Traditionally network elements have been classified into two main categories: switching NEs and transport NEs. A colleague has stumped me by asking in which category the BSC (Base Station Controller) and the BTS (Base Transceiver System) would fall. Rather "instinctively" I told him that BSC falls in the switching NE category while the BTS falls in the transport NE category. However, this set me thinking whether this broad classification of NEs still holds.
Thanks, Bhat
Telcordia specification GR?2991?CORE, TMN Fault Management, seems to provide a more detailed classification of NEs:
- Transport NEs
- Congestible NEs (popularly known as Switching NEs)
- Subscriber access NEs
- Signalling NEs.
Let me quote from this spec for clarification:
Transport NEs originate, terminate, and groom (i.e. packing of lower speed traffic streams like OC-3, OC-12, etc. into higher-speed streams like OC-48) telecommunications signals. These signals are usually of high bandwidth or bit rate and carry a payload composed of many client signals supporting many customer service instances.
A transport NEs may or may not support electronically changeable cross-connections. A transport NE may provide test access points to paths (trails or connections) that it supports.
Congestible NEs, such as telephone switches, packet routers and concentrators, are NEs that are capable of receiving a greater load of customer demand than they can serve. Congestible NEs are engineered so that they can met demand under normal circumstances, but they can be bottlenecks when demand is high. Examples of congestible NEs are circuit switches, Digital Loop Carrier (DLC) Remote Digital Terminals (RDTs), Fiber In The Loop (FITL), Host Digital Terminals (HDTs), ATM switches, IP routers, and other packet switches. Congestible NEs often terminate high-rate paths and circuits so they may have all the characteristics of transport NEs, including supporting stable cross-connections. In addition, they contain scarce resources that are capable of serving only a fraction the theoretically possible demand that could be placed on them. Examples of these scarce resources include: a switching fabric, a signal buffer, a server, a bus, and memory storage.
Subscriber access NEs support such technologies as digital loop carrier, hybrid-fibercoax, fiber-to-the-curb and wireless. They are distinct from transport NEs when they provide concentration, a switching function. They are distinct from switching NEs in that they do not route calls and that they are located outside of central offices, a distinction that is not strong for many purposes.
Signaling NEs are the Signal Transfer Points (STPs) and Signal Control Points (SCPs) (sometimes called Network Systems) that support Common Channel Signaling (CCS) and Intelligent Network (IN) service features. They are very similar to switching NEs, except that they do not carry customer services and although they support routing of traffic, they do not do the actual switching. Nevertheless, they do transport and switch signaling information.
Having quoted the spec, I have a question. Are there different software design considerations that we need to be kept in mind while attempting to manage all these types of NEs?
Thanks, Bhat
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