[asterisk-users] Question about SS7

[Alexander Lopez]

SS7 was a replacement for the in-band signaling that was used in the
PSTN (as my 13 y/o would say...  Back in the Day). It allows for call
information to be exchanged without the use of a circuit being built
from switch to switch. For example:

 

Without SS7.

 

You place a call from NYC to LA. The NYC Switch would request a Long
Distance trunk, that trunk would them be built (literally) from NYC to
LA. Then the LA switch would dial your Aunt in LA, and ring her phone.
This would require time and resources to do and you wouldn't know if the
line was busy until the switch in LA told you so.

 

With SS7

 

A packet of information is send on the SS7 network. Comprising but not
limited to, BTN/ANI*, Destination number, etc... The network responds if
the other side is busy, out of service, available, etc.  The two sides
then negotiate how the call will be routed and the call is then setup.
This is WAY oversimplified but it has the bulk of the ideas.

 

How does SS7 help me and when would I have to use it.

 

SS7 helps carriers maximize the use of the circuits that interconnect
them with others. Instead of using a channel and having it open for 30
seconds as the call is setup, user gets signaling (busy, ringing, not in
service), and call is torn down. It can  get the result in a split
second with out using any of my channels, all out of band and digital
rather than analog, (see 2600 signaling)

 

Most would never need to interface, or even know, what SS7 is and what
is does.  The SS7 network is the traffic control system, where as the
calls are the buses, cars, and trucks that use the 'streets' of the
PSTN.  When you stop at a red light, you may not realize that it my be
synchronized with all the street lights in the area and that they are
controlled from a central point, YOU just stop on red, go on green, and
go faster on Yellow!!!

 

If you want to know more about SS7 I would start be Gogooleing for Phone
Phreaking, Blue Boxing, Capt. Crunch.  This was the dominant BUSINESS
reason for pushing through the adoption of SS7 as a replacement for SS5

 

Look at the Wikipedia under SS5 and SS7 for a better understanding

 

http://en.wikipedia.org/wiki/Signaling_System_5

http://en.wikipedia.org/wiki/Signaling_System_7

 

 

Alex

 

 

 

 

*See other thread about this one!!!

 

________________________________

From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of mark
morreny
Sent: Wednesday, May 14, 2008 4:22 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] Question about SS7

 

Hi Mik

 

Could you elaborate on what you mean by " SS7 allows you to receive
large amounts of data, allows you to grow your
network over 100 T1's, etc."?  Why is SS7 a compusory requirement for a
large network instead of "all" network?  I have read quite a bit about
SS7 from Google and the part that is not discussed about is the
relationship of SS7 with VOIP.  When is SS7 needed in VOIP and what kind
of benefits SS7 can deliver and how?

 

Thanks alot for your info.

 

Regards,

Mark

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