SS7:- It is a Common Channel Signaling system designed by ITU –T in response to a demand for more features & integrated data services. It defines the architecture, procedures & protocols for information exchange over digital network. It is designed to support call setup, routing, billing, database information, & special services of PSTNs.
The gateway office uses application protocol of SS7 for more than one interface, such as MAP for C/D, BSAP for A interface.
• MTP (Message Transfer Part)
MTP: - It is responsible for transmitting signaling messages for its users. It ensures reliable signaling message transfer over signaling network by avoiding or minimizing message loss, duplicate or out-of-sequence in case of any system fault or signaling network fault.
It consists of 3 functional layers:-
1. Signaling data link function (MTP-1)
2. Signaling link function (MTP-2)
3. Signaling network function (MTP-3)
MTP-1:- It defines the physical, electrical & functional characteristics of a signaling data link, as well as access method. It is same as physical layer of OSI model. It used to generate & receive signals on physical channels.
MTP-2:- It corporate with MTP-1 to provide a signaling link for reliable signaling message transfer between 2 signaling points. Its function includes signal unit delimitation, signal unit alignment, error detection & correction, initial alignment, flow control & signaling link error monitoring.
MTP-3:- It enables management message transmission between signaling point for the purpose of ensuring a reliable transfer of signaling message over the signaling network, in the case that signaling link or signaling transfer point fails.
Signaling network functions are divided into signaling message handling & signaling network management.
Signaling Message Handling - This function ensures that signaling message originated by a particular user part at a signaling point (originating) are delivered the same user part at destination point indicated by sending user part.
Signaling Network Management - It is used to provide re-configuration of signaling network in case of failure & to control traffic in case of congestion (heavy traffic). It includes signaling traffic management, signaling link & route management.
SCCP (Signaling Connection Control Part):-
It provide additional function to MTP to cater both connection-less & connection oriented network services to transfer circuit related & non-circuit related signaling information & other type of information between switches & specialized centers in telecommunication network through SS7 network.
It is also used for transfer of circuit related & non-circuit related signaling information
of the ISDN user part with or without end to end signaling connection.
SCCP Services falls into 4 classes
1. Class 0 - Basic connectionless services.
2. Class 1 - In sequence delivery connectionless services.
3. Class 2 - Basic connection-oriented services.
4. Class 3 - Flow control connection-oriented services.
TCAP (Transaction Capabilities Application Part):-
It refers to the capabilities of providing information, request & responses. It provided functions & procedures, irrerevalent to a large variety of application between switches & databases in telecommunication network. It consists of
• TCAP - It corresponds to layer 7 of OSI model.
• ISP (Intermediate Service Part) - It corresponds to layer 4 to 6 of OSI model.
It uses SCCP supported addressing mode & is based on connection-less & connection oriented services of the SCCP.
Connection-less mode is applied in case of real-time transfer of a small amount of data.
Connection oriented mode is applied in case of non-real-time transfer of a large amount of data.
MAP (Mobile Application Part):-
This protocol defines how messages are exchanged between network entities for the purpose of realizing the MS roaming function.
The network entities involve here includes MSC, HLR, AUC (Authentication Center), MC, SCP.
In CDMA, C, D, E, T & Q interfaces all can transfer MAP messages therefore they all are referred as MAP interfaces.
MAP Functions:-
1. Location & data management - They are the basis of other services of mobile network.
It function includes
• Realizing MS automatic roaming & roaming restriction.
• Providing subscriber data for other services.
• Maintaining data consistency between HLR & VLR.
• Protecting network resources from being accessed by invalid subscribers.
2. Handoff Management - It ensures interconnection & interworking between mobile equipment of different suppliers, so that subscriber can roam freely in different MSC's. It function includes
• Basic handoff function namely forward handoff, backward handoff & handoff to third party.
• Transparent signaling transmission after handoff.
• Circuit Management.
3. Call Function - It includes origination request used to obtain calling subscriber data from the HLR or SCP.
• Location request used to obtain location information of called subscriber from HLR.
• Forwarding request to obtain forward-to request.
4. Supplementary Services - It supports various call related & non-call related supplementary services, like conference calling. The MAP can identify & support SCP oriented features operations.
5. Intelligent Network (IN) Services - It supports following IN functions
• Intelligent controls.
• SCP based forwarding services.
• Service recovery.
• In prepaid charging (PPC) service, MAP is responsible for restoring the MSCe or SCP in the case of any exception.
6. SMS Services - MAP support following functions
• MS initiating a short message.
• MS termination a short message.
• Short message broadcast.
• Short message notice.
BSAP (Base Station Application Part):-
It is the application protocol used for A interface. Interface between MSC & BSC is A interface. The A interface includes A1, A2 & A5 interface.
A1 - It transfers call control related signaling.
A2 - It transfer 64Kbps PCM voice service.
A5 - It transfer circuit-switched data service.
BSAP describes 2 types of messages -
• BS Management Application Part (BSMAP)
• Direct Transfer Application Part (DTAP)
BSMAP supports the resources management & circuit equipment management procedures between MSC & BSC.
DTAP transfers mobility management messages between BSC & MSC.
BSAP protocols defines message format & procedures to support the wireless service function between MSC & BSC. Major A interface signaling procedure includes Mobile origination, Mobile Termination, Call Clearing.
TUP (Telephone User Part):-
It defines the circuit signaling function necessary for call control, namely the content of signaling message transferred between switching offices.
ISUP (Integrated Service Digital Network User Part):-
It defines signaling messages functions & procedure required to control voice & non-voice services. It not only implements the function of TUP & Data User Part (DUP) but also realize diversified ISDN services.
The ISUP supports basic bearer services i.e. establishing, monitoring & releasing 64Kbps circuit between subscriber terminals & providing lower layer message transfer capabilities for subscriber.
It also support following supplementary services,
• Calling Line Identification Presentation & Restriction (CLIP & CLIR).
• Connected Line Identification Presentation & Restriction (COLP & CLOR).
• Call Forwarding, Call Holding, Call Waiting, User to User Signaling, Three-Way Calling, Conference Call.
ISUP also supports MultiDestination signaling point function.
Read more at http://telecomtigers.blogspot.com/search/label/Signaling#mBYH8xE9StpIHC58.99
The gateway office uses application protocol of SS7 for more than one interface, such as MAP for C/D, BSAP for A interface.
It is classified into 2 parts
• User Part• MTP (Message Transfer Part)
MTP: - It is responsible for transmitting signaling messages for its users. It ensures reliable signaling message transfer over signaling network by avoiding or minimizing message loss, duplicate or out-of-sequence in case of any system fault or signaling network fault.
It consists of 3 functional layers:-
1. Signaling data link function (MTP-1)
2. Signaling link function (MTP-2)
3. Signaling network function (MTP-3)
MTP-1:- It defines the physical, electrical & functional characteristics of a signaling data link, as well as access method. It is same as physical layer of OSI model. It used to generate & receive signals on physical channels.
MTP-2:- It corporate with MTP-1 to provide a signaling link for reliable signaling message transfer between 2 signaling points. Its function includes signal unit delimitation, signal unit alignment, error detection & correction, initial alignment, flow control & signaling link error monitoring.
MTP-3:- It enables management message transmission between signaling point for the purpose of ensuring a reliable transfer of signaling message over the signaling network, in the case that signaling link or signaling transfer point fails.
Signaling network functions are divided into signaling message handling & signaling network management.
Signaling Message Handling - This function ensures that signaling message originated by a particular user part at a signaling point (originating) are delivered the same user part at destination point indicated by sending user part.
Signaling Network Management - It is used to provide re-configuration of signaling network in case of failure & to control traffic in case of congestion (heavy traffic). It includes signaling traffic management, signaling link & route management.
SCCP (Signaling Connection Control Part):-
It provide additional function to MTP to cater both connection-less & connection oriented network services to transfer circuit related & non-circuit related signaling information & other type of information between switches & specialized centers in telecommunication network through SS7 network.
It is also used for transfer of circuit related & non-circuit related signaling information
of the ISDN user part with or without end to end signaling connection.
SCCP Services falls into 4 classes
1. Class 0 - Basic connectionless services.
2. Class 1 - In sequence delivery connectionless services.
3. Class 2 - Basic connection-oriented services.
4. Class 3 - Flow control connection-oriented services.
TCAP (Transaction Capabilities Application Part):-
It refers to the capabilities of providing information, request & responses. It provided functions & procedures, irrerevalent to a large variety of application between switches & databases in telecommunication network. It consists of
• TCAP - It corresponds to layer 7 of OSI model.
• ISP (Intermediate Service Part) - It corresponds to layer 4 to 6 of OSI model.
It uses SCCP supported addressing mode & is based on connection-less & connection oriented services of the SCCP.
Connection-less mode is applied in case of real-time transfer of a small amount of data.
Connection oriented mode is applied in case of non-real-time transfer of a large amount of data.
MAP (Mobile Application Part):-
This protocol defines how messages are exchanged between network entities for the purpose of realizing the MS roaming function.
The network entities involve here includes MSC, HLR, AUC (Authentication Center), MC, SCP.
In CDMA, C, D, E, T & Q interfaces all can transfer MAP messages therefore they all are referred as MAP interfaces.
MAP Functions:-
1. Location & data management - They are the basis of other services of mobile network.
It function includes
• Realizing MS automatic roaming & roaming restriction.
• Providing subscriber data for other services.
• Maintaining data consistency between HLR & VLR.
• Protecting network resources from being accessed by invalid subscribers.
2. Handoff Management - It ensures interconnection & interworking between mobile equipment of different suppliers, so that subscriber can roam freely in different MSC's. It function includes
• Basic handoff function namely forward handoff, backward handoff & handoff to third party.
• Transparent signaling transmission after handoff.
• Circuit Management.
3. Call Function - It includes origination request used to obtain calling subscriber data from the HLR or SCP.
• Location request used to obtain location information of called subscriber from HLR.
• Forwarding request to obtain forward-to request.
4. Supplementary Services - It supports various call related & non-call related supplementary services, like conference calling. The MAP can identify & support SCP oriented features operations.
5. Intelligent Network (IN) Services - It supports following IN functions
• Intelligent controls.
• SCP based forwarding services.
• Service recovery.
• In prepaid charging (PPC) service, MAP is responsible for restoring the MSCe or SCP in the case of any exception.
6. SMS Services - MAP support following functions
• MS initiating a short message.
• MS termination a short message.
• Short message broadcast.
• Short message notice.
BSAP (Base Station Application Part):-
It is the application protocol used for A interface. Interface between MSC & BSC is A interface. The A interface includes A1, A2 & A5 interface.
A1 - It transfers call control related signaling.
A2 - It transfer 64Kbps PCM voice service.
A5 - It transfer circuit-switched data service.
BSAP describes 2 types of messages -
• BS Management Application Part (BSMAP)
• Direct Transfer Application Part (DTAP)
BSMAP supports the resources management & circuit equipment management procedures between MSC & BSC.
DTAP transfers mobility management messages between BSC & MSC.
BSAP protocols defines message format & procedures to support the wireless service function between MSC & BSC. Major A interface signaling procedure includes Mobile origination, Mobile Termination, Call Clearing.
TUP (Telephone User Part):-
It defines the circuit signaling function necessary for call control, namely the content of signaling message transferred between switching offices.
ISUP (Integrated Service Digital Network User Part):-
It defines signaling messages functions & procedure required to control voice & non-voice services. It not only implements the function of TUP & Data User Part (DUP) but also realize diversified ISDN services.
The ISUP supports basic bearer services i.e. establishing, monitoring & releasing 64Kbps circuit between subscriber terminals & providing lower layer message transfer capabilities for subscriber.
It also support following supplementary services,
• Calling Line Identification Presentation & Restriction (CLIP & CLIR).
• Connected Line Identification Presentation & Restriction (COLP & CLOR).
• Call Forwarding, Call Holding, Call Waiting, User to User Signaling, Three-Way Calling, Conference Call.
ISUP also supports MultiDestination signaling point function.
Read more at http://telecomtigers.blogspot.com/search/label/Signaling#mBYH8xE9StpIHC58.99
No comments:
Post a Comment