[asterisk-ss7] KNK SS7-27 - first experiences - part 1

Marcelo Pacheco marcelo at m2j.com.br
Tue Jun 25 23:14:42 CDT 2013

There are no stupid questions, correct.

However most of us that started using the internet back when nettiquete
was the rule of the land, know that asking questions that have been
asked dozens of times before is rude.
RTFM was coined a long time ago and Google is your friend is as old as
Google's popularity.

And there is people who want to "wing it" deploying stuff they don't
understand in production and expecting others to help him make money,
with almost zero learning effort.
SS7 isn't for the faint of heart, it's complex. It isn't ISDN.
And it's done for profit.
Some even have the nerve to request urgency.

I do judge those. If that makes me stupid in your opinion, than that's
your democratic right to judge me too.

The number of cases people deploy libss7 / chan_ss7 without even
understanding how to align the CIC numbers define those who don't
deserve much respect at all.

And the most absurd part is with google and a little patience those
questions can be answered without bothering hundreds of people.

Whenever someone ask questions that have been answered dozens of times,
without using a search engine prior, is showing disrespect for others.

I'd love to answer a new question... ONCE. And have people google it
> There are no stupid questions :-), there are just stupid people, which
> judge the other's questions :-).
>   I think that there is no simple answer to your question. It may depend
> on many circumstances, like the network topology, internal traditions and
> rules in different countries etc.
>   In such a simple setup as this one discussed, the signaling links are
> obviously occupying one of the timeslots in one of the bearers (we use
> E1s in Europe). So, for example, the case discussed here uses 8 E1s between
> Asterisk and the other switch (EWSD), i.e. 8x31 timeslots, and the first
> timeslot on the first E1 (which would have CIC 1) is used for signaling
> link. In the case of more signalink links in the linkset, the second one
> would occupy the first timeslot in the second E1 etc. However, there are
> countries which prefer TS 16 instead of TS1. And some carriers have strict
> SS7 routing rules and direct links between switches are forbidden - in
> such a case the links must be connected to the STP(s), which require to
> drop/insert them out of the E1 stream using some muxing equipment.
In E1 land, TDM switches can make a semi permanent call, TDM switching
between two channels that stays up until removed.
All traditional TDM switches and newer NGN switches can do it. Even
DAHDI can do it (see dacs in system.conf).
On E1 land, this is the way of connecting to a 3rd party STP, I worked
for four different Brazilian telcos, and I'm yet to get a direct
connection to a third party STP.
>> More specifically is the SS7 interconnect with the CO done using
>> grouped PRI trunks mapped in a T&E1/3 transport layer. Or A-Links,
>> STM-1.....
Direct E3 / STM1 connections to TDM switches also extremely rare. Most
TDM switches don't even have those, E1 only.
>> I really want to experiment with an interconnect using the SS7
>> signaling to help bring to light what I have been studying. What is
>> the minimum I would need to ask a service provider for in terms of
>> service (i.e., T1 with SS7 signaling?), and hardware.
Between two asterisks, TDMoE can be used, just ethernet.
At some point you'll need to learn T1 timing, alarms, all the beginners
mistakes, TDMoE masks that lower level stuff.
TDMoE is nice cause you can create a 100 channel trunk, even multiple
large trunks, without any extra cables.
Just sugest using only gigabit ethernet, with a 100% gigabit path, using
a single switch, you can connect 3 or more asterisks and create
scenarios of more complexity without lots of cables lying around.
Gigabit essentially prevents jitter and packet loss. TDMoE requires a
perfect connection.

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