Bài giảng Báo hiệu và điều khiển kết nối Signalling and Connection Control

HỌC VIỆN CÔNG NGHỆ BƯU CHÍNH VIỄN THÔNG Báo hiệu và điều khiển kết nối Signalling and Connection Control KHOA VIỄN THÔNG 1Giảng viên: Hoàng Trọng MinhEmail: Hoangtrongminh@yahoo.comAug 2012 Bài giảng môn học MMMĐề cương môn học MMMM1.Tổng quan về báo hiệu và điều khiển kết nối 1.1 Giới thiệu chung1.2 Giải pháp điều khiển hệ thống viễn thông 1.3 Nguyên tắc điều khiển hệ thống viễn thông 1.4 Kiến trúc và phân loại báo hiệu 2. Báo hiệu trong mạng cố định2.1 Kiến trúc mạng hội tụ 2.2 Hệ thống báo hiệu số 7 2.3 Giao thức báo hiệu H.323 2.4 Giao thức điều khiển cổng phương tiện H.248/Megaco 2.5 Giao thức khởi tạo phiên SIPĐề cương môn học MMMM 3. Báo hiệu trong mạng thông tin di động 3.1 Tổng quan về báo hiệu trong mạng di động tế bào3.2 Các thủ tục báo hiệu mạng truy nhập3.3 Thủ tục xử lý báo hiệu trong mạng lõi 4. Báo hiệu trong phân hệ đa phương tiện IP 4.1 Kiến trúc phân hệ đa phương tiện IP4.2 Báo hiệu khởi tạo phiên SIP4.3 Thiết lập phiên trong IMS qua báo hiệu SIP4.4 Các giao thức báo hiệu khác trong IMSĐề cương môn học MMMM 5. Báo hiệu và điều khiển kết nối liên mạng 5.1 Các giải pháp công nghệ tiên tiến 5.2 Các chuẩn kết nối và điều khiển truy nhập 5.3 Các giao thức báo hiệu liên mạng [1] Bài giảng báo hiệu và điều khiển kết nối (đang biên soạn)[2] Popovskij, Vladimir, Barkalov, Alexander, Titarenko, Larysa, “Control and Adaptation in Telecommunication Systems”, Springer, 2011. [3] John G. van Bosse, Fabrizio U. Devetak, “Signaling in Telecommunication Networks”, second edition, John Wiley & Sons, Inc., 2007.[4] Travis Russell, “THE IP MULTIMEDIA SUBSYSTEM (IMS): Session Control and Other Network Operations”, The McGraw-Hill, 2008.[5] Ralf Kreher, Torsten Ruedebusch, “UMTS Signaling: UMTS Interfaces, Protocols, Message Flows and Procedures Analyzed and Explained”, John Wiley & Sons, Inc., 2012. Tài liệu tham khảo1.Tổng quan về báo hiệu và điều khiển kết nối MMMMNB wirelineLEXRSUMSCBSCGSMSSPSSPSCPServSCPServCircuit BackboneNB wirelineBB wirelineSGSNGGSNGSMNASAAADSLAMBASATMSwitchPacket Backbone@1.Tổng quan về báo hiệu và điều khiển kết nối MMMM1.Tổng quan về báo hiệu và điều khiển kết nối MMMM7Trunk GatewayAccess GatewayResident GatewaySignalling GatewayTDMSS7/ISUPE1(voice)SIGTRANMGCPMGCPMGCPSIPH323VoIP Internet domainE1/R2MFCPOTSMGCP PhoneMGCPPOTSAPP serverH323GKSIP serverBICC/SIPT1.Tổng quan về báo hiệu và điều khiển kết nối MMMM1.Tổng quan về báo hiệu và điều khiển kết nối MMMM1.Tổng quan về báo hiệu và điều khiển kết nối MMMM1.Tổng quan về báo hiệu và điều khiển kết nối MMMM1.Tổng quan về báo hiệu và điều khiển kết nối MMMMSignaling is used between user and the network, or between two network elements to exchange various control information like:+ Traffic Descriptors+ Service Descriptors+ Channel IdentifiersIn other words, Signaling is used to dynamically establish, monitor, and release Connections (including physical, virtual and logical connections).1.Tổng quan về báo hiệu và điều khiển kết nối MMMMSignaling is used only for establishment and release of dynamic connectionsStatic connections are configured, manually or otherwise, and may or may not require signaling.Signaling provides the means for resource reservation.In essence, Signaling provides the means to exchange connection-related information prior to and/or after information transfer.1.Tổng quan về báo hiệu và điều khiển kết nối MMMMTraditionally, use of signaling in Telecom Networks was bare minimum. It was restricted to establish/release a voice channel in order to allow telephonic conversation.Now, with advent of supplementary services (e.g., CLIP, Call Forwarding, etc.), signaling is becoming more complex. For e.g., SS7 which has an advanced network architecture provides feature-rich signaling.1.Tổng quan về báo hiệu và điều khiển kết nối MMMMIf Permanent Virtual Circuits (PVCs) are established, generally, no signaling is required.For Switched Virtual Circuits (SVCs), signaling takes place using well-defined signaling protocol.The signaling complexity is dependent upon the underlying technology.For e.g., Q.2931/Q.2971 (signaling protocol for ATM) is much more complicated vs Q.933 (signaling protocol for frame relay).1.Tổng quan về báo hiệu và điều khiển kết nối MMMMDatagram networks, generally, do not require signaling. This is because by very definition, a connectionless network does not entail connection setup.To provide QoS, some of resource reservation and hence some form of signaling is required.For e.g., newer protocols like MPLS and RSVP require some form of signaling message exchange and resource reservation.1.Tổng quan về báo hiệu và điều khiển kết nối MMMM1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Telecom Network:In band signaling refers to using the same voice frequency band to carry signaling information as that used to carry voice (i.e., 300-3400Hz). In contrast, out band signaling refers to using frequencies above the voice band (but below the upper threshold of 4000Hz) to carry signaling information.1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Datacom Network:In band signaling refers to using the same virtual channel to carry signaling information as that used to carry data. In contrast, in Out band Signaling the signaling information and data are carried on different virtual channels. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Telecom Network:In Inchannel signaling, the same physical channel carries signaling information as well as voice and data. In contrast, Common Channel Signaling uses a separate channel for solely carrying signaling information for a number of connections.1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Datacom Network:To some extent, inchannel signaling and common channel signaling in telecommunication networks is analogous to inband signaling and outband signaling of data communication networks respectively. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Telecom Network:Both these techniques are variants of Common Channel SignalingIn Associated signaling, the signaling channels and the data paths pass through the same network elements. In Non-associated signaling, there is no correspondence between signaling channels and data paths. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Telecom Network:Both these techniques are variants of Common Channel SignalingIn Associated signaling, the signaling channels and the data paths pass through the same network elements. In Non-associated signaling, there is no correspondence between signaling channels and data paths. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Datacom Network (for ATM):In Channel associated signaling, all the signaling messages for each VP is exchanged on VCI=5 of that virtual path. In Channel non-associated signaling, all the signaling messages of all the virtual paths are exchanged on VPI=0 and VCI=5.Associated Signaling versus Non-Associated Signaling1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Another technique metasignaling finds mention in various signaling standards. Metasignaling refers to the process of establishing signaling channels using signaling procedures. The signaling channel so established is then used to establish channels for data transfer.1.Tổng quan về báo hiệu và điều khiển kết nối MMMMAcknowledgementsTimer protectionParameter negotiationCall/Connection identificationFinite state machine modellingMessage encoding and decoding (TLV format)1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Required due to unreliable nature of transmission media.The classical two-army problem suggests that no scheme can provide full-proof acknowledgement for an unreliable media. However, 2 or 3 handshakes is typically sufficient for a normal case.1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Timers are used to avoid inordinate delays in case the signaling messages get lost or corrupted.Timer is started after message transmission. In case message is lost or discarded, the timer expires and message is retransmitted. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM If the message reaches safely and is acknowledged, the timer is stopped.Choosing the correct timeout value is important.If this value is too small, then timers will timeout very frequently. If a very large value is chosen, it may defeat the purpose of keeping timers.Typical value is twice the round-trip propagation time..1.Tổng quan về báo hiệu và điều khiển kết nối MMMM This entails arriving at a common set of parameters.The nature and scope of parameter negotiation depends on the number of handshakes.In a two way handshake, negotiation is bare minimal.A three way handshake provides more scope for negotiation.1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Consider the following steps:An end-system A sends a connection establishment request to BA sends another request to end-system B for connection establishmentA then receives a reply from B. How does A identify to which request has B replied to?The solution is to generate a uniq_num and accompany it with every message1.Tổng quan về báo hiệu và điều khiển kết nối MMMM A Call goes through three phasesCall establishmentData transferCall releasingThe FSM accepts messages only if the message is permitted in that state.The state change happens when 1) a message is received from peer, 2)Timer expires and 3) User Request. received from User. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Generally, messages are encoded in Type-Length-Value (TLV) format.Type: Identifies the typeLength: Length of message (total length or length excluding the header)Value: The actual contentsInformation blocks within the message may also be encoded in TLV format.1.Tổng quan về báo hiệu và điều khiển kết nối MMMM 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Point-to-Point signaling model is used to establish and release connections between two end-points.The is the most common model of signaling.Not only is this model popular, it is also very simple to implement.1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Point-to-Multi Point signaling model is used to establish and release connections between a root and multiple end-points. This form of signaling is mainly used for multicasting or broadcasting applications (e.g., distant learning).1.Tổng quan về báo hiệu và điều khiển kết nối MMMMA PMP call is generally started by the root.The root may take this step voluntarily,Or, it may do the same after receiving an explicit request from a leaf. The leaf can send the connection establishment request to the root through signaling channel or through other means. The first connection is established following point-to-point procedures1.Tổng quan về báo hiệu và điều khiển kết nối MMMMAfter a PMP call is established, parties are added by the root. The root is informed either through a signaling message, or through some other means. Subsequent parties have no say in determining the parameters of the connection, as it has already been fixed1.Tổng quan về báo hiệu và điều khiển kết nối MMMMA leaf of a point-to-multipoint call can drop itself out of the connection by sending a message to the root.It is mandatory for the root to entertain this request, and drop that particular party. If the root drops itself out of the connection, the whole connection is cleared. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMMBy definition, a PMP call is one in which the data flows from the root to the leaves (i.e. unidirectional in nature). Theoretically, nothing precludes bi-directional data-flows in PMP calls. However, if leaves are allowed to send data to the root, there is a multipoint-to-point connection along with the point-to-multipoint call. 1.Tổng quan về báo hiệu và điều khiển kết nối MMMM Advantages+ Saving of network resources like bandwidth. The % saving depends upon the breadth and the depth of the PMP tree.Disadvantages- PMP connections are difficult to establish, manage, and release. - It is not easy for the leaves to indicate the root to start a connection. - The unidirectional nature2. Giải pháp điều khiển hệ thống viễn thông MMMMIntroduction into Control Technologies for QoS Providingtelecommunication systems (TCS)the practical QoS includes the following characteristics: delay of connection; data throughput; transmission quality.Logic structure for formation of SLA2. Giải pháp điều khiển hệ thống viễn thông MMMMIntroduction into Control Technologies for QoS ProvidingTechniques for the control plane.The technique CAC (Call Admission Control) controls new requests for traffictransmission through the network.The technique of QoS routing provides the choice of a route satisfied to a required quality of service for a given data flowThe third technique is called the resource reservation.2. Giải pháp điều khiển hệ thống viễn thông MMMMIntroduction into Control Technologies for QoS ProvidingTechniques for data plane.The technique of buffer management is reduced to the control of packages whichare waiting in a transmission queue. RED The mechanism of congestion avoidance support the level of network’s loadinga bit below of its throughput.The approach of packet marking is used to denote a particular service level fordifferent packages.2. Giải pháp điều khiển hệ thống viễn thông MMMMIntroduction into Control Technologies for QoS ProvidingTechniques for data plane.The main goal of techniques from the group of queuing and scheduling is thechoice of a package for transmission from the buffer into a communication channel.The majority of service procedures (disciplines, or schedulers) is based on the rule FIFO (first in – first out).discipline of privileged (high-priory) service, example is a mechanism of weighted fair queuing (WFQ)discipline which is based on classification of data flows according with their classes of services. It is named CBQ (Class-Based Queuing) .2. Giải pháp điều khiển hệ thống viễn thông MMMMIntroduction into Control Technologies for QoS ProvidingTechniques for data plane.The techniques of the traffic classification are connected with classification ofpackages on the input of a network.The goal of traffic shaping is control of speed and size of data flows from the input of a network. “a leaky bucket” and “a token bucket”The management plane of QoS includes techniques responsible for maintenance, administration, and control of a network in respect to user traffic.2. Giải pháp điều khiển hệ thống viễn thông MMMMIntroduction into Control Technologies for QoS ProvidingBasic components of models for service providing2. Giải pháp điều khiển hệ thống viễn thông MMMMPeculiarities of RACS ApproachThe Resource and Admission Control Sub-System (RACS) executes the controlfunctions for access network and boundary node of the kernel execution level.The component A-RACF (Access Re-source and Admission Control Function) executes some functions connected with the access to network resources, as well as control functions of these resources.The component SPDF (Service-Based Policy Decision Function) executes control using the access politics to service on the boundary of the level of the network kernel. 2. Giải pháp điều khiển hệ thống viễn thông MMMMPeculiarities of RACS ApproachArchitecture of RACS subsystemRCEF. Resource Control Enforcement Function.C-BGF Core Border Gateway FunctionNetwork Attachment Subsystem (NASS)2. Giải pháp điều khiển hệ thống viễn thông MMMMPeculiarities of RACS ApproachThe service level takes responsibility for the exchange of signaling messages among the applications. The transport level is responsible for both reliable transmission of the data packages and traffic’s control.The ITU determines the management architecture of QoS in its standard. The main idea of the management architecture of QoS is independence of the transport level from the service level.the speech is transmitted using the IP protocol through the Internet The traffic can run further through a network of a mobile operator. 2. Giải pháp điều khiển hệ thống viễn thông MMMMPeculiarities of RACS ApproachArchitecture of RACF subsystemThe function of RACF determines the availability ofnetwork resources and executes their control.Subscriber signalling PSTNSwitching in exchangesSubscriber signalling (analog or ISDN=DSS1)Network-internal signalling (SS7)Transmission (PDH, SDH)Databases in the network (HLR)Analog subscriber signallingThe calling party (user A) tells the local exchange to set up (disconnect) a call by generating a short (open) circuit in the terminal => off-hook (on-hook) operation.The dialled called party (user B) number is sent to the local exchange in form of Dual Tone Multi-Frequency (DTMF) signal bursts.Alerting (ringing) means that the local exchange sends a strong sinusoid to the terminal of user B.In-channel information in form of audio signals (dial tone, ringback tone, busy tone) is sent from local exchange to user. User can send DTMF information to network.1234Analog subscriber signalling in actionLE AUser AUser BRinging signalOff-hook (user B answers)Off-hookSS7 signalling (ISUP)Dial toneB numberRingback tone (or busy tone)LE BConnection establishedLE = local exchangeISDN subscriber signalling in actionLE AUser AUser BRingingOff-hook (user B answers)Off-hookSS7 signalling (ISUP)B numberTones generated in terminalLE BSetupCall procSetupAlertConnAlertConnDSS1 signalling messagesConnection establishedWhat does ISDN originally mean?1. End-to-end digital connectivity2. Enhanced subscriber signaling3. A wide variety of new services (due to 1 and 2)4. Standardized access interfaces and terminalsISDN is not a “new” network separated from the PSTN. Interworking with “normal” PSTN equipment is very important.ISDN terminalPSTN terminalinteraction is possibleIdea originated in the 1980’sPSTN vs. ISDN user access300 3400 Hz analog transmission band“Poor-performance” subscriber signaling2 x 64 kbit/s digital channels (B channels)16 kbit/s channel for signaling (D channel) => Digital Subscriber Signalling system nr. 1 (DSS1)PSTNBasic Rate Access ISDNPrimary Rate Access ISDN30 x 64 kbit/s digital channels (B channels)64 kbit/s channel for signaling (D channel)Mainly used for connecting private branch exchanges (PBX) to the PSTN.End-to-end digital signallingISUPQ.931Q.921I.430Q.931Q.921I.430MTP 3MTP 2MTP 1Q.931Q.921I.430Q.931Q.921I.430ISUPMTP 3MTP 2MTP 1contains the signalling messages for call controlUser interfaceUser interfacePSTN NetworkDSS1SS7DSS1Signalling System nr. 7 (SS7) PSTNSwitching in exchangesSubscriber signalling (analog or ISDN=DSS1)Network-internal signalling (SS7)Transmission (PDH, SDH)Databases in the network (HLR)History of inter-exchange signallingSS6 = CCIS (common channel interoffice signaling) was deployed in North America as an interim solution, but not in Europe. CCIS is not the same thing as SS7. Starting from 1980 (mainly in Europe), CAS was being replaced by SS7. The use of stored program control (SPC) exchanges made this possible. Like CCIS, signalling messages are transmitted over separate signalling channels. Unlike CCIS, SS7 technology is not monolithic, but based on protocol stacks.Before 1970, only channel-associated signalling (CAS) was used. In CAS systems, the signalling is carried in-band along with the user traffic.CASCCISSS7Channel-associated signalling (CAS)CAS means in-band signalling over the same physical channels as the circuit-switched user traffic (e.g. voice).Signalling to/from databases is not feasible in practice (setting up a circuit switched connection to the database and then releasing it would be extremely inconvenient).ExchangeExchangeExchangeCircuit switched connectionSignalling is possibleSignalling is not possible before previous circuit-switched link is established CAS has two serious draw-backs:Setting up a circuit switched connection is very slow. Common channel signalling (CCS)In practice, CCS = SS7.ExchangeExchangeSignalling is possible anywhere anytimeDatabaseEnd-to-end signalling is possible before ca