Re: RFC 4666 on Signaling System 7 (SS7)Message TransferPart 3 (MTP3) - User Adaptation Layer (M3UA)

Tolga,

In my config ASP11 has a single path, so does that ASP12....
Multihoming is not involved in the two ASPs for various reasons...

Regarding
"BTW, your assumption of SCTP not being able to failover between paths with
no message loss is not correct. SCTP does this without message loss and
missequencing."

SCTP does not exist as a single entity and there is always an ULP involved..
If the ULP does not request for retrieval, SCTP will not do the retrieval..
SCTP has the capability not to lose messages on path failures...but all 
depends on the ULP.....
M2PA does that as there is MTP3 involved which does the retrieval/retrans...
M3UA does not do that..

Regards,
Satya Prasad





Tolga Asveren wrote:

>Satya,
>
>If SCTP association to ASP11 is lost, this implies that ASP11 host is down,
>because network redundancy is provided with SCTP multihoming and proper IP
>network engineering. When ASP11 is down, there is no way to retrieve
>anyhting. The possibility of loosing SCTP association without a host failure
>should be guranateed to be below some acceptable threshold value, i.e.
>really really low.
>
>BTW, your assumption of SCTP not being able to failover between paths with
>no message loss is not correct. SCTP does this without message loss and
>missequencing.
>
>     Thanks,
>     Tolga
>-----Original Message-----
>From: Satya Prasad Nemana [mailto:[email protected]]
>Sent: Thursday, September 21, 2006 9:27 AM
>To: Tolga Asveren
>Cc: [email protected]
>Subject: Re: [Sigtran] RFC 4666 on Signaling System 7 (SS7)Message
>TransferPart 3 (MTP3) - User Adaptation Layer (M3UA)
>
>
>Tolga,
>
>Consider the situation
>
>SP1 is routing  ISUP messages to  AS1 (which has ASP11, ASP12) via SG- SG1
>in loadshared...
>SG1 has sent 1000 msgs to AS1 via SCTP assoc of ASP11..
>When SCTP assoc of ASP11 fails and AS1 has acked via SACK 940 msgs..
>The current implementations do not have the capacity to retransmit the
>remaining 60 msgs...
>They are lost although we have ASP12 for redundancy purposes.
>
>Considering the case of Multi Homing also...
>even if ASP11 is multi homed and loses one path with a similar situation,
>there is still no chance of
>retransmitting the msgs as M3UA does not define any such method for
>retrieval ....
>
>Regards,
>Satya Prasad
>
>
>
>Tolga Asveren wrote:
>
>Satya,
>
>In M3UA network redundancy is provided by SCTP multihoming and host
>redundancy by using multiple ASPs for an AS.
>
>For the configuration you are mentioning, if the ASP host is down, there is
>no message retrieval possible in SS7 as well for the similar case. If the
>SCTP association is lost to an ASP, this shouldn't happen due to network
>problems (this property be guaranteed with SCTP multihoming and proper IP
>network configuration) and should indicate a host failure.
>
>     Thanks,
>     Tolga
>
>
>-----Original Message-----
>From: Satya Prasad Nemana
>[mailto:[email protected]]
>Sent: Thursday, September 21, 2006 5:05 AM
>To: [email protected]
>Cc: [email protected]; [email protected]; [email protected]
>Subject: Re: [Sigtran] RFC 4666 on Signaling System 7 (SS7) Message
>TransferPart 3 (MTP3) - User Adaptation Layer (M3UA)
>
>
>
>A general comment on ASP failover cases,
>M3UA does not have any method of doing retrieval /retranamission
>Although SCTP does have the capability through multi homing,
>the ULP should have the request in place to do the
>retrieval/retransmission
>In the case of a single AS having only a single ASP configured, there is
>no chance of retrieval (but this is the most rare configuration
>as networks
>are configured  not to go down with a single point of failure)
>In case the AS is configured with two ASPs and each having a different
>SCTP assoc with a single path in  each of the assoc..
>there is no chance of message retrieval... as per the current rfc.
>
>No idea if this was not felt important in a telecom network!!
>
>[email protected] wrote:
>
>
>A new Request for Comments is now available in online RFC libraries.
>
>
>       RFC 4666
>
>       Title:      Signaling System 7 (SS7) Message
>                   Transfer Part 3 (MTP3) - User
>                   Adaptation Layer (M3UA)
>       Author:     K. Morneault, Ed.,
>                   J. Pastor-Balbas, Ed.
>       Status:     Standards Track
>       Date:       September 2006
>       Mailbox:    [email protected],
>                   [email protected]
>       Pages:      124
>       Characters: 292991
>       Obsoletes:  RFC3332
>       See-Also:
>
>       I-D Tag:    draft-ietf-sigtran-rfc3332bis-06.txt
>
>       URL:        http://www.rfc-editor.org/rfc/rfc4666.txt
>
>This memo defines a protocol for supporting the transport of any SS7
>MTP3-User signalling (e.g., ISUP and SCCP messages) over IP using the
>services of the Stream Control Transmission Protocol.  Also,
>provision is made for protocol elements that enable a seamless
>operation of the MTP3-User peers in the SS7 and IP domains.  This
>protocol would be used between a Signalling Gateway (SG) and a Media
>Gateway Controller (MGC) or IP-resident Database, or between two
>IP-based applications.  It is assumed that the SG receives SS7
>signalling over a standard SS7 interface using the SS7 Message
>Transfer Part (MTP) to provide transport.  This document obsoletes
>RFC 3332.  [STANDARDS TRACK]
>
>This document is a product of the Signaling Transport
>Working Group of the IETF.
>
>This is now a Proposed Standard Protocol.
>
>STANDARDS TRACK: This document specifies an Internet standards track
>protocol for the Internet community,and requests discussion and
>suggestions for improvements.Please refer to the current edition of the
>Internet Official Protocol Standards (STD 1) for the standardization
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>USC/Information Sciences Institute
>
>...
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