11.2.Networks
\(11.2.\)Networks
1.The Physical Interface
The adapter provides the physical interface to the network.
Data received from the network are copied from the adapter typically by a DMA transfer.
2.Ethernet Segment
One end is attached to an adapter on a host, and the other end is attached to a port on the hub.
A host can send a chunk of bits called a frame to any other host on the segment.
Every host adapter sees the frame, but only the destination host actually reads it.
3.LAN
Multiple Ethernet segments can be connected into larger LANs(Local Area Network), called bridged Ethernets, using a set of wires and small boxes called bridges.
Bridges automatically learn over time which hosts are reachable from which ports and only copy frames from one port to another when necessary.
4.Internet
Multiple incompatible LANs can be connected by specialized computers called routers to form an internet.
Each router has an adapter(port) for each network it connected to.
5.Protocol Software Layer
A layer of protocol software smoothes out the differences between the different networks. This software implements a protocol that governs how hosts and routers cooperate in order to transfer data.
The following figure shows an example of using protocol software layer for data transferring:
- The client on host A invokes a system call that copies the data from the client's virtual address space into a kernel buffer.