Network Interface Cards

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Network Interface Cards
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Types
RJ45
BNC
LC
Fiber optic
Coaxial
Wired netcard
Dongles
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History of NIC
In 1973 Robert Metcalfe needed something that was
fast, could connect hundreds of computers, and
span a whole building. To solve this problem,
Metcalfe developed a rudimentary form of LAN and
dubbed it Ethernet. The original Ethernet sent
roughly a paragraph of data over thick coaxial
cable and could handle a distance of one
kilometer.
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History of NIC
In 1975 Xerox filed a patent listing Metcalf,
David Boggs, Chuck Thacker and Butler Lampson as
inventors. In 1976 Metcalf wrote a seminal paper
that stated the transfer rate was 3 Mbits/second.
Metcalf left Xerox in 79 to start the company
3com.
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History of NIC
In 1981, 3COM built the first 10 Mbits/sec
Ethernet adapter.
In mid 1980s, Tim Rock, Richard Bennett, Pat
Thaler, and others develop StarLAN, the basis for
1BASE5 ethernet
In late 1980s the twisted pair design started to
replace the coaxial cables.
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How the NIC transfers data

• The app you are using generates the data you
  would like to send to another computer.
• Your NIC accepts the data from your motherboard
  and transfers it to a small buffer on the card.
• The NIC adds its address (set by the
  manufacturer) plus the destination address and
  the type of data to the buffer.
• Your NIC calculates the checksum, or CRC, for the
  data in the buffer.

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How the NIC transfers data

• The information is arranged into a frame.
• The NIC listens to the network for other
  transmissions. If a transmission is heard, it
  will wait until the transmission is complete.
• The NIC begins to serially transmit the frame
  over the network.
• The receiving NIC calculates the checksum for the
  received frame, then compares it to the checksum
  it received.
• If there are no errors, the receiving station
  acknowledges the received data.

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Translated into 5 steps

• The network application retrieves the data being
  sent.
• The NIC puts the address of the other computer
  onto the data.
• The NIC calculates for errors.
• The data is arranged into a packet and sent over
  the network.
• The receiving card checks for errors, if there
  are none, it acknowledges the data.

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Transportation
The Network interface cards use differing amounts
of voltage to transport the 1s and 0s of binary
across the cable.
For fiber optic cable, different wavelengths of
light are passed along.
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This layer translates the data so it can be sent
along the network. It is sometimes called the
syntax layer.
This layer establishes, manages and terminates
connections between applications. The session
layer sets up, coordinates, and terminates
connections at each end. It deals with session
and connection coordination.
This layer provides transparent transfer of data
between end systems, or hosts, and is responsible
for end-to-end error recovery and flow control.
It ensures complete data transfer.
This layer provides routing technologies,
creating paths, known as virtual circuits, for
transmitting data from computer to computer.
Routing and forwarding are functions of this
layer, as well as addressing, internetworking,
error handling, congestion control and packet
sequencing.
At this layer, data packets are encoded and
decoded into bits. The data link layer is divided
into two sub layers The Media Access Control
(MAC) layer and the Logical Link Control (LLC)
layer. The MAC layer controls how a computer on
the network gains access to the data and
permission to transmit it. The LLC layer controls
frame synchronization, flow control and error
checking.
This layer conveys the bit stream - electrical
impulse, light or radio signal -- through the
network at the electrical and mechanical level.
It provides the hardware means of sending and
receiving data on a carrier, including defining
cables, cards and physical aspects. Fast
Ethernet, RS232, and ATM are protocols with
physical layer components.
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Token Ring Process

• Phase 0 (Lobe Check) The station checks to
  ensure it can receive these frames without error.
  
• Phase 1 (Physical Insertion) A station then
  sends a 5 volt signal to the MSAU to open the
  relay.
• Phase 2 (Address Verification) A station then
  transmits MAC frames with its own MAC address in
  the destination address field of a token ring
  frame. When the frame returns and if the address
  copied , the station must participate in the
  periodic (every 7 seconds) ring poll process.
  This is where stations identify themselves on the
  network as part of the MAC management functions.
• Phase 3 (Participation in ring poll) A station
  learns the address of its Nearest Active Upstream
  Neighbor (NAUN) and makes its address known to
  its nearest downstream neighbor, leading to the
  creation of the ring map. Station waits until it
  receives an AMP or SMP frame with the ARI and FCI
  bits set to 0. When it does, the station flips
  both bits (ARI and FCI) to 1, if enough resources
  are available, and queues an SMP frame for
  transmission. If no such frames are received
  within 18 seconds, then the station reports a
  failure to open and de-inserts from the ring. If
  the station successfully participates in a ring
  poll, it proceeds into the final phase of
  insertion, request initialization.
• Phase 4 (Request Initialization) Finally a
  station sends out a special request to a
  parameter server to obtain configuration
  information. This frame is sent to a special
  functional address, typically a token ring
  bridge, which may hold timer and ring number
  information with which to tell the new station
  abort

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How the procedure works.
Simpler than a token ring, the procedure for
coaxial is as following

• Main procedure, it states and asks
• Asks is the frame ready for transmission.
• Is medium idle? If not, wait until it becomes
  ready and wait the interframe period
• Starts transmitting.
• Asks did a collision occur? If so, it goes to
  collision detected procedure.
• Resets retransmission counters and end frame
  transmission.
• If a collision is detected it
• Continues the transmission until minimum packet
  time is reached to ensure that all receivers
  detect the collision.
• Counts how many times it retransmitted
• Asks was the maximum number of transmission
  attempts reached? If so, abort transmission.
• Calculates and wait random back off period based
  on number of collision
• Re-enters main procedure at stage 1.

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How long the card waits between retransmission
The card counts how many collisions occurred.
Then, back-off algorithms determine when the
colliding stations retransmit.
N number of collisions
The card can wait up to 16 collisions, anything
higher and it quits.
Slot Time Twice the time it takes for an
electronic pulse to travel the length of the
maximum theoretical distance between two nodes.
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The Frames
A runt frame is a packet smaller than the 64
bytes. This usually occurs because of a collision
or an error.
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Differences in the cards

• The major difference between the cards are the
  way the data is converted to transmit over the
  network. Each type of network has its own type of
  transceiver (transmitter receiver). 10baseT
  networks have a specialized transceiver that
  translates the data into 10baseT Ethernet
  standards, then transmits it. It also receives
  information from the network and translates it
  back into a form the NIC card can use.

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Differences in the cards (continued)

• 10base2 Ethernet networks have almost the same
  NIC except for the transceiver. Some NICs have
  two transceivers, normally 10baseT and 10base2.
  These dual type cards are known as combo NICs.

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Major Manufacturers

• ZTE
• Cisco Systems
• Hewlett-Packard
• 3Com
• Linksys
• Belkin
• Dlink

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FDDI
Fiber Distributed Data Interface
Can support thousands of users Uses duel token
ring setup Due to their speed, cost and ubiquity,
fast Ethernet and (since 1998) Gigabit Ethernet
have largely made FDDI redundant.
Needs two Token ring supportable cards or two
jacks on the card.
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Price

• The cards can range in price from 10 to 800.
  Most cards are actually around 20.

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References

• Webopedia.com
• Howstuffworks.com
• http//everything2.com/title/HowNetworkAdapters
  Work
• Wikipedia.com
• Bestbuy.com

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