Re: M3UA AS override mode from SGP perspective

Mikhail,

The scenario that you have described is not valid - if SGP_1 and SGP_2 are both part of SG, then there must be
inter-communication between them. Otherwise they are just two independent SGs.

In override mode, from the viewpoint of the SG there will still be only one active ASP in the AS, regardless of whether
or not SGP1 and SGP2 distributed across two hosts.

Barry Nagelberg
Adax, Inc.

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Mikhail Plotkin
Sent: Friday, October 01, 2010 8:38 AM
To: Brian F. G. Bidulock; Chris Benson
Cc: [email protected]
Subject: Re: [Sigtran] M3UA AS override mode from SGP perspective


Thanks, Chris and Brian!
What I understood is that in my configuration there could be only one active SCTP association, but in general case there
could be more active SCTP associations depending on how many SGPs are connected with the active ASP. That's clear.

Then another question. According to RFC4666 Appendix A, it is possible to have SGP1 and SGP2 distributed between two
hosts. So, ASP1 may activate in SGP1 and then ASP3 may activate in SGP2. If SGP1 and SGP2 have no inter-communication,
ASP1 will not receive Notify (Alternative ASP active), so there will be two active ASPs in the AS which contradicts to
the override concept.
How should this issue be solved? By management layer at the ASP side or by some kind of inter-communication between
SGPs?

Best regards,
Mikhail.

> 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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