RE: M3UA notify message

Brian,

> -----Original Message-----
> From: Brian F. G. Bidulock [mailto:[email protected]]
> Sent: Friday, February 24, 2006 2:59 AM
> To: [email protected]
> Cc: [email protected]; [email protected]
> Subject: Re: [Sigtran] M3UA notify message
>
>
> prabind.chaubey,
>
> I think that you understand the situation well now.
>
> Because AS state depends upon ASP state, it is really not
> possible to coordinate AS state across multiple SGP without also
> coordinating ASP state.  That is why I feel that Greg stated the
> situation well in 1.4.1 when he said:
>
>   "Where an SG contains more than one SGP, the MTP3 routeset, SPMC and
>    remote AS/ASP states of each SGP SHOULD be coordinated across all the
>    SGPs.  Rerouting of traffic between the SGPs MAY also be supported."
>
> Also note that we never required that a full-mesh of SCTP
> associations be formed between ASPs and SGPs.  And, certainly,
> as you illustrate below, the failure of an association (or two)
> can reduce a full-mesh to a sparse set of SCTP associations
> anyway.  A full mesh would likely only be for network
> redundancy.  If I have 2 ASPs, 2 SGPs and 2 networks, the most
> efficient arrangement from a performance/failure perspective
> would be as follows:
>
>   ASP1  -------network A------- SGP1
>         \______network B______/
>          ______network B_____/\
>         /                      \
>   ASP2  -------network A------- SGP2
[TOLGA]No, this is not really how it should be done -it is not wrong, but
one should be ready to face consequences with such a setup-. I would expect
both networks to be used between each peer with SCTP multihoming. We
discussed this several times  that SCTP multihoming with multiple networks
is practically necessary for a carrier grade environment.
>
> In that way if only network A fails, each ASP is still connected
> to a different SGP (for performance), and the same is true if
> only network B fails.  If network B fails, the situation
> degrades to
>
>   ASP1  -------network A------- SGP1
>
>
>   ASP2  -------network A------- SGP2
[TOLGA]If SCTP multihoming is used properly, there won't be any isolation
because each STP association would utilize both networkA and networkB.
>
> The ability of the system to operate, should not be adversely
> affected by the loss off network B.  If the SG does not
> coordinate AS/ASP state, in scenarios like the 2+k scenario you
> detail, the system will not function to the same degree as that
> where AS/ASP state is coordinated.  Good reason for the SHOULD.
[TOLGA]If SCTP multihoming is used utilizing both networks, ability of the
system is not affected at all when networkB fails.