[asterisk-ss7] Asterisk like a SS7 STP

Mehdi Shirazi mahdi_shirazi at yahoo.com
Fri Mar 16 22:52:41 CDT 2012

>On Fri, Mar 16, 2012 at 12:37 PM, Marcelo Pacheco <marcelo at m2j.com.br>wrote:

>>  Gustavo,
>> I think you're confusing the general function of an STP with the external
>> signaling network architecture used by ANSI countries.
>> All incumbent networks in Brazil make heavy usage of STPs.
>> They have lots of
>TDM switches, and to avoid a full mesh of signaling links between all TDM
>> switches that have voice trunks between them, STPs are used to aggregate
>>SS7 traffic.

>STP is single point of failure unless used in pairs; using STP pairs
>requires combined linkset - does ITU have this capability?  don't think so
>- SLS is only 4 bits; it's 5 bits in ANSI

>of course it is what it is - but i'm curious how the fault tolerance vs
>management ease balance out - mildly curious

>> Also STPs are also used as billing entities and for resolving LNP in some
>> carriers.
>> This seems to me to be the motivation for using STPs.

> >I'm pretty sure STPs have lots of usage in other ITU countries.
>> Poland. "Lots" is a relative term.  You do see them.  Seems like they were
>being introduced about the same time that VoIP was coming in too.  Now
>what? Keep building TDM or cap it and go to VoIP?  I think we all know how
>that is turning out.

>> However they don't have a fully separate signaling network, 64kbps SS7
>> links make maximum usage of semi permanent call setups, specially for
>> interconnects with other carriers (using bearer channels of existing E1
>> voice trunks).
>> However competitive carriers use redundant soft switch architecture don't
>> need STPs, since signaling flows through the IP network, without explicit
>> signaling channels.
>>I fell more important than the capability of Asterisk performing as an
>> STP, is much more important full linkset functionality as a regular
>> signaling point. For instance, the following scenario can't be implemented
>> with libss7 today:
>> Asterisk --x-- STP A ---x--- Switch1,2,3,4,5,6,7,8
>>                STP B
>> Where Asterisk has voice CICs with all 8 switches, and all signaling needs
>> to be shared across a pair of signaling links, one with each STP. Specially
>> with E1s with all 8 switches can't fit on a single Asterisk box.

>Are you describing the combined linkset?  When I've seen things like this
>in ITU networks, A was primary and B was alternate (used when A was not
>available), instead of the ANSI model where A and B are peers and normally
>used equally using a 5 bit SLS.

you can use one of SLS 4Bits for loadsharing between 2 Linksets to 2 STPs(you still can have 2x8 signaling links)
if a ITU network needs 4 STPs they can use 2 bits for Linkset loadsharing or in every LX divide trunkgroups to two parts and for one part set STP1,2=>priority=1 STP3,4=priority=2 
and other part vice versa.

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