[asterisk-ss7] SS7 + T1 on Asterisk?

Thu Dec 8 00:14:28 CST 2011

I have a working setup on my personal system with a north american switch using an F Link over the 24th channel of a DS1, with the remaining 23 being bearer channels. It speaks 56k links like most north american switches, and has no problems whatsoever. It was pretty trivial, though to be honest I don't have a lot of time to do technical support for non customers.

I have a few tweaks in place regarding link timers that help it be a bit more compatible with my employer's Taqua T7000, but they're by no means mandatory.

Don't do goofy things like ITU signaling and E1s, you'll just confuse your DMS guy since I'm relatively certain the DMS-100 supports neither.

Here's my settings in chan_dahdi.conf (note that my link is on the 4th T1 in my chassis, you'll have to modify "cicbeginswith" and "sigchan" and "channel" accordingly. XXX is the anonymized point code of the employer's switch, YYY is one of our spare point codes in our block that I use for this test system)

group=2 ; DAHDI/g2/xxxx, if you set group=1 you use DAHDI/g1/xxxx
signalling=ss7
ss7type = ansi
networkindicator = national
cicbeginswith=73 ;changeme
adjpointcode = 005-108-XXX
pointcode = 005-108-YYY
defaultdpc = 005-108-XXX
linkset=1 ;must match setting in far end switch - this is a sane default
slc=1 ; must match setting in far end switch - this is a sane default
sigchan=96 ; changeme
echocancel=64
echocancelwhenbridged=yes
echotraining=yes
channel => 73-95 ;changeme

and in /etc/dahdi/system.conf (again, remember I am using the 4th t1 on my system)
span=2,1,1,esf,b8zs
56k=96 ;changeme
bchan=73-95 ; changeme
echocanceller=mg2,73-95 ; changeme

-Paul

On Dec 7, 2011, at 5:12 PM, Marcelo Pacheco wrote:

> Typically T1 (american) signaling ss7 links run at 56kbps instead of 64kbps.
> If your switch can run 64kbps links over a T1 timeslot, than the only remaining variable is ITU versus ANSI ISUP. They are incompatible (different message formats due to different network address sizes and other details).
> We use ITU ISUP all over the place without trouble. If the switch can do 64kbps links and ITU ISUP, then you should be able to use all existing E1 direct connection samples (without STP), except for the obvious E1=31 timeslots while T1=24 timeslots difference..
> ANSI might work. I won't go there because I have zero experience with ANSI SS7/ISUP (stability wise).
> With 2 T1 and a single signaling link it should allow for 47 voice channels and one signaling link.
> 
> Search for libss7 ansi 56kbps for the most difficult scenario. But if you can do ITU ISUP + 64kbps links, I would suggest that instead.
> We hardly see people talking about ANSI ISUP setups on this list, so it could be far less stable (at least it seems to get less usage).
> 
> On 12/07/11 16:25, Matt wrote:
>> In this case, our supplier is ourselves.  We have a DMS100, but the
>> switch guy is someone other than myself - I am the IP guy.
>> 
>> So basically if I understand you properly, I should be able to do the
>> SS7+T1 and get proper operation, provided the configuration on both
>> sides is right.
>> 
>> On Wed, Dec 7, 2011 at 1:06 PM, Marcelo Pacheco<marcelo at m2j.com.br>  wrote:
>>> If the DMS100 switch can talk signalling directly with Asterisk, without an
>>> STP, it should be possible to use a single timeslot for ss7 signalling, so
>>> with 2 T1 you could have 47 voice calls and one signalling channel. This is
>>> common with E1 setups. Also with E1 its common for a timeslot to be
>>> statically switched over to an STP (semi permanent call), allowing for
>>> access to the signaling network without a dedicated physically separate
>>> signaling link, but that's not usual in T1 land.
>>> 
>>> But what you ask is technically possible... However its important to
>>> PROPERLY LEARN SS7 terms to be able to communicate with your supplier.
>>> SS7 is a CARRIER LEVEL PROTOCOL. However people insist on winging it without
>>> proper training.
>>> Its like trying to become a backbone internet provider without properly
>>> learning inter and intra network routing protocols (like BGP and OSPF).
>>> 
>>> If you knew the general SS7/ISUP knowledge, you could quickly find the
>>> information you're looking for on Google.
>>> 
>>> PS: I live in E1 land... I'm just quoting information from the top of my
>>> head. I have no need for T1+SS7. E1+SS7 is a little simpler with Asterisk
>>> than T1+SS7 due to 56kbps data links, ANSI ISUP/SS7 and some other quirks.
>>> 
>>> Good luck. You'll need it.
>>> 
>>> 
>>> On 12/07/11 14:47, Matt wrote:
>>>> If I were to get a 2 span T1 card for Asterisk... and connect it to a
>>>> Nortel DMS100... can I run call traffic over the T1 and run SS7
>>>> signaling FOR the T1 over the other port?
>>>> 
>>>> Is there documentation on doing this anywhere?
>>>> 
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