Subject: TCP Connection Identifiers in IPv6

From: "Narsimharao Nagampalli" <[email-masked]>
Date: Mon, 17 Jul 2000 05:35:59 -0600

Hi,

In IPv4 a TCP connection was uniquely distinguished with the help of  the 4 tuple.  Does this hold good with IPv6? I can think of the following scenario caused by scoping, where such a identification might fail.

In IPv6 scenario, if a  node with multiple links having same link local addresses on both the interfaces exists, then it is possible that the 4 tuple is no longer sufficient to determine a connection uniquely. There has to be an interface identifier added as the 5th element to now distinguish across connections. 

Any comments/suggestions?

Thanks,
Narsi

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From: "Dave Thaler" <[email-masked]>
Date: Mon, 17 Jul 2000 09:41:02 -0700

This can be true in IPv4 as well...  for example,
if the IPv4 stack allows multiple interfaces to have 
the same "autonet" (169.254...) addresses, which
are roughly equivalent to link-local addresses.

-Dave

-----Original Message-----
From: Narsimharao Nagampalli [mailto:[email-masked]]
Sent: Monday, July 17, 2000 4:36 AM
To: [email-masked]
Subject: TCP Connection Identifiers in IPv6

Hi,

In IPv4 a TCP connection was uniquely distinguished with the help of
the 4 tuple.  Does this hold good with IPv6? I can think of the
following scenario caused by scoping, where such a identification might
fail.

In IPv6 scenario, if a  node with multiple links having same link local
addresses on both the interfaces exists, then it is possible that the 4
tuple is no longer sufficient to determine a connection uniquely. There
has to be an interface identifier added as the 5th element to now
distinguish across connections. 

Thanks,
Narsi

---

From: Brian Zill <[email-masked]>
Date: Mon, 17 Jul 2000 19:58:05 -0700

Yes, you need to do this in order to support link-local (and also
site-local) addresses properly.  To be more general, it is best to tag
incoming packets with appropriate scope id values based upon their arrival
interface and address scopes.  And then add those to the connection lookup
criteria.  This is what we do in our implementation.

--Brian

> Sent: Monday, 17 July, 2000 04:36
> In IPv4 a TCP connection was uniquely distinguished with the 
> help of  the 4 tuple.  Does this hold good with IPv6? I can 
> think of the following scenario caused by scoping, where such 
> a identification might fail.
> 
> In IPv6 scenario, if a  node with multiple links having same 
> link local addresses on both the interfaces exists, then it 
> is possible that the 4 tuple is no longer sufficient to 
> determine a connection uniquely. There has to be an interface 
> identifier added as the 5th element to now distinguish across 
> connections. 
>