![]() ![]() PXE is a protocol or booting a host with an image retrieved from the network. Most operating systems enable interrupt coalescing hardware dynamically and only under times of load, in order to keep from increasing packet processing latency under lightly loaded conditions (when interrupt coalescing would delay a packet while awaiting the arrival of others).įlash support for Preboot eXecution Environment (PXE). By aggregating packets as they arrive and issuing a single interrupt for a batch, the overhead due to interrupt processing can be reduced. Under heavy load, frequent interrupts can degrade performance by trading useful work for interrupt handling. Traditional NICs interrupt the operating system upon packet arrival. This frees the CPU to do other work and, in general, makes better use of PCI bandwidth. This hardware support allows the system to post the addresses and sizes of main memory buffers and, with a few PCI commands, manage the transfers on its own. Traditional implementations require software on the CPU to read and write control registers on the device in order to manage the packet movement between ring buffers and main memory. Receive and transmit rings (i.e., circular FIFOs) in the MAC chip stage packets as they enter and leave the system. Hardware support for receive and transmit ring management. Consider the following sample mechanisms supported by the Intel 82546GB. Modern Ethernet silicon supports additional features intended to simplify use or improve performance and efficiency. ![]() The MAC/PHY data path is reached from the host through the PCI bus. The management data input/output bus (MDIO) is by the MAC to send controller information to the PHY. GMII is backward compatible with MII, the corresponding bus interface for 10/100 Mbps Ethernet. The PHY connects to the MAC/controller, which governs the operation of link-level Ethernet protocol across the gigabit media independent interface (GMII) with one bus going in each direction GMII is clocked at 125 MHz with an 8-bit wide data path. The Ethernet frame data path consists of the off-chip medium dependent interface (MDI), which represents an Ethernet port, and the PHY device (or transceiver), which manages the signal transmission and reception across the physical medium. Block Diagram of the Intel® 82546-GB Dual Port Gigabit Ethernet Controller. It is considered by the master node as a node failure, and its corresponding slot is removed.įIGURE 12.8. When a node leaves the network, it no longer sends packets in its corresponding slot. Once a node has finished the synchronization phase, it sends a join request including its identifier (which is calculated using information provided by sync messages) to the master node, which increases the number of network members and adds a new slot for the incoming node. In the first round of a TDMA cycle, there is a resync slot after the sync slot which is used to send join requests by new nodes during the synchronization phase. Each node has only an identifier when it joins the network, and this identifier is used to determine the action performed by this node. This special packet contains protocol state information, including the number of network members. ![]() Membership is managed in a centralized fashion by the master, which sends a sync packet in the first slot of each TDMA round. RTL-TEP allows new nodes to join and to leave the group dynamically and also to detect node failures. Joan Vila, in Fieldbus Systems and Their Applications 2005, 2006 5.1 Dynamic group management ![]()
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