Re: M3UA AS override mode from SGP perspective

Andrew,

Now you are talking of something different: it is always the
case that at most one ASP can be active for an override AS
for the entire SG.  However, how the SG determines what ASP
is different from what other depends on several things
foreseen by the RFC:

 - whether the SG can identify the ASP by the network address
   that it uses to connect,

 - whether the SG demands an ASP Id and enforces its uniqueness
   per SGP,

 - whether it knows by some other mechanism (such as ASP1 only
   connects to SGP1, ASPn to SGPn).

If the SG plain refuses to identify any ASP, then each ASP should
only connect once and to one SGP to increase interoperability.

You know, I had to fight long and hard to get ASP Id included
in the various SIGTRAN RFCs.  Perhaps now someone can see its
usefulness.

--brian


Andrew Booth wrote:                             (Wed, 13 Oct 2010 11:37:24)
>    Hi Brian,
>    Thanks for the response, I found it quite helpful even if you
>    found it futile :)
>    However, I am still confused about the recent thread on override
>    mode.  Some of the statements seems contradictory to me and I'd
>    like to be sure I'm drawing the correct conclusions.
>    Suppose we have an SG with 5 SGPs and 3 SCTP Associations
>    connecting to each SGP.  As per the discussion we just had, each
>    SCTP Association is considered by the SG as a separate ASP.
>    From the SG perspective then, there are 15 ASPs connecting to 5
>    SGPs, regardless of whether any of the associations terminate at
>    the "same remote ASP process".
>    In this configuration, how many ASPs can be active at once for
>    an AS in Override mode?
>      (1) At most one ASP, for the entire SG
>      (2) At most one ASP on each SGP (at most 5 ASPs)
>      (3) It depends on some other details of the configuration
>      (4) Other
>    Andrew
>    [email protected] wrote: -----
> 
>      To: Andrew Booth <[email protected]>
>      From: "Brian F. G. Bidulock"
>      Sent by: [email protected]
>      Date: 10/12/2010 05:34PM
>      Cc: [email protected], [email protected], [email protected]
>      Subject: Re: [Sigtran] M3UA AS override mode from SGP perspective
> Andrew,
> Andrew Booth wrote:                                                 (Tue, 12 Oct
>  2010 16:49:55)
> >
> >    Could the ASP vendor legitimately claim that an ASPAC message sent
> >    from the ASP process to the SG on either of its two associations
> >    should make the ASP active on both associations (assuming the SG
> >    accepts the ASPAC)?  After all, the language in RFC4666 is all about
> >    messages exchanged between ASPs and SGPs, not specifically about
> >    associations.
> No, they cannot.  If you look in Figure 3, SCTP CDI/RI
> causes transition from the ASP-ACTIVE and ASP-INACTIVE
> state to the ASP-DOWN state.  So, loss of an association
> is considered loss of communication with the ASP.  They
> might try to convinve themselves that the model supports
> it, but it does not.
> Also, as I said, the SG can enforce one ASP per association
> for these fancy-pants ASP vendors, whoever they might be,
> by requiring an ASP Id thus enforcing its uniqueness.  This
> is clearly laid out in the RFC, so if they want their ASP
> to work with SGs they should certainly support one ASP per
> association.
> But this discussion is futile: I give ASP designers more
> credit than that.
> --brian
> --
> Brian F. G. Bidulock
> [email protected]
> [1]http://www.openss7.org/
> _______________________________________________
> Sigtran mailing list
> [email protected]
> [2]https://www.ietf.org/mailman/listinfo/sigtran
> 
> References
> 
>    1. http://www.openss7.org/
>    2. https://www.ietf.org/mailman/listinfo/sigtran

-- 
Brian F. G. Bidulock
[email protected]
http://www.openss7.org/