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Shared Variable
Published in Rick Bitter, Taqi Mohiuddin, Matt Nawrocki, LabVIEW™ Advanced Programming Techniques, 2017
Rick Bitter, Taqi Mohiuddin, Matt Nawrocki
Shared variables are transported across networks via a protocol called the NI Publish-Subscribe Protocol (PSP). The PSP protocol is proprietary in nature, so it is not possible to go into significant detail of message exchanges. There are several aspects of the protocol that can be discussed and we will begin with the underlying transport. The PSP protocol itself uses UDP/IP as the underlying transport protocol. UDP is not a reliable protocol; it is possible for PSP packets to be lost during transmission. The advantage to using UDP for the transport protocol is the lack of TCP-related overhead. TCP is reliable, but its windowing algorithm and associated acknowledgments can create what is called network jitter. When a TCP packet is lost, almost every TCP stack in commercial use makes a fundamental assumption: the packet was lost due to network congestion. The TCP stack will then perform a delay and then attempt to retransmit the packet. The trouble with this mechanism is that the application sending the message is unable to control the retransmission delay. Retransmission delay is called jitter. Jitter is undesirable in shared variable applications because retransmissions end up delaying applications. If a front panel control is bound to a shared variable, the goal is to attempt to acquire a current value for the control. TCP-based communications could leave the application in a position of waiting around for the TCP windowing to push data up to the application.
High-Performance Switch/Routers
Published in James Aweya, Designing Switch/Routers, 2023
DNS uses UDP for the majority of DNS messages because DNS Query and Response messages are often short and the application can tolerate message losses. When a sent message is not received, a new DNS Query message is simply issued. With UDP, the source and destination UDP port numbers are set to the “well-known” port number 53. The maximum size of a DNS Response message using UDP is 512 bytes. Out of this, the IP header takes a minimum of 20 bytes, and the UDP header takes another 8 bytes. This means the maximum DNS message size over UDP can only be 484 bytes. With this, the typical DNS Query consists of a single UDP message from the client which is followed by a single UDP Response message from the DNS server.
Overall Architecture of an Intent-Driven Campus Network
Published in Ningguo Shen, Bin Yu, Mingxiang Huang, Hailin Xu, Campus Network Architectures and Technologies, 2021
Ningguo Shen, Bin Yu, Mingxiang Huang, Hailin Xu
SNMP is a machine-to-machine interface that consists of a set of network management standards (application layer protocols, database models, and a set of data objects) for monitoring and managing devices connected to the network. SNMP, based on the User Datagram Protocol (UDP), is the most commonly used network management protocol on TCP/IP networks. It is not a configuration-oriented protocol and lacks a secure, effective mechanism for committing configuration transactions. Therefore, SNMP is typically used for performance monitoring, but not for network device configuration.
An investigation on adaptive HTTP media streaming Quality-of-Experience (QoE) and agility using cloud media services
Published in International Journal of Computers and Applications, 2021
Selvaraj Kesavan, E. Saravana Kumar, Abhishek Kumar, K. Vengatesan
Streaming is the process of dividing data in the file is bro-ken into small packets that are sent in a steady and continuous flow, as a stream to the end device. As soon as few initial data packets received, the playback starts as the rest of the packets are transferred to the end user's device while playing. The client plays out buffer makes sure that the playback to continue uninterrupted despite variations in the rate of received rate and network delay. RTP over UDP widely used in low latency media and entertainment applications such as streaming, video telephony, video conference, set top box application and push-to-talk features. RTP and RTCP protocols are used for payload transmission and control, respectively. Generally Real Time Streaming Protocol (RTSP) over TCP is used for session initiation and description even though specification allows RTSP over UDP.