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Simultaneous support single exchange and double exchange in M3UA

+1 vote

Can one implementation support single exchange and double exchange models of IPSP at the same time ? Or does it have to be configured and only one of the models can be active at a time ? Is there any M3UA procedure which can help in dynamic negotiation of SE/DE models.

posted Aug 2, 2013 by Sanketi Garg

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1 Answer

+1 vote
Best answer

SE support is mandatory. DE support is optional. Therefore, when an implementation supports DE it must also support SE.

Some implementations might only support one model at a time for a given AS/ASP, but that is a (minor) limitation of that implementation.

There is no need for negotiation: all implementations supporting IPSP MUST support SE: so just use that.

Nevertheless, when an IPSP sends an ASP-UP message and receives an ASP-UP message in response, or sends an ASP-ACTIVE message and receives an ASP-ACTIVE message in response, it can determine that the peer is using DE mode and proceed accordingly.

It can also determine DE mode from REGREQ messages in a similar manner when registration is used.

answer Aug 18, 2013 by anonymous
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Going thought the RFC 3332 and have a doubt about RC, in M3UA we have a concept of routing context to identify an AS but same can be achieve by the routing Key (it seems) then what the purpose RC is serving.

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Assume you have the conditions (one AS, etc.) to allow RC to be optional, does the RFC permit one side (IPSP SE mode for example) to still send an RC and the other to not include an RC? I think the answer is yes, but I can't find an explicit reference permitting it.

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This is regarding M3UA SSNM messages.
1. Take an ASP with 2 SCTP link sets with each link set having 2 associations, connecting to two different SGs.

| - - - - -> Link Set 1 (2 Associations) - - - - -> SG 1 - - - - - >|ASP | | HLR-1| - - - - -> Link Set 2 (2 Associations) - - - - -> SG 2 - - - - - >|

If all connections between SG-1 and the HLR-1 break, the ASP would be notified with a DUNA.My question is through which SCTP connection between the ASP and SG-1, the DUNA would be sent in a proper SG implementation?Would it be sent to both connections or to a randomly selected one ?

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I was referring the rfc4666 for M3UA and have few concerns regarding the DUPU SSNM message. The specification says that a DUPU indicates the unavailability of a certain user part.
If I may quote "The DUPU message is used by an SGP to inform concerned ASPs that a remote peer MTP3-User Part (e.g., ISUP or SCCP) at an SS7 node is unavailable"
I have two questions.
1. How these concerned ASPs are identified. Is it upon receiving a MTP-Transfer for a particular user part (say SCCP) or can it be sent periodically for a given ASP ?
2. I could not find any SSNM message that indicates a User Parts Availability. Am I wrong here to expect such a message and if so how come a concerned ASP know if a certain User Part is available at a given point code.

It would be an immense help if anyone could clarify the aforementioned concerns.