> Unprotected callback channels also permit Denial of Service attacks
> against the cache manager because any IP address can send the cache
> manager RPCs that invalidate the contents of the cache.

The rxgk callback protection described in the document does not prevent that. 
In particular:

>   Only RPCs issued over an rxgk protected connection should receive
>   rxgk protected callbacks

And in any event, Why can't the attacker just send RXAFSCB_InitCallbackState3 
and invalidate the cache that way? There is no way to require that call be 
protected (think fileserver restart where the state save/load didn't work).

I also find this notion that callback revocations could be used in an 
amplification attack silly. The CM is not going to respond to every 
RXAFSB_CallBack() with RXAFS_FetchStatus(). It will only do that the next time 
that afs vnode is touched by a 
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