networking

• LAN interface handles all details of frame transmission and reception
  • Adds hardware addresses, error detection codes, etc. to outgoing frames
  • May use DMA to copy frame data directly from main memory
  • Obeys access rules (e.g., CSMA/CD) when transmitting
  • Checks error detection codes on incoming frames
  • May use DMA to copy data directly into main memory
  • Checks destination address on incoming frames
• If destination address on incoming frame matches the local station's address, a copy of the frame is passed to the attached computer
• Frames not addressed to the local computer are ignored and don't affect the local computer in any way.

LAN Transmission Methods

LAN data transmissions fall into three classifications: unicast, multicast, and broadcast.
In each type of transmission, a single packet is sent to one or more nodes.

In a unicast transmission, a single packet is sent from the source to a destination on a network. First, the source node addresses the packet by using the address of the destination node. The package is then sent onto the network, and finally, the network passes the packet to its destination.

A multicast transmission consists of a single data packet that is copied and sent to a specific subset of nodes on the network. First, the source node addresses the packet by using a multicast address. The packet is then sent into the network, which makes copies of the packet and sends a copy to each node that is part of the multicast address.

A broadcast transmission consists of a single data packet that is copied and sent to all nodes on the network. In these types of transmissions, the source node addresses the packet by using the broadcast address. The packet is then sent on to the network, which makes copies of the packet and sends a copy to every node on the network.