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.

What is Dynamic synchronous transfer mode (DTM)?

Dynamic synchronous transfer mode or the DTM is a technology developed for optical networking. The ETSI (i.e., the European telecommunications standards institute) standardized this technology in the year of 2001 marked with the following beginning specification ‘ETSI ES 201 803 – 1’. 

This is a circuit switching network technology that doubles as a time division multiplexing technology too. Actually, this technology is built up on a combination of the switching and transport.

This technology guarantees to provide QoS or quality of service for services that are involved with the streaming of videos. 

However, it might be used for packet – based services also. It is marketed for the following:

1. Professional media networks
2. Mobile TV networks
3. DTT or digital terrestrial television networks
4. Content delivery networks
5. Consumer oriented networks (for example, triple play)

What is Switching?

- Switching of the channels is specified by DTM. 

- This is what that makes it different from the other transmission techniques that we have, for example, SONET (synchronous optical networking), SDH (synchronous digital hierarchy) and so on. 

- End to end provisioning is done for the DTM channel over a network with general topology through the use of control signaling.

- DTM therefore represents a circuit switched system. 

- The switches are nothing but time space switches that guarantee the QoS property. 

- The allocation of the resources is done physically for each channel in the switch. 

- This is quite contrary to the switches that are based up on packets or cells. 

- In those kind of switches there is always a competition for resources between the packets and cells. 

- Such a competition leads to delaying and discarding of the packets and cells. - Other methods offer a shared resource allocation mechanism that draws a limit for the packet and cell switches regarding their utilization of the network in such way that the QoS is maintained at a certain level. 

- But DTM does not follow this shared allocation mechanism rather it implies that a network can be loaded up to full limit theoretically and still can guarantee the QoS. 

- Thus, here real utilization is more like a question of adaptation of the network topology as well as its link capacities considering the actual traffic matrix.

- Packet and cell based switching technologies are more suited to statistical multiplexing.

- It means whenever a packet streams in a router come at an outgoing link that is common to all of them, buffering is carried out until the resources are free on that particular link.

- In this way, it becomes possible to make use of the outgoing link to the maximum degree possible without causing many delays. 

- This also proves fitting for the best effort traffic. 

- But there are certain QoS requirements of the streaming media that cannot be ignored. 

- Streaming traffic is by nature not statistical and therefore is better maintained by end to end resource allocation.

- This category is applicable for audio and video services.

- This is not exclusive of the IP traffic gained via guaranteed QoS transport if majority of the content is audio and video. 

- Some other technologies such as that of IP and Ethernet were also adopted for the same purpose. 

- Multi protocol label switching or MPLS can be applied to the carriage network for improving the reliability as well as determinism that is required by most of the streaming media. 

- This technology is applied along with the techniques such as the forward error correction.

- Ethernet has been made supportive for audio and video transmission by improvement in technologies such as the provider backbone bridge traffic engineering. 

- The development of dynamic synchronous transfer mode took place at the royal institute of technology.