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Introduced by:
Almarshood, Yosef
Bahaitham, Ahmed
Alrashudi, Ahmed
Term Paper
Ethernet
Outline
• Introduction to LANs
• What is Ethernet?
• Network topology
• Ethernet communications & collisions
• Ethernet frame format
• Ethernet products
Introductions to LANs
• In 1970s, many commercial atmospheres of production and business
recognized the need of sharing data and works.
• It was not practical or cost-effective for businesses to use floppy disks to
share data, hence, the Local Area Network (LAN) was introduced.
• LAN is a collection of independent computers that communicate with one
another over a shared network medium.
Introductions to LANs (cont.)
• LAN technologies:
• Ethernet: a local area network, using a bus topology, which
provides reliable high-speed communications in a limited geographic
area.
• Token Ring: A local area network in which all computers are
connected in a ring or star with a token passing schem.
• FDDI (Fiber Distributed
Data Interface): A very high speed network
protocol uses fiber optic cable.
Closer look
• A Network Interface Card, or LAN adapter, is your gateway of network
communication to and from a PC.
• It provides a physical connection between the networking cable and the
computer's internal bus.
• NIC is an important icon for LANs because it is the interface for each
host.
• Most NICs in the market are found to support Ethernet.
What is Ethernet?
• The name comes from the word "the Ether" ; a medium, or the air,
through which radio, or electromagnetic, waves travel.
• It was introduced in 1970s.
• Ethernet is a family of networking technologies. Generally speaking,
these are common families of Ethernet:
What is Ethernet? (cont.)
• The 10-Mbps bandwidth was enough in the 1980s.
• In 1995, IEEE announced a standard for a 100-Mbps Ethernet. This was
followed by standards for Gigabit Ethernet in 1998 and 1999.
• The IEEE defines the Ethernet standard as IEEE Standard 802.3.
Ethernet naming standards
•The new supplements are given a one or two letters label such as
802.3x. An abbreviated description, called an identifier.
• The identifier consists of the following elements:
( Number, Word, Number or Letter )
Data rate 10 Mbps
Max. segment link 200 m
10Base2
Baseband or broadband
Twisted pair
10BaseT
Network topology
• Physical topology
Defines the actual layout
of the media.
• Logical topology
Defines how hosts access media
to send data.
Two most common logical topologies:
• Broadcast:
Sending data to all hosts on the network
medium. First come, first serve.
• Token passing:
an electronic token is passed sequentially
to each host.
Ethernet adopts, commonly, Bus and Broadcast topologies.
Ethernet signaling technique
• Baseband
e.g.
• The entire bandwidth is used.
• Data signal is transmitted directly over
the medium.
• Broadband
e.g.
• Uses modulated carrier signal to transmit
data.
Ethernet relies on Baseband signaling technique. It used to use
broadband signaling in the 10BROAD36 standard but now it is not
considered anymore.
Ethernet
communications & collisions
• Communication & Media Access Control Address
• Elements (send/receive) data in terms of Frames.
• Unique MAC (Media Access Control) address as an identifier for each
element.
• NIC within every element uses MAC addresses as an address of a
house, determining if a frame carries its own address in the sake of
passing it on to upper layers (accepted) or take no action because it is
directed to another element.
• The NIC does not use CPU processing time to make this assessment,
enabling better communication times on Ethernet network.
• All devices that are connected to the Ethernet LAN have MAC
addressed interfaces. This includes workstations, printers, routers, and
switches …etc.
Ethernet
communications & collisions
• Collisions
• Ethernet is a shared media with broadcast and bus topology.
• Possible: Two or more Ethernet stations are transferring a frame to
the network at the same time, results a collision.
•
CSMA/CD (Carrier Sense Multiple Access/Collision
Detection)
• Probabilistic protocol (Listen-before-transmit-mode).
• Physically monitoring traffic on the network line.
• Exponential back off algorithm is applied to resend data and back to
normal after a collision has occurred.
The CSMA/CD access method is internationally standardized in Ethernet.
Ethernet
communications & collisions
• From signal point of view, networking devices detects a collision when the
amplitude of the signal on the media gets increased significantly (doubled).
• When a collision occurs, the sending stations transmit a 32-bit “jam”
signal that will enforce the collision.
Ethernet Auto-negotiation
• Ethernet stations transmit a link pulse about every dozens of
milliseconds, whenever the station is not engaged in transmitting a
message.
• This pulse known as Normal Link Pulse (NLP).
• Auto-negotiation can be used by devices that are capable of different
transmission.
• These devices then choose the best possible mode of operation that is
shared by them.
Ethernet Frame Format
The Basic Ethernet Frame Format:
IEEE 802.3 defines a basic data frame format required for all
MAC implementations.
•
Preamble (PRE): alternating pattern of ones and zeros,
provides a means of synchronization.
•
Start-of-frame delimiter (SOF): alternating pattern of ones
and zeros, two consecutive 1-bits indicating that the next is the
destination address.
•
Destination address (DA): indicates the receiving station(s).
Individual/group address. Globally/locally administered.
Ethernet Frame Format (cont.)
•
Source addresses (SA). Identifies the sending station. The SA
is always an individual address.
•
Length/Type: Indicates either the number of MAC-client data
bytes, or the frame type ID.
•
Data: sequence of n bytes of any value less than or equal to
1500. If it is less than 46, the Data field is extended by adding
a filler (pad) to bring the Data field length to 46 bytes.
•
Frame check sequence (FCS): This contains a 32-bit cyclic
redundancy check (CRC) value created by the sending MAC
station, used to check damaged frames
Ethernet Products
•
Network Interface Card (NIC), connect pc to a network.
3 types.
•
Transceiver, connect stations and nodes to different Ethernet
media. Most NICs contain a built-in transceiver.
•
Hubs/Repeater, interconnect clients and servers,
repeating/amplifying signals. Wiring concentrators.
•
Routers, determine the next network point (destination).
network layer of OSI.
•
Bridges, connect two networks usually with the same type.
2 layer. Smarter than repeater.
•
Switch, filter and forward packets between LAN segment.
data link layer. So, support any packet protocol.
Thank you for listing
Term Paper
Ethernet