[Guy Harris <guy@xxxxxxxxxx>]

On Thu, May 22, 2003 at 05:25:07PM -0400, Dave Piscitello wrote:
> I worked on the IEEE and ISO committees that created the LLC/SNAP 
> headache/header, nearly 20 years ago, and no standard I know specifies this.
> 
> I have this fuzzy recollection of a "version" of CLNP called "null", where 
> there's no CLNP header, only the single, initial protocol identifier with a 
> value of zero.

Yes, there is - it's the "inactive subset" of CLNP.

> If every host you ever wanted to have communicate is connected to an 802.3 
> network, you could in theory use MAC addressing and framing(the network 
> layer in this situation doesn't provide any added function), then 
> encapsulate TP4 in a null CLNP (one octet of zero), and then indicate it's 
> CLNP in the LLC SAP value Guy mentions, in the 802.3 frame.

We already handle the inactive subset of CLNP, and dissect the stuff
after the inactive subset as COTP, so that's presumably not what he's
seeing on his network.