Re: M3UA AS override mode from SGP perspective

Brian, I'm confused!

> 3. In override mode only one ASP in the AS can be receiving traffic
>   (usually all can send traffic).

Does it mean, that ASP can usually send traffic before sending ASP-AC
message?

The RFC4666 says:
If the SGP or IPSP receives any Data messages before an ASP Active message
is received, the SGP or IPSP MAY discard them.
...
In the case of an Override mode AS, receipt of an ASP Active messageat an
SGP causes the (re)direction of all traffic for the AS to the ASP that sent
the ASP Active message.  Any previously active ASP in the AS is now
considered to be in the state ASP-INACTIVE and SHOULD no longer receive
traffic from the SGP within the AS.  The SGP or IPSP then MUST send a Notify
message ("Alternate ASP_Active") to the previously active ASP in the AS and
SHOULD stop traffic to/from that
ASP.  The ASP receiving this Notify MUST consider itself now in the
ASP-INACTIVE state, if it is not already aware of this via inter-ASP
communication with the Overriding ASP.


I thought that data exchange in override mode is normal only for one
ASP-SGP.


2010/10/1 Brian F. G. Bidulock <[email protected]>

> Mikhail,
>
> Please see comments below:
>
> Mikhail Plotkin wrote:                     (Fri, 01 Oct 2010 01:19:32)
> >
> > Local Side                         Remote Side
> >                                    +------------+
> >               -------assoc11-------|ASP_1       |
> > +----------+ /                     |            |
> > |     SGP_1| --------assoc12-------|ASP_2       |
> > |          |                       |            |
> > | SG       |                       |        AS  |
> > |          |                       |            |
> > |     SGP_2| --------assoc23-------|ASP_3       |
> > +----------+ \                     |            |
> >               -------assoc24-------|ASP_4       |
> >                                    +------------+
> >
> > If the AS works in an Override mode, then how many associations (max)
> > may be simultaneously active in this configuration?
>
> 1. The four SCTP associations (connected or not) are independent of
>   Override mode.  One would expect that in the normal case, all four
>   SCTP associations are connected.
>
> 2. Equally, one would expect that in normal operation, all four ASPs are
>   in the ASP-UP state.
>
> 3. In override mode only one ASP in the AS can be receiving traffic
>   (usually all can send traffic).
>
> If this arrangement is not just hypothetical, one should really run
> full-mesh with regard to SCTP associations and SGP.  That is, four
> associations should be added: assoc13, assoc14, assoc21 and assoc22.
> Associations are cheap, but failover between ASPs usually is not.
>
> --
> Brian F. G. Bidulock
> [email protected]
> http://www.openss7.org/
> _______________________________________________
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