use
another IPv6 address (with a different prefix, corresponding to
another Internet connection point of the target site) for future
communications?

This brings another issue that is also interesting: DNS support of
multiple addresses to the same node, through a number of connection
points as in the example above.

Regarding the (2), the originating node, prior to establishing
connection, knows that it needs a service from the target node
which is inside the site. Typically, I would imagine it to be a WWW
server. In this case, that WWW server potentially has several
addresses by which it can be reached from the Internet, each valid
while connection point is operational. A requesting node would go to a
DNS server to get information about all available IPv6 addresses for
the server. From this primary questions would be:

3) Does DNS currently support storing multiple IPv6 addresses for
cases as in the example above? (I have not read dynamic DNS RFC)

4) Are there specifications of how IPv6 nodes should behave in cases
of changes in sets of active prefixes for a given destination?

At the top level, this is all. I hope to hear good comments and
references to what have already been done regarding the problems that
mention here. 

Thank you.
--vc
--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [email-masked]
--------------------------------------------------------------------

---

From: [email-masked]
Date: Wed, 12 May 1999 11:21:01 +0900

I agree that there are something needs to be done for multi-homed
	site support.

>the prefix of the corresponding connection point. There is no problem

	Big problem with the above sentence, regarding to the use of
	site-local addresses (where did you read the above behavior?).

	Rewriting IPv6 header at the border router will damage IPsec between
	your node and outside nodes.  That is what IPv6 would like to avoid
	and you will be using global IPv6 address.

itojun