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Components of an SS7 Network
Darkcyde Communications 1999.
digiphreq@webcrunchers.com
written 3.29.99 released a long time afterwards....

This paper is intended as a brief overview of the components that make up a
SS7 network.  What they do, how they relate to other components and so on.
This file won't be very complicated, but more of a small tutorial which just
scrapes the surface of SS7 as a whole.  This will focus more on networking
than anything else.

I. STP
II. SP
III. Datalinks
		A. Access Links
		B. Bridge Links
		C. Cross Links
		D. Diagonal Links
		E. Extended Links
		F. Fully Associated Links
IV. A Good Fuck You, I'm Out

I. STP:
	The STP or Signaling Transfer Point is basically the "switch" of the
SS7 network. It's rather similar to the switch in the PSTN.  While there is a
difference in that a switch of the PSTN routes voice calls/connections, the
STP routes digital traffic in the SS7 network.  It basically routes to the
outside world.  The pairing or networking of these is pretty simple yet quite
complex.  They work on a simple ladder, tree, or more sophisticated a
hierarchical basis.  You basically have some STPs that provide access and
routing for a node or local network.  Next you have the STPs which
connectother network's STPs together through Access Links (discussed later).
Next you have STPs which completely run the show.  They work on a much larger
scale and route everything from a selectided Wide Area Network of WAN.
Graphically it looks kind of like this.

		Local to Local
		Local to Regional
		Regional to Regional
		Regional to International
		International to International
		Regional to International
		Regional to Regional
		Local to Regional
		Local to Local

II. SP:
        The SP of Singaling Point is a lot like a telephone number on the
PSTN.  In the case of SS7 they are called SPC or Signal Point Codes.  Thus
making a service with such a code a Signaling Point.  At the same time SP is
also considered a suffix to much larger grouping acronyms.  You have the SSP,
SCP, AND THE MSC.

                SSP- This is basically a branch of the SS7 network which
                offers voice connections. Which is part of a SS7 Telephone
                Network (SS7TN).

                SCP- This brach offers database services.  Not really part of
                the whole scheme of things.

                MSC- This branch is in control of the mobile units which
                provide voice connections.

III. Data Links:
	In the SS7 network you must send data of numerous types to other SPs
and this is done through links.  Basically they don't concern themselves with
how they transmit the data, but more on what they are actually transmitting.
Which then breaks this down further so you have several types of links.
Which categorize each data type.

	(A) Access Links
	(B) Bridge Links
	(C) Cross Links
	(D) Diagonal Links
	(E) Extended Links
	(F) Fully Associated Links

	Access Links- These provide the link between the basic node and STP
        pairs. They are what opens the connection between the STP and keeps
        it up and running.

	Bridge Links- These are what more or less connect STPs on local to
        local networks. The more of these Bridge Links you have the more
        flexibility in routing the services through STPs you will have.  Four
        of these links are required to connect all the linked STPs of one
        area to the STPs of another area.
	
	Cross Links- In the whole scheme of making sure one of the STPs of a
        pair doesn't get screwed up they don't have a way to provide service,
        you have Cross Links which connect two paired STPs together as so
        they are more able to communicate. In most cases the pair is doing
        the same task and this can also cause the pair to speed the overall
        performance.
	
	Diagonal Links- These are exactly like Bridge Links only that they
        connect the smaller network of local networks and STPs to a Regional
        STP which might have several of these smaller networks hooked to it.
        Just remember they are Bridge Links on steriods which connect Local
        to Regional.
	
	Extended Links- These again are nothing more than really large Bridge
        Links.  Instead of hooking a STP pair to a regional to then another
        local STP pair these link them directly.  Kind of like this.

				______________Regional STP__________________
			   /											\
			  /												 \
	     STP Pair 1----------Extended Link---------------STP Pair 2
	   
	 Fully Associated Links- These occur when a company owns two or more
         nodes and wishes to connect them internatlly while avoiding a STP.
         This is only done when a company owns the two nodes and at no other
         time.  Thus making the nodes assocciated through the same company
         which is why these links are called Associated Links...
	 
Ok, well that's it.  If it thoroughly confused you, read it again.  If you
allready knew this crap good for you smart ass.  Why don't you go learn
something new now.  I hope to put a more detailed article on Components of an
SS7 Network up soon.
	

