1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-1000668.1999(R2015) Signalling System Number 7 (SS7) Facility Request to Pivot (FRP) As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys most-pressing busine
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11、ce does not in any respect preclude anyone, whether he has approvedthe standards or not, from manufacturing, marketing, purchasing, or usingproducts, processes, or procedures not conforming to the standards.The American National Standards Institute does not develop standards andwill in no circumstan
12、ces give an interpretation of any American NationalStandard. Moreover, no person shall have the right or authority to issue aninterpretation of an American National Standard in the name of the AmericanNational Standards Institute. Requests for interpretations should beaddressed to the secretariat or
13、 sponsor whose name appears on the titlepage of this standard.CAUTION NOTICE: This American National Standard may be revised orwithdrawn at any time. The procedures of the American National StandardsInstitute require that action be taken periodically to reaffirm, revise, orwithdraw this standard. Pu
14、rchasers of American National Standards mayreceive current information on all standards by calling or writing the AmericanNational Standards Institute.American National StandardPublished byAmerican National Standards Institute, Inc.11 West 42nd Street, New York, NY 10036Copyright 1999 by Alliance fo
15、r Telecommunications Industry SolutionsAll rights reserved.No part of this publication may be reproduced in anyform, in an electronic retrieval system or otherwise,without prior written permission of the publisher.Printed in the United States of AmericaiContentsPageForeword ii1 Scope, Purpose, and A
16、pplication . 12 Normative References 13 Abbreviations and Definitions . 14 Description of Network Capability. 35 Functional Capabilities and Information Flows . 136 Protocol and Procedures 19Tables1 Pivot and Transit Pivot Active State Transitions. 152 Pivot Capability Format 203 Pivot Routing Indic
17、ator Format. 20Figures1 Typical call before Pivoting. 32 Typical call after Pivot Routing . 43 Typical Call Routing after Pivot failure 44 SDL Diagram for the Pivot node. 75 SDL Diagram for the Request node . 116 FE Model for FRP. 137 Information Flow for the Simple FRP Network Capability. 168 Infor
18、mation Flow for the FRP Network Capability with Failure Scenario 179 Information Flow for the FRP Network Capability with Cancel Scenario 1810 SDL for the FRP Network Capability 25iiForeword (This foreword is not part of American National Standard T1.668-1999.)FRP is a network capability that allows
19、 an application process or other network capa-bility at a switch, having determined that a received call should be connected to adestination switch other than itself, to have the connection established from a switchearlier in the call path. If the connection attempt from the earlier switch to the de
20、stina-tion switch fails, the current switch will forward route the call to the destination switch.FRP has been developed for use between U.S. networks to meet the anticipatedneeds and applications of those entities. This standard is the result of extensive workby members of the T1S1.3 Working Group
21、on U.S. Standards for Common ChannelSignalling.This standard is intended for use in conjunction with American National Standard forTelecommunications - Signalling System Number 7 (SS7) - ISDN User Part (ISUP),ANSI T1.113-1995, which includes an overview, messages and signals, protocol for-mats, proc
22、edures, and a chapter on performance. It should be noted, however, thatsome procedures specific to this standard are extensions beyond ANSI T1.113-1995.Footnotes are not officially part of this standard.Future control of this document will reside with Accredited Standards Committee onTelecommunicati
23、ons, T1. This control of additions to the specification, such as proto-col evolution, new applications and operational requirements, will permit compatibilityamong U.S. networks. Such additions will be incorporated in an orderly manner withdue consideration to the ITU-T layered model principles, con
24、ventions, and functionalboundaries.Suggestions for improvement of this standard will be welcome. These should be sentto the Alliance for Telecommunications Industry Solutions, T1 Secretariat, 1200 GStreet, NW, Suite 500, Washington, DC 20005.This standard was processed and approved for submittal to
25、ANSI by the AccreditedStandards Committee on Telecommunications, T1. Committee approval of this stan-dard does not necessarily imply that all committee members voted for its approval. Atthe time it approved this standard, the T1 Committee had the following members:Gerald H. Peterson, ChairmanE. Raym
26、ond Hapeman, Vice-ChairmanAlvin Lai, SecretaryJay Hilton, Technical EditorRanga Dendi, Technical EditorOrganization Represented Name of RepresentativeEXCHANGE CARRIERSAmeritech . L. Richard WoodLarry A. Young (Alt.)AT otherwise, it enters thePivot active statec) after having received Pivot Routing I
27、nformation from the R FE, check that the call does not appear tobe involved in an infinite loop of Pivot requests and then initiate the connection to the Destination noded) on connection initiation toward the Destination node, release the call leg between itself and the Re-quest nodeANSI T1.668-1999
28、14e) if connection initiation toward the Destination node is not possible, send a Pivot failure indication to theRequest nodef) if Pivot Cancel Information is received from the Request node, abandon the connection initiation to theDestination node. If the Pivot Cancel Information is received after t
29、he connection initiation toward theDestination node, the P capability once again will release the call between itself and the Requestnode.If the Pivot FE while in Transit Pivot active state receives the Pivot Routing Information and there is a priorpivot active node in the call path, the Pivot FE pe
30、rforms the functions described in 5.1.1.1.The Pivot FE can signal the Pivot capability on a service-by-service or call-by-call basis. The Request FErequires that the Pivot FE explicitly identify which calls are eligible for Pivot treatment and which are not.Therefore, a Pivot FE will pass forward to
31、wards the Request FE an indication of the latest call state forwhich the P capability is supported for this call.5.1.1.1 Description of Transit Pivot Active StateThe Pivot FE is in Transit Pivot active state when it is still Pivot capable and there is a prior Pivot activenode in the call path. In su
32、ch a situation, P FE passes the Pivot Routing Information to the prior Pivot ac-tive FE. If the Pivot FE while in this Transit Pivot active state, receives the Pivot failure indication from theprior Pivot FE, it will pivot route the call to the Destination node and release the call leg to the Reques
33、tnode as described in 5.1.1. The Pivot FE passes the Pivot Cancel Information from Request node to theprior pivot active node.5.1.1.2 Pivot and Transit Pivot Active State TransitionsThe Pivot Capability column in Table 1 shows the Pivot Capabilities offered by the two P FEs. For eachcombination of P
34、ivot capability at two Pivot capable nodes, this table illustrates the state of a P FE initially encountered in the call path (Initial P FE) the state of P FE subsequently encountered in the call path (subsequent P FE) the resultant ability of a R FE to request Pivot Routingas the call progresses th
35、rough the basic call states.ANSI T1.668-199915Table 1 - Pivot and Transit Pivot Active State TransitionsPivotCall Progress States CapabilityCall State ACM ACM Call State ANM ANM Call StateInitialP FESubseq.P FEInitialP FESubseq.P FERequestFEInitialP FESubseq.P FERequestFEInitialP FESubseq.P FEReques
36、tFEACM ACM PT A I I I I I IACM ANM PT A IP A I I IACM REL PT A IP A IP AANM ACM PT A PI A I I IANM ANM PT A PT A I I IANM REL PT A PT A IP AREL ACM PT A PI API AREL ANM PT A PT API AREL REL PT A PT APT ALegend: P = Pivot active, T = Transit Pivot active, I = Inability, A = AbilityThe column headed b
37、y “Call State ACM” shows the states of the P and R FEs prior to receiving anACM. Similarly columns headed by “ACM Call State ANM” and “ANM Call State” show the states ofthe P and R FEs after receiving ACM but before receiving ANM and after receiving ANM respectively. Ta-ble cell values P, T, and I r
38、epresent respectively the Pivot active, Transit Pivot active, and Inactive statesfor P FEs. Table cell values A and I represent the resultant Ability or Inability of the R FE to request PivotRouting.5.1.3 Description of Request Functional EntityThe R FE is in a Request node. The R FE contains the pi
39、vot requesting capability that can- receive Pivot Capability Information pertaining to a specific call,- send Pivot Routing Information to the Pivot functional entity and start the Pivot timer if Pivoting is in-voked,- proceed with the call setup to the Destination node if the Pivot failure indicati
40、on is received from theP FE, and- if the Pivot timer expires, send the Pivot Cancel Information to the Pivot node to withdraw its earlierpivot request. At this point R FE initiates the call setup to the Destination node.5.1.4 Description of the Supplementary Functional EntitiesSp, Sr, and Sdrepresen
41、t supplementary FEs that invoke the P function, the R function, or that provide ad-ditional supplementary services related to the call in the Destination node. The supplementary FEs repre-sent actions performed to support supplementary services or other network capabilities at the Pivot, Re-quest, a
42、nd Destination nodes. They may also represent node management actions controlling the opera-tion of FRP. Except for their role in controlling P and R FEs, as defined in this subclause, the actions ofthese FEs are outside the scope of the FRP network capability.The supplementary FEs can access inform
43、ation from basic and supplementary call control messages re-layed by their associated basic call control FEs. They may also direct the basic call control entities totransmit information required for their operation in basic or supplementary call control messages.The Request supplementary functional
44、entity, Sr, invokes the R FE, derives the new destination informa-tion to be passed from its associated R FE to P, and may derive additional optional information to bepassed. (Optional information used by the supplementary services is outside the scope of FRP.)ANSI T1.668-199916The Pivot supplementa
45、ry functional entity, Sp, may direct its associated P FE to signal or withhold the sig-nal of its capability for providing the P function. On receipt of a Pivot Request with Pivot Routing Informa-tion for a call whose incoming call setup message indicated the existence of a Pivot active node earlier
46、 inthe call path, Sp, may direct P to pass Pivot Request to the earlier Pivot active node (the default action) orto establish the call to the destination node.5.1.5 Description of the Intermediate Functional EntitiesThe intermediate FEs I1, I2, I3, and I4represent functions taking place at intermedi
47、ate nodes between anycombination pair of Pivot, Request, and Destination nodes. These functions are the basic call control, andrelaying of the supplementary information. For R and P FEs, the supplementary information is either PivotCapability Information, Pivot Routing Information, or Pivot Cancel I
48、nformation. Information relayed on be-half of the supplementary FEs is outside the scope of FRP.5.2 Information Flow ModelThe normal procedures of FRP are described in five parts as described in 4.3.2.2 Invocation and Opera-tion. The following paragraphs describe the FRP information flow model by us
49、ing the same five parts.Part 1: FRP Eligible CallTo invoke the FRP capability, a P FE has to receive a call request, and to be in the process of setting up acall to a R FE. When it, in cooperation with the supplementary FEs, decides that a call will be eligible forFRP, the P FE sends Pivot Capability Information to the R FE. If P FE received the Pivot Capability Infor-mation in the incoming call setup, it will send toward R FE the Pivot Capability value reflecting the larger(later) of the received capability and its own capability.If FRP capability is not desired on a call, no Piv
