Re: Something improper with ASP state change procedures.

Naveen,
The M3UA layer at the ASP will NOT see those re-transmissions. The SCTP
layer would know that these are re-transmissions (as the TSN would be the
same) and therefore will not pass those messages to M3UA. So, in the
scenario you describe, the state at the ASP would still be ACTIVE.

Regards,
Aditya

On Tue, Nov 23, 2010 at 9:00 PM, Naveen Kottapalli
<[email protected]>wrote:

> The previous state was INACTIVE.  So, the ASP will be moved back to
> INACTIVE instead of reactivating.  Is my assumption right?
>
> Yours,
> Naveen.
>
>
> On 23 November 2010 14:46, Dario Filjar <[email protected]> wrote:
>
>>   Hi Naveen,
>>
>> it seems that ASP does not behave correctly after reception of out-of-blue
>> ASP Up Ack message.
>> According to RFC4666, section 4.3.4.1:
>>
>> "If the ASP receives an unexpected ASP Up Ack message, the ASP should
>> consider itself in the ASP-INACTIVE state. If the ASP was not in the
>> ASP-INACTIVE state, it should send an Error message and then initate
>> procedures to return to its previos state."
>>
>> So in your case, ASP shall initiate ASP Active procedure again after which
>> it will align the state with SGP.
>>
>> BR Dario
>>
>>
>> --- On *Tue, 11/23/10, Naveen Kottapalli <[email protected]>* wrote:
>>
>>
>> From: Naveen Kottapalli <[email protected]>
>> Subject: [Sigtran] Something improper with ASP state change procedures.
>> To: [email protected]
>> Date: Tuesday, November 23, 2010, 3:36 PM
>>
>>
>>  Hi All,
>>
>> We are seeing some strange in the M3UA ASP state change procedures.
>> Please find the description of the problem below.
>>
>> ASP                                                              SGP
>> =======================================
>> ASPUP               -------------->  Processes ASPUP and sends ASPUP_ACK
>>
>> Move ASP to
>> INACTIVE state   <-------------   ASPUP_ACK
>>
>> SCTP-SACK
>> for ASPUP_ACK  ------------->  Missed or lost in the network
>>
>> ASPAC               -------------->  Processes ASPAC and sends ASPAC_ACK
>>
>> Move ASP to
>> ACTIVE state      <-------------   ASPAC_ACK
>>
>>  SCTP-SACK
>> for ASPAC_ACK  ------------->  Missed or lost again in the network
>>
>>  Move ASP to
>> INACTIVE state   <-------------   SCTP layer at SGP retransmits the
>> ASPUP_ACK, ASPAC_ACK because of lost SACKs.
>> because of
>> ASPUP_ACK
>> in ACTIVE state
>>
>> SCTP-SACK        ------------->  Reached the SCTP layer of SGP
>>
>> In the above behavior the M3UA at SGP thinks that the ASP is in ACTIVE
>> state whereas it is not the case.  Since ASP is in INACTIVE state, all the
>> data packets that were sent by SGP will be dropped (without sending any
>> error message back to network).  The above problem will lead to a potential
>> message loss in the network.
>>
>> Considering the above behavior, I think the state machine should be tuned
>> accordingly.
>>
>> Please pass on the comments on this.
>>
>> Thanks & Regards,
>> Naveen.
>>
>> -----Inline Attachment Follows-----
>>
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>>
>
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