quot;Digital national standard" control network specification description (Continued) - Control Technology - Smart Home Industry

quot;Digital national standard" control network specification description (Continued) - Control Technology - Smart Home Industry

1, LONWORKS Protocol Specification GB/Z20177.1-2006 "LONWORKS control network specification," Part 1, "Protocol specification" amendment by ANSI/CEA-709.1 "Control Network Protocol", that LonTalk protocol.

GB/Z20177.1-2006 agreement as shown in Figure 3, composed of layers, each layer described below.

GB/Z20177.1-2006-based systems allow a variety of physical layer protocol and data encoding method, each encoding method and media. So GB/Z20177 network supports a variety of communications media, such as twisted pair, power line, wireless, fiber optic, coaxial cable, etc..

1.MAC sublayer GB/Z20177.1-2006 Media Access Control (MAC) sublayer easy media access, with optional priority and optional collision detection / conflict resolution. It can be predicted using the p-maintained CSMA (Carrier Sense, Multiple Access) protocol, similar to the p-CSMA protocol to maintain set. Can predict p-CSMA is a way to avoid conflict to keep the technology. The use of the channel load forecast random access of the channel. By adjusting the size of the window as a random function of the load forecast, this method keeps the conflict rate remains unchanged, and has nothing to do with the load.

Support of this Agreement based on the priority of a particular channel. The priority of each channel the number of time slots 0-127, first time slice is not usually used by competition, but the only node assigned to the channel. Time slice is assigned a priority to each packet the node does not have to use it, whether to use the priority allocated time slice, is a node of each packet to decide the case. Also assigned to the same channel a priority for all nodes in the same time slice. Application can determine a message is high priority and try to give priority to send. If the node has not been assigned to the first time slice, then the packet is sent in the usual manner, if the packet through the channel at its destination router priority of the time slice, then the packet should be used to transmit the priority of the router . If the router does not give priority to time slice, the packet will be forwarded in the usual way.

2. Link Layer Order to simplify the multicast protocol and is compatible with such a number of reasons, the link layer to support a simple connectionless service, its functions limited to framing, frame coding and error detection, error recovery retransmission mechanism. Link layer provides the subnet range, orderly, and no confirmation of LPDU presented, with error detection, but no error recovery. Once the CRC checksum is wrong, it will damage the frame discarded.

CRC calculation of the NPDU, including L2Hdr field. CRC generated by the following polynomial:

X16 + X12 + X5 +1 3. Network Layer The standard protocol to support a variety of topologies to meet the needs of a variety of applications. Within a single channel, topology can be bus-type, ring, star, or "free" type (see Figure 4). Free topology is defined as the entire network cabling no other rules, only one terminal device anywhere on the network. So the free ring topology may include, star, bus type, or any combination of them.

The agreement supports physical layer repeater and store and forward repeater from one channel to another channel to resend the packet. The agreement also supports the bridge, the bridge from one domain to another channel channel resend all packets. In addition, support for self-learning type and configuration-based routers, and traffic segmentation, to improve overall system performance.

Network layer processing of data packet transmission in the region, does not provide inter-domain communication, network service is connectionless, no confirmation, does not support message segmentation does not support packet re.

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