Transcript PPP - Ivailo Chakarov

Introduction to IT and
Communications Technology
Ethernet Fundamentals
CE00378-1
Justin Champion
C208 – 3292
Content

What we are looking at
 Ethernet
technology
How did it develop
 How and why it works
 Features of the Technology

Evolution of Ethernet

The most widely used technology LAN
based network technology is Ethernet
(IEEE 802.2)
 This
technology is based on broadcast radio,
used within a cable
 The technology is widely used due
Cheapness of installation
 Reliability
 Ease of expansion and extension of the networks
 Ability to adapt to multi types of usage

Evolution of Ethernet

One part of Ethernet is an extension of the
Alohanet which was developed in the 1960’s
 This
was a radio technique which was used to allow
multiple people on a network, using radio technology
to access computer systems

The access techniques used for this network was used for
Ethernet
Evolution of Ethernet

Ethernet is a broadcast medium
 The
only change to this is with various new pieces of kit,
which will be covered later in the course



Switch
Router
Bridge
 If
a device send a message from device A to D, device B
and C will also receive it

They recognise it is not for them due to the MAC address and
ignore it
A
B
C
D
MAC addresses

Media Access Control (MAC) address
 Are
a unique address which is assigned to a network
card when manufactured
 This address can NOT be changed and is based on a
48bit sequence

Made up of a 24 bit OUI and a vendor assigned 24 bits

http://idogan.istanbul.edu.tr/oui.html list of OUI’s
Ethernet technologies: 3 part names

The names used in Ethernet tell you about the
technology
 i.e.

10BaseT
10 Mbps, BaseBand using Unshielded Twisted pair cabling
802.3 Ethernet in relation to the OSI
model

Ethernet as with all other network communications
 Integrates
with the OSI model
 Ethernet standards are concerned with layers 1 and 2

1 – Physical


Transfer of the signal across the medium
2 – Data Link



Allowing access to layer 1
Formatting the data correctly
Addressing the data
IEEE ?

Institute of Electrical and Electronic Engineers (IEEE)


These are not for profit group with a worldwide base
They develop standards for electrical and electronic products


The standards are based on the input of the members of the IEEE, to
agree on the best standards
Currently there are 900 IEEE standards with many more being
developed





IEEE 802.3 - Ethernet
IEEE 1284 – Parallel Port
IEEE 802.11b – Wireless LAN
http://wally.rit.edu/pubs/guides/ieeestds.html list of standard groups
The peer review methods allow for standards to be developed that take
account of worldwide concerns for a technology
IEEE 802.x standards
OSI Layer 1 Vs layer 2
Frames to bits

Ethernet Frame
 This
is how Ethernet combines the bits to transfer the data
 Additional information is added to the data by layer 2
Generic frame format

Ethernet Frame
 By
putting the data into a known sequence i.e. the frame
 Each part of the frame can be known
 If data was “Just” transferred how would the recipients
know when the data started and ended

The frame fields are usually measure in Octets for brevity

8 Bits = 1 Octet
IEEE 802.3 Ethernet
Ethernet II frame format
Ethernet and IEEE 802.3 formats

Ethernet Types
 There
is the small 1 octet difference between the formats
 Both can be used interchangeably without concern
Common LAN technologies

A number of different physical topologies exist for
LANs
 Ethernet
 Uses a shared medium with devices communicating when silence
is detected
 Token Ring
 Devices can only communicate when they control of the token
 Fibre Distributed Data Interface (FDDI)
 High speed fibre optic data transfer using token technology
Ethernet – Collisions !

Ethernet is a shared broadcast
technology

Transmitting when silence is
detected on the cable


This becomes a issue if multiple
devices want to communicate
They will both detect silence and
start transmitting


Causing a collision and corrupting
the data which is on the cable
The method of dealing with this is
CSMA/CD


Carrier Sense Multiple Access /
Collision Detection
This is the same method as used
for Alohanet, discussed earlier
CSMA/CD process
Bit time

Bit Times
 These
times are the transmission times for a single bit of
data
 So 10 bits can be transferred in the time that a single 10
Mbps version of Ethernet can send a bit
Interframe spacing
This is the delay time between sending successful frames, the value
is fixed at 96 bits, but the rate of transmitting bits varies between
technologies
Slot time parameter
In the event of a collision the slot time is used in increments to back
off before attempting retransmission
Slot time only applies to half-duplex Ethernet links
Routine error handling in a 10Mbps
collision domain
Summary of collision types: local,
remote and late
10Base2/10Base5 local collision
Long frame
Short frame
FCS errors
NLP Vs FLP timing
Actual FLP auto-negotiation burst
Transmission priority rank
Summary of Today's lecture

What was looked at today
 Ethernet



technology
How did it develop
How and why it works
Features of the Technology