While I was studying for my net work Plus Class I ran Across this introduction to the Basic Functions of a Network interface Adapter..


All information Can Be founrd On pages 95-97

Academic Learning Series Network + Certification Fourth Edition
Published By Microsoft Press
A Division Of Microsoft Corporation
One Microsoft Way
Redmond, Wa 98052-6399
Copy Right 2006 By Microsoft Corporation


Understanding Network Interface Adapter Functions
Network interface adapters and their drivers perform many functions that are
crucial to getting data to and from the computer over the network. The sequence
of functions that occurs each time a network interface adapter transmits data over
a network is described in the following list:
1. Data transfer Data originating in an application remains in the computer’s
memory as it’s passed down through the protocol stack to the
data-link layer. At the data-link layer, the data is transferred from system
memory to the network interface adapter using a system technology
such as programmed input/output (I/O) or, in some cases, direct
memory access (DMA) or shared memory.

2. Data buffering Network interface adapters transmit and receive
data one frame at a time, so they have built-in buffers that let them
store data arriving from the computer or from the network until a
frame is complete and ready for processing. An Ethernet network interface
adapter for a desktop computer typically has 4 KB of buffer space—
2 KB for its transmit buffer and 2 KB for its receive buffer. Network
interface adapters for servers or for other protocols, such as Token
Ring, can have more buffer space—often 64 KB or more—that is divided
between transmit and receive buffers using one of several configurations.

3. Data encapsulation The network interface adapter and its driver
build the data-link layer frame around the data generated by the network
layer protocol and passed down to the data-link layer for transmission.
For incoming traffic, the adapter verifies that the packets have
arrived without errors, using the cyclical redundancy check (CRC)
value stored in the frame’s footer. The adapter then scans the destination
address in the frame’s header to determine whether the packet
should be passed up to the network layer. If the packet is passed up,
the network interface adapter strips off the data-link layer frame and
sends the payload data to the network layer protocol specified in the
frame header.

4. Media Access Control (MAC) The network interface adapter implements
the MAC mechanism that the data-link layer protocol uses to
regulate access to the network medium.
In networks using the Carrier Sense Multiple Access with Collision
Detection (CSMA/CD) mechanism, the adapter does the following:
❑ Listens to the network
❑ Transmits when the medium is clear
❑ Detects packet collisions when they occur
❑ Retransmits packets as needed
In token passing networks, the adapter does the following:
❑ Captures the token frame
❑ Transmits its data
❑ Removes the data from the ring when it returns to its source
❑ Generates a new token

5. Parallel/serial conversion In parallel communications, systems
send multiple bits at one time, using a separate channel for each bit.
For example, the communication between a computer and a network
interface adapter is nearly always parallel, because the expansion
buses that the computer and the adapter use to communicate are 16 or
32 bits wide.
The only exception to this is an adapter that connects to the computer
using a universal serial bus (USB). In serial communications, the systems
send one bit at a time. For a network interface adapter to transmit
the data it receives from the computer over the network, it must convert
each 16 or 32 bits it receives simultaneously over the bus connection
into a stream of 16 or 32 sequential bits that it can send on the
network medium. For data arriving from the network, the adapter
must perform the same conversion in reverse by sending a series of
incoming serial bits to the computer using parallel communications.
All baseband LANs use serial communication.

6. Signal encoding and decoding The network interface adapter
implements a physical layer encoding scheme, such as Manchester
encoding on Ethernet networks or Differential Manchester encoding
on Token Ring networks. The physical layer encoding scheme converts
the binary data generated by the network layer, now encapsulated in
the data-link layer frame, into a pattern of electrical voltages, light
pulses, or whatever other signal type the network medium uses. For
packets arriving from the network, the adapter converts the signals
back into their original binary data.

7. Data transmission and reception Finally, the network interface
adapter takes the data it has encoded, amplifies the signals to the
appropriate amplitude, and transmits them over the network medium
For incoming data, the adapter detects and reads signals of the appropriate
type and amplitude arriving from the network.
When a packet is received, these same steps occur in reverse (with the exception
of step 4, which is not needed for incoming traffic). In addition to these basic
functions that all network interface adapters perform, specific models have additional
features, such as those described in the following sections.





































































































































































ertifacation [/U]

Ok....is there a question in your message, or are you sharing this info for the rest of us?

I am making this post for the general benefit of the community here on LQ.

You probably should not be publishing significant portions of copyrighted material on the Internet.