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Thursday, March 28, 2013

What is the basic principle behind Dynamic synchronous transfer mode (DTM)?


- Dynamic synchronous transfer mode or DTM is one of the most interesting of all the networking technologies. 
- The basic objective behind implementing this technology is to achieve high speed networking along with the transmissions of top quality.
- It also possesses the ability of adapting the bandwidth in varying traffic conditions quickly. 
- DTM was designed with the purpose of being used in integrated service networks including both the one to one communication and distribution.
- Furthermore, it can be used in application to application communication. 
- Nowadays, it has also found its use as a carrier for IP protocols (i.e., high layer protocols). 
- DTM is a combination of 2 basic technologies namely packet switching and circuit switching. 
- It is because of this that the DTM has many advantages to offer. 
- It also comes with a number of services access solutions for the following fields:
Ø  City networks
Ø  Enterprises
Ø  Residential as well as other small offices
Ø  Content providers
Ø  Video production networks
Ø  Mobile network operators

Principles of Dynamic synchronous transfer mode (DTM)

 
- This mode has been designed to work up on a unidirectional medium. 
- This medium also supports multiple access i.e., all the connected nodes can share it. 
- It can be built up on various topologies such as:
  1. Ring
  2. Double ring
  3. Point – to – point
  4. Dual bus and so on.
- TDM or time division multiplexing is what up on which the DTM is based. 
- Here, a fiber link’s transmission capacity is broken down in to smaller units of time. 
- The total link capacity is broken down in to frames of fixed size of 125 microseconds. 
The frames are then further subjected to division in to time slots of 64 bit. 
- How many time slots will be there in one frame is determined by its bit rate. 
- These time slots consist of many separate control slots and data slots. 
- In some cases more control slots might be required, then the data slots can be turned in to control slots or vice versa.
- The nodes that are attached to the link possess the right to write both the kinds of slots. 
As a consequence of this, same time slot position will be occupied by the all the time slots within each frame. 
- Each node possesses the right to at least one slot which can be used by the node for transmitting control messages to the other nodes. 
- These messages can also be sent when requested by the user as a response to messages sent by the other nodes or for some purpose of network management.
- A small fraction of the whole capacity is constituted by the control slots, while a major part is taken by the data slots that carry payload. 
- With the number of control slots, the signaling overhead in DTM varies though it is usually very low.
- Whenever a communication channel is established, a portion of the available data slots is allocated to the channel by the node. 
- There has been an increasing demand of the network transfer capacity because of the globalization of the network traffic and integrated audio, video and data transmission. 
Optical fibers’ transmission capacity is increasing by great margins when compared to any other processing power. 
- DTM still holds the promise for providing full control to the network resources.


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