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Local Leased Circuits - What are These?


Local leased circuits (LLCs) - what are these? Are they the same as local loops (LL)? These are perplexing technical terms that are core to telecoms issues - recently discussed by local and overseas regulators and operators. 

Local leased circuits (LLCs) - what are these? Are they the same as local loops (LL)? These are perplexing technical terms that are core to telecoms issues - recently discussed by local and overseas regulators and operators.

To the uninitiated, 'LLCs' and 'LL' will simply be meaningless acronyms among others in Singapore. What exactly do they mean?

Local Loops

Local loops (LL) in the local context, refers to the twisted copper pairs that run from telecom exchange buildings to end-users' premises. Local loops are usually used for voice telephony services as well as Internet access services, for example, via Asymmetrical Digital Subscriber Line* (ADSL). The bandwidth capacity (speed) that may be carried over local loops are generally restricted to 2Mbps and below. This is because signal quality will decrease as the length of the local loops increase.

* Asymmetrical Digital Subscriber Line (ADSL) is a physical-layer protocol. The asymmetrical aspect of ADSL technology makes it ideal for Internet browsing, video on demand, and remote Local-Area Network (LAN) access. Users of these applications typically download more information than they send. ADSL can support up to 8 Mbps downstream bandwidth (speed) and up to 1 Mbps upstream bandwidth.

Local loops are also commonly termed 'last mile', because they are the 'final' links in the telecom network that provides connections or access to end-users. However, there are also other telecom services that are considered to provide 'last mile' access too, for example, local leased circuits (LLCs).

What, then, are local leased circuits, and how are they different?

Local Leased Circuits

Brief Comparison between Local Loops and Local Leased CircuitsLocal leased circuits (LLCs) are mostly fibre-optic cables that are able to provide connections of higher bandwidth capacity (speed) over longer distances, in comparison to local loops. Local leased circuits, as the term implies, are circuits that establish connections between individual locations within Singapore.

LLC connections can be generally divided into different segments. Connections between a business (end user) or multiple businesses, and a telephone exchange are commonly termed LLC 'tail circuits'. These tail circuits are the segments of the LLC network that are also considered 'last-mile'.

LLC connections between a telephone exchange and the operators' network site, are commonly termed LLC 'trunk circuits'. These can also be connections between two telephone exchanges, and are of equal or higher bandwidths than LLC tail circuits. LLC trunk circuits are also commonly known as 'head-end' circuits.

Diagrammatic representation of a multiple-point to single-point LLC connection.

LLCs are reliable and versatile, and provide dedicated capacity for the exclusive use of the buyer, and are available at bandwidths (speeds) from below 64 Kbps to more than 155 Mbps. They are fundamental building blocks for many corporate telecom services, such as high-speed Internet access and data services. LLCs are commonly leased (from LLC service providers) by operators to provide telecom services, and by businesses, such as banks and multinational companies, for voice or data communication with local and international offices.

With these characteristics, LLCs have made it possible for you to withdraw money from your savings account at neighbourhood Automated Teller Machines (ATMs), because they form the telecom link between banks and ATMs. They also provide connections between your office's local area network (LAN) and the Internet.

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