Re: [Isms] ISMS/SSH and notifications

[Juergen Schoenwaelder <j.schoenwaelder at jacobs-university.de>]

On Wed, May 28, 2008 at 12:25:51PM +0200, tom.petch wrote:
 
> TCP is different and the TCP source port is usually used cyclically, starting at
> some value, may be determined by the implementation but sometimes appears to be
> pseudo-random.  But does it have to be?
>
> (I remain convinced that reusing a CR/CG connection for a NO+CR entity remains
> the simplest deployment, even if the CR/CG is just used for the retrieval of a
> one well-known object eg snmpTsmHereiamsendmenotificationsplease )

As I pointed out in some WG meeting, reusing a SSH (or simply TCP)
connection means to install SNMP target configuration that is only
meaningful as long as the connection exists. I doubt it very much that
there is a portable way to share a listening TCP endpoint and a
connection TCP endpoint; I would be surprised if this works at all in
any meaningful way if I look at the TCP state machine.

Hence, when the SSH (or simply TCP) connection goes away, the SNMP
target configuration pointing to it needs to be garbage collected.
This implies that once the TCP connection is gone, there is either no
way to send a notification anymore or you have to have a backup SNMP
target configuration to be used after the connection has disappeared
(which again requires configuration information so that the SNMP
engine hosting the notification originator knows about this fail-over
situation).

To make this work, several extensions to the SNMP target tables are
needed and I recall that we abstained from this when we wrote the SNMP
over TCP mapping since all this creates several new failure modes.

/js (speaking as technical contributor)

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>
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