Multi-Service Networks ISDN Integrated Services Digital Network Narrowband ISDN (Schmalband-ISDN) www.comnets.uni-bremen.de ISDN - 9-1
Integrated Services Digital Network: Service Integration telephone data graphics text voice ISDN universal communication socket telefax text system computer www.comnets.uni-bremen.de ISDN - 9-2
Interests: Users Standardization Bodies: ITU Network Operators Manufacturers ISDN standardization ISO ETSI ISDN Recommendations (ITU): I.1xx General I.2xx Services I.3xx Network Aspects I.4xx User Interface www.comnets.uni-bremen.de ISDN - 9-3
ITU Standards Groups related to ISDN E Telephony www.itu.org G Transmission systems and media, digital systems and networks I ISDN (http://www.itu.int/publibase/itu-t/itutallbyseries.asp?serie=i) t/itutallbyseries.asp?serie I) I.1xx General I.2xx Services I.3xx Network Aspects I.4xx User Interface M TMN (Telecommunications Management Network) and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile, leased circuits Q Switching and signalling (Zeichengabe) T Terminals for telematic services V Data communication over the telephone network X Data networks and open system communication Z Languages and general software aspects for telecomm. systems www.comnets.uni-bremen.de ISDN - 9-4
ISDN Basic Rate Interface: (BRI,S 0 ) (ISDN-Basisanschluss) Raw data rate of 144 kbit/s on a single twisted t pair Sub-channels 2B+D: two 64 kbit/s B (for bearer) channels one 16 kbit/s D (for data) channel Each B channel can carry a separate telephone or data call Combination of the two B channels forms a single 128 kbit/s data channel through a process called bonding A channel is the smallest usable physical unit of a channel structure www.comnets.uni-bremen.de ISDN - 9-5
ISDN Primary Rate Interface (PRI, S 2M ) (ISDN-Primärmultiplexanschluss) Pi ltil Germany/Europe/Most of the World: 30 B-channels 1 D-channel with 64 kbit/s Sum =? USA/Japan: 23 B-channels 1 D-channel with 64 kbit/s Sum =? www.comnets.uni-bremen.de ISDN - 9-6
www.comnets.uni-bremen.de ISDN - 9-7
ISDN Reference Configuration NT12 TE1 NT2 NT1 LT ET TE2 TA ET R S T U V TE Terminal Equipment ET Exchange Termination NT Network Termination LT Line Termination TA Terminal Adapter R,S,T,U,V: interface www.comnets.uni-bremen.de ISDN - 9-8
User Plane Management Plane Control Plane ISDN Network I.451 Q.931 nagement Plane Ma I.441 Q.921 ISDN LLC LAPD I.430 Basic Rate Interface I.431 Primary Rate Interface ISDN Reference Model LAPD Link Access Procedure on the D channel www.comnets.uni-bremen.de ISDN - 9-9
TE TE Network user data NT ET ET NT user data 7 6 5 4 3 2 1 user data user data 7 6 5 4 3 2 1 Protocol architecture between two ISDN compatible end systems www.comnets.uni-bremen.de ISDN - 9-10
end system D n x B switch Signaling System No. 7 bearer channels switch D n x B end system Mapping B-channels and D-channel between switches www.comnets.uni-bremen.de ISDN - 9-11
Signaling Analog Network: In-Band signaling ring voltage signal is sent to ring the bell in the phone Digital Network: Out-of-Band signaling a digital packet is sent on a separate channel no disturbance of established connections call setup time is very fast (e.g., a V.34 modem typically takes 30-60 s to establish a connection in an analog network) an ISDN call usually takes less than 2 seconds Signaling also indicates calling number, number dialed, type of call (data/voice), which allows intelligent call management www.comnets.uni-bremen.de ISDN - 9-12
S 2PM /S 2M V 2PM ISDN compatible PABX 30 x B + D M Local exchange (ISPBX) NT 2PM 30 x B + D M LT 2 (ET) Primary Rate Interface ET Exchange Termination German Telekom LT Line Termination NT Network Termination www.comnets.uni-bremen.de ISDN - 9-13
Primary Rate Interface: Frame Structure 125 μs 15 B-channels (64 kbit/s) 15 B-channels (64 kbit/s) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1920 21222324252627282930 31 frame synchronization (64 kbit/s) 8 bit D-channel (64 kbit/s) complete data rate = 32 x8bit 125 s 2048kbit / s www.comnets.uni-bremen.de ISDN - 9-14
H channels provide a way to aggregate B channels. They are implemented as: H0=384 kbps (6 B channels) H10=1472 kbps (23 B channels) H11=1536 kbps (24 B channels) H12=1920 1920 kbps (30 B channels) - International (E1) only www.comnets.uni-bremen.de ISDN - 9-15
H0-Channel allocation: H0(1) H0(3) H0(5) H0(2) H0(4) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 D H11-Channel allocation: H11 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 242526 2728 2930 31 D H12-Channel allocation: H12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 D www.comnets.uni-bremen.de ISDN - 9-16
Layer 2 - Data Link Layer ITU Q-series documents Q.920 - Q.923 Q.921 spec: Signaling on the D channel The ITU-T specifications Q.921 and Q.931 DSS1 (Digital Subscriber Signaling 1) are the baseline international specifications used throughout the world. The European specification from ETSI represents a modified form of Q.931, known as EDSS1 (European Digital Subscriber Signaling). Due to the early acceptance within the industry EDSS1 is the common variant of Q.931. (D-Kanal-Protokoll für Euro-ISDN. Als einheitlicher Standard in Europa löste das DSS1/EDSS1 1994 das 1TR6 (nationales ISDN) ab.) see also www.etsi.org download area (free registration) www.comnets.uni-bremen.de ISDN - 9-17
LAPD Provides both unacknowledged (best-try) try) and acknowledged (connection-oriented) services Best-try used for transfer of ISDN management information Connection oriented, is used to relate user call setup information needs to be reliable www.comnets.uni-bremen.de ISDN - 9-18
LAPD Frame Structure Flag Address (01111110) (16 bit) Control Information (8-16 bit) Information Field for DL-SDU (0-260 octets) FCS Flag (16 bit) (01111110) SAPI CR EA0 TEI EA1 (6 bit) (1) (1) (7 bit) (1) SAPI (Service Access Point Identifier) C/R (Command/Response) bit: indication if frame is command or response EA0 (Address Extension) bit: indication for final octet of the address TEI (Terminal Endpoint Identifier) 7-bit device identifier EA1 (Address Extension) bit: same as EA0 www.comnets.uni-bremen.de ISDN - 9-19
Control (2 octets) - The frame level control field indicates the frame type (Information, Supervisory, or Unnumbered) and sequence numbers (N(r) and N(s)) as required. Information - Layer 3 protocol information and User data CRC/FCS (2 octets) - Cyclic Redundancy Check/Frame Check Sequence, low-level test for bit errors on the user data, generator polynomial: l X 16 + X 12 + X 5 +1 = CCITT 16 Flag (1 octet) - always 7E 16 (0111 1110 2 ) www.comnets.uni-bremen.de ISDN - 9-20
SAPI: Service Access Point Identifier SAPI: 6-bit field that identifies the point where Layer 2 provides a service to Layer 3. SAPI Description 0 Call control procedures 1 Packet Mode using Q.931 call procedures 16 Packet Mode communications procedures 32-47 Reserved for national use 63 Management Procedures Others Reserved for Future Use www.comnets.uni-bremen.de ISDN - 9-21
Terminal Endpoint Identifier (TEI) Terminal Endpoint Identifiers (TEIs) are unique IDs given to each device (TE) on an ISDN S/T bus Identifier can be dynamic; the value may be assigned statically when the TE is installed, or dynamically when activated. TEI Description 0-63 Fixed TEI assignments 64-126 Dynamic TEI assignment (assigned by the switch) 127 Broadcast to all devices www.comnets.uni-bremen.de ISDN - 9-22
Establishing the Link Layer The Layer 2 establishment process is very similar to the HDLC (X.25 LAP-B) setup 1. The TE (Terminal Endpoint) and the Network initially exchange Receive Ready (RR) frames, listening for someone to initiate a connection. 2. The TE sends an Unnumbered Information (UI) frame with a SAPI of 63 (management procedure, query network) and TEI of 127 (broadcast). 3. The Network assigns an available TEI (in the range 64-126) and sends the TEI with an unnumbered frame to the TE. 4. The TE sends a Set Asynchronous Balanced Mode (SABME) frame with a SAPI of 0 (call control, used to initiate a SETUP) and a TEI of the value assigned by the network. 5. The terminal/network responds with an Unnumbered Acknowledgement (UA), SAPI=0, TEI=assigned. At this point, the connection is ready for a Layer 3 setup. www.comnets.uni-bremen.de ISDN - 9-23
User Network TE1 TE2 NT/ET Packet Data Q.931 Signalling Q.931 Signalling Q.931 Signalling Packet Data CES B 1 B 1 B 1 2 1 B 1 B 16 1 1 Layer 3 Layer 2 1 16 SAPI TEI=24 TEI=127 TEI=24 TEI=127 TEI=77 TEI=127 Broadcast data link connection Point-to-point data link connection DLCI = SAPI + TEI CEI = SAPI + CES (Connection Endpoint Suffix) D-channel SAPI=1 SAPI=16 Layer 2 Service Access Points www.comnets.uni-bremen.de ISDN - 9-24
Layer 3 - Network Layer The ISDN Network Layer is specified by the ITU Q-series documents Q.930 through Q.939. Layer 3 is used for the establishment, maintenance, and termination of logical network connections between two devices. www.comnets.uni-bremen.de ISDN - 9-25
Information local/global Type number Direction of transmission Phase of connection setup SETUP global 5 all directions SETUP ACKNOWLEDGE locall 13 all directions ALERTING global 12 all directions CALL PROCEEDING local all directions CONNECT global 7 all directions CONNECT ACKNOWLEDGE local 15 all directions PROGRESS global 3 all directions Phase of connection USER INFORMATION CONGESTION CONTROL SUSPEND SUSPEND ACKNOWLEDGE SUSPEND REJECT RESUME RESUME ACKNOWLEDGE RESUME REJECT NOTIFY Phase of disconnection DISCONNECT RELEASE RELEASE COMPLETE RESTART RESTART ACKNOWLEDGE Further Administr. Information SEGMENT INFORMATION STATUS STATUS ENQUIRY FACILITY global local locall local local local local local global global locall local local local global local local local l l www.comnets.uni-bremen.de ISDN - 9-26 32 121 37 45 33 38 46 34 110 69 77 90 70 78 96 123 125 117 98 all directions all directions user-network network-user network-user user-network network-user network-user all directions all directions all directions all directions all directions all directions all directions all directions all directions all directions ll di i FACILITY local 98 all directions
Network Layer: Functional Blocks Protocol Control (sub-layer) Finite state machine (Zustandsautomat) per network layer connection Connection identifier: Call Reference (local id between end system and exchange, Flag differentiates the generating instance) NPDUs contain Call Reference Call Control (sub-layer) One block per protocol control block Resource Control Channel Structure Management Channels are reserved based on availability Resource control is part of the management layer www.comnets.uni-bremen.de ISDN - 9-27 Call Control Protocol Control
Call Control Protocol Control ALERTING Request DISCONNECT Request INFO Request MORE INFO Request NOTIFY Request PROCEEDING Request PROGRESS Request REJECT Request RELEASE Request RESUME Request SETUP Request SETUP Response SUSPEND Request STATUS ENQUIRY Request Protocol Control Call Control ALERTING Indication DISCONNECT Indication INFO Indication MORE INFO Indication i NOTIFY Indication PROCEEDING Indication PROGRESS Indication REJECT Indication RELEASE Confirm RELEASE Indication RESUME Confirm SETUP Indication SETUP Confirm SETUP COMPLETE Indication SUSPEND Confirm STATUS Indication ERROR Indication www.comnets.uni-bremen.de ISDN - 9-28
Information Field Structure The Information Field is a variable length field that contains the Q.931 protocol data. Information Field 1 2 3 4 5 6 7 8 Protocol Discriminator i i 0 0 0 0 Length of CRV Call Reference Value (1 or 2 octets) 0 Message Type Mandatory & Optional Information Elements (variable) www.comnets.uni-bremen.de ISDN - 9-29
Fields in a Q.931 header Protocol Discriminator (1 octet) - identifies the Layer 3 protocol. If this is a Q.931 header, this value is always 08 16. Length (1 octet) - indicates the length of the next field, the CRV. Call Reference Value (CRV) (1 or 2 octets) - used to uniquely identify each call on the user-network interface. This value is assigned at the beginning of a call, and this value becomes available for another call when the call is cleared. Message Type (1 octet) - identifies the message type (i.e., SETUP, CONNECT, etc.). This determines what additional information is required and allowed. Mandatory and Optional Information Elements (variable length) - options that are set depending on the Message Type www.comnets.uni-bremen.de ISDN - 9-30
Octet number Header Bit number 1 2 3 4 5 6 7 8 1 2 3 F l a g Protocol ldiscriminatori i Call reference length = L 3 + L Message Type Information element No.1 Length of element L 1 Call reference value coded in L octets Information element No.1 coded in 2+L 1 octets 6 + L + L 1 Information element No.2 Length of element L2 L 2 Information-element No.2 coded in 2+L 2 octets www.comnets.uni-bremen.de ISDN - 9-31
Layer 3 Call Setup These are the steps that t occur when an ISDN call is established. In the following example, there are three points where messages are sent and received: 1) the Caller, 2) the ISDN Switches, and 3) the Receiver. 1. Caller sends a SETUP to the Switch. 2. If the SETUP is OK, the switch sends a CALL PROCeeding to the Caller, and then a SETUP to the Receiver. 3. The Receiver gets the SETUP. If it is OK, then it rings the phone and sends an ALERTING message to the Switch. 4. The Switch forwards the ALERTING message to the Caller. 5. When the receiver answers the call, it sends a CONNECT message to the Switch. 6. The Switch forwards the CONNECT message to the Caller. 7. The Caller sends a CONNECT ACKnowledge message to the Switch. 8. The Switch forwards the CONNECT ACK message to the Receiver. 9. Done. The connection is now set up. www.comnets.uni-bremen.de ISDN - 9-32
Calling subscriber A Subscriber Local Exchange A Transit Exchange Subscriber Local Exchange B Called subscriber B Setup Alerting IAM ACM CPG ANM IAM ACM CPG ANM Setup Alerting Connect Connect Traffic Channel Disconnect Release REL RLC REL RLC Disconnect SS7 Successful ISDN connection set-up www.comnets.uni-bremen.de ISDN - 9-33
Manufacturers of Switching Equipment Ericsson: AXE 10 Siemens: EWSD SEL/Alcatel: System 12... www.comnets.uni-bremen.de ISDN - 9-34
Layer 3 NT Timers Example Quelle: ISDN Vorlesung Uni Dortmund http://www-esv.e-technik.uni-dortmund.de/vs_iv/kap6.html www.comnets.uni-bremen.de ISDN - 9-35
Timers (ETS 300 102-2) www.comnets.uni-bremen.de ISDN - 9-36
Timers (cont.), e.g. T301 www.comnets.uni-bremen.de ISDN - 9-37
Trunk Line Technologies Connect Pairs of Switches Plesiosynchronous Digital Hierarchy (PDH) Trunk Line North American Digital Hierarchy Speed 56 kbps (DS0 Signaling) 56 kbps (sometimes 64 kbps) T1 (DS1 Signaling) T3 (DS3 Signaling) CEPT Multiplexing Hierarchy 1.544 Mbps 44.7 Mbps 64 kbps 64 kbps E1 E3 2.048 Mbps 34.4 Mbps www.comnets.uni-bremen.de ISDN - 9-38
Trunk Line Technologies Synchronous Digital Hierarchy (SDH) Synchronous Optical Network (SONET) Trunk Line SONET/SDH* OC3/STM1 OC12/STM4 Speed ~ 155 Mbps ~ 622 Mbps OC48/STM16 ~ 2.5 Gbps OC192/STM64 OC768/STM256 Notes: SONET and SDH speeds are multiples of 51.84 Mbps. OCx is the SONET designation. STMx is the SDH designation. www.comnets.uni-bremen.de ISDN - 9-39 ~ 10 Gbps ~ 40 Gbps
Tutorials: e.g. References English: http://www.cse.ohio-state.edu/~jain/cis788-95/ftp/isdn.pdf German: http://www.ba-stuttgart.de/~schulte/digiisdn.htm htm www.comnets.uni-bremen.de ISDN - 9-40