25-08-2017, 09:32 PM
Network Interface Cards
[attachment=35424]
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. A
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.
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.
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.
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.
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
How the procedure works.
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.
[attachment=35424]
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. A
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.
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.
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.
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.
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
How the procedure works.
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.