| Protocol Issues | | | | However, Multicast protocols were developed in |
| Designing a network protocol which supports | | | | order to minimise this sort of replication. Such |
| streaming media can be quite involved. | | | | protocols send just one stream from the source to a |
| | | | group of recipients. Whether Multicast transmissions |
| The following protocols have been particularly | | | | are feasible depends on the network infrastructure |
| designed to deliver streaming media over networks: | | | | and type. One possible downside of multicasting is |
| Real-time Streaming Protocol, Real-time Transport | | | | the loss of the ability to utilise video on demand. In |
| Protocol, and the Real-time Transport Control | | | | the case of continuously streaming radio or television |
| Protocol. | | | | material, the user will be unable to control playback. |
| Dependable protocols, such as the Transmission | | | | The use of servers with the ability to cache, digital |
| Control Protocol, ensure the correct delivery of each | | | | set top boxes, and buffered media players are all |
| bit in the media stream. However, in order to achieve | | | | methods which will tend to limit this problem. |
| this, they use a system of timeouts and retries, | | | | The ability to send a single data stream to a number |
| which makes them more complex to implement. The | | | | of end users on a computer network is available with |
| downside is that when the network suffers from is a | | | | IP Multicast. Since routers and firewalls must allow the |
| loss of data, the media stream is put on hold while | | | | flow of data destined for multicast groups, this must |
| the protocol handlers detect the loss and retransmit | | | | be considered when deploying IP multicast. |
| the missing data. By buffering the display data, it is | | | | In the case of educational, government, and |
| possible to reduce this effect quite noticeably. | | | | corporate intranets where the organization that is |
| When using Unicast protocols, an alternative copy of | | | | serving the content has control over the network |
| the data stream is sent from the server to each | | | | between server and recipients, then routing protocols |
| user. Unicast is most commonly used for most | | | | such as IGMP and PIM can be used to deliver stream |
| Internet connections. However, it does not perform | | | | content to multiple LAN segments. |
| well when large numbers of users want to view the | | | | Arranging for pre-recorded streams to be sent |
| same program at the same time. When there are | | | | between computers forms the basis for Peer-to-peer |
| many recipients receiving Unicast content streams | | | | (P2P) protocols. In this way, the server and its |
| independently, there tends to be data replication with | | | | network connections are free from experiencing |
| consequent server/network loads. Even when the | | | | bottlenecks. There are, however, certain matters |
| streaming content is the same as that provided by | | | | that may need to be resolved when using of such an |
| the associated streaming server, there will still be a | | | | arrangement. These include technical, effectiveness, |
| requirement for multiple connections from the Unicast | | | | accuracy of data, and various legal issues. |
| Connections. | | | | |