3.9 Network integrity
The Telecommunications Act 1997 at s376 empowers the ACMA to make Technical Standards for Customer Equipment (CE) and Customer Cabling (CC) in relation to a restricted list of matters. In particular, it provides for Standards that contain ‘...such requirements as are necessary or convenient for ... protecting the integrity of a telecommunications network or facility’. There is no definition provided in the Act, however an interpretation of the expression is given in the Explanatory Memorandum where it is explained that the basic underlying intention is to protect the networks and facilities from harm from CE or CC.
That is, so the CE or CC does not adversely affect:
- the switching, signalling, transmission, metering, charging and billing systems and equipment; or
- the reliability of telecommunications networks or facilities.
While this sets a limit on the ACMA’s standards making powers, the ACMA is expected to also to consider matters that arise from the COAG Guidelines on regulatory Standards and the need to prepare regulatory impact statements which may lead it to decide to exercise its powers to a lesser extent. As a result, Working Committees should not consider technical requirements in isolation and must consider the costs and benefits arising from the requirements they propose.
Because the actual clauses in the Standards are so varied and have a range of impacts, examples of the matters that could be relevant are used. The examples provided may be relevant for a particular Standard and should be evaluated in the context of the Standard to assess whether related requirements are required to protect network integrity.
On this basis, network integrity should be considered in relation to any matter which has the potential to cause harm to a telecommunications network or facility operated by a Carrier or Carriage Service Provider (C/CSP), and in particular adversely affect the:
- operation of the switches, softswitches, routers, gateways, firewalls, proxy servers and any other associated network equipment.
- operation of the application servers and any other associated network equipment.
- operation of the content servers and any other associated network equipment.
- operation of the metering, charging and billing systems.
- operation of the service activation, provisioning and assurance systems.
- operation of any other IT systems and network equipment used in the telecommunications network or facility.
- operation of the access and transmission network equipment including RF based elements, e.g. base stations, microwave links, satellites.
- reliability of network cabling, equipment and systems.
From these principles the following examples may be relevant to a particular Standard.
Switching and Signalling Aspects
Switching and signalling aspects which relate to network integrity could include CE signals affecting call charging, network loading, support of complex protocols, such as ISDN, GSM MAP and IP, shared access networks and control of network equipment.
a) Call Charging
Incorrect answer/busy/no charge signals can be incorrectly sent by CE in some circumstances, resulting in incorrect C/CSP charging, directly compromising the C/CSP’s ability to collect revenue and meet standards for accurate call charging and billing.
b) Network Traffic Loading
Excessive bids by CE to establish connections or utilise other network resources have the potential to overload the IT systems and network equipment used in the telecommunications network or facility, resulting in delays for other callers or failure of the telecommunications network or facility affecting all customers connected to that telecommunications network or facility.
c) Keypad Signalling
The layout and alphanumeric designation of keys on a keypad dial may impact on the operation of the telecommunications network or facility. A uniform approach to alphanumeric keypad layout is desirable, however, the key designation for all keypads must be unambiguous.
d) Complex Protocols
Complex protocols such as GSM MAP, IP, ISDN and CCS7, if offered as a customer interface, have the potential to tie up or disrupt switch processor resources if incorrect messages or messages out of expected sequences are received by the telecommunications network or facility. Further, CE may be required to respond to network originated messages and failure to respond appropriately, or to respond within a set period, may also cause difficulties to occur.
e) Shared Access Networks
In mobile networks, hybrid fibre coaxial cable and DSL networks, the customer access network is based on a shared medium. Incorrect operation by CE could potentially adversely affect other users, for example, by disrupting channel allocation or tying up access network resources.
f) Control of Network Equipment
Remote control and monitoring of network equipment is an essential feature of Carrier operations, for example, for fault detection, configuration control and alarm collection. Uncontrolled loop backs of network equipment could disable common equipment and disrupt Carrier initiated loop backs and testing. CE therefore must not be able to send any such control signals into the Carrier's telecommunications network or facility automatically or under operator control.
Transmission Performance Aspects
Transmission aspects which relate to network integrity include cross talk, overload, electrical damage, interfering signals, impedance matching, interference with network systems and ability to perform to specifications.
Signals of excessive magnitude can be coupled into both adjacent cables and also adjacent pairs within the same cable sheath and affect the services of other users. These signals can be speech, data or signalling tones either continuous or intermittent. Therefore signals must be constrained to be within a power level frequency spectrum mask.
Some analogue circuits are sensitive to the magnitude of customer signals. High level signal powers on one channel may cause excessive noise in other channels on the same bearer. Limits may be required until fully digital networks are established. Also, excessive acoustic or electrical coupling between transmit and receive paths may cause a circuit to oscillate. Therefore signals must be constrained to be within a power level frequency spectrum mask.
c) Electrical Damage
Excessive voltages could cause electrical damage to network equipment and must not be sent by CE.
d) Impedance Matching
Impedance mismatches cause reflections of transmitted signals. The reflected signal may cause errors or be detected as echo if the round trip delay on the call is significant. Impedance balance about earth may influence the noise performance of a connection and reduce the reliability of the call set up.
e) Interference with Network Systems
Active transmission systems require electrical or optical signals to be delivered in a defined manner, otherwise transmission failure occurs and alarms are raised and circuits may be automatically busied out, leading to congestion in the telecommunications network or facility and affecting other users.
Customer Cabling and Cabling Components
Impedance, impedance unbalance and crosstalk performance potentially affect network integrity. Characteristics of the cable should be suitable for the purpose of the circuit for example high speed digital signals may be coupled into other circuits in a cable with poor crosstalk performance. Cabling products should not be liable to water entry or corrosion which could affect other services or the reliability of network equipment, for example underground cable should be impervious to water entry and water migration along the core, while connectors, sockets, terminal strips, frames and battery supplies must be adequately plated or protected.
Installed cable and equipment should be suitably located or protected to avoid foreseeable damage that may affect network integrity, for example underground cabling should be installed at a suitable depth or clearly identified to prevent damage during minor excavation or digging such as for cultivation, gardening or laying paths.