OUT-OF-BAND SIGNALING Thought For The Week No Question Is A Bad Question!

INTRODUCTION In Telephone Circuits, Signals Can Be Sent In Two Different Ways: In-Band Out-of-Band Signals Include: Digits That You Dial Dial Tone Ringing Disconnect Signals etc.

In-Band Signaling

IN-BAND vs. OUT-OF-BAND In-Band Signaling Signaling Made Up Of Tones Which Pass Within The Voice Frequency Band And Are Carried Along The Same Circuit As The Talk Path. Out-of-Band Signaling Signaling That Is Separated From The Channel That Is Carrying The Information, e.g. Voice.

Voice Routing If Endpoints In Same CO For Example Lucent 5ESS Nortel DMS Class 5 Office Local Loop Local Loop If Endpoints In Same CO 95% Of Local Loop Circuits Are In-Band Signaling

Voice Routing If Endpoints Connect To Different CO’s (One-Hop) Class 5 Office Class 5 Office Local Loop For Example Lucent 4ESS Local Loop Class 4 Office (W/ Tandem Switch) If Endpoints Connect To Different CO’s (One-Hop) Interoffice Signaling Via In-Band Signaling

Out-Of-Band-Band Signaling

Separate Signaling Network COMMON CHANNEL SIGNALING (CCS) Common Channel Signaling Is The Most Prominent Out- of-Band Signaling System. Common Channel Interoffice Signaling A Way Of Transmitting All Signaling Information For A Group Of Trunks In A Separate Channel. Class 5 CO Class 5 CO Voice Path Separate Signaling Network

COMMON CHANNEL SIGNALING (SS7) Common Channel Signaling System No. 7 (i.e. SS7) A Global Standard For Telecommunications Defined By The International Telecommunication Union (ITU) Telecommunication Standards Sector (ITU-T). The ITU Definition Of SS7 Allows For National Variants Such As The American National Standards Institute (ANSI) Standards Used In North America And The European Telecommunications Standards Institute (ETSI) Standard Used In Europe.

COMMON CHANNEL SIGNALING (SS7) The SS7 Network And Protocol Are Used For: Basic Call Setup, Management, And Tear Down. Wireless Services Such As Personal Communications Services (PCS), Wireless Roaming, And Mobile Subscriber Authentication. Local Number Portability (LNP). Toll-free (800/888) And Toll (900) Wireline Services. Enhanced Call Features Such As Call Forwarding, Calling Party Name/Number Display, And Three-way Calling Efficient And Secure Worldwide Telecommunications.

SIGNALING SYSTEM 7 (SS7) SCP SCP STP STP STP STP SSP SSP Voice Path BRI BRI Residential PRI Residential PRI PBX PBX

SIGNALING SYSTEM 7 (SS7) There Are Three Kinds Of Elements In The SS7 Network. SSP - A Service Switching Point (Class 5 CO Switch). SSPs Are Switches That Originate, Terminate, Or Tandem Calls. An SSP Sends Signaling Messages To Other SSPs To Setup, Manage, And Release Voice Circuits Required To Complete A Call.

SIGNALING SYSTEM 7 (SS7) - CONTINUED - An SSP May Also Send A Query Message To A Centralized Database (An SCP) To Determine How To Route A Call (E.G., A Toll-free 1-800/888 Call In North America). SCP – Service Control Point, Various Data Bases. An SCP Sends A Response To The Originating SSP Containing The Routing Number(s) Associated With The Dialed Number.

SIGNALING SYSTEM 7 (SS7) - CONTINUED - An Alternate Routing Number May Be Used By The SSP If The Primary Number Is Busy Or The Call Is Unanswered Within A Specified Time. Actual Call Features Vary From Network To Network And From Service To Service.

FUNCTIONS OF THE SS7 NODES THE SERVCE SWITCHING POINT (SSP) The SSP Is The Local Exchange To The Subscriber And The Subscribers Interface To The Network. The SSP Creates SS7 Signaling Units At The Sending SSP And Translates Them At The Receiving SSP. The SSP Supports Database Access Queries For 800/900 Numbers.

FUNCTIONS OF THE SS7 NODES THE SERVCE TRANSFER POINT (STP) The STP Is A Router For The SS7 Network. It Relays Messages Through The Network, But Does Not And Translates Them At The Receiving Originate Them. STPs Are Installed As A national STP. An International STP. A Gateway STP. SS7 Is An International Standard, Nevertheless, There Are “Some” Differences Between The Way That Countries Implement SS7.

FUNCTIONS OF THE SS7 NODES THE SERVCE TRANSFER POINT (STP) In The United States, SS7 Is Implemented To ANSI Standards. In Many Other Countries SS7 Is Implemented To ITU-T

STP FUNCTIONS In The United States, STPs Provides Conversions Between ANSI SS7 And ITU-T SS7. Collect And Store Traffic And Usage Statistics For OAM. Collects Billing Information.

FUNCTIONS OF THE SS7 NODES THE SERVCE CONTROL POINT (SCP) Acts As The Interface Into The Telephone Company Databases. Business Services Database (BSDB) Depends On RBOC and Subscriber Call Management Services Database (CMSDB) Routing Information, Some Billing Information Reaction To Congestion SCP

FUNCTIONS OF THE SS7 NODES THE SERVCE CONTROL POINT (SCP) Acts As The Interface Into The Telephone Company Databases. Line Information Database (LIDB) Calling Card, Billing, Third Party Billing. PINs, Custom Calling Features. Home Location Register (HLR) Used In Cellular Networks. Visitor Location Register (VLR) SCP

SS7 LINK CLASSIFICATION A Link Is Another Name For A Communications Channel Or Circuit. A Link Known Also As Access Links. Used To Connect SSP s And SCPs To STPs. B Link Known Also As Bridge Links. Used To Connect Mated STP Pairs To Other Mated STP Pairs. C Link Known Also As Cross Links. Used To Connect STPs Together To Form Mated Pairs.

SS7 LINK DIVERSITY STPs Are Deployed As Mated Pairs. Uses A Fully Meshed Topology Which Provides 100 Percent Redundancy. Any Single Point Of Failure Does Not Bring Down The System. C Link Known Also As Cross Links. Used To Connect STPs Together To Form Mated Pairs.

LOGICAL vs. PHYSICAL ADDRESSES The Telephone User Should Not Have To Worry About SS7 Addresses. A Customer Should Only have To Enter A Called Party Telephone Number – Even Non-Conventional Telephone Numbers Such As 911, A Mobile Phone Number, Or An 800/900 Number. SS7 Accepts These Logical Addresses And Translates Them To Routable Numbers. C Link Known Also As Cross Links. Used To Connect STPs Together To Form Mated Pairs.

SUMMARY Signaling Is The Exchange Of Information Between The Components Of A Telephony For The Purposes Of Establishing, Monitoring, Or Releasing Phone Circuits. The Four Main Functions Of Switch Signaling Are: Alerting Transmitting Address Information Supervising Transmitting Information.

SUMMARY - CONTINUED Common Channel Signaling Was Developed By AT&T In The 1970s After They Had Lost Significant Revenue To Fraudulent Use Of In-Band Signaling. Signaling System No.7 (SS7) Is A Particular Type Of CCS Employed By Modern Telephone Networks. SS7 Is A Standard Developed And Published By The ITU. In SS7, Any Central Office Or Other Telecommunications Switching Facility Is Called A Service Switching Point (SSP). SCPs Supply Customer Information To STPs. STPs Act As Intermediaries For Signals Moving Between SCPs And SSPs.

Toll Call Using AT&Ts Five-Level Network Five-Level PSTN Network Class 1 Regional Center Norway, IL Class 1 Regional Center Rockdale, GA Class 2 Section Center Eau Claire, WI Toll Call Using AT&Ts Five-Level Network Class 2 Section Center Greensboro, NC Class 3 Primary Center Stevens Point, WI Class 3 Primary Center Fayetteville, NC Class 4 Toll Center WaUsau, WI Class 4 Toll Center Fayetteville, NC Digital Line Card Analog Line Card Analog Line Card Digital Line Card Intra-Office Call Digital T1 Local Loop Class 5 Local Office (Wausau, WI) Analog Local Loop Class 5 Local Office (Raeford, NC) Analog Local Loop Digital T1 Local Loop Office Office Residence Residence