Dasar Telekomunikasi. Pensinyalan

Transkripsi

1 Dasar Telekomunikasi Pensinyalan

2 Definition The IEEE defines signaling as the exchange of information specifically concerned with the establishment and control of connections and the transfer of user-to-user and management information in a telecommunication network Conventional signaling has evolved with the telephone network

3 With telephony, signaling is broken down in three functional areas: Supervisory Address Call progress: audible-visual Another signaling breakdown is Subscriber signaling Interswitch (interregister) signaling

4 Supervisory Signaling Supervisory signaling provides information on line or circuit condition It informs a switch whether a circuit (internal to the switch) or a trunk (external to the switch) is busy or idle, when a called party is off-hook or on-hook, and when a calling party is on-hook or off-hook

5 Address Signaling Address signaling directs and routes a telephone call to the called subscriber It originates as dialed digits or activated push-buttons from a calling subscriber The local switch accepts these digits and, by using the information contained in the digits, directs the call to the called subscriber If more than one switch is involved in the call setup, signaling is required between switches (both address and supervisory) Address signaling between switches is called interregister signaling

6 Call Progress: Audible-Visual This type of signaling we categorize in the forward direction and in the backward direction In the forward direction there is alerting This provides some sort of audible-visual means of informing the called subscriber that there is a telephone call waiting This is often done by ringing a telephone s bell A buzzer, chime, or light may also be used for alerting.

7 In the backward direction, among these are audible tones or voice announcements that will inform the calling subscriber the following: Ringback This tells the calling subscriber that the distant telephone is ringing. Busyback This tells the calling subscriber that the called line is busy ATB-All Trunks Busy There is congestion on the routing. Sometimes a recorded voice announcement is used here. Loud Warble on Telephone Instrument Timeout This occurs when a telephone instrument has been left off-hook unintentionally

8 Klasifikasi Signaling Signalling Subscriber - exchange Exchange - exchange Channel associated Common channel

9 Areas of Signaling There are mainly three areas of signaling during a telephone call : between subscribers and exchanges. within exchanges. between exchanges. between exchanges Exchange A Exchange B within exchange between Subscriber and exchange

10 Subscriber Exchange Signaling Dari pelanggan ke sentral Informasi kondisi off-hook Informasi nomor B (nomor tujuan) Informasi jumlah uang yang dimasukkan (khusus untuk payphone) Informasi kondisi on-hook ketika panggilan usai Dari sentral ke pelanggan A (nomor pemanggil) Informasi bahwa sentral siap menerima nomor B Informasi mengenai status B (busy atau tidak) Informasi kongesti atau interception Sinyal charging (khusus untuk payphone) Dari sentral ke pelanggan B Sinyal ringing untuk menarik perhatian pelanggan B

11 Pelanggan A mengangkat telepon, hal ini dapat berarti A ingin menghubungi seseorang Pesawat A berbunyi lalu menjawab Sentral dapat mendeteksi keadaan telepon apakah merupakan panggilan atau jawaban Sentral menanggapi panggilan dengan mengirimkan dial tone A mengirimkan digit nomor B (B number) Sentral menganalisa digit lalu mencek apakah B ada dan tidak busy. Ringing tone dikirimkan ke A sedangkan sinyal ringing ke B B mengangkat handset, sentral mendeteksinya sebagai jawaban Ketika A dan B menyimpan handset, sentral mendeteksi sebagai sinyal clear lalu koneksi diputuskan N O M O R A sentral Off-hook Dialling tone Ringing tone Ringing signal ~425Hz ~90V, Hz answer conversation Clear forward Clear back B

12 Off-Hook Signaling (Analog) Loop Start (almost all telephones) Seizure is detected when current flows through local loop, due to off-hook Ground Start (antar PBX (Private Branch Exchange) atau antara PBX dengan Sentral Lokal) Seizure (upaya pendudukan kanal komunikasi) is detected when one wire is grounded Seizure can be initiated in both directions Untuk mengindikasikan status on/off-hook ke sentral lokal Ground Start Source: Cisco Interactive Mentor

13 Loop Start Ground Start Switch Switch

14 Exchange exchange Signaling Channel Associated Signalling (CAS) Common Channel Signalling (CCS)

15 Common Channel Signaling Signaling dilakukan menggunakan kanal yang juga digunakan untuk mentransfer informasi

16 Common Channel Signalling Informasi speech dan informasi signalling mengalir melalui jalur yang sama Beberapa macam CAS Signalling dilakukan secara bersama pada kanal untuk speech (DC signalling, inband) Signalling dilakukan pada kanal yang sama dengan speech tetapi menggunakan frekuensi yang berbeda (out-band) Contoh: Signalling dilakukan melalui timeslot 16 (PCM signalling)

17 Pelanggan A Pelanggan B sentral sentral seizure Seizure acknowledgment B number answer A- hangs up conversation Clear back Clear forward B- hangs up

18 Forward and Reverse direction Forward signal mengalir dari sentral telepon tempat A berada menuju sentral telepon tempat B berada Backward signal mengalir pada arah yang berlawanan dengan forward signal

19 Channel Associated Signaling Signaling menggunakan kanal yang terpisah dari kanal untuk mentransfer informasi Terdapat jaringan signaling tersendiri

20 Signaling System NO. 7 Signaling System Number 7 (SS #7)

21 Signaling System No. 7 (SS No. 7) was developed to meet the stringent signaling requirements of the all-digital network based on the 64-kbps channel It is a data network entirely dedicated to interswitch signaling defined by Telecommunication Standardization Sector (ITU-T). defines the procedures and protocol by which network elements in the PSTN exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup,routing and control.

22 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, andthree-way calling efficient and secure worldwide telecommunications

23 SS No. 7 is described as an international standardized general-purpose common-channel signaling system that: Is optimized for operation with digital networks where switches used stored-program control (SPC) Can meet present and future requirements of information transfer for interprocessor transactions with digital communications networks for call control, remote control, network database access and management, and maintenance signaling Provides a reliable means of information transfer in correct sequence without loss or duplication

24 SS7 Signaling Points Diagram

25 Signaling Architecture Components Component Signal Switching Points (SSP's) Function SSP's are telephone switches (end offices or tandems) equipped with SS7-capable software and terminating signaling links. They generally originate, terminate, or switch calls. STP's are the packet switches of the SS7 network. The receive Signal Transfer Points (STP's) and route incoming signaling messages towards the proper destination. They also perform specialized routing functions. SCP's are databases that provide information necessary for Signal Control Points (SCP's) advanced call-processing capabilities

26 Basic SS7 Signalling Architecture

27 SS7 Signaling Links

28 SS7 Link Types A Link: An access link connects a SSP or SCP to an STP. B Link: A bridge link connects an STP to another STP. C Link: A cross link connects two mated pair STP. This is done to improve reliability D Link: A diagonal links similarly to a B link E Link: An extended link connects an SSP to an extra STP in the event that the A link cannot reach one. F Link: A fully associated link connects SSP s

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30 CCS7 Network Components The CCS7 Network consists of the following Components : SP Signaling Point : The SP is the source or originating entity of the signaling message. STP Signaling Transit Point : These entities transfer the signaling message to another SP or STP without processing the signaling message. SRP Signaling Relay Point : These are STPs with ability to process the signaling message. SEP Signaling End Point : The SEP is defined to be the terminating point of the signaling message

31 SS7 Network Architecture A typical SS7 network is a mixture of various SPs STPs SRPs and SEPs, As shown below : STP (SPC=200) SP (SPC=100) SRP (SPC=400) SEP (SPC=500) STP (SPC=300)

32 CCS7 Terminologies SPC : SPC is defined as signaling point code which uniquely identifies each element within the SS7 network. Signaling Links : The signaling links transmit signaling messages between the communicating entities. Signaling Link Set : A signaling link set is a collection of signaling links between two signaling entities. Signaling Route : A signaling route is defined to be the path through which signaling messages are exchanged between two entities. There can be multiple signaling routes between two SPCs, wherein there will be one primary route and several alternate routes.

33 SS7 Routing Modes Associated Mode : In the associated mode, the signaling link is routed together with the circuit group belonging to the link. In other words, the signaling link is directly connected to signaling points which are also the terminal points of the circuit group. This mode of signaling is recommended when the capacity of the traffic relation between the signaling points A and B is heavily utilized. Associated Mode of Signaling

34 SS7 Routing Modes Quasi associated mode : In the quasi-associated mode of signaling, the signaling link and the circuit group run along different routes, the circuit group connecting the signaling point. A is directly connected with the signaling point B. For this mode the signaling, the circuit group is carried out via one or more defined signaling transfer points. This signaling mode is favorable for traffic relations with low capacity utilization, as the various signaling links can be used for several destinations.

35 SS7 Network Structure SPC=100 NAT 1 SPC=300 SPC=200 SPC=800 SPC=100 NAT 0 SPC=400 SPC=400 SPC=600 NAT 1 SPC=500 SPC=700 NAT 1 SPC=900 SPC=100 SPC=100 INAT 0 SPC=200 SPC=300 SPC=800

36 SS7 Protocol Structure SS7 protocol stack can be broadly divided into two main categories : A ) MTP Message Transfer Part : The message transfer part has three levels, namely MTP Layer 1, Layer 2 and Layer 3. The message transfer part (MTP) represents a user-neutral means of transport for messages between the users. B ) User Parts (UP) : Each user part (UP) encompasses the functions, protocols and coding for the signaling via SS7 for a specific user type (e.g. data service, ISDN). In this way, the user parts control the set-up and release of circuit connections, the processing of facilities as well as administration and maintenance functions for the circuits.

37 SS7 Protocol Structure SS7 Users B S S A P TCAP Users TCAP SCCP I S U P M U P Other User Parts MTP Layer 3 (Network Management) MTP Layer 2 (Signaling Link) MTP Layer 1 (Signaling Data Link)

38 Contoh signaling CCS#7 IAM: Paket pertama yang membawa informasi nomor B Sisa nomor berikutnya dibawa oleh SAM ACM: Paket yang berisi konfirmasi dari sentral B bahwa seluruh digit sudah diterima; selain itu paket ini berisi pula informasi apakah panggilan dapat di-charge atau tidak juga apakah pelanggan tujuan sibuk atau tidak Ketika pelanggan B offhook, sentral B mengirimkan sinyal ACN untuk mengaktifkan charging