Re: M3UA: Synchronizing DPC availability state between ASPs in the same AS

From: Dan Gora
> Sent: 08 April 2017 05:48
 
> Hi All,
> 
> We have a distributed M3UA implementation with two ASPs on different
> physical hosts servicing a single AS talking to a single SGP in a
> single SG:
> 
> SG1       AS1
> ---      -----
> SGP1 --- ASP 1
>      +-- ASP 2
> 
> It's unknown who the SGP/SG vendor is, but our customer is claiming
> that when we start ASP 1 and ASP 2 that both will enter the ASP-Active
> state with SGP1, then both ASP 1 and ASP 2 will each send a DAUD
> message to SGP1.  However the problem is that the SGP will only reply
> with a DAVA/DUNA to ASP 1.  Subsequent DAUD messages from ASP2 to
> SGP1 are "replied to" by the SGP1 by sending the DAVA/DUNA to ASP
> 1, not ASP 2.  They also claim that this "should be sufficient".
> They also claim that we should not need to send DAUD from ASP 2 at
> all, that we should "coordinate" the DAUD sending so that only one
> ASP sends a DAUD message.
> 
> Now this feels wrong to me.  There is nothing in the spec which
> specifically states that the ASPs have to synchronize the destination
> states between themselves just because they belong to the same AS.
> 
> There is also numerous places (RFC 4666: 3.4.1 (DUNA) and 3.4.2)
> where it says that the DUNA/DAVA message is sent to "all concerned
> ASPs" and in 4.5.1 where it says:
...

This is a difference between rfc 4666 and the older 3332.

AFAICT one major network equipment manufacturer has not updated their
protocol stack to conform to rfc4666.

We've a horrid bodge that detects the missing indications.

	David