Re: [shim6] Problems with ULID (IP) over longer sessions.

[Javier Ubillos <[e-mail]>]

On Fri, 2010-04-30 at 02:02 -0700, Erik Nordmark wrote:
> On 04/28/10 05:20 AM, Javier Ubillos wrote:
> > Hi folks.
> >
> > Some time ago I heard a discussion about a potential issue with shim6.
> > That the Upper Layer Identifier (ULID), chosen as the first pair of
> > locators used in the communication, could cause
> > problems/confusion/somethingelse when those locators where no longer
> > used by the hosts. I.e not in the locator lists.
> >
> > I'm unsure about the details of what would cause the problem or what the
> > consequences could be.
> >
> > My own first reaction is that if a software believes it's communicating
> > with an IP (a shim6 ULID), it might try to spawn more sockets/flows to
> > that IP.
> >
> > Have this kind of issues been discussed previously on this list? ( I
> > couldn't find any discussions about it).
> > Have any one on this list some more detailed thoughts/experience about
> > what could cause issues?
> 
> Section 1.5 in RFC 5533 says that the communication must be terminated 
> should the ULID become invalid. That handles the case of a ULID 
> potentially being assigned to a different host.
> 
> Note that a ULID might be unreachable and hence unusable as a locator 
> without being invalid.
> 

It looks as if 1.5 was what I was unknowingly referring to.

However, if not when the locator becomes unreachable, when is an ULID
declared invalid?

When that locator _does_ respond, but with invalid context (or some
other expected 'error' behavior)?
When it becomes un-routable? (prefix change)


> > I'm asking this because a couple of colleges and I are looking at using
> > alternative ULIDs which hopefully would be more of a match with session
> > identifiers/FQDNs or similar.
> 
> It is possible to extend SHIM6 to handle 128-bit ULIDs that are never 
> usable as locators. It has performance impact because one would need to 
> do a ID->locator lookup before sending the first packet. A possible way 
> to do this was written up in draft-nordmark-shim6-esd.
> 

Thank you for that tip. I'll make sure I read up!


Thank you
// Javier