How SS7 Works

jrambar · February 2008

Can someone explain SS7 to me and how it works? What type of medium can SS7 be transfered through? DS3's?

Cucumber · February 2008

You can run SS7 over DS0's, E1's, etc.

SS7 follows a layered architecture that can be mapped to the OSI layers

jrambar · February 2008

And since a DS3 is 672 DS0's, it can run through that too? I'm a newbie in the voice architecture world, so excuse my questions.

Next question, do you think SIP is phasing out SS7? I have been reading up on it and there have been pro's and con's...being that one is packetized and the other channelized.

Cucumber · February 2008

Well I worked with SMS systems. Those boxes where connected to the SS7 network through a couple of DS0s, so yes, you can run SS7 over DS0s. Provided you have the appropiate network interfaces at the box and at the MTPs (I think thats the name of the SS7 "hubs", cant remember).

I dont have numbers regarding the quantity of poviders using SIP vs providers using SS7.

Anyway, what do I know is that SS7 networks are huge worlwide. At least that was 4 years ago when I was working for a cell phone company, they used SS7, so all the others cell companies they had roaming agreements with. All their SS7 networks where connected to each other and there was even a range of "SS7 addresses" (PointCodes IIRC) organized per-country. That huge.

I would make a wild guess and say they will still use SS7 for many years, all their (very expensive) gear uses and is designed to work with SS7.

Hope this info helps.

dtlokee · February 2008

I was looking at a network design for one of the carriers that had many 10 gigabit links in it to carry SS7 over IP in band, so I would guess it's still huge and going to be around for a long time to come.

Cucumber · February 2008

Im sorry I think I was overlooking the questions at hand. Reading too fast here.

I dont know wether a DS3 can work with SS7, you would have to check whether you have proper interfaces at the box you want to connect and at the MTP.

Regarding the operation of SS7, its somewhat simple. You have MTPs instead of routers, the topology is a redundant star network (all devices hook into two MTPs for redundancy), the equivalent of IP addresses are known as Point Codes, and you have also SSN numbers that are somewhat like a TCP port number.

Point Codes may be ANSI or ITU, ITU PCs may have leading zeroes whereas the ANSI Point Codes can not. This is a nuissance when you are connecting SS7 networks together in that case you need an ITU-ANSI gateway.

Thats all I can remember now, its been a while.

How SS7 Works

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