Ethernet
3-3
Technology Basics
All the information necessary for a station to receive and comprehend the
network transmission is contained in the packet. The Ethernet packet contains
other fields related to Ethernet operation which are not essential to a basic
understanding of the technology.
Procedures
Ethernet stations follow four basic procedures when dealing with transmission
and reception. The treatment of these procedures given below is a highly
simplified view of network packet operations. The four procedures are
preparation, transmission, reception, and examination. Preparation and
transmission are both performed by the sending station, while reception and
examination are performed by all receiving stations.
Preparation
: When the workstation or device has information that it needs to
send out to the network, it prepares that information for transmission by
generating a packet. The packet, as described above, consists of some network
control information, the station or stations to which the packet must go, the
address of the sending station, and the actual data of the transmission.
Transmission
: Once the packet is ready to be transmitted, the Ethernet device
checks its connection to the network. This monitoring determines if the
network is currently being used. If the network is in use, transmitting would
cause both the signals to become garbled. This is called a collision. The
monitoring of the media helps to avoid collisions.
If the media is not in use, the station will add some futrther control
information to the packet, effectively encapsulating it in what is called an
Ethernet frame. Once the frame has been generated, it will be transmitted. It
then returns to monitoring the network to see if the frame it just sent is
involved in a collision. Even though the media was monitored before the
frame was sent, collisions can, and do, still occur in Ethernet networks.
Reception
: The frame that has just been sent spreads along the Ethernet
network. As the signal travels throughout the cables and devices, all the
stations on the network read in the entire frame.
Examination
: Once a station has received the frame in its entirety, the portion
of the frame that contains the destination address is examined by the
receiving station. If the destination address of the frame matches the address
of the receiving station, the frame is processed. The station removes the frame
information from the transmission, stripping it back down to a packet. The
packet is passed up to the higher layers of the OSI model and the information
in the data portion of the packet is acted upon. If the destination address of
the received frame does not match the address of the receiving station, the
frame is discarded.
More complete treatments of the organization, content, and processing of frames
may be found in documents dedicated exclusively to Ethernet operations. A more
complete depiction of the operation of the Ethernet network technology may be
found in Chapter 5, Ethernet.
Summary of Contents for MMAC-5FNB
Page 1: ...Cabletron Systems Networking Guide MMAC FNB Solutions ...
Page 2: ......
Page 4: ...ii ...
Page 10: ...viii ...
Page 188: ...Expansion Ethernet 8 12 Port Assignment and Virtual LANs ...
Page 194: ...Expansion Token Ring 9 6 Port Assignment ...