1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0!.$G0G0)3$.15!,)49G0G0/ the calling pattern (which is usually residential in nature) may be different than the normal pattern (whichis usually business-oriented).A combination of these f
2、actors can result in a network that is highly congested and which requires carefulplanning and extensive network management controls to optimize service and revenues.It should be noted that many peak calling days may also be public holidays. As a result, staffing in telephoneexchanges and administra
3、tive offices may be minimal and some traffic data and service measurements may not bereadily available. These factors should also be considered in peak-day planning.3.2 Peak-day plans may include information on the following, as appropriate: Network management staffing requirements and expected hour
4、s of operations, and the exchange of suchinformation with other network management centres. Provision of temporary additional circuits. Directionalization of both-way circuits where appropriate. Temporary alternative routings to take advantage of anticipated idle capacity. Controls to inhibit altern
5、ate routing via transit points that are expected to be congested. Identification of anticipated hard-to-reach points and planned controls to reduce attempts to hard-to-reachpoints. Special calling procedures for operators, including the exchange of network status information withoperator centres. Ad
6、vance testing of new controls, or those infrequently used (including the testing of the rerouting to ensureproper operation and the ability to complete to a terminating number via the transit point). Consideration of limiting installation and maintenance activity just prior to the peak day to only e
7、ssentialwork in order to insure that all available circuits and switching equipment are in service. Procedures to take into account special situations, such as inter-ISC circuit groups, circuit multiplicationsystems, etc.4 Transmission system failure planning4.1 The impact on service of the failure
8、of an international transmission system will depend on a number ofvariables:Fascicle II.3 - Rec. E.413 3 the size of the failed transmission system and its relationship to the total network capacity; its loading (the number of channels that are assigned for use) (this may change frequently); the des
9、tinations and/or services assigned to the transmission system and their relationship to theirrespective totals (this may change frequently); the traffic intensity during the period from the onset of a failure until restoration or repair (this can varysignificantly); the duration of the failure (this
10、 is usually unpredictable); the availability of restoration capacity (this can vary).Thus, it can be seen that it is difficult, if not impossible, to predict the precise impact on service of a failure at agiven point in time. However, recognizing the increasing size and loading of modern transmissio
11、n systems, the impactof a failure on service can often be severe, and as a result, significant effort has been expended by Administrations todevelop and refine transmission system failure restoration plans.Experience has shown that network management actions can also play a significant role in minim
12、izing theadverse impact of failures on service. However, it should be noted that these network management actions will usuallycomplement or enhance a transmission failure restoration plan and do not necessarily supplant the need for such plans.For short duration failures, e.g., solar interference on
13、 satellites, network management plans may be the only viablesolution.4.2 When an international transmission system fails, network management and transmission restoration activitiesshould proceed in parallel on a coordinated basis. The network management centre will become aware of the impact of a fa
14、ilure on service via its networksurveillance capacity; in some cases, this will occur before the specific details of the failure are known. Thenetwork management centre can identify the affected routes, destinations and/or services. This informationwill guide the application of network management co
15、ntrols and may also be useful to the restorationcontrol point (Recommendation M.725) in setting priorities for restoration. The first response of the network management centre should be to consider the use of temporary alternativeroutings in order to complete traffic which is being blocked by the fa
16、ilure. In many cases, these actions canbegin immediately, before the decision is made to activate a transmission restoration plan. If significant congestion continues despite the expansive controls, protective controls should be considered.Emphasis should be placed on the identification of destinati
17、ons that are hard-to-reach and the selectivereduction of traffic to these points so that the remaining network can be used by traffic with a higherprobability of success.4.3 It is recommended that a network management plan for the failure of a major international transmission systemshould include th
18、e following, as appropriate: identification of destinations or points affected for originating and terminating traffic, temporary alternative routings which may be utilized to bypass the failure, and hours of availability, notification lists, special call handling procedures for operators, controls
19、which may be required in connected networks, controls to be requested of distant network management centres, actions to be taken after fault correction to restore the network to its normal configuration, special recorded announcements to customers, when necessary.5 International exchange failure pla
20、nning5.1 The impact on service of the failure of an international exchange will depend on a number of variables, whichinclude: whether there is a single or multiple international exchange(s), the routing plan and the distribution of circuit groups among the international exchanges, the traffic inten
21、sity during the failure, the duration of the failure, the size (capacity) and the current loading of the failed exchange, and its relationship to the totalinternational switching capacity.4 Fascicle II.3 - Rec. E.413In any case, the failure of an international exchange usually will have a severe imp
22、act on service. Networkmanagement exchange failure plans can provide considerable benefits during the failure by limiting the spread ofcongestion to connected exchanges and providing alternative ways of routing traffic to bypass the failed exchange.5.2 It is recommended that a network management exc
23、hange failure plan should include the following information,as appropriate: general information about the exchange and its function in the network, including diagrams of the normalnetwork configuration and the reconfigured network during a failure, actions to be taken to verify a total failure of an
24、 exchange to differentiate it from certain fault recoveryactions in SPC exchanges which may, at first, appear similar, notification lists, initial control actions to be taken upon verification of exchange failure, additional control actions to be taken based on the prognosis of the failure, controls
25、 to be applied within the national network, controls to be requested of distant network management centres, modifications which may be required to automatic controls, sequence of control removal when the exchange is restored to normal operation.5.3 It is recommended that network management exchange
26、failure plans be reviewed and up-dated whenever asignificant change in network configuration occurs, or at least annually. A network management exchange failure planshould be prepared for a new international exchange before it is introduced into the network.6 Common channel signalling (CCS) failure
27、planning6.1 When a failure in the common channel signalling system interrupts the flow of traffic, the affected traffic maybe diverted by network management controls to other unaffected circuits groups. It is preferable that these actions beplanned in advance. These plans should identify the modific
28、ations to the automatic CCS flow control responses whichmay be required in the exchanges to permit the planned actions to be taken for example, to change the normalprogrammed response to the receipt of a transfer prohibited signal (TFP).6.2 It should be noted that, as more of the international netwo
29、rk converts to common channel signalling, theavailability of potential alternative routing may become limited, which will increase the need for careful planning.7 Mass-calling planning7.1 Uncontrolled mass-calling has the potential to seriously disrupt calling in the network. However, with properpla
30、nning, the adverse effects of many mass-calling situations may be minimized. The key to success is advancewarning and interdepartmental cooperation and planning.This requires that the Administration be alert to potential mass-calling situations so that the proposed use of thenetwork can be evaluated
31、 in advance to determine the potential for congestion. When congestion appears likely,alternative serving arrangements may be proposed, which may include the use of network management controls.7.2 With widespread availability of call-gapping controls (see Recommendation E.412), certain mass-callinga
32、pplications may be provided without harm to the network. The call-gap controls can be set at each exchange to limitoutgoing calls to only the amount necessary to keep the called lines filled. It must be noted, however, that no mass-calling control strategy can prevent originating congestion and dial
33、 tone delays in local exchanges if a large number ofcustomers simultaneously attempt to dial a service or specific number.8 DisastersDisasters can be natural (for example, a typhoon, an earthquake) or man-made (an airplane or railroadaccident). These events can result in either damage to network fac
34、ilities or in an extraordinary number of calls, or both.While it is difficult to predict such a disaster, the effects of a disaster on the telephone network can be predicted withsome degree of accuracy and plans developed accordingly. These plans should include: contact and notification lists, contr
35、ol actions required locally and/or in other Administrations, arrangements for additional staffing and extended hours of operation.(See Recommendation E.411, 6.5.)Fascicle II.3 - Rec. E.413 59 Planning for the introduction of new servicesThe introduction of new services in the network may result in n
36、ew or unusual traffic flow characteristics,and/or unusual traffic demand, particularly when there is strong initial interest in the new service. Therefore, thepotential impact on the network of a new service should be evaluated to identify where congestion or deterioratedservice might occur, and to
37、identify what special network management surveillance and control capabilities may berequired. It is important that this analysis take place well in advance of the planned service availability date, so that thenecessary modifications to the exchange and/or network management operations system softwa
38、re can be completed in atimely manner. This will help to insure that the necessary surveillance and control capabilities will be available whenthe new service is introduced.10 Negotiation and coordination10.1 Administrations should exchange information concerning their network management capabilitie
39、s as part of thenetwork management planning process. Specific plans should be negotiated in advance on a bilateral or multilateralbasis, as appropriate. Negotiation in advance will allow time to fully consider all aspects of a proposed plan and toresolve areas of concern, and will permit prompt acti
40、vation when needed.10.2 The use of any network management plan must be coordinated with the involved Administrations at the time ofimplementation. This will include (as appropriate): determining that planned transit exchange(s) have switching capacity to handle the additional traffic, determining th
41、at there is capacity in the circuit group(s) between the planned transit point and thedestination, advising the transit Administration(s) that transit traffic will be present in its circuit groups and exchanges, arranging for the activation of controls at distant locations, arranging for surveillance of the plan while in effect to determine the need to modify the plan.When the use of a plan is no longer required, all involved Administrations should be notified of itsdiscontinuance, so that the network can be restored to its normal configuration.
