1、 ATIS-0100011 PRIORITY FOR NS/EP SERVICES IN NGN/IP ENVIRONMENT ROLE OF TSP TECHNICAL REPORT The Alliance for Telecommunication Industry Solutions (ATIS) is a technical planning and standards development organization that is committed to rapidly developing and promoting technical and operations stan
2、dards for the communications and related information technologies industry worldwide using a pragmatic, flexible and open approach. Over 1,100 participants from over 300 communications companies are active in ATIS 22 industry committees and its Incubator Solutions Program. Notice of Disclaimer and 2
3、) restoration: 1. A provisioning priority is obtained to facilitate priority installation of new telecommunications circuits. Provisioning on a priority basis becomes necessary when an end user has an urgent requirement for a new NS/EP circuit that must be installed 6This is available from the IP/MP
4、LS Forum website . ATIS-0100011 3 immediately (e.g., an emergency) or by a specific due date (e.g., essential) that can be met only by a shorter than standard service vendor provisioning timeframe. 2. A TSP code indicating a priority for restoration is assigned to a new or existing telecommunication
5、s circuit to ensure that restoration of a TSP circuit takes place before non-TSP circuit restoration. Priority restoration should be assigned to a new circuit when interruptions may have a serious, adverse effect on the supported NS/EP function. TSP restoration priorities must be requested and assig
6、ned before a circuit outage occurs. In the Public Switched Telephone Network (PSTN), the use of TSP is illustrated by the following two examples: 1. Private Line Service: A private line DS3 circuit could be requested to support NS/EP services. If a TSP provisioning priority is granted by the NCS Off
7、ice of Priority Telecommunications, the provisioning of such a circuit must be afforded the service providers “best effort” to complete the installation. Orders subject to TSP must be worked with higher priority than the provisioning of other non-TSP circuits. When TSP restoration is applicable to t
8、he circuit, restoration in the event of failure must take into account the TSP classification to ensure that “best efforts” are made to restore the circuit as soon as possible. Restoration efforts for TSP circuits are to have priority over non-TSP circuits. TSP codes do not apply to automated restor
9、ation processes such as SONET ring rerouting of all DS3 circuits provisioned on it. In this example, all DS3s on the ring are re-routed regardless of their TSP priority. If however, no automated restoration mechanisms are available, then the TSP circuit receives priority for manual repair over non-T
10、SP circuits. 2. GETS: The Government Emergency Telecommunications Service (GETS) is a restricted service that permits individuals authorized by the NCS to make prioritized calls. This service differs from the private line service in that no physical circuits are being considered for provisioning. Ra
11、ther, the GETS is assigned a signaling priority whereby the Signaling System 7 (SS7) recognizes the initiation of a GETS call, and provides preferential treatment to the GETS call over a non-GETS call for admission into the PSTN. Another feature that enhances priority treatment for GETS calls is exe
12、mption from Network Management controls. Thus, TSP codes do not apply in the signaling priority assignments, although SS7 links per the TSP Report and Order 4are exempt from TSP and may have priority over TSP. These two examples provide an illustration as to how TSP rules/codes apply directly and in
13、directly. The NS/EP private line circuit provisioning (and restoration/repair) is a direct application of TSP. The priority for provisioning this circuit is done according to TSP codes over other circuits, as is the assignment of TSP codes for circuit repair. By contrast, GETS is an NS/EP applicatio
14、n. Other non-NS/EP mechanisms are required to ensure the automated preferential treatment for NS/EP applications. For GETS, the SS7 message priority is not dictated by TSP codes. Rather, the SS7 message priority for GETS ensures that such calls are recognized and treated preferentially over non-GETS
15、 calls in the PSTN. ATIS-0100011 4 6 ROLE OF TSP IN AN NGN/IP ENVIRONMENT In the new environment of NGN/IP networks, the role of TSP can be examined by using the same two examples stated above. 6.1 Physical Facilities As in the PSTN case, NS/EP services can request the use of physical circuits in NG
16、N/IP networks. For example, DS3 or OC-3 circuits can be requested for designated NS/EP use. As above, direct TSP rules and codes apply for provisioning such circuits, as well as in the case for manual repair if automated restoration means are not available. 6.2 Emergency Telecommunications Service (
17、ETS) The evolution of the GETS in the PSTN to a broader class of services in NGN/IP environments - known as Emergency Telecommunications Service (ETS) - will require enhancements for automated preferential treatment. ETS encompasses real-time Voice over IP (VoIP) calls, as well as other forms of tel
18、ecommunications traffic data, video, and multimedia 3. As in the case with GETS in the PSTN, TSP codes do not apply directly here. Rather, as in the case for GETS in the PSTN, priority rules and mechanisms will be needed in NGN/IP environments in order to facilitate preferential admission and restor
19、ation policies. Specifically, priority agreements will be needed to classify ETS as a preferred service over other services, signaling extensions will need to be developed to communicate the high priority of ETS and - finally - priority-enabling mechanisms will be required that recognize the signale
20、d priority and provide desired actions. 6.2.1 Priority Classification In NGN/IP networks, three admission control/resource allocation priority levels have been established for all services 5, 6 1) “High”; 2) “Normal”; and 3) “Best Effort”. The “High” priority level is exclusively reserved for ETS ca
21、lls over all other calls. In NGN/IP networks, three service restoration priority levels have been established for all services under the assumption that automated restoration methods will be able to support multiple levels of restoration priorities 7 1) “High”; 2)“Normal”; and 3)“Best Effort”. ETS i
22、s included in the “High” priority level for services that require automated restoration. 6.2.2 Priority Signaling The priority levels established for ETS above need to be signaled to various network elements such that appropriate preferential treatment is enacted. In the IETF, two signaling protocol
23、s that signal service priority levels are as follows: 1. SIP Resource Priority Header (RPH) 8: The IETF Session Initiation Protocol (SIP) working group has established a Resource Priority Header for SIP messaging that indicates the priority nature of ETS. All ETS calls in IP environments are designa
24、ted with an “ets” ATIS-0100011 5 namespace with five priority sub-divisions that convey levels of importance in the application layer (within SIP elements). Incoming ETS calls/sessions are assigned the “ets” designation in the RPH header. In the transport layer, ETS calls/sessions are recognized by
25、the presence of the “ets” namespace RPH value in the SIP message, and accorded the “High” priority described above for resource reservation/assignment such that preferential treatment can be enacted. A similar namespace designation of “wps” accompanied by five priority sub-division values is availab
26、le for calls in wireless/3GPP networks. 2. Next Steps in Signaling (NSIS) 9, 10: The NSIS Working Group is standardizing a transport layer signaling protocol for the transport of upper layer signaling. Reservation and restoration priority attributes are included in the list of parameters that will b
27、e supported by NSIS. 6.2.3 Priority Mechanisms Priority enabling mechanisms in the transport layer of NGN/IP networks should be able to recognize the signaled “High” priority values of incoming ETS calls/sessions and provide appropriate action. Two examples of mechanisms under consideration are as f
28、ollows: 1. Diffserv-Aware MPLS Traffic Engineering: Combining DiffServ and MPLS-based Traffic Engineering can lead to true Quality of Service (QoS) in IP packet backbones 11,12. To achieve this functionality, networks have to be carefully engineered with traffic engineering applied on a per-class ba
29、sis; this is the essence of DiffServ-Aware MPLS Traffic Engineering (DS-TE) 13. An aggregated grouping of Traffic Trunks based on the class of service requirements such that they share the same bandwidth reservation is called Class Type (CT). Up to eight Class Types are allowed. Each CT has a priori
30、ty attribute ETS CT tunnels can be assigned/reserved with a “High” priority requirement. 2. MPLS Fast Re-route 14: This capability supports extensions to establish back-up Label Switched Path (LSP) tunnels for automated re-routing of tunnels that have been disrupted by failures. Priority for these t
31、unnels is supported tunnels with ETS traffic can be assigned “High” priority for re-routing in case of failures. 7 RECOMMENDATION FOR TSP USE IN NGN/IP NETWORKS The recommendation for TSP code usage in NGN/IP networks is stated as follows: A request for a physical circuit dedicated for NS/EP (e.g.,
32、private line) requires the use of TSP codes for provisioning and manual repair per current practice. Once provisioned, if this circuit can be restored via automated capabilities under failure conditions (e.g., circuit provisioned over a SONET ring), then TSP codes do not apply for the automated rest
33、oration process. If manual repair is necessary, then priority for repair is dictated by TSP codes per current practice. A request for an NS/EP service such as ETS that requires signaling procedures for call/session setup does not require the use of TSP codes. In such cases, the service request is es
34、tablished by signaling the “High” priority for call/session setup and service restoration in case of failure conditions. NS/EP services are classified with the highest available priority for admission control and service restoration. Signaling protocol extensions and underlying transport mechanisms that can support these classifications are under consideration and development.
