Subject: FW: [rddp] STag validation semantics

From: "Mukund, Shridhar" <[email-masked]>
Date: Mon, 30 Sep 2002 15:47:02 -0700

Caitlin,

Isn't it true that a connection can be associated with 
multiple protection domains at the same time? 

Are you assuming otherwise? Why?

-Shridhar Mukund

>...
> 
> -- Protection Domain equivalent: an STag is valid on all
> connections that are part of the same Protection Domain
> equivalent. This provides ULP control, and is very
> compatible with InfiniBand.
> 
> -- Explicit: the STag is valid only on those connections
> that the ULP has specifically enabled it for. It may enable
> it for any set of connections. This provides complete ULP
> flexibility. It is also a very simple specification.
> 
> The implementation you suggest would be a valid method of
> implementing that Explicit option. The protection domain
> option could be implemented by a table that took the
> Protection Domain and STag as the key, with the Protection
> Domain being an attribute of the connection. This is a
> simpler table. The obvious corroralaries is that it is
> easier to implement but that there are options that cannot
> be represented. The fact that the same options could not be
> represented under InfiniBand is a strong argument that this
> is an acceptable simplification.
> 
> 
> 
> Caitlin Bestler
> http://asomi.com/CaitlinBestler/
> 
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From: Bill Sommerfeld <[email-masked]>
Date: Mon, 30 Sep 2002 20:52:17 -0400

> multiple protection domains at the same time? 

Certainly unix allows multiple processes to have an open descriptor to
the same connection.

On the other hand, an rddp-enabled connection should not allow a
communicating peer to overwrite arbitrary data within a program's
address space.

Perhaps the right model here is akin to shared memory segments -- one
segment per connection.  If connections are shared between processes,
the segment could be, too..

						- Bill

---

From: Caitlin Bestler <[email-masked]>
Date: Mon, 30 Sep 2002 20:05:45 -0500

>Are you assuming otherwise? Why?

The Protection Domain model I was referring to comes from
InfiniBand. Each QP(connection) is associated with exactly
one Protection Domain. Each R-Key(STag) is also associated
with exactly one Protection Domain. An R-Key with the 'wrong
Protection Domain' for a QP is rejected.

This requires far less NIC-accessible table space, and fewer
cycles, to validate than a generalized validating lookup on
the QP/R-Key combination.

Caitlin Bestler