Re: Design pattern

["Randy Presuhn" <randy_presuhn@mindspring.com>]

Hi -

> From: "David T. Perkins" <dperkins@dsperkins.com>
> To: <mreview@ops.ietf.org>
> Sent: Thursday, June 12, 2003 10:09 AM
> Subject: Design pattern
...
>        DESCRIPTION
>         "The Next Value for a MediaGateway LinkId.  Assists the
>          manager in selecting a value for medGwyGatewayLinkId.
>          Using the TestAndIncr syntax, A Manager will 'lock' this
>          variable, ensuring single access."
...

I have one comment, not so much on the design pattern as on
the phrase "ensuring single access."  If communication is over
a non-reliable protocol, e.g. UDP, then the use of TestAndIncr
doesn't provide as much assurance as one might expect.  If
two managers collide, and the response to the one whose
request fails the TestAndIncr test is lost, the managed system's
state will appear to that manager as though its request had
suceeded.

Randy