Soft Real-time Communication in LAN

The term Real- time means the live communication between the devices. It involves expressing the thoughts of one person to the other using the telecommunication system. The time taken for the message is instant and enables live meetings through Zoom or Google Meet calls. This quick delivery of messages is possible as there are no storage parts between the client and the server. It increases the transfer time in other message transfer protocols like email.

Soft Real-Time Communication

Soft real-time communication provides an efficient transfer of messages from the host to the client with a minimal loss is tolerable. The Messaging connections are classified into three main types namely −

  • Open System

  • Hard Real-time System

  • Soft Real-time System

In LAN (Local Area Network), communication is usually done within a particular region or building. So soft real-time applications like personal computers, laptops, and audio and video systems are involved in communication using the method of soft real-time communication. But it does not provide a complete Quality of Service to the systems. Even though during the communication if any missed deliveries, it won’t be taken into consideration and continues its data delivery.

Examples of Soft Real-time communications Systems

Ethernet also known as LAN is the best example of this soft real-time system in which the data is transferred from the sender called the Ethernet Programmable Controller to the End device using a connectionless service provider and vice versa. The Connectionless protocol can be the User Datagram Protocol (UDP) which comes under the fourth layer of the OSI model. Using the Ethernet, there will be increased delays and a drop in the overall throughput.

Protocols used in Soft Real-Time Communication in LAN

The Different types of protocols used in the soft real-time are −

  • Global Priority Protocols

  • Encoding Techniques – CBR and VBR

Global Priority Protocol

The Messages are assigned a separate priority value. Based on this value, the protocol will transmit the data to the specific destination.

The Algorithm used during the data transmission with this protocol is the RMA and EDF (Earliest Deadline First). When the data transmission starts it cannot be stopped in the middle. This protocol will deliver the priority message first, but it is difficult for it to find which are given priority. Because in LAN, there are numerous nodes connected in a distributed fashion.

Encoding Techniques – CBR and VBR

The data transmitted from the sender is encoded using the CBR and VBR encoding techniques. As real-time applications involve video streaming or sharing with the client, the bitrates play a major role.

Bit rates are the number of data that can be transferred for a specific time. While in CBR, the data is transferred with a constant bit rate, and in VBR, it can have variable bit rates.

Working of Soft Real-Time Communication

To implement soft real Time communication in LAN technology and some advantages are low price and quality transmission. So these types of systems can be built in any manufacturing or automation company.

This communication is deployed using Transport layer protocols like TCP/IP and UDP. It faces some difficulties as the Ethernet MAC protocol gives delayed characteristics. When both the real-time packet that has a higher priority queue and non-real-time packets with less priority is transmitted through the LAN which consists of many nodes. These nodes will experience the delay for the below cases −

  • When there are many packets within the same node then there may be conflict in the node.

  • There may be a collision between packets from other nodes of the network.

Algorithm of Soft Real-Time Communication in LAN

To avoid the variance between the real and non-real-time packets, the algorithm called adaptive traffic smoothing came into existence. The algorithm was proposed by Kweon and Shin. This traffic smoother will allow the real-time packets on priority later the other packets are allowed. The packets are smoothened to avoid collision with the Real-time packets to minimize the packet-collision ratio, followed by transmission.

As the LAN consists of numerous nodes, each node is installed with the traffic smoother to maintain a decent rate when the non-RT packets are transferred through the channel. This traffic smoother is just like an add-on to the existing operating system without affecting the Ethernet. This algorithm is similar to the leaky bucket algorithm that includes two primary parameters, they are −

  • Credit Bucket Depth (CBD) − The Maximum number of credits the buckets hold after each refresh.

  • Refresh Period (RP) − It includes the buckets with new credits.


Soft Real-time Communication is applied to the systems in the LAN technology. The main difference is that all the tasks are completed on time constraints in a hard RT system and the tasks are completed based on priorities set to the packets. Due to this higher and lower priority, there may be some delay in the whole transfer process.

Updated on: 04-May-2023


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