ATIS 1000047-2011 Signaling System 7 (SS7) and Internet Protocol (IP) Transport Networks Signaling Interworking and Compatibility.pdf

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1、 TECHNICAL REQUIREMENTS ATIS-1000047 SIGNALING SYSTEM 7 (SS7) AND INTERNET PROTOCOL (IP) TRANSPORT NETWORKS SIGNALING INTERWORKING AND COMPATIBILITY ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven standards for

2、 the information, entertainment and communications industry. More than 200 companies actively formulate standards in ATIS Committees, covering issues including: IPTV, Cloud Services, Energy Efficiency, IP-Based and Wireless Technologies, Quality of Service, Billing and Operational Support, Emergency

3、 Services, Architectural Platforms and Emerging Networks. In addition, numerous Incubators, Focus and Exploratory Groups address evolving industry priorities including Smart Grid, Machine-to-Machine, Connected Vehicle, IP Downloadable Security, Policy Management and Network Optimization. ATIS is the

4、 North American Organizational Partner for the 3rd Generation Partnership Project (3GPP), a member and major U.S. contributor to the International Telecommunication Union (ITU) Radio and Telecommunications Sectors, and a member of the Inter-American Telecommunication Commission (CITEL). ATIS is accr

5、edited by the American National Standards Institute (ANSI). For more information, please visit . Notice of Disclaimer Changeback; Forced rerouting; Controlled rerouting; MTP restart; Management inhibiting; and Signalling traffic flow control. R-3 SG supporting MTP3 is required to support signalling

6、link management procedures as specified in ATIS-1000111 on the SS7 network interface: Signalling link activation, restoration, and deactivation; Link set activation; and Automatic allocation of signalling terminals and signalling data links. R-4 The SG supporting MTP3 is required to support signalli

7、ng route management procedures as specified in ATIS-1000111 on the SS7 network interface: Transfer-prohibited procedure. Transfer-allowed procedure. Transfer-restricted procedure. Signalling-route-set-test procedure. Transfer-controlled procedure . ATIS-1000047 14 Signalling-route-set-congestion-tes

8、t procedure. The signaling transport for TCAP applications (e.g., query/response applications) involves support and use of the SCCP protocol in addition to the MTP protocol by network elements providing interconnection for TCAP applications. R-5 The SG network elements providing signaling SCCP inter

9、connection between the SS7 network and the IP-based NGN for TCAP applications are required to support an SCCP interface as specified in ATIS-1000112. 6.2 SS7 Application Layer Protocols (TCAP and ISUP) The application layer is not within the scope of this document. However, for completeness, it is n

10、oted that a SG providing signaling interconnection between the SS7 network and the IP-based NGN based on a SS7 Signaling Termination Architecture (see Section 5.2) will support ISUP as specified in ATIS-1000113. Also, a SG providing signaling interconnection between the SS7 network and IP-based NGN

11、for TCAP applications based on a SS7 Signaling Termination Architecture (see Section 5.2) will support TCAP as specified in chapters T1.114.1 through T1.114.4 of ATIS-1000114. 6.3 IP Transport Network Interface Requirements The following general requirements are applicable to the NGN side of SGs tha

12、t are providing signaling interconnection between PSTN/SS7 and NGN: R-6 The SG is required to support the IP-based transport network interface as specified in the applicable protocols: IETF RFC 791, Internet Protocol DARPA Internet Program Protocol Specification. IETF RFC 793, Transmission Control P

13、rotocol DARPA Internet Program Protocol Specification. IETF RFC 768, User Datagram Protocol, J. Postel, ISI. R-7 The SG providing SS7 over IP transport signaling associations is required to support an interface to the IP-based transport network using the Stream Control Transmission Protocol (SCTP) a

14、s specified in IETF RFC 4960. R-8 The SG providing SS7 over IP transport is required to support an interface to the IP-based transport network using applicable SS7 Adaptation protocol(s): IETF RFC 3331, Signaling System 7 (SS7) Message Transfer Part 2 (MTP2) - User Adaptation Layer. IETF RFC 4165, S

15、ignaling System 7 (SS7) Message Transfer Part 2 (MTP2) - User Peer-to-Peer Adaptation Layer (M2PA). IETF RFC 4666, Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User Adaptation Layer (M3UA). IETF RFC 3868, Signaling Connection Control Part User Adaptation (SUA). 6.4 IP Network Applicatio

16、n Layer (SIP) The application layer is not within the scope of this document. However, for completeness, it is noted that SG providing signaling interconnection between the SS7 network and IP-based NGN based on a SS7 Signaling Termination Architecture (see Section 5.2) will support the SIP protocol

17、on the interface on the NGN side. ATIS-1000047 15 6.5 Interworking Requirements The SG will terminate SS7 links on its SS7 side and transport the SS7 call control and service control protocols (i.e., ISUP and TCAP) to the IP nodes in the NGN. Similarly, the SG will receive SS7 call control and servi

18、ce control messages from the IP nodes in the NGN, and is responsible for the appropriate formatting of the messages for transmission on the SS7 links. To enable seamless operation end-to-end, the SG has to provide the necessary interworking functions between the transport protocols on its SS7/PSTN s

19、ide and its IP/NGN side. This also includes necessary functions to interwork the MTP/SCCP network management procedures on its SS7 side with the management procedures of the transport connections between the SG and the IP nodes in the NGN. This function is viewed as an implementation-specific functi

20、on and will depend on vendor-specific solutions. Specifically, the SG should be capable of taking specific actions based on management events in the SS7 network, provide the necessary interworking actions on the transport connections to the IP nodes in the NGN, and inform the IP Nodes in the NGN to

21、take certain actions depending on these interworking actions. The following general requirements are applicable to interworking network management protocol and procedures at the SG providing interconnection between the PSTN and the NGN: R-9 The SG shall support functions and procedures to enable sea

22、mless end-to-end interworking and interoperability between SS7 transport and IP transport networks. This includes, but is not limited to, functions and procedures to handle events related to: Signaling node failure and recovery. Signaling node congestion. Signaling routes failure and recovery. SIP s

23、ignaling routes congestion. Internal node congestion control. Section 7 provides additional guidelines for SS7 and IP Transport Network Signaling Interworking. 6.5.1 Signaling Point Code (SPC) Assignment The SS7 MTP3 signaling management procedures are based on the use of a unique SPC to identify th

24、e affected point code for which the signaling control procedure applies. The IP Nodes in the NGN may not be addressed by SPCs, resulting in difficulties having effective management control procedures end-to-end for certain implementation and deployment scenarios. Consider the example where a SG assi

25、gned a single SPC in the PSTN is used to route messages to multiple IP Nodes in the NGN. If a single IP Node was to fail, there is no effective means to control the traffic destined to the failed IP Node back at the source SEPs in the SS7 network without impacting all SS7 traffic arriving at the SG.

26、 An example approach to address this problem would be to assign multiple SPCs to the SG and use accordingly to allow signaling management control of the individual signaling relationships with the associated IP Nodes. However, although use of multiple SPCs is possible, there is no mandatory requirem

27、ent for the support or use of multiple SPCs. The design and deployment of the SG together with the associated IP Nodes in the NGN should take into account appropriate measures to ensure that the MTP3 signaling route management procedures for availability and congestion control are supported as inten

28、ded. O-1 It is an objective that the NGN provider takes into account appropriate measures to ensure that the MTP3 signaling route management procedures for availability and congestion control are supported as intended as part of the design and deployment of the SG together with the associated IP Nod

29、es in the NGN. Specifically, signaling point codes should be assigned to the SG so that the MTP3 management are supported as intended by the protocol specification ATIS-1000111. ATIS-1000047 16 6.6 Performance Objectives The performance objectives for SS7 transport network are specified in chapter T

30、1.111.6 of ATIS-1000111. The SG MTP interface should adhere to the performance requirements specified for MTP in chapter T1.111.6 of ATIS-1000111 independent of whether the SG is assigned one or multiple SPCs in the PSTN. 6.7 Security Requirements and Objectives It is necessary that appropriate secu

31、rity measures be taken to protect the integrity, confidentiality, and availability of the signaling control procedures provided by the SG. ATIS-1000012 provides SS7 network and NNI interconnection security requirements and guidelines. R-10 The SG shall support the security requirements and objective

32、s specified in ATIS-1000012 as appropriate based on the NGN provider security policy. IETF RFC 3788 discusses how Transport Layer Security (TLS) and IPsec can be used to secure communication for SIGTRAN protocols. R-11 The SG shall support and use capabilities to secure SIGTRAN communications as app

33、ropriate based on the NGN provider security policy. ATIS-1000029 provides NGN security requirements. Given that the SG is viewed as a network element of the NGN, the security requirements are also applicable ATIS-1000029. R-12 The SG shall support security requirements specified in ATIS-1000029 as a

34、ppropriate based on the NGN provider security policy. 7 Guidelines for SS7 & IP Transport Network Signaling Interworking 7.1 Overview This section provides guidelines for SS7 and IP Transport Network Signaling Interworking focusing on actions to be taken by SG network elements. This section is organ

35、ized based on the following grouping of the SS7 signaling route management procedures: 1. Guidelines for Availability Control. 2. Guidelines for Congestion Control. 7.2 Guidelines for Signaling Route Availability Control 7.2.1 Overview This section provides guidelines related to signaling route avai

36、lability procedures. The MTP3 procedures related to signaling route availability control are: Transfer-prohibited (TFP) control procedure. Transfer-allowed (TFA) control procedure. Transfer-restricted (TFR) control procedure. Signalling-route-set-test procedure. ATIS-1000047 17 The precise criteria

37、for handling interworking of the signaling route availability control procedures between the SS7 transport network and the IP transport network are dependent on the particular SG implementation, the protocols employed (e.g., SCTP, M2PA, M2UA, M3UA, or SUA) and deployment scenario. 7.2.1.1 SS7 Transp

38、ort Network Availability Control Procedures As stated in Section 6, the SG is required to support the MTP3 signaling route availability control procedures as specified in chapter T1.111.4 of ATIS-1000111. The effectiveness of the MTP signaling route availability control procedures will depend on the

39、 network architecture design and signaling point code assignment to the SG. The following best practice guidelines should be taken into consideration: 1. Appropriate measures should be taken for the SG implementation and the SG deployment architecture design to ensure the effectiveness of the MTP si

40、gnaling route availability control procedures on the SS7 side. 2. Appropriate engineering measures should be taken in the deployment design of both the SG and associated IP nodes so that the MTP3 signaling route availability control procedures (TFP, TFA, and TFR) in the SS7 network is effective. Spe

41、cifically: a. Measures should be taken to ensure that appropriate action is taken by the SG, or the nodes in the IP network, or both depending on the network architecture design to ensure that the MTP signaling route avaiability control procedure is effective in controlling signaling traffic to the

42、affected destination identified in received TFP, TFR, and TFA as intended by the MTP specification. b. If the traffic is not controlled at the sources (i.e., nodes in the NGN/IP network), appropriate engineering measures should be implemented at the SG to ensure that the MTP signaling route availabi

43、lity control procedures are effective in controlling signaling traffic to the affected destination identified in received TFP, TFR, and TFA messages as intended by the MTP specification. 3. Appropriate engineering measures should be taken in the deployment design of both the SG and associated IP nod

44、es to ensure that appropriate action is taken by the SG, or the nodes in the IP network, or both (i.e., SG together with the associated IP node) depending on the network architecture design to ensure that the signalling-route-set-test procedure is effective as intended by the MTP specification. 7.2.

45、1.2 Loss of SS7 Network Connectivity Failure events are possible resulting in loss of the SG connectivity to the SS7 network. In addition, local failure of the SGs MTP may occur, which result in loss of connectivity to the SS7 network. If loss of connectivity to the SS7 network occurs, appropriate a

46、ctions must be taken on the SG IP/NGN interface and the IP Node to stop the traffic. Note that the notification from MTP3 that SS7 connectivity has been lost and the detection of local MTP failure are implementation-dependent. The following guidelines should be considered regarding detection and not

47、ification of loss of connectivity to the SS7 network: The SG should support the capability to monitor the status of the local MTP3 availability and conveying status changes to the IP Nodes. Upon detection of MTP3 failure (and thus loss of connectivity to the SS7 network), the SG should notify the IP

48、 Node that connectivity to the SS7 network has been lost. The methods for monitoring the local MTP3 and providing notifications to the IP Node are implementation-dependent. Upon detection that the local MTP3 (which has previously failed) has been restored, the SG should notify the IP Node that conne

49、ctivity to the SS7 network has been restored. The methods for monitoring the local MTP3 and providing notifications to the IP Node are implementation-dependent. ATIS-1000047 18 7.2.1.3 Loss of IP/NGN Node Network Connectivity Failure events are possible that result in the SG loss of connectivity to the IP network. When all SG connectivity to the IP network is lost, action must be taken on the SS7 interface to restrict the traffic being received from the SS7 network.