Preface
Rules of the code relating to calling line identifications
Rules of the code relating to connected line identification
1.1 The provision of Customer Line Identification display and other related services, including the ETSI CLIP and COLP services, requires that there is end-to-end availability and control of this information, and that this information is generated in a consistent way. Unless this is achieved these services cannot be provided efficiently as the status of the message (e.g. the validity of the numbers displayed) cannot be guaranteed by the provider of the display service. Therefore, consistency is required between the network where the messages are generated and the network where the messages are displayed
Where interconnection between two or more networks occurs, some way of ensuring that all networks adhere to the same rules is required if customers of display and other related services are to have confidence in such a service.
1.2 The cardinal principles for the use of Customer Line Identities are:
Privacy: Customers who wish to withhold their line identity should always be able to do so and be confident that their wishes will be respected by all parties in a call;
Authenticity: The line identity should always represent the correct identity of the calling or called customer or the number where return or subsequent calls are desired to be made;
Integrity: The line identity and its associated privacy marking should be respected and maintained by all parties in a call.
1.3 Against the foregoing background, this Code of Practice (CoP) is designed to achieve a number of objectives:
1.4 The CoP has been the subject of a public consultation and has been drawn up by an industry group which included network operators, consumer representatives, the Data Protection Registrar and Oftel. Network operators have agreed to abide by the CoP and it forms part of their agreements for interconnection.
1.5 The CoP is not a technical standard, rather its purpose is to form a mutually agreed set of rules about how customer line identities are implemented in order to protect UK consumers by ensuring a necessary degree of consistency.
2.1 This document constitutes a CoP for operators of UK telecommunication networks interconnected with public telecommunication systems in the UK. This CoP governs the responsibilities of such operators in relation to customer line identity information in connection with the provision of a display or related services. In particular it covers the responsibilities of networks in relation to the origination of customer line identity information, the transmission across networks of such information, and the delivery to a network terminating point of customer line identity information, including the details concerning the status of that information.
2.2 As UK telecommunication networks develop it may be necessary for the Rules in this CoP to cover networks and call types not currently included in Paragraphs 2.3 and 2.4 below. This will be achieved by the use of the mechanism to change the content of the CoP, as set out in Paragraph 3 below, in conjunction with, where necessary, other regulatory means.
2.3 Networks covered: This CoP covers all public networks in the UK supporting both PSTN and/or public ISDN interfaces, including GSM networks.
2.4 Call types covered: All circuit-switched calls originating or terminating on networks which are covered by this CoP. (Transit calls that neither originate nor terminate in the UK are not covered.)
2.5 The operation of this CoP does not affect the
ability of networks (both public and private) to use customer line identity information
for network and/or account management purposes and, in co-operation with the relevant
authorities, for emergency calls and the tracing of malicious calls and similar
activities. However, the privileged access that public network operators have to
customers’ CLIs, whether or not CLI Restriction has been invoked, may only be used
for the purposes described above. Network operators will respect the privacy of calling
customers who have invoked CLIR by not exploiting their CLIs for telemarketing or any
commercial purpose other than billing.
3.1 This CoP, and modifications to this CoP, shall be published by the Director General of Telecommunications.
3.2 The Oftel research and intelligence unit will keep up to date copies of the CoP which will be available to the public either free or at a price that reflects the costs of copying the CoP.
3.3 Modifications to this CoP shall only be made by the Director General under the following circumstances:
after consultation with public network operators and any other bodies or individuals that the Director General considers appropriate. (All representations received by the Director General shall be reasonably considered.)
This CoP shall be incorporated in the interconnection
agreements between Public Network Operators (PNOs). However, nothing in this CoP absolves
a PNO from operating according to the terms of its licence and/or any other legal
instrument (including European regulations) which is applicable to that operator. Where a
licence condition or UK or EU regulation conflicts with this CoP the licence condition UK
or EU regulation shall take precedence.
| CLI | Calling Line Identity |
| CLIP | Calling Line Identification Presentation |
| CLIR | Calling Line Identification Restriction |
| COL | Connected Line Identity |
| COLP | Connected Line Identification Presentation |
| COLR | Connected Line Identification Restriction |
| CoP | Code of Practice |
| ETS | European Telecommunications Standard |
| ETSI | European Telecommunications Standards Institute |
| EU | European Union |
| ISDN | Integrated Services Digital Network |
| NN | Network Number |
| NP | Network Provided |
| NTP | Network Termination Point |
| PN | Presentation Number |
| PNO | Public Network Operator |
| PSTN | Public Switched Telephone Network |
| UPNV | User Provided Not Verified |
| UPVP | User Provided Verified and Passed |
In this CoP there are some terms used that do not have precise meanings in everyday use. For the interpretation of this CoP they have been given the following, more precise, meanings:
6.1 Calling Line Identification (CLI):
The CLI is either a:
network number that unambiguously identifies the
ingress port to the public network.
or a
presentation number that identifies the NTP to which a
return call can be made.
6.2 Classification of CLI information:
For display purposes CLI information can have one of three classifications:
6.2.1 Available: condition in which the CLI exists and can be passed to the called customer’s NTP on the terminating network.
6.2.2 Unavailable: condition in which the CLI does not exist or the originating network does not support the CLIR service or interworking has been encountered and consequently the CLI cannot be passed.
6.2.3 Withheld: condition in which the CLI is not for transmission to the called customer’s NTP on the terminating network, because the calling customer is directly connected to a network that supports the CLIP service and has invoked CLIR.
6.3 Classification of COL information:
For display purposes COL information can have one of three classifications:
6.3.1 Available: condition in which the COL exists and can be passed to the calling customer’s NTP on the originating network.
6.3.2 Unavailable: condition in which the COL does not exist or the terminating network does not support the COLR service or interworking has been encountered, and consequently the COL cannot be passed.
6.3.3 Withheld: condition in which the COL is not for transmission to the calling customer’s NTP on the originating network, because the connected customer is directly connected to a network that supports the COLP service and has invoked COLR.
6.4 CLI display service and related services:
the delivery to the customer’s NTP of information that allows that customer to gain access to the caller’s CLI. This could be in the form of information that is displayed, recorded, interpreted by a database or provided by means of an audio message or by other means.
6.5 CLIP – Calling Line Identification Presentation:
a supplementary service that provides the called party with the possibility of receiving identification of the calling party
6.6 CLIR – Calling Line Identification Restriction:
a supplementary service which allows the calling user to prevent presentation of his CLI to the called access (NTP). The CLIR service may operate in two modes, determined by a subscription option:
Permanent Mode The CLIR supplementary service is invoked automatically by the network on all calls originated by the calling user.
Temporary Mode This mode allows the served user to indicate on per call basis whether or not presentation of the served user’s calling line identity is allowed.
Where CLIR temporary mode is used, a ‘Temporary Mode Default’ is supplied as a subscription option. This is either:
Presentation Not Restricted CLIR is not invoked unless explicitly requested by the caller
Presentation Restricted CLIR is always invoked unless explicitly disabled by the caller
Note 1: These terms are standardised in ETS 300 090 for ISDN and ETS 300 649 for the PSTN.
Note 2: ETSI standards require that a network which supports CLIR must support at least CLIR Temporary Mode.
6.7 Connected Line Identification (COL):
The COL is either a:
Network Number that unambiguously identifies the
egress port from the public network.
or a
Presentation Number that identifies the NTP to which a
subsequent call can be made.
6.8 COL display service and related services:
the delivery to the customer’s NTP of information that allows that customer to gain access to the COL. This could be in the form of information that is displayed, recorded, interpreted by a database or provided by means of an audio message, or by other means.
6.9 COLP – Connected Line Identification Presentation:
the supplementary service that provides the calling party with the possibility of receiving identification of the connected party
6.10 COLR – Connected Line Identification Restriction:
the supplementary service that allows the connected user to prevent presentation of their COL to the calling access (NTP). The COLR service may operate in two modes, determined by a subscription option:
Permanent Mode The COLR supplementary service is invoked automatically by the network on all calls received by the connected user.
Temporary Mode This mode allows the served user to indicate on per call basis whether or not presentation of the served user’s connected line identity is allowed.
Where COLR temporary mode is used, a ‘Temporary Mode Default’ is supplied as a subscription option. This is either:
Presentation Not Restricted COLR is not invoked unless explicitly requested by the connected user
Presentation Restricted COLR is always invoked unless explicitly disabled by the connected user
Note 1: These terms are standardised in ETS 300 095 for ISDN.
Note 2: ETSI standards require that an ISDN which supports COLR must support at least COLR Temporary Mode.
6.11 Indirect Access Network:
a network that provides telecommunication service to an end user via the switched access network of another network operator.
6.12 Network Number (NN):
the digits that comprise a unique E.164 [2] number that unambiguously identifies the ingress port to, or egress port from, the public network, ie the network termination point (NTP).
Note 1: This number identifies the actual network termination from which the call originates, or at which the call terminates, and has additional uses in connection with charging and malicious call identification.
Note 2: Network Number is also known as administration number, electric number, or network provided billing number.
Note 3: A network number may be network provided (NP), user provided verified and passed (UPVP) or user provided not verified (UPNV). However, the use of a UPNV-NN is not permitted.
Note 4: The use of one number to identify both ingress and egress points is permitted by this definition, but only where both points are owned by one network operator, or where agreement for its use is reached between the operators involved.
Note 5: Where the ingress or egress port consists of multiline access, e.g. a PBX group, a single network number may apply to the whole group.
6.13 Network Provided (NP) number:
a number that is stored in the network and which identifies a NTP.
Note 1: A network provided number may also be referred to as a default number.
Note 2: A network provided number may be a network number or a presentation number.
Note 3: On ISDN calls it is forwarded by the network if there is no special arrangement, and the customer’s equipment does not send a number, or the number sent fails screening.
6.14 Network Terminating Point:
has the same meaning as Annex A 2(I) of BT’s Licence for fixed link terminating networks, and is the air interface for terminating mobile networks.
6.15 Originating Network:
the network to which the customer who originates the call is directly connected.
Note: This means that the CoP puts a responsibility on the Originating Network even if the customer is paying for the call via another network – eg indirect access – but the CoP does not specify how the classification of CLI information is to be passed between networks. In this case it could be by means of the passing of the digit stream ‘141’, or by some other means.
6.16 Presentation Number (PN):
a number that identifies the network termination point (NTP) to which a return or subsequent call can be made.
Note 1: Presentation Number is used when the network number of the calling or connected customer is not suitable for display. This is important where PABXs have segregated incoming and outgoing lines.
Note 2: Presentation Number is also known as diallable number.
Note 3: A presentation number may be network provided (NP), user provided verified and passed (UPVP) or user provided not verified (UPNV).
6.17 Receiving Network:
the network in receipt of a call across any interconnect. The receiving network will also be a transit network or a terminating network for that call.
6.18 Special Arrangement:
an agreement between a customer and a public network operator whereby the customer undertakes to provide for display only authentic calling party numbers which are not screened by the public ISDN.
6.19 Standard CLI blocking prefix:
this is the prefix generally used (currently ‘141’) to invoke the CLIR service where it is provisioned in Temporary Mode with default ‘presentation not restricted.’
6.20 Standard CLI unblocking prefix:
this is the prefix generally used (currently ‘1470’) to prevent invocation of the CLIR service where it is provisioned in Temporary Mode with default ‘presentation restricted.’
6.21 Terminating Network:
the network to which the customer who receives a call is directly connected.
6.22 Transit Network:
a network through which a call passes, but which is neither the originating network nor the terminating network for that call.
6.23 User Provided, Not Verified (UPNV) number:
a number that is supplied by a user which identifies a NTP and has not been subjected to screening or editing by the network.
6.24 User Provided, Verified and Passed (UPVP) number:
a number whose most significant part is network provided and whose least significant part is supplied by a user and successfully checked by the network for length and range, and which identifies a NTP.
Note 1: A user provided, verified and passed number may be a network number or a presentation number.
7 RULES OF THE CODE RELATING TO CALLING LINE IDENTIFICATION
The following rules apply equally to ‘network numbers’ and ‘presentation numbers.’
7.1 Classification of CLI information
For CLI display purposes CLI information shall have one of three classifications (for definitions see Paragraph 6.2 ):
‘Available’
‘Unavailable’
‘Withheld.’
The network number may be classified as Available, Unavailable or Withheld, and presentation number may be classified as Available or Withheld.
The classification of the CLI information shall be determined by the originating network for calls originated in the UK. The classification determined by the originating network shall be maintained for calls originating outside the UK.
7.2 Responsibilities of the Originating Network
7.2.1 Classification of CLI information
It is the responsibility of the Originating Network to ensure that CLI information is correctly classified. The rules for classifying the CLI information depend on the availability of the CLIR service.
For calls from analogue terminals where CLIR Temporary mode is provisioned with the Temporary Mode Default set to ‘presentation not restricted’ then the CLIR service shall be invoked by the caller dialling the standard CLI blocking prefix before their required number, or by some other means (see Rule 6).
For calls from analogue terminals where CLIR Temporary mode is provisioned with the Temporary Mode Default set to ‘presentation restricted’ then the CLIR service shall usually be overridden by the caller dialling the standard CLI unblocking prefix before their required number, or by some other means (see Rule 7).
The rules below describe how the originating network
classifies the CLI information. These rules give rise to the following combinations of
classifications:
| Network Number | Presentation Number | |
| CLIR operational but not invoked, PN not available | available | not applicable |
| CLIR operational but not | available Note 1 |
available |
| invoked, PN available | unavailable Notes 1 and 2 |
available |
| CLIR operational and invoked, PN available | withheld | withheld |
| CLIR operational and invoked, PN not available | withheld | not applicable |
| CLIR not operational, PN not available | unavailable | not applicable |
Note 1: The choice between available and unavailable for NN is a customer subscription option.
Note 2: As an interim measure some networks may use ‘withheld.’
7.2.2 Conditions to be met by Presentation Number:
Note: A Presentation Number service will operate only where the originating network supports origination of a presentation number, and the terminating network supports display of a presentation number.
Note: Premium rate numbers appear on the ICSTIS list Premium Rate Dialling Codes and Charges.
It is further required:
(a) that the originating operator providing the presentation number service has the following responsibilities:
(i) to have established and recorded the consent of the party to whom a connection would be made for their associated national dialling sequence to be used for that purpose;
(ii) to have established (with another operator, if applicable) that the same associated national dialling sequence has been and remains allocated to the presentation number applicant;
(iii) to have established the consent of the party to whom a connection would be made for their associated dialling sequence to be available for reverse searches made in the interests of good administration;
(iv) to correctly datafill a presentation number;
(b) that an operator who has allocated a party a dialling sequence as a Network Number, and informed an originating operator of that allocation, shall, if requested by that originating operator, for the purpose of facilitating a presentation number service, enter into an agreement with that operator to inform it if and when that allocation should cease.
7.2.3 Calls where CLIR is not operational
Rule CLI-1 Where CLIR is not operational, dialling the standard CLI blocking or unblocking prefix shall either have no effect on the call (which should therefore be routed to the destination indicated by the remaining digits of the called party number), or the call shall be terminated at the originating network.
Rule CLI-2 All CLI information emerging from networks where CLIR is not operational shall be classified ‘unavailable.’
Rule CLI-3 All CLI information originating on any part of any network where CLIR is not operational shall be classified ‘unavailable.’
Rule CLI-4 All CLI information originating on parts of networks where customers have not been informed that CLI will be forwarded unless they invoke the CLIR supplementary service shall be classified ‘unavailable.’
Note: Since presentation numbers cannot be classified ‘unavailable’, then presentation numbers shall not be sent in the above cases.
7.2.4 Calls where CLIR is operational
Rule CLI-5 CLI information originating on parts of networks where CLIR is operational, and customers have been informed, shall be classified as follows:
Note: The choice of whether the network number is classified ‘available’ or ‘unavailable’ in this case is network or customer specific.
* As an interim measure some networks may use ‘withheld.’
Rule CLI-6 Where the originating network supports invocation of the CLIR supplementary service in the temporary mode with default value ‘presentation not restricted’ via a means other than the standard CLI blocking prefix, then dialling the standard CLI blocking prefix shall preferably result in a message (uncharged) which tells the customer what prefix to dial (or other action to take) in order to invoke CLIR. Alternatively dialling the standard CLI blocking prefix shall cause the call to fail (eg number unobtainable tone).
Rule CLI-7 Where the originating network supports overriding of the CLIR supplementary service in the temporary mode with default value ‘presentation restricted’ via a means other than the standard CLI unblocking prefix, then dialling the standard CLI unblocking prefix shall preferably result in a message (uncharged) which tells the customer what prefix to dial (or other action to take) in order to not invoke CLIR. Alternatively dialling the standard CLI unblocking prefix shall cause the call to fail (eg number unobtainable tone).
Note: Networks where customers making calls are contracted for those calls to a service provider shall have satisfied the requirement to inform customers that CLI will be forwarded if CLIR is operational. The originating network shall have informed the service provider no later than a period equal to two billing cycles in advance of: the start of CLIP services or the start of the sending of CLI for display or related services (whichever is the earlier,) or the fact that CLI will be forwarded unless CLIR has been invoked.
7.2.5 Verification of CLI information supplied by the calling customer
CLI information may be supplied by the calling customer from ISDN originating lines. The Originating Network has a responsibility to verify that CLI information supplied by the calling customer is valid for the particular calling customer. How this responsibility is discharged depends on whether a ‘Special Arrangement’ to forward user provided information without verification applies.
7.2.6 ‘Special Arrangements’ do not apply
Rule CLI-8 Where a ‘Special Arrangement’ does not apply, the Originating Network must ensure on a call by call basis that CLI information either wholly or partly supplied by the calling customer’s equipment is valid for the particular calling customer. Where the CLI information supplied by the calling customer is found to be invalid, the Originating Network shall supply alternative information in accordance with the rules of this CoP.
7.2.7 ‘Special Arrangements’ apply
Rule CLI-9 Where a ‘Special Arrangement’ applies, the customer must enter into an explicit agreement to ensure that the information he supplies is valid. The Originating Network’s responsibility to ensure the validity of the information is discharged by means of this explicit agreement and the Originating Network need not perform any call by call verification upon the CLI information supplied by the customer’s equipment.
7.3 Responsibilities of Terminating Network
It is the responsibility of the Terminating Network to ensure that the classification of calls is respected in the delivery of that call to the final destination. The following rules shall apply:
Rule CLI-10 A Terminating Network that supports a CLIP service and/or related services shall ensure that CLI information shall be available at the called customer’s NTP only if it is classified as ‘available.’ In addition, any other service that allows the called party to call back or gain access to the calling line identification shall similarly be available only in relation to CLI information with the ‘available’ classification.
Rule CLI-11 Where the Terminating Network supports
a CLIP service the information delivered to the destination NTP must adhere to the
following:
| Indicator at interconnect | Information at NTP (Note 1) |
| Withheld | Withheld indicator, no CLI information |
| Unavailable | Unavailable indicator, no CLI information (Note 2) |
| Available | CLI information |
Note 1: This CoP does not determine how the indicators should be displayed.
Note 2: The indicator for ‘unavailable’ might be an empty data set. The crucial factor is that it can be distinguished in some way from the ‘withheld’ indicator.
Rule CLI-12 Where the Terminating Network is not capable of supporting CLIP or related services no action is required on the basis of the call classification.
Rule CLI-13 Where a Terminating Network offers a service which screens ‘anonymous’ calls to its customers, this service shall not operate in such a way as to have anti-competitive effects (eg by rejecting all calls where the CLI information is classified as ‘unavailable'). This does not preclude the offering of other services which treat calls where the CLI information is classified as ‘unavailable’ on a legitimate, differentiated services, basis (eg where the called customer is part of a closed user group).
7.4 Responsibilities of Transit Networks
Rule CLI-14 Except as allowed for by Rule 16, a Transit Network shall ensure that the caller’s CLI information and classification do not alter from the point of entry to the point of exit except where such alterations are part of a service offered by the Transit Network and explicitly requested by the calling party (eg Intelligent Network service).
Rule CLI-15 Where it is not technically possible to comply with Rule 14 the following shall apply:
(a) if the integrity of the CLI information cannot be maintained, but the classification can, then an ‘available’ classification shall be changed to ‘unavailable’ and other classifications shall remain unchanged. This shall result in a presentation number being discarded;
(b) if the integrity of the classification cannot be maintained, the exit classification shall be ‘unavailable.’
7.5 Responsibilities of Networks providing additional services
A network that is not the originating network can also offer a CLIR service, or other CLI-related services, if it wishes. The method by which these services are offered is up to the network providing additional services. A networks offering such services takes on the responsibilities of an Originating Network in respect of the classification of the CLI information, if its customers activate this service. Such a scenario could apply where an intermediate network forwards a personal number on a charge card call or indirect access call.
Rule CLI-16 A network offering additional CLIR services, or other CLI related services, must ensure that CLI information on calls where its customers have activated these services is correctly classified, according to the Rules for Originating Networks, upon handover to another operator.
A network providing additional services supplying CLI must offer per call blocking, or obey the per call blocking instructions received from the originating network before it can send forward a CLI. Equally, a network providing additional services which changes an ‘unavailable’ to ‘available’ can only do so if it offers the caller a per call blocking code and the other requirements for Originating Networks.
7.6 Calls received from Networks that do not conform to this CoP
The responsibility for ensuring the integrity of the CLI information and classification lies with the Originating Network and any Transit Networks from and via which that information is being received. However, where these networks have declared that they are unable to meet the Rules outlined above, it is the responsibility of the network receiving the call to ensure that CLI information and classification defaults to values meeting the requirements of this CoP.
7.6.1 Calls received from networks covered by the CoP
Rule CLI-17 If the network(s) from which CLI and/or classification information is being received cannot, or do not, conform to the Rules set out above, the receiving network shall operate Rule 15 at the point of entry to determine the classification of the call.
7.6.2 Calls received from networks not covered by the CoP
Rule CLI-18 Calls received from networks not covered by this CoP (eg International calls) shall be classified by the receiving network as follows:
(a) if an explicit indication is received that the calling party wishes that his CLI should not be made available at the called customer’s NTP then the CLI information shall be classified as ‘withheld;’
(b) otherwise, if CLI information is available, then it shall be classified as ‘available.’
8 RULES OF THE CODE RELATING TO CONNECTED LINE IDENTIFICATION
The following rules apply equally to ‘network numbers’ and ‘presentation numbers.’
8.1 Classification of COL information
For COL display purposes COL information shall have one of three classifications (for definitions see Paragraph 6.3 ):
‘Available’
‘Unavailable’
‘Withheld.’
The network number may be classified as Available, Unavailable or Withheld, and presentation number may be classified as Available or Withheld.
The classification of the COL information shall be determined by the terminating network for calls originated in the UK. The classification determined by the terminating network shall be maintained for calls originating outside the UK.
8.2 Responsibilities of the Terminating Network
8.2.1 Classification of COL information
It is the responsibility of the Terminating Network to ensure that COL information is correctly classified. The rules for classifying the COL information depend on the availability of the COLR service.
For calls to ISDN terminals where COLR Temporary mode is provisioned with the Temporary Mode Default set to ‘presentation not restricted’ then the COLR service shall be invoked by the connected user before answering the call .
For calls to ISDN terminals where COLR Temporary mode is provisioned with the Temporary Mode Default set to ‘presentation restricted’ then the COLR service shall be overridden by the connected user before answering the call.
For calls to analogue terminals COLR is not possible in Temporary mode.
The rules below describe how the terminating network classifies the COL information.
These rules give rise to the following classifications:
| Network Number | Presentation Number | |
| COLR operational but not invoked, PN not available | available | not applicable |
| COLR operational but not | available Note 1 |
available |
| invoked, PN available | unavailable Notes 1 and 2 |
available |
| COLR operational and invoked, PN available | withheld | withheld |
| COLR operational and invoked, PN not available | withheld | not applicable |
| COLR not operational, PN not available | unavailable | not applicable |
Note 1: The choice between available and unavailable for NN is a customer subscription option.
Note 2: As an interim measure some networks may use ‘withheld.’
8.2.2 Conditions to be met by Presentation Number:
Note: A Presentation Number service will operate only where the originating network supports origination of a presentation number, and the terminating network supports display of a presentation number.
Note: Premium rate numbers appear on the ICSTIS list ‘Premium Rate Dialling Codes and Charges.’
It is further required:
(a) that the terminating operator providing the presentation number service has the following responsibilities:
(i) to have established and recorded the consent of the party to whom a connection would be made for their associated national dialling sequence to be used for that purpose;
(ii) to have established (with another operator, if applicable) that the same associated national dialling sequence has been and remains allocated to the presentation number applicant;
(iii) to have established the consent of the party to whom a connection would be made for their associated dialling sequence to be available for reverse searches made in the interests of good administration;
(iv) to correctly datafill a presentation number;
(b) that an operator who has allocated a party a dialling sequence as a Network Number and informed a terminating operator of that allocation shall, if requested by that terminating operator, for the purpose of facilitating a presentation number service, enter into an agreement with that operator to inform it if and when that allocation should cease.
8.2.3 Calls where COLR is not operational
Rule COL-1 All COL information emerging from networks where COLR is not operational shall be classified ‘unavailable.’
Rule COL-2 All COL information originating on any part of any network where COLR is not operational shall be classified ‘unavailable.’
Rule COL-3 All COL information originating on parts of networks where customers have not been informed that COL will be returned unless they invoke the COLR supplementary service shall be classified ‘unavailable’.
Note: Since presentation numbers cannot be classified ‘unavailable’, then presentation numbers shall not be sent in the above cases.
8.2.4 Calls where COLR is operational
Rule COL-4 COL information originating on parts of networks where COLR is operational, and customers have been informed, shall be classified as follows:
If COLR has been invoked, then COL information shall be classified as ‘withheld;’
If COLR has not been invoked, then the COL information shall be classified as ‘available;’
Note: Networks where customers receiving calls are contracted for those calls to a service provider shall have satisfied the requirement to inform customers that COL will be returned if COLR is operational. The terminating network shall have informed the service provider no later than a period equal to two billing cycles in advance of: the start of COLP services or the start of the sending of COL for display or related services (whichever is the earlier,) of the fact that COL will be returned unless COLR has been invoked.
8.2.5 Verification of COL information supplied by the connected customer
COL information may be supplied by the connected customer from ISDN terminating lines. The Terminating Network has a responsibility to verify that COL information supplied by the connected customer is valid for the particular connected customer. How this responsibility is discharged depends on whether a ‘Special Arrangement’ to forward user provided information without verification applies.
8.2.6 ‘Special Arrangements’ do not apply
Rule COL-5 Where a ‘Special Arrangement’ does not apply, the Terminating Network must ensure on a call by call basis that COL information either wholly or partly supplied by the connected customer’s equipment is valid for the particular connected customer. Where the COL information supplied by the connected customer is found to be invalid, the Terminating Network shall supply alternative information in accordance with the rules of this CoP.
8.2.7 ‘special Arrangements’ apply
Rule COL-6 Where a ‘Special Arrangement’ applies, the customer must enter into an explicit agreement to ensure that the information they supply is valid. The Terminating Network’s responsibility to ensure the validity of the information is discharged by means of this explicit agreement, and the Terminating Network need not perform any call by call verification upon the COL information supplied by the customer’s equipment.
8.3 Responsibilities of the Originating Network
It is the responsibility of the Originating Network to ensure that the classification of calls is respected in the delivery of COL information to the calling user. The following rules shall apply:
Rule COL-7 An Originating Network that supports a COLP service and/or related services shall ensure that COL information shall be available at the calling customer’s NTP only if it is classified as ‘available’. In addition, any other service that allows the calling party to gain access to the connected line identification shall similarly be available only in relation to COL information with the ‘available’ classification.
Rule COL-8 Where the Originating Network supports a
COLP service the information delivered to the originating NTP must adhere to the
following:
| Indicator at interconnect | Information at NTP (Note 1) |
| Withheld | Withheld indicator, no COL information |
| Unavailable | Unavailable indicator, no COL information (Note 2) |
| Available | COL information |
Note 1: This CoP does not determine how the indicators should be displayed.
Note 2: The indicator for ‘unavailable’ might be an empty data set. The crucial factor is that it can be distinguished in some way from the ‘withheld’ indicator.
Rule COL-9 Where the Originating Network is not capable of supporting COLP or related services no action is required on the basis of the call classification.
8.4 Responsibilities of Transit Networks
Rule COL-10 Except as allowed for by Rule COL-12, a Transit Network shall ensure that the connected user’s COL information and classification do not alter from the point of entry to the point of exit except where such alterations are part of a service offered by the Transit Network and explicitly requested by the connected party (eg Intelligent Network service).
Rule COL-11 Where it is not technically possible to comply with Rule COL-10 the following shall apply:
(a) if the integrity of the COL information cannot be maintained, but the classification can, then an ‘available’ classification shall be changed to ‘unavailable’ and other classifications shall remain unchanged. This shall result in a presentation number being discarded;
(b) if the integrity of the classification cannot be maintained, the exit classification shall be ‘unavailable.’
8.5 Responsibilities of Networks providing additional services
A network that is not the terminating network can also offer a COLR service, or other COL-related services, if it wishes. The method by which these services are offered is up to the network providing additional services. A networks offering such services takes on the responsibilities of a Terminating Network in respect of the classification of the COL information, if its customers activate this service. Such a scenario could apply where an intermediate network returns a personal number.
Rule COL-12 A network offering additional COLR services, or other COL related services, must ensure that COL information on calls where its customers have activated these services is correctly classified, according to the Rules for Terminating Networks, upon handover to another operator.
On calls to ISDN terminals, a network providing additional services supplying COL must offer per call blocking, or obey the per call blocking instructions received from the terminating network before it can return a COL. Equally, a network providing additional services which changes an ‘unavailable’ to ‘available’ can only do so if it offers the connected user a per call blocking code and the other requirements for Terminating Networks.
8.6 Calls passed to Networks which do not conform to this CoP
The responsibility for ensuring the integrity of the COL information and classification lies with the Terminating Network and any Transit Networks from and via which that information is being received. However, where these networks have declared that they are unable to meet the Rules outlined above, it is the responsibility of the network receiving the COL information to ensure that the information and classification defaults to values meeting the requirements of this CoP.
8.6.1 Calls passed to networks covered by the CoP
Rule COL-13 If the network(s) from which COL and/or classification information is being received cannot, or do not, conform to the Rules set out above, the network receiving the COL information shall operate Rule COL-11 at the point of entry to determine the classification of the COL information.
8.6.2 Calls passed to networks not covered by the CoP
Rule COL-14 Calls passed to networks not covered by this CoP (eg International calls) shall be treated by the network receiving the COL information as follows:
(a) if an explicit indication is received that the connected party wishes that their COL should not be made available at the calling customer’s NTP then the COL information shall be classified as ‘withheld;’
(b) otherwise, if COL information is available,
then it shall be classified as ‘available.’
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