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Techniques for transmission of data
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| bet | 14/32 | | Sana | 22.07.2021 | | Hajmi | 0.89 Mb. | | #15652 |
4.5 Techniques for transmission of data
The data being transmitted by the application is bulky Real Time Data, so the best protocol for transmitting this data would be UDP as appose to TCP. UDP has very little protocol overheads in comparison to TCP, and since the reliability characteristics and the slow-start congestion controls of TCP is not required then UDP would be the better choice.
The main issue in terms of the transmission of data is the format of the packet header. There are two alternative solutions either with the use of a bespoke header or with the use of RTP (Real-time Transmission Protocol)
RTP was designed to support a wide variety of applications; the header is twelve bytes long and using profiles which can be specified by the programmer allows the network to detect the type of data being transported. It has the standard fields expected within a header such as version, extra padding, and a sequence number which would be useful for the VoIP application. RTP also contains a Synchronization Source within the header which is a random number representing the source number, this allows the application to determine where the stream originated from without having to look at the lower-level protocols.
The benefits of using RTP would be that it is a standard well known header; it contains everything that is needed. On the other hand the only functionality of RTP which would be used would be the sequence number, so this means there would be a lot of wasted space if RTP was used. On the other hand to reduce the size of the RTP header compression could be used which compresses the RTP header into around 3-4 bytes as appose to 12, however this adds to the complexity of the application especially since the other fields offered by RTP are not required.
A bespoke header could be used as an alternative since all that is required from a header is it simply contains the packet number. A packet number is required so the application can detect lost packets and re-order packets if they arrive out of order. The advantage of using a purpose designed header is that only the data which is required within the header is stored again reducing the amount of redundant data transmitted. However the disadvantages of this, is that some networks which use traffic shaping to try and deliver real time data on time, read the header to determine the type of data being carried, such that, if a none standard header is used then no advantages of traffic shaping will occur.
For this application a purpose built header containing only a 32bit long representing the packet number will be used. This will be the more efficient than RTP since no redundant information will be sent.
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