As far as the field of computer networking and telecommunications is concerned, a large number of people prefer to make use of TDM in place of IP. TDM over IP can be defined as ideal emulation of time-division multiplexing over PSN. PSN stands for packet switched network. TDM includes T1, E1, T3 and E3 signals. On the other hand, PSN makes use of IP or MPL’s or Ethernet. Another technology, which is related to the concept of TDM, is circuit emulation. This technology is specifically beneficial when it comes to enabling transport of TDM traffic over cell-based networks. So, call it TDM over IP, call it E1 to IP converter, basically they all refer to same application.
In other words, it can also be said that TDM is a specific kind of pseudowire. However, there is one basic difference between other traffic types, which can be carried over pseudowire and TDM. Unlike Ethernet, Frame Relay and ATM, TDM has some unique characteristics and it is a real-bit stream.
TDM has a number of other features, in terms of which it has a definite edge over other networks. These additional features help to make use of specific signaling systems, which are necessary to support a number of telephony features and Operations and Management (OAM) mechanisms, which are extremely well developed.
These factors need to be taken into account if an individual is looking forward to use TDM over their standard PSN. Another serious issue, which needs to be addressed while implementing TDM, is the clock recovery. In the regular TDM networks, the physical layers help to carry the information about the accurate timing along with the TDM data. However, when an individual tries to emulate TDM over PSN, this feature becomes redundant and is unable to execute itself.
Yet another factor, which needs to be addressed, is TDM over IP packet loss concealment. The TDM data is usually delivered at a standardized rate by a single channel. It is possible that the native service of TDM may have some errors, but the good thing is that the data, which is being transferred over, can never be lost in transit.
On the other hand, most of the PSN’s suffer from loss of data while it is being transferred from one source to another in packet form. This loss of data can easily be compensated for by making use of TDM over PSN. TDM can be used to carry bit stream at a standard rate of G.703. However, there are also specific methods available, which allow an individual to carry these bit streams in larger units, although they contain the same number of bits. These bits are also known as frames.
Unlike the unframed TDM networks, where all the bits are made available for payload, the system of Framed TDM requires an individual to dedicate a certain number of bits in every frame for the purpose of synchronization and to perform several other functions. This kind of TDM networks are generally used in multiplex voice channels, which is better known as “channelized TDM”.