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Ports became necessary after computers became capable of executing more than one program at a time and were connected to modern packet-switched networks. Links when the computers at each end could only run one program at a The protocols that primarily use ports are the transport layer protocols, such as the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).Ports were unnecessary on direct point-to-point Port number: 80", which may be written 1.2.3.4:80 when the protocol is A port is identified for each address and protocol by a 16-bit number, commonly known as the port number.įor example, an address may be "protocol: TCP, IP address: 1.2.3.4, (And in case you were wondering, there areĪ port is always associated with an IP address of a host and the protocol type of the communication, and thus completes the destination or origination network address of a communication session. Ports that have specific purposes (such as the HTTP port)Īre also known as well-known ports. Internet, for instance, data is being routed through TCP port 80. Since we need each port to be specific to a certainĪpplication, there are thousands of ports for use.
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This is accomplished through ports andĪ port is simply an internal address that acts as a pathway toĬontrol data flow. Simultaneous connections to a computer- yet the receiving computer still knows We mentioned earlier that a transport protocol can have The transport is provided by TCP and UDP protocols A typical example of layerĤ is the Transmission Control Protocol (TCP). To achieve this, transportĬonnections between two devices are made available. Whether all packets have been received completely. The transport layer coordinates the transmission of data packets. Limited link once a packet is fragmented, it stays fragmented until it reaches Packet by the destination machine (not by the machine at the other end of the
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The fragments are then reassembled into the full Limitations on packet size along that link) into smaller packets, called fragments , Packet that otherwise couldn't traverse some network link (because of One of the features of IP is its ability to divide a large Its structure at the IP layer (the IP headers are duplicated into eachįragment), but it may mean that the body contains only a part of a packet at
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That is too large to cross a given network into a series of smaller packetsĬalled fragments. Internet layer protocols are ARP, IP and ICMP An example of this layer is the Internet protocol (IP). It handles the addressing of the frames and how they are routed The network layer is responsible for routing and correct forwarding of theīlocks of data.
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The bits into blocks of data and adds address information required to transmit The data link layer is responsible for reliable transfer of the data. It transfers the data from one device to another over a network. The physical layer is responsible for the physical connection between twoĭevices.