Internet access is the current backbone for any business telecommunications infrastructure. Do not take any risks with poor services or not designed for business class. When choosing an internet access line, it is important to consider the following features:
- Band width. This is the key parameter for any line and defines the capacity of a circuit to transmit information (in multiples of bits per second: kilo, mega, giga) in both directions: to the Internet (upstream) and from the Internet (downstream). Unfortunately, operators give trade names to their lines that do not correspond to their actual capacity, creating confusion in the market. Under pressure from the European Commission, the Spanish regulator (CMT) is trying to correct this situation.
- Symmetry. Depending on the needs, especially if the offices sends information to other locations, it is preferable to use symmetric lines (upstream equal to downstream) rather than asymmetric lines (upstream much lower than downstream). Using symmetric lines increases costs considerably.
- Stability. Depending on the applications to be used (applications with little fault tolerance such as VoIP, encryption, video streaming, etc…), it is important for the lines’ technical features (bandwidth, latency, jitter, etc …) to remain constant over time. Usually symmetric lines offer greater stability.
- Warranties. It is necessary to know what performance guarantees are offered by line operators. Normally operators guarantee a percentage of bandwidth, meaning that when the circuit works, the client will have at least X% (usually 10%, 25%, 50%, 75% or 100%) of the bandwidth that they contract. Operators offering business services also offer contractual guarantees of availability (what percentage of time the circuit will be operating), repair time (how long it will take to repair a fault) and installation time.
- Latencies. The delay that occurs in packet switching — latency — and its variability — jitter — are key parameters for the proper working of some applications. Latencies depend heavily on the physical medium on which the circuit is operated (fibre optics offer the best latencies on the market; wireless communication usually gives the worst) and on the quantity and quality of the equipment over which data packets circulate.
- Physical medium. The most common medium, due to its widespread instalment in most locations, are copper pairs, whose management in Spain corresponds by law to Telefónica. A circuit usually relies on different physical media in its various stages and some operators may create confusion by talking about fibre optics for example, when they really mean coax in the last mile, the part which is most difficult to provide. Wireless communication is, by definition, a shared medium and can become saturated due to external factors.
- Aggregation. There are services that are provided in aggregate form, i.e. the same physical medium is used to provide for more users than the medium itself allows, counting on the fact that it is improbable that all users will access the service simultaneously. This is usually applied to domestic services, such as ADSL provision, and not the business sector. It is also popular among small and medium size companies.
- Technology. Many of the properties explained here are predetermined by the choice of a particular technology. For example, EoSDH technology implies the use of fibre optics, with good equipment, low latencies, and so on.
- Possibility of Duplication. When considering the likelihood of failure (non availability of the line), a measure that can improve the service is to duplicate network elements: duplicate lines (with different media), duplicate equipment, etc. In those locations where a connection is important, it will be necessary to identify the most likely causes of failure so as to protect against them.
We give below a summary of the different technologies currently available, in terms of their scalability, symmetry and aggregation:
|Ethernet F Mile||40 Mbps||Sí||No|
|SHD SL||2 Mbps||Sí||No|
This table summarises them in terms of appropriateness for delay-sensitive services, such as VoIP:
|Ethernet F Mile||Cobre||Baja||Muy estable||Apropiada.|
|VDSL||Cobre / Coaxial||Mala||Pobre||No recom.|