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The Signaling Connection Control Part (SCCP) is defined in ITU-T Recommendations Q.711-Q.716. SCCP sits on top of Message Transfer Part 3 (MTP3) in the SS7 protocol stack. The SCCP provides additional network layer functions to provide transfer of noncircuit-related (NCR) signaling information, application management procedures and alternative, more flexible methods of routing.
SCCP provides a routing function that allows signaling messages to be routed to a signaling point based on dialed digits, for example. This capability is known as Global Title Translation (GTT), which translates what is known as a global title (for example, dialed digits for a toll free number) into a signaling point code and a subsystem number so that it can be processed at the correct application.
Routing rules are configured using the Command Line Interface as explained Section 5.4, “SCCP Management”
GTT is performed in two stages. First is matching the rule and second is actual translation.
For matching the rule, the called party address global title digits are matched with <digits> configured in
sccp rule create
Section 5.4.1.1, “Create Rule” command above. Once the digits match actual
translation is done
As explained in sccp rule create
Section 5.4.1.1, “Create Rule” command the
<digits> can be divided into sections using the "/" separate character. Each section defines set of
digits to be matched. Wild card * can be used to match any digits and ? can be used to match exatcly one digit
For example Rule is to match starting 4 digits (should be 1234) and doesn't care for rest; the <digits> in the command will be 1234/*. If the Rule is such that starting 3 digits should be 123, doesn't care for other three digits but last two digits should be 78; the <digits> in the command will be 123/???/78. If digit to digit matching is needed the the <digits> in the command will be exact digits to be matched without sections.
For translation each section in <mask> defined in sccp rule create
command defines how
replacement operation is performed. If <mask> defines K, the originally dialed digits are kept and if
<mask> defines R the digits from primary address or back address are used. The primary/backup address
should always define the point code and the translated address will always have this point code. If the primary/backup
address defines the subsystem number the translated address will also have this subsystem number. The address-indicator
of translated address is always from primary/backup address. See bellow examples
Match a eight digit number starting "800", followed by any four digits, then "9". If the translated digits is not null and if the primary/backup address has no Global Title, the Global Title from dialed address is kept with new translated digits.
Match "800800", followed by any digits Remove the first six digits. Keep any following digits in the Input. Add a PC(123) and SSN (8).
Match any digits keep the digits in the and add a PC(123) and SSN (8). If the translated digits is not null and if the primary/backup address has no Global Title, the Global Title from dialed address is kept with new translated digits.
The instance of org.mobicents.protocols.ss7.sccp.SccpStack
acts as starting point.
All the sccp messages sent by SCCP User Part are routed as per the rule configured in Router
The term SCCP User Part refers to the applications that use SCCP's services.
The SCCP User Part gets handle to SccpStack
by doing JNDI look-up as
explained in Section 7.3, “Access Point”
SccpStack
exposes org.mobicents.protocols.ss7.sccp.SccpProvider
that interacts directly with SccpStack. This interface defines the methods that will be used by SCCP User Part to send
org.mobicents.protocols.ss7.sccp.message.SccpMessage
and register
org.mobicents.protocols.ss7.sccp.SccpListener
's to listen for incoming SCCP messages.
SCCP User Part registers SccpListener for specific local subsystem number. For every incoming SccpMessage, if the called subsystem matches with this local subsystem, the corresponding SccpListner is called.
SccpProvider also exposes org.mobicents.protocols.ss7.sccp.message.MessageFactory
and
org.mobicents.protocols.ss7.sccp.parameter.ParameterFactory
to create new concrete SccpMessage viz.,
org.mobicents.protocols.ss7.sccp.message.UnitData
or
org.mobicents.protocols.ss7.sccp.message.XUnitData
passing the corresponding parameters created by leveraging
ParameterFactory.
SS7 Service
provides user with access point to SCCP
protocol/stack.
To get handle to SccpStack
do the JNDI look-up passing the
JNDI name configured in SS7 service as explained in Section 3.4.6, “Configuring SS7Service”
private static SccpProvider getSccpProvider() throws NamingException {
// no arg is ok, if we run in JBoss
InitialContext ctx = new InitialContext();
try {
String providerJndiName = "/mobicents/ss7/sccp";
return ((SccpStack) ctx.lookup(providerJndiName)).getSccpProvider();
} finally {
ctx.close();
}
}
Below is SCCP User Part example listening for incoming SCCP message and sending back new message
public class Test implements SccpListener {
private SccpProvider sccpProvider;
private SccpAddress localAddress;
private static SccpProvider getSccpProvider() throws NamingException {
// no arg is ok, if we run in JBoss
InitialContext ctx = new InitialContext();
try {
String providerJndiName = "/mobicents/ss7/sccp";
return ((SccpStack) ctx.lookup(providerJndiName)).getSccpProvider();
} finally {
ctx.close();
}
}
public void start() throws Excetpion {
this.sccpProvider = getSccpProvider();
int translationType = 0;
int subSystemNumber = 0;
GlobalTitle gt = GlobalTitle.getInstance(translationType,
NumberingPlan.ISDN_MOBILE, NatureOfAddress.NATIONAL, "1234");
localAddress = new SccpAddress(gt, 0);
this.sccpProvider.registerSccpListener(localAddress, this);
}
public void stop() {
this.sccpProvider.deregisterSccpListener(localAddress);
}
public void onMessage(SccpMessage message) {
if (message.getType() == MessageType.UDT) {
throw new IlleagalArgumentException("Dont like UDT");
} else if (message.getType() == MessageType.XUDT) {
XUnitData xudt = (XUnitData) message;
localAddress = ((XUnitData) message).getCalledPartyAddress();
SccpAddress remoteAddress = ((XUnitData) message)
.getCallingPartyAddress();
// now decode content
byte[] data = xudt.getData();
// some data encoded in
CallRequest cr = new CallRequest(data);
byte[] answerData;
if (cr.getCallee().equals(this.localAddress)) {
EstablihsCallAnswer eca = new EstablihsCallAnswer(cr);
answerData = eca.encode();
} else {
TearDownCallAnswer tdca = new TearDownCallAnswer(cr);
answerData = tdca.encode();
}
HopCounter hc = this.sccpProvider.getParameterFactory()
.createHopCounter(5);
XUnitData sccpAnswer = this.sccpProvider
.getMessageFactory()
.createXUnitData(hc, xudt.getProtocolClass(),
message.getCallingPartyAddress(), this.localAddress);
this.sccpProvider.send(sccpAnswer);
}
}
}