LAN hardware and packet filtering
- 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.
(Or)
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.