TCP/IP

The TCP/IP protocol suite is fundamental for network communication, providing the foundation for data exchange in industrial automation systems. Understanding TCP/IP protocols and related calculations is crucial for optimizing and troubleshooting networked automation systems.

Overview of TCP/IP Protocol

TCP/IP (Transmission Control Protocol/Internet Protocol) is a set of communication protocols used to interconnect network devices on the internet. It includes several layers, each with specific functions:

• Application Layer: Provides network services to end-users and applications.
• Transport Layer: Manages end-to-end communication and data integrity (TCP and UDP).
• Internet Layer: Handles packet forwarding and routing (IP).
• Network Interface Layer: Defines protocols for data transmission over physical networks.

TCP Protocol

TCP (Transmission Control Protocol) is a connection-oriented protocol that ensures reliable data transmission between devices. Key concepts include:

• Three-Way Handshake: Establishes a connection between the sender and receiver.
• Flow Control: Manages data transmission to prevent congestion.
• Error Checking: Ensures data integrity using checksums.

Calculating TCP Retransmission Timeout (RTO)

The retransmission timeout (RTO) is calculated to determine how long to wait before retransmitting unacknowledged data. The formula involves the round-trip time (RTT) and its deviation (RTTVAR):

Formula: RTO = SRTT + max (G, 4 × RTTVAR)

• RTO: Retransmission Timeout
• SRTT: Smoothed Round-Trip Time
• RTTVAR: Round-Trip Time Variation
• G: Clock Granularity

Example Calculation:

• Task: Calculate the RTO with SRTT = 100 ms, RTTVAR = 20 ms, and G = 1 ms.
• Solution: Use the formula RTO = SRTT + max (G, 4 × RTTVAR).
• • RTO = 100 ms + max (1 ms, 4 × 20 ms)
  • RTO = 100 ms + 80 ms = 180 ms

IP Protocol

IP (Internet Protocol) is responsible for addressing and routing packets between devices. Key concepts include:

• IP Addressing: Uniquely identifies devices on a network.
• Subnetting: Divides a network into smaller sub-networks.
• Routing: Determines the path packets take to reach their destination.

Calculating Subnet Mask

Subnetting involves dividing an IP network into smaller sub-networks. The subnet mask determines the network and host portions of an IP address.

Example: For an IP address 192.168.1.0/24, the subnet mask is 255.255.255.0.

Calculating Number of Hosts in a Subnet

The number of hosts in a subnet is calculated using the subnet mask. The formula is:

Formula: Number of Hosts = 2^{(32 - Subnet Bits)} - 2

• Example Calculation:

• Task: Calculate the number of hosts in a /24 subnet.
• Solution: Use the formula Number of Hosts = 2^{(32 - 24)} - 2.
• • Number of Hosts = 2⁸ - 2
  • Number of Hosts = 256 - 2 = 254

UDP Protocol

UDP (User Datagram Protocol) is a connectionless protocol that allows data to be sent without establishing a connection. It is suitable for applications where speed is critical, and error checking is not necessary.

UDP Header Format

The UDP header contains the following fields:

• Source Port: The sending port number.
• Destination Port: The receiving port number.
• Length: The length of the UDP header and data.
• Checksum: Used for error-checking the header and data.

Applications of TCP/IP in Industrial Automation

TCP/IP protocols are widely used in industrial automation for various applications, including:

1. Remote Monitoring and Control

Enables real-time monitoring and control of industrial processes over the network.

2. Data Acquisition

Facilitates the collection and transmission of data from sensors and devices to centralized systems.

3. Communication between PLCs

Enables communication between programmable logic controllers (PLCs) for coordinated control of industrial processes.

4. Industrial IoT

Supports the integration of industrial devices with the Internet of Things (IoT) for enhanced connectivity and data analysis.