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. 

What is meant by Ovonic Unified Memory?

There is much requirement in the IT industry for a high – speed memory plus that is non–volatile too. A solution to this is provided by the ovonic unified memory. 

- Ovonic Unified Memory is an approach to such a memory. Further, it offers reduced bit rate and cost. 

- There are some other characteristic features of this memory:

1. High endurance
2. Low power consumption
3. Non – volatile RAM
4. Readily scaled.
5. Merged memory/ logic simplified

- Since the ovonic unified memory is readily scaled it is not required to scale the barriers of flash and DRAM memories.

- This represents a new semiconductor technology – a creation of the Energy Conversion Devices, inc. however later it was licensed to the ovonyx inc.

- This technology makes use of a structural phase change that is reversible i.e., from a crystalline phase to the amorphous phase. 

- The material used here is the thin–film chalcogenide alloy. 

- This all constitutes the data storage mechanism of ovonic unified memory (OUM). 

- Each memory cell consists of an active medium in a small volume that acts as the programmable resistor. 

- This resistor switches between the low and high resistance in the dynamic range of greater than 40x. 

- The phase change technology is currently being used in the PD, CD RW, DVD RW and DVD RAM. 

- The basic advantage offered by OUM is in the terms of performance and cost when compared to its conventional counterparts namely the flash and the DRAM memories. 

- OUM has got compatibility with the merged memory/log. 

- A conventional CMOS process is used in the OUM technology along with some additional layers in order to form the memory elements. 

- The OUM products have been commercialized under various licensing agreements. 

- The alloy used in OUM consists of Se and Te elements.

- They exhibit the property of electronic threshold switching phenomenon because of which the OUM memory cells can be programmed at quite low voltages irrespective of which state they are in i.e., whether conductive or resistive. 

- The measurement of the resistance of cell is used to read the information stored. 

- The programming of the OUM devices is done electrically by the alteration of its structure of the alloy. 

- These OUM devices show metallic behavior are independent of the temperature.

- The OUM devices are known for their excellent data retention property in the case of high density array applications. 

- Also, the OUM cells have more than normal life cycle i.e., they can tolerate up to 10¹³ write and erase cycles without any failure. 

- These devices possess quite a large dynamic range.

- This allows them to be programmed for enabling the multi–state data storage at intermediate resistance values.

- For multi–stage data storage, every cell needs to support multiple–bit storage. 

- The technology behind the ovonic unified memory is the device modeling. 

- Here, simple analytical methods show the trends in the properties and size of the material for structures that are spherically equivalent. 

- Other numerical models are inclusive of the mesh evaluation plus the device geometry.

- The behavior of the OUM devices can be predicted using the numerical simulation. 

- The behavior of the OUM material depends up on its bulk properties which have a characteristic that they can be quantified. 

- There are 3 considerations of this model:

1. Phase–change: It includes heat of fusion, crystal growth and nucleation.
2. Electrical: It includes current density, electric field and percolation conduction.
3. Thermal: It includes percolation conduction and the heat equations.

Apart from the cost, another advantage of OUM is its near – idle memory qualities such as:

1. Static
2. Random accessible
3. Non – destructive read