A Consultation Document issued by the Director General of Telecommunications
March 1999
Chapter 1 The regulation of CLI
Chapter 2 Presentation numbers
1 The subject of this consultation – the use of presentation numbers within Calling Line Identification (CLI) – sounds rather technical and complicated. But it is in fact an important consumer issue. If changes are not made in current policy on how CLI can be used, networks could in future reject many calls which customers would have wished to have received. It is important that Oftel hears customers’ views on this issue.
2 CLI services were first introduced into the UK in November 1994. CLI enables the person being called to identify the number from which a call has been made. For example, with special equipment customers can read the caller’s number before answering the phone. A second example is the service where by dialling 1471 the called party can hear a network announcement giving the last caller’s number.
3 Callers are able to withhold their number if they want to – either on a call-by-call basis by dialling 141 before the called number or by asking the network provider to withhold CLI on their lines permanently. Some companies have chosen to do this because within the current rules, which require the network to check the caller’s number, the CLI given could be confusing to the customer. The network may only be able to check the number at which the call enters the PSTN. Thus the CLI might only give the main switchboard number of a company rather than the diallable extension of a person calling within a firm.
4 Up to now, this has been inconvenient but not serious. New EU legislation will, however, change this. New requirements will oblige telecoms operators to provide customers with the option of rejecting automatically all calls where CLI is withheld. Companies could find that calls which both they and the customer wanted to be completed will fail.
5 This can be avoided if the previous requirements that CLI numbers must be checked by the network are relaxed. Oftel proposes that in future companies’ equipment would be able to insert their own meaningful CLI. Networks could do some checking but would not check all numbers and in addition network operators would be able to vet companies who would be allowed to use this service. This would offer some reassurance to customers that the CLI is authentic and reduce scope for misuse. Oftel considers this would meet the concerns of customers to continue to receive well-intentioned business calls while giving reasonable assurance that the CLI will be accurate and helpful.
6 Because of the technical and regulatory complexities of this subject, some background material is included in this document – Annex 1 offers a general introduction to CLI services and Chapter 1 looks at the regulatory framework. The immediate subject of the consultation is addressed directly from Chapter 2.
7 Chapter 1 surveys the regulatory framework within which CLI services have developed in the UK. It introduces Oftel’s three cardinal principles of privacy, authenticity and integrity. The Network Code of Practice and the impact of the Revised Voice Telephony Directive and the Telecoms Data Protection Directive are reviewed.
8 Chapter 2 describes the three types of presentation numbers and the rules surrounding their use. It then considers whether the rules ought to be changed to permit presentation numbers that are applied by a customer’s equipment and not subjected to network checking procedures – type 3 presentation numbers – and assesses the advantages and disadvantages accruing to customers by such a rule change.
9 Chapter 3 reviews the range of safeguards that could be set in place to prevent any abuse of type 3 presentation numbers.
10 This document seeks to involve the wider public in a debate that has up to now only taken place within industry circles. Although the issue of whether to allow presentation numbers without network verification has a technical dimension the key issues are those touching on individuals’ privacy and data protection rights. Oftel’s aim is to create the conditions within which CLI services, which have undoubtedly already brought considerable advantages to consumers, are developed and extended while maintaining customer confidence in their integrity.
The regulation of CLI
1.1 Because CLI services make personal telephone numbers accessible to third parties, and because telephone numbers are a form of personal data (that is, automatically processed information from which a person may be identified), the development of CLI has raised serious privacy and data protection issues. As a result the development of CLI services has been subject to extensive regulation, both in the UK and abroad.
1.2 Oftel produced a consultative document, Calling line identification, in September 1993 and followed it up with a policy paper, The introduction of calling line identification, in July 1994, in advance of the service’s introduction. The Data Protection Registrar has also had a continuing involvement in protecting the rights of individuals in the context of CLI and has produced a statement on the use of personal data captured by caller display. This statement is published as an annex to A Consumer's guide to Calling Line Identification services, available on the Oftel web site.
Oftel’s three cardinal principles
1.3 Oftel policies on CLI have been developed on the basis of three cardinal principles which address the privacy and consumer protection issues associated with CLI. The three are privacy, authenticity and integrity. They are defined in the Network Code of Practice (see paragraph 1.4 below) as:
1.4 To ensure that these principles are respected by network operators who offer CLI services Oftel has promoted the development of a Code of practice for network operators in relation to customer line identification display services and other related services [hereafter referred to as the Network code of practice], first published in December 1996 with a second edition on June 1998. The Network code of practice was produced by an industry working group of operators and equipment manufacturers and is published by Oftel.
1.5 With the multitude of operators in the UK it is quite possible for a call to originate on one network, pass through one or more transit networks before terminating on yet another network. The Network code of practice sets out rules for the consistent handling of CLI information and the obligations of originating, transit and terminating networks. It also contains rules for the use of presentation numbers. [These are diallable numbers to which a return call can be made, though not necessarily the same number as that from which the call was made. For example, a company may give a Freephone presentation number for return calls.] Compliance with the Network code of practice rules is a contractual obligation on network providers entering into an interconnect agreement with BT.
1.6 CLI services have also been the subject of regulation by means of two important European Directives, the Revised Voice Telephony Directive (RVTD) and the Telecommunications Data Protection Directive (TDPD).
The Revised Voice Telephony Directive
1.7 The Revised Voice Telephony Directive - Directive 98/10/EC - was transposed into UK law by SI 1998 No.1580, The Telecommunications (Open Network Provision) (Voice Telephony) Regulations 1998 and entered into force on 21 July 1998. It establishes a basic set of standards for all operators offering fixed public voice telephony and defines the level of universal service that should be offered. It requires operators with Significant Market Power, which in the UK are BT and Kingston, to offer CLI services. Moreover, the Directive requires member states to remove any regulatory restrictions preventing the provision of CLI services and so looks forward to CLI services being available across national boundaries.
The Telecommunications Data Protection Directive
1.8 The Telecommunications Data Protection - Directive 97/66/EC - applies the general principles of the Data Protection Directive (95/46/EC) with respect to the processing of personal data in the telecommunications sector. The principal Data Protection Directive has already brought about a new Data Protection Act – the TDPD is expected to be transposed into UK law by means of DTI Regulations by mid-1999.
1.9 The TDPD contains a number of important provisions regarding CLI services. Although the Directive in general is concerned with the protection of personal data, as opposed to that of companies or other legal entities, in the articles relating to CLI it carefully discriminates between the rights of subscribers and users. Subscribers can either be individuals or companies but must have entered into a contract with a telephone company for the supply of telecoms services. Users are individuals using a publicly available telecoms service to which they need not have subscribed.
1.10 The main provisions regarding CLI are:
note: this is the feature known as call blocking and has been available on UK networks since the introduction of CLI services using the 141 code on ordinary phone lines
note: this is the feature known as line blocking and has been available on UK networks since the introduction of CLI services
note: this feature is primarily aimed at charitable helplines which may wish to guarantee anonymity to clients calling in to their services
note: the right only applies in circumstances where the CLI is presented prior to the establishment of the call (ie by the use of caller display equipment). Oftel believes that the most effective way to implement this provision is for the network to reject calls where CLI is withheld. This is known as Anonymous Call Rejection (ACR)
note: connected line identification is a feature available on ISDN lines whereby the number to which the call has been connected is presented at the caller’s end - where a call has been forwarded this will not be the same as the number the caller actually dialled
1.11 The transposition of this Directive into UK law will represent a significant landmark for
CLI policy in the UK. For the first time, customers’ privacy and data protection rights in respect of their CLI will rest on a firm set of legal requirements which will be enforced by the Data Protection Commissioner. In this enforcement work the Commissioner will be able to draw on the full range of remedies, liabilities and sanctions provided by the new Data Protection Act.
1.12 The new right for customers to be able to reject incoming calls where callers have withheld their CLI could create difficulties for organisations that currently withhold CLI because it would not give the called customer a meaningful number to return the call. The rest of this document is about this issue.
Presentation numbers
2.1 A CLI will either be a network number that identifies the actual number from which a call enters the public network (technically speaking, the ingress port) or a presentation number, a useful diallable number to which a return call may be made. The wider availability of presentation numbers would allow for a greater degree of flexibility in the way CLI services can be used as well as offering more information to customers. However this has to be balanced against the need to maintain the existing level of customer confidence in the authenticity of CLI numbers.
Three types of presentation number
2.2 The Network Code of Practice identifies three types of presentation number. They are categorised on the basis of whether they are network or customer provided and the level of network verification they are subject to. The three types are:
type 1 - network provided (NP)
type 2 - user provided, verified and passed (UPVP)
type 3 - user provided, not verified (UPNV)
2.3 The Network Code of Practice currently permits the use of type 1 and type 2 presentation numbers which are already being made available by some network operators. However the use of type 3 presentation numbers is conditional on customers entering into special arrangements with network operators which need to vetted by Oftel. Because this type of presentation number is not checked by the network – a significant departure from the way presentation numbers currently operate - Oftel has not been willing to approve any special arrangements until the issues involved have been publicly raised and discussed. The purpose of this consultation is to establish whether Oftel should now begin to approve special arrangements and if so, on what terms.
Existing rules for presentation numbers
2.4 When CLI services were originally launched in the UK, presentation numbers were not an immediate issue. The primary concern was with the basic CLI service and the vital need to secure users’ privacy and data protection rights. Accordingly, the use of presentation numbers has been surrounded by a number of safeguards and regulatory prohibitions. The complete set of rules applying to the use of presentation numbers are contained in the Network code of practice. They are extremely elaborate and their essential points are summarised in Annex 2 to this document.
2.5 In Oftel’s view it is now right to consider whether these rules need to be revisited in the light of the greater experience and knowledge that customers have acquired in using CLI services. In particular should Oftel allow the commercial availability of type 3 presentation numbers?
2.6 The main customer benefit to be derived from making type 3 presentation numbers available is where calls are made from large private networks, of the kind used by national and local government as well as by companies and other organisations. These networks generally route outgoing calls within the private network so that they break out on to the public network as close to the ultimate destination as possible, thus obtaining the cost advantages of local call tariffs. This is known as far-end breakout. For example, a call made from London to an Arbroath number may break out on to the public network through a switchboard in Dundee.
2.7 The problem arises that the CLI displayed in such circumstances would be that of the Dundee number. The presentation of this number as a CLI to a called party – who has no means of knowing that the CLI represents a far-end breakout number – carries no meaningful information and raises the possibility that return calls might be attempted to a switchboard operator who has no knowledge of the original call.
2.8 To avoid presenting such misleading CLIs many organisations that use private networks withhold their CLI altogether. Hitherto this has not posed a problem – the called party simply receives a number withheld display. However, as noted in Chapter 1, when the Telecoms Data Protection Directive becomes law and anonymous call rejection (ACR) becomes more widely available, calls where the caller has withheld CLI and the called party has invoked ACR will not be connected. This inability to complete calls may have serious consequences.
2.9 Research published by Oftel in April 1996, BT’s calling line identification services: customer attitudes and awareness, revealed that of a sample of 1632 respondents, 13% said they were "very likely" to use ACR if available, and 18% "quite likely". If these figures are still representative of customer attitudes, almost a third of all users might be expected to opt for ACR. Where CLIs are withheld, this would result in a significant proportion of telephone calls not being connected, in turn leading to mounting levels of customer frustration, revenue loss for network providers and a wasteful use of network resources.
The balance of consumer advantage
2.10 Permitting private networks to provide their own CLI numbers would represent a significant change to the current presentation number service. Such a change could only be made if, on balance, the advantages to the consumer outweigh any disadvantages What needs to be balanced is the trade-off between more informative CLI numbers and the risks of a lesser degree of authenticity.
2.11 On the positive side, the advantages are that:
2.12 To be set against these advantages is the risk that the principle of authenticity might be compromised. Because type 3 presentation numbers cannot be checked on a call-by-call basis by network operators there is consumer concern that some callers might be tempted to abuse the service by sending "junk" - misleading or meaningless - CLIs. In the worst case this might result in the called party receiving a number which did not accurately identify the caller or offer the possibility of making a return call.
2.13 The next chapter examines some of the safeguards which, in Oftel’s view, will maintain the authenticity of type three presentation numbers. However the use of type 3 presentation numbers does raise a fundamental question of principle.
Views are invited as to whether, on balance, consumers would benefit if the use of type 3 presentation numbers, subject to sufficient safeguards, were to be permitted.
Safeguards
3.1 Oftel will not permit the use of type 3 presentation numbers unless it can clearly be demonstrated that any safeguards imposed will not only maintain the principle of authenticity, but equally important, preserve customer confidence in the trustworthiness and reliability of CLI information. In this chapter the range of possible safeguards is reviewed.
3.2 The primary safeguard is the undertaking required by a customer that only authentic CLIs will be provided. This will become a contractual obligation entered into by the subscriber with a network operator. The final form of any such undertaking under special arrangements will be a matter for the industry as a whole to determine and Oftel to approve. The draft agreement at Annex 3 to this document is intended to identify the key elements that need to be included and to provide a starting point for discussion.
Views are invited on the effectiveness of the draft Special Arrangements agreement and how it might be improved to maintain customer confidence in the authenticity of the CLIs presented?
3.3 Even after the subscriber has entered into an undertaking, the use of type 3 presentation numbers signifies a lessening of the control that network operators have exercised up to now over the CLI information received by a called party. To ensure that this lessening of control does not undermine the credibility of CLI services there are a range of additional safeguards, some that will apply in any case, others that Oftel could set in place.
3.4 At this stage Oftel has no firm view as to precisely where the balance needs to be struck between, on the one hand promoting the development of a more flexible and informative presentation number service and, on the other, ensuring that the cardinal principles of authenticity and integrity are maintained. A judgement as to where this balance lies will determine what additional safeguards are required.
3.5 The range of possible safeguards includes:
i) special arrangements will need to be applied for on an individual basis and network operators will be expected to make exhaustive checks of each application
ii) special arrangements will not necessarily be available to all customers – it will be restricted to those who have a demonstrable need for them
iii) type 3 presentation numbers could be accompanied by a ‘health warning’ such as a text message UNVERIFIED or an agreed symbol – similar warnings could be given in 1471 recorded network announcements
iv) terminating networks might be required to have systems in place to log the details of type 3 presentation numbers where there is evidence of abuse – this is only likely to come to light when an attempt to return the call is made
v) the undertakings given under special arrangements could be supplemented by corresponding obligations in the class licences applying to business and residential users
Additionally the following two safeguards are not discretionary but will apply under general law:
vi) any abuse of special arrangements involving a misuse of personal data, such as someone else’s telephone number, will constitute a breach of Data Protection principles and be a criminal offence under the Data Protection Act 1998
vii) the sending of false messages for the purpose of causing annoyance, inconvenience or needless anxiety is an offence under section 43 of the Telecommunications Act 1984
3.6 It must be emphasised that networks’ abilities to trace malicious or nuisance calls or handle 999 calls would not be compromised by the availability of type 3 presentation numbers – call tracing techniques rely on the network number which is always present in the signalling by which a call is conveyed, not the presentation number.
Views are invited as to which of the above safeguards is desirable or essential to maintain customer confidence in the authenticity of CLI information.
The consultation will run until 14 May 1999 followed by a further period of up to 28 May 1999 during which comments are invited on any submissions made to Oftel during the initial period. Comments are invited in particular on questions highlighted in the text of the document.
Written comments should be directed to:
Frank Phillips
Consultation on Presentation Numbers
Oftel
50 Ludgate Hill
London EC4M 7JJ
Fax: 0171 634 8945
Written comments will be made publicly available on Oftel’s web site except where respondents indicate that their response or parts of it are confidential. Respondents are therefore asked to separate out any confidential material into a confidential annex which is clearly marked as such. In the interests of transparency, respondents are requested to avoid confidentiality markings wherever possible.
Oftel is willing to set up a link between this document on Oftel’s pages and any responses placed on respondents’ own Internet pages. Please contact Lauren Ryner at Oftel on 0171 634 8753 should you wish to arrange this.
Confidential responses should not be sent via the Internet.
Alternative formats
Oftel documents are also available in alternative formats. Copies on disk in various formats and in large print are available. We also offer braille and tape copies of the summary on request. Please contact the Oftel Research & Intelligence Unit on 0171 634 8761, or e-mail, or call Textphone 0171 634 8769 for more information.
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An introduction to CLI services:
1 Calling Line Identification (CLI) is a term that describes the capability of modern telephone networks to identify and present the number from which a call has been made to the called party.
2 CLI services were introduced into the UK by BT in November 1994. Since then they have become widely available and are offered by most public network operators and providers. The main exceptions are analogue mobile networks and those few parts of the country where BT’s local exchanges are not equipped with modern digital signalling. There are also a number of smaller operators using technically less-advanced signalling systems which do not support CLI technology.
Caller Display and Call Return
3 The two CLI services most widely available to consumers are Caller Display and Call Return.
4 Caller Display is a service which displays the number from which a call has been made. As well as the number the display may also include a limited set of brief text messages, such as PAYPHONE or INTERNATIONAL. On fixed networks caller display is generally only made available as a subscription service, for which the network provider makes an additional charge over and above the line rental. The subscriber also needs special equipment - either a telephone with an integrated screen or a separate display unit.
5 Some caller display equipment has the additional capability of maintaining a log of incoming calls and, when used with CTI (computer telephony integration) technology can link a calling number, as soon as it is connected, with information relating to that number stored in a data base.
6 Call Return is a service by which the called party dials a short code, generally 1471 on fixed networks, to receive a network announcement giving the number of the last call and the date and time it was made, where this information is available.
Presentation numbers
7 There may be a variety of circumstances in which the presentation of the originating CLI (that is, the number at the point where a call passes onto the public network) would be of little assistance to the called party. For example, the CLI from calls routed through analogue switchboards is that of the switchboard number itself rather than that of the calling extension. There could be hundreds of extension lines behind a switchboard and a switchboard operator would not be able to tell from which one a particular outgoing call was made. Other examples are where a subscriber uses different network providers for outgoing and incoming calls or where a call is automatically initiated by a computer, say in response to a social alarm call (which transmits a distress message from people at risk to social services or emergency organisations). In all these cases the originating CLI is not going to provide useful information to enable the called party to return the call.
8 For these reasons an alternative to displaying the actual number from which a call is made (the network number) is to display a presentation number. This is not the network number, but a diallable number to which a return call may be made. Presentation numbers allow for a degree of flexibility, so that, for example, organisations may give a Freephone/Freecall (0800) or LoCall (0345/0845) number for return calls or ensure that all return calls are routed to and dealt with by a customer services unit.
9 Complex rules have been devised to ensure that a Presentation Number offered will be authentic. These are summarised in Annex 2 of this document.
CLI unavailable and withheld
10 There are two sets of circumstances in which the CLI of the incoming call will not be displayed to the called party.
11 Firstly, a CLI may simply not be available because one of the networks involved in the conveyance of a call is technically incapable of supporting a CLI service. A call originates on one network (the originating network), may terminate on the same or another network (the terminating network), and pass thorough any number of intermediate networks between the originating and the terminating networks (transit networks). Where any one of these networks does not support CLI, the CLI will be described as unavailable.
12 Secondly, the caller may not want their CLI to be displayed. To protect the caller’s privacy it has been a fundamental principle, not only in the UK but virtually everywhere in the world where CLI services have been offered, that a CLI service may only be implemented where the caller is able to withhold CLI, either by prefixing the number dialled with a short code, generally 141 in the UK (known as call blocking), or by requesting their network provider to withhold CLI from being sent on their line (known as line blocking). In either case the CLI will be described as withheld.
13 To sum up, where CLI services are operating the status of CLI information that a called party will receive falls into one of three categories. If the CLI is available, either a network number or a presentation number will be shown. If the calling party does not want their number to be shown and withholds it the CLI will be classified as withheld and if one of the networks conveying a call is technically incapable of supporting CLI, the CLI will be classified as unavailable.
14 This range of outcomes is summarised in the table below:
| calling party action | called party receives |
| does not withhold CLI | network number or presentation number |
| Withholds CLI by call or line blocking | number withheld |
| Uses network which either does not support CLI or a caller’s ability to withhold it | number unavailable |
Benefits to the consumer
15 The introduction of CLI services has brought several benefits to consumers. With its ability to remove a caller’s anonymity CLI has re-balanced the relationship between calling and called parties. Caller Display confers many advantages on the user, who is put in the position of knowing who is calling, or to be more precise, the number from which a call is being made, before deciding whether to answer it or not. This is comparable to a spy-hole in the front door. Call Return gives users information about the most recent call they have received and enables them to return the call. In this way it reproduces some of the features of an answering machine.
16 The presence of CLI acts as a deterrent to malicious callers. The introduction of CLI services in November 1994 led to an immediate decrease of approximately 20% in the number of malicious calls reported to BT.
Note: A fuller technical introduction is given in the document A Consumer’s guide to Calling Line Identification.
Summary of Network code of practice rules applying to presentation numbers
A draft special arrangements agreement
1 The subscriber hereby undertakes to the network provider that any number provided for display will be:
(i) a diallable number to which a return call may be made;
(ii) a number that does not appear on the ICSTIS list Premium Rate Dialling Codes;
(iii) a number that has either been -
(a) allocated to the same individual, legal entity or Licensee's Group (within the terms of the Class Licence for the running of self provided telecommunication systems granted by the Secretary of State under section 7 of the Telecommunications Act 1984 on 9 September 1996) to whom the network number has been allocated, or
(b) where the subscriber to whom that number has been allocated has consented in writing to its use for display purposes by the subscriber to whom the network number has been allocated.
2 In entering into this agreement the subscriber recognises that any failure on his or her part to fully comply with its terms may lead to the network provider withdrawing the special arrangement without further notice and irrespective of any contrary contractual obligations.
Note: paragraph 1(iii)(b) would represent a change to the current Presentation Number rules which require linked presentation and network numbers to have been allocated to the same person or legal entity – this rule prevents people working from home from using their employer’s number as a presentation number during working hours
Anonymous call rejection - a service which prevents calls from being connected or put through where a caller has withheld CLI
Available - a CLI number that is available for display, because the caller has been given the option of withholding it and has chosen not to
Call blocking - a service which enables a caller to withhold CLI on a call by call basis
Call return - a service which enables a return call to be made to the CLI number of the most recent incoming call
Caller display – on fixed lines a subscription service (but generally free on digital mobile networks) which displays the number from which a call has been made - it requires a caller display unit with a screen, either on the telephone or as a separate attachment
Calling line identification - a network facility that enables the number of the line from which a call is made to be identified
Connected line identification - a network facility that enables the number of the line to which a call has been connected to be identified
Direct Dialling In (DDI) - a switchboard’s capability to route an incoming call to the extension dialled without the intervention of an operator
Far-end breakout - a feature of private networks that routes a call made to a public network number to breakout on to a public network as close to that number’s line as possible
Line blocking - a service which enables a caller to withhold CLI on all outgoing calls
Network number (NN) - a number allocated by a telephone company which identifies the line from which a call has been made, usually the same as the directory number
Network Provided (NP) number - a number stored in the network and applied as the CLI of an outgoing call – it can be either a network or a presentation number
Originating network - the network to which a caller who makes a call is directly connected
Presentation number - a number chosen by a caller to which return calls may be made
RVTD (the Revised Voice Telephony Directive) - European Parliament And Council Directive of 26 February 1998 on the application of open network provision (ONP) to voice telephony and on universal service for telecommunications in a competitive environment (98/10/EC). A European Directive establishing a basic set of standards for all operators offering fixed public voice telephony and which defines the level of universal service that operators should offer
Special arrangement - an agreement between a customer and a public network operator whereby the customer undertakes to provide for CLI display purposes only authentic calling party numbers which are not checked by the public network
TDPD (the Telecoms Data Protection Directive) - European Parliament And Council Directive of 15 December 1997 concerning the processing of personal data and the protection of privacy in the telecommunications sector (97/66/EC). A Directive that applies the general principles of the Data Protection Directive within the field of telecommunications
Terminating network - the network to which a customer who receives a call is directly connected.
Transit network - a network through which a call passes, but which is neither the originating network nor the terminating network for that call.
Unavailable - where no CLI number is available for display, because one of the networks over which a call has passed is incapable of supporting CLI services
UPNV (User Provided, Not Verified) 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.
UPVP (User Provided, Verified and Passed) 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
Withheld - where a caller has chosen not to allow a CLI to be presented to the caller
