NDI Protocols type - NDI 5 - NDI 4 - NDI 3 - NDI 1

Reliable UDP – NDI 5
The default communication mechanism in NDI version 5 is a Reliable UDP protocol that represents state-of-the-art communication protocols, implemented by building on all that experience we have seen in the real world with NDI across a massive variety of different installations.

Reliable UDP, also known as RUDP, was a transport protocol designed to take the best of both worlds: the low latency and simplicity of UDP combined with the reliability of TCP. This is particularly for real-time multimedia applications where timeliness is an essential factor to be held.

In the context of NDI, Reliable UDP is a method for delivering video and audio streams in a reliable and timely manner. It achieves this through several mechanisms:

Sequencing: Reliable UDP assigns a sequence number to each packet it sends. The receiving end thus can detect missing or out-of-order packets and may request retransmissions if necessary.

Retransmissions: The receiving end can request a retransmission of the lost packet(s) using the sequence number information, in case a packet is lost or if a packet is received out of order.

Flow control: Reliable UDP has flow control, which regulates the amount of data to be sent at a given time. It will not flood the network or the receiving device with more data than it can handle, hence a better experience in streaming.

Congestion control: RUDP also contains algorithms for congestion control, to avoid network congestion and unnecessary packet loss. It will dynamically adjust the transmission rate according to the network condition in order to keep the optimum throughput without flooding the network.

Multipath TCP – NDI 4
This protocol enables transport over multiple NICs and all network paths. It is designed to utilize hardware-accelerated network adapters with adaptive bandwidth sharing over NICs.

Multipath TCP is a transmission protocol bearing the benefits of maximizing throughput, optimal resource utilization, and enhancement of network redundancy. It can easily integrate multiple network paths, including wireless and mobile networks. It really comes into its own when used with NDI equipment that makes use of multiple Gigabit connections to exchange hundreds of NDI streams.

However, when the interfaces of 10Gbit are connected with 1Gbit interfaces, then Multipath TCP is not that effective. The main reason behind this factor is that network switches cannot control congestion over the network in such instances. Thereby, the protocol may not be able to provide the best possible performance in such particular network setups.

UDP with Forward Error Correction – NDI 3

This is an alternative protocol to TCP when the reliable delivery of data packets is not needed. UDP is mainly used where timeliness is of higher priority than accuracy, such as in streaming media, teleconferencing, and voice-over-IP (VoIP). FEC is a way of obtaining error control in data transmission where the source (transmitter) sends redundant data to the destination (receiver).

The User Datagram Protocol (UDP) with Forward Error Correction (FEC) can be quite useful where the network is error-prone or not completely reliable. It provides a solution to correct errors in the case of lost or corrupted data packets during transmission.

It should, however, be noted that the use of UDP coupled with FEC increases processing most on the receiver side. The receiving side has to implement algorithms and mechanisms regarding the error correction process: it decodes the received data, performing an error correction technique to recover any lost or corrupted packets.

Single TCP – NDI 1

This network communications protocol allows two host systems to establish a connection and exchange data packets, ensuring the delivery of the data intact to the right destination. TCP is most commonly coupled with IP, or Internet Protocol, and together is also known as TCP/IP. Single-TCP is available with all NDI versions. Other transmission modes will probably be more performant, but this most basic compatibility mode will work with all NDI clients.