Re: [nbs] NBS and TCP connection identification

Erik Nordmark <> Tue, 21 September 2010 03:29 UTC

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Date: Mon, 20 Sep 2010 20:30:24 -0700
From: Erik Nordmark <>
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To: Christian Vogt <>
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Subject: Re: [nbs] NBS and TCP connection identification
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On 09/20/10 06:15 PM, Christian Vogt wrote:
> Hi Erik:
> Thanks for reviewing both documents.  A few comments; Javier will
> fill in the rest.
> - You are right that TCP connections will be identified by a pair of
> DNS names.  Implementation-wise, this could be realized by hashing
> the DNS names into 128-bit strings.  Then, a TCP-for-IPv6
> implementation could pretty much be reused.

But that requires that the hash of the DNS name be carried in the TCP 
SYN and SYN|ACK, since you can't setup that state after the connection 
is setup. This adds complexity (and the details are missing) since TCP 
needs to handle both a NBS peer and a normal TCP peer (the latter will 
create a connection based on the IP addresses.)
I don't know how this is intended to work for UDP.

> - Security-wise, the idea is to bind DNS names to IP addresses by
> means of a forward lookup in the DNS.  This gives the same level of
> security that we have for DNS-based applications today, except that
> the forward lookup would not just be done by the connection
> initiator, but also by the connection responder.  Where higher
> security is required, we recommend DNSSEC.  Thus we can avoid extra
> cryptographic identifiers.

If X can predict that A will talk to B (using port1/port2), then X can 
send a SYN claiming to have A's name (and port1) destined to B/port2.
Later when A sends its SYN something on B has to be able to resolve 
things. The easy way is to verify that the initiator actually "owns" the 
name A before creating the TCP state for A/port1.

I don't understand what you mean by the forward lookup being done by the 
responder. Clearly the responder can't do a forward lookup when it 
receives a SYN packet, because that can be used to DoS the responder out 
of existence.

> - Hosts that don't have a name registered in the DNS will derive a
> DNS name from their IP address.  This will give them session
> continuity, albeit no reachability.

But that doesn't allow them to use SHIM6 to move around.
A CBID as a name allows them to move around.