Re: Query: IPSP-SE definition

Soni,

Soni Goel wrote:                                                                      (Tue, 22 Nov 2005 03:31:35)
> Hi, 
> 
> In one of the earlier mails , I saw the following configuration being
> discussed. I have related query.
> 
> It is an IPSP-IPSP Single Ended communication. We have AS1 served by
> IPSP1. IPSP2 and IPSP3 are in the same Application Server (AS2). Every
> IPSP is operating in Override traffic mode, where IPSP1 and IPSP2 are
> configured to be in the ASP-ACTIVE state and IPSP3 is acting as
> backup.
> 
>    ________           ________     ________ 
>   |        |         |        |   |        |
>   |  AS1   |         |  AS2   |   |  AS2   |
>   | PC = X |         | PC = Y |   | PC = Y |
>   |________|         |________|   |________|
>       |                  |            |     
>    ___|____           ___|____     ___|____ 
>   |        |         |        |   |        |
>   | IPSP1  |         | IPSP2  |   | IPSP3  |
>   |  IP@1  |         |  IP@2  |   |  IP@3  |
>   |Override|         |Override|   |Override|
>   |(Active)|         |(Active)|   |(Backup)|
>   |________|         |________|   |________|
>        |                  |            |    
>        |__________________|____________|    
> 
> As per the RFC -
> "In the case of an Override mode AS, reception of an ASP Active
> message at 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 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. ""
> 
> In the following scenario, IPSP1 on receiving ASP Active Ack from
> IPSP2, redirects all the traffic to IPSP2 and considers IPSP3 as
> Inactive. Isn't this contradicting with the RFC paragraph (stated
> above)? As per the RFC, the SGP or IPSP receiving ASP-Active message
> redirects the traffic and sends NTFY(Alt ASP-Act), not the IPSP
> receiving the ASP-Active Ack.  If this is true, then if IPSP1 needs to
> use Override mode towards AS2 (consisting of IPSP2 and IPSP3), then
> ASP-Active messages must be initiated by IPSP2 and/or IPSP3, not by
> IPSP1.


No, you should follow the RFC as above.

Let me make one change to your diagram:

   IPSP1                   IPSP2                   IPSP3
     |                        |                      |
     |-------------------ASP Active----------------->|
     |<----------------ASP Active Ack----------------|
     |                        |                      |
     |-------ASP Active------>|                      |
     |<------ERR[Mgmt Blking]-|                      |
     |                        |                      |
     |                        |                      | 

A standby IPSP need not accept an ASP Active from an IPSP.

--brian

> 
>  IPSP1                   IPSP2                   IPSP3
>    |                        |                      |
>    |-------------------ASP Active----------------->|
>    |<----------------ASP Active Ack----------------|
>    |                        |                      |
>    |-------ASP Active------>|                      |
>    |<------ASP Active Ack---|                      |
>    |                        |                      |
>    |----------------NTFY(Alt ASP-Act)------------> |
>    |                        |                      | 
> 
> 
> Thanks,
> Soni
> 

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