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Transcript rollover cable
DCN286
INTRODUCTION TO DATA COMMUNICATION
TECHNOLOGY
Network Physical Layer
Connection
Purpose of Physical Layer
The role of the OSI physical layer is to encode the
binary digits that represent data link layer frames
into signals and to transmit and receive these
signals across the physical media---- cooper
wires, optical fiber, and wireless that connect
network devices.
Network Access Layer
The network access layer is concerned with all of the
issues that an IP packet requires to actually make a
physical link to the network media.
It includes the LAN and WAN technology details, and all
the details contained in the OSI physical and data link
layers.
Popular Copper Media Standards
TIA (Telecommunications Industry
Association) and EIA (Electronic Industries
Alliance) work together to publish
commercial building telecommunications
cabling standards TIA/EIA-568-B which
defines how to use the pins on the
connectors on the ends of the cables.
IEEE (Institute of Electrical and Electronic
Engineers) publishes LAN standards such
as IEEE802.3 which will define cable
requirement.
Coaxial cable
Gradually outdated from LAN
Can run for longer distances than either
STP or UTP
Less expensive than fiber-optic cable
though it is expensive than STP or UTP
Still popular for TV and home internet
service
STP (Shielded Twisted Pair) cable
Shielding provides better electrical
signals by reducing noise and
attenuation.
Shielding makes the cable more
expensive, heavier and hard to
bend.
UTP (Unshielded Twisted Pair)
Flexible and easy install
Offer the same data speeds
Inexpensive
RJ45 connector (RJ11 is for phone cable).
UTP Implementation
UTP Implementation
Straight-through Cable
Switch to Router
Switch to PC or Server
Hub to PC or Server
Cross-over Cable
Switch to Switch; Switch to Hub; Hub to Hub
Router to Router; PC to PC; Router to PC
Roll-over Cable (Configuration Purposes)
PC to Router; PC to Switch
UTP Implementation
Straight-Through cable
A cable that maintains the pin connection all the
way through the cable.
Cat 5 and Cat5e: Only wires 1, 2, 3, and 6 are
used
Gigabit Ethernet uses all the wires
To connect devices such as PC or routers to
other devices as hub or switches.
UTP Implementation
Cross-over cable
A cable that crosses the critical pair to properly
align, transmit, and receive signals on the device
with line connections
Pin 1 at one end and Pin 3 at the other end
Pin 2 at one end and Pin 6 at the other end
Used to connect similar devices:
Switch to switch
Hub to hub
TIA/EIA568-A and B pin outs
Pin #
1
2
3
4
5
6
7
8
Function
TD+
TDRD+
Unused
Unused
RDUnused
Unused
568A wire color
White/Green
Green
White/Orange
Blue
White/Blue
Orange
White/Brown
Brown
568 B wire color
White/Orange
Orange
White/Green
Blue
White/Blue
Green
White/Brown
Brown
Straight through cable
Can be used to connect PC and other
network equipments to LAN hub/switch
Wire 1 and 2 are used to transmit data
Wire 3 and 6 are used to receive data
Cross-over cable
It is used to connect two same equipments
such as PC-to-PC.
Both ends need to send data on pin 1 and
2; receive data on pin 3 and 6.
In 568B, one end has white/orange and
orange on pin 1 and 2; another has
white/orange and orange on pin 3 and 6.
In 568B, one end has white/green and
green on pin 3 and 6; another end has
them on pin 1 and 2.
Rollover cable
Usually used as console cable.
Change the sequence on another end.
Rollover or Console Cable
The cable used between a terminal and a
console port is a rollover cable with RJ-45
connectors.
Rollover cable (or Console cable) has a
different pinout than the straight-through or
crossover cable.
The pinout for a rollover cable is:
1 to 8, 2 to 7, 3 to 6, 4 to 5, 5 to 4, 6 to 3, 7 to 2,
and 8 to 1.
Connector and Adapter
The 8 Position 8 Contact
(8P8C) (often called
RJ45) connector
Cross over adapter
Optic media
Fiber-optic cable has the strongest ability to resist
EMI (electromagnetic interference), RFI (Radio
Frequency Interference)
Fiber’s bandwidth is much higher than any other
media.
Fiber is highly secure and it is easy to detect
intrusion.
Fiber uses light signal transmission and its
attenuation is much less than electrical signals. Its
length could be very long
Optical fiber cable components
Core: usually made by
silicon dioxide (from
sand)
Cladding: coated on the
core to reflect light and
seal it inside
Buffer: physical protect
cladding and core
Jacket: prevent damage
from abrasion, solvents
and other contaminants
Optical Fiber Connector (Optional)
LC/PC connector and
SC/PC connectors
have caps covering
the ferrules
Other connectors are
ST, SC, MT, MT-RJ,
MU, etc, etc
Multimode fiber
Fiber with large (greater than 10 μm) core
diameter may allow light coming in with
different angles. (It must be in limit of
acceptance cone)
Single mode fiber
Fiber with a core diameter less than about
ten times the wavelength of the
propagating light and it can only allow light
coming in from one direction.
LAN Connectivity Devices
Repeaters
Hubs
Switches
Bridges
Routers
Repeaters
A repeater can be used to increase the length
of your network by eliminating the effect of
attenuation on the signal.
It connects two segments of the same network,
overcoming the distance limitations of the
transmission media.
Some repeaters also serve as transmission
media adapters, connecting two different types
of media.
Repeaters
Repeaters can connect segments that have the
same access method. (CSMA/CD, Token
Passing, Polling, etc.)
Disadvantages
Repeaters do not filter data
Its use is inappropriate when there is a heavy network
traffic.
Repeater
10base5 – 500meter cable length limit;
10base2 - 200meter cable length limit;
10BaseT - 100meter cable length limit;
Repeater is to amplify signal and extend the
cabling distance.
Working in layer 1 (Physical) of TCP/IP
model
Repeaters
Figure11-6
Hub
Central connection of Ethernet LAN.
Physically Star topology and could be
logically RING, Bus and/or Star
May have built-in repeater
Working in layer 1 (Physical) of TCP/IP
model
Hubs
A hub is used as a central point of
connection among media segments.
Cables from network devices plug in to the
ports on the hub.
Hubs are referred as Concentrators or multiport repeater
Hubs receive signals from connected
devices and transmit them to the other
connected devices
Hubs
Regenerate and repeat signals
Propagate signals through the network
Can not filter network traffic
Can not determine the best path
Are used as network concentration points.
Hubs
Types of Hubs
Passive Hubs
Active Hubs
Intelligent Hubs (Switches)
Passive Hub
It functions only as a connection point for
the signals
The signal pass through a passive hub
without regeneration or amplification.
Active Hub
It regenerates or amplifies the signal
before they are retransmitted.
Drawback:
The noise is also regenerated
Switch
Think switch as a hub with bridge functioning on
each port (interface):
1. Switch will offer central connection to all hosts.
2. Switch will only forward frame according to
destination MAC address on per-port base.
3. Will regenerate signals (repeater function)
4. Most switches are working in layer 2 (Data
Link) of TCP/IP model.
Switches
LAN Switch
broadcast
traffic
LAN switch
Broadcasts to all ports on LAN
sw itch.
Single Switch Virtual LANs
broadcast
source
Forwarding Frame based on Destination
MAC Address
The switch maintain table, called a MAC table,
that maps destination MAC addresses with ports
used to connect to each node. For each
incoming frame, the destination MAC address in
the frame header is compared to the list of
addresses in the MAC table. If a match is found,
the port number in the table that is paired with
MAC address is used as exit port for the frame.
The MAC table can be referred to by many
different name. It also called Switch table or
Bridge table.
Switch Operation
To accomplish Frame Forwarding, Ethernet LAN
switches use five basic operations:
Learning: The Mac table must be populated with
MAC addresses and their corresponding ports.
The learning process allows these mappings to
be dynamically acquired during normal
operation.
Aging: The entries in the MAC table acquired by
the learning process are time stamped. This time
stamp is used as a means for removing old
Continues Slide-37
entries in the MAC table. After it is made in the
MAC table, a procedure begins count down,
once it reaches count 0, the entry is aged out
and remove from the table.
Flooding: If a switch does not have a MAC address
entry in its MAC table that matches the
destination MAC address of received frame, the
switch will flood the frame. Flooding involves
sending a frame to all ports except the port on
which the frame arrived.
Switch Continues
Selective Forwarding:
Selective forwarding is the process of examining
the destination MAC address of a frame and
forwarding it out to the appropriate port.
Filtering: In some cases, a frame is not forwarded.
This process is called frame filtering e.g. a
switch does not forward a frame to the same
port on which it arrived. A switch will also drop a
corrupt frame. If a frame fails a CRC check, the
frame is dropped.
Ethernet Bridge
Intelligent device to forward frame according to
destination Media Access Control (MAC)
address
Forwarding: If the destination MAC address has
a port different to the originate port, the frame
will be sent.
Filtering: If the destination MAC address is
reachable with the same interface when it
arrived, the frame will be discarded.
Working in layer 2 (Data Link) of TCP/IP model
Layer 2 Bridging
Bridges
Segmentation
80% of LAN traffic stays on local LAN
20% of LAN
traffic travels
between LANs
LAN A
bridge
LAN B
Router
Redirect packets according to destination
logical address (IP address).
Can build routing path between different
network segments (subnets)
Can act as firewall
Can work as VPN (server) connection
Working in layer 3 (Network) of TCP/IP
model
Routers
Figure 11-7
Wireless tech introduction
Infrared
Bluetooth
Microwave
Radio
Wi-Fi
In general, wireless network is secondary because
of two concerns: speed and security. But, it does
offer mobility and convenience.
Wireless Networking Media
Radio frequency (RF)
Laser
Infrared (IR)
Satellite/Microwaves
Wireless transmission techniques to carry
wireless signals
Wireless signals are electromagnetic waves
that travel through the air.
Wireless Networking Media
Infrared
Line of sight
Short distances
No obstacles between transmitter and receiver
Radiofrequency
Allows devices to be in different room or even
buildings
Limited radio
Can be single or multiple (Spread spectrum)
frequencies
Single Frequency
Is subject to outside interference and
geographic obstructions
Insecure (Easily monitored by others)
Spread Spectrum
Multiple frequencies
More secure
Security in the Wireless Environment
The first level of security in a wireless LAN
consists of protecting the radio frequency
waveform itself.
Security in the Wireless Environment
Wireless Access Points
Wireless Bridges
Encryption
WEP – Wireless Equivalence Privacy
EAP – Extensible Authentication Protocol
(IEEE 802.1X)
Wireless LAN Topology
Wireless Bridges
Wireless Security
If you think someone might eavesdrop on
your LAN radio links…..
Encryption is the key
Wireless Security Approaches
WEP – Wired Equivalency Privacy
IEEE 802.1X or Extensible Authentication
Protocol (EAP)
Wireless Equivalent Privacy
WEP
It is a security mechanism defined with the
IEEE 802.11 standard.
Designed to protect over the over-the-air
transmissions between wireless LAN access
points and NICs.
IEEE 802.11b requires 40-bit encryption keys
Cisco supports the optional 128-bit standard.
WEP Goals
Deny access to the network by
unauthorized users who do not possess
the appropriate WEP key.
Prevent the decoding of captured WLAN
traffic hat is WEP-encrypted without the
possession of the WEP key.
Should be supplemented with additional
higher-level security mechanisms such as
VPNs or Firewalls.
802.1X/EAP
Extensible Authentication Protocol
It is an alternative WLAN security approach
to WEP
802.1X/EAP focuses on providing:
Centralized authentication
Dynamic key distribution
It is a standard for port-based network
access control
Cabling the WAN
Wide Area Network (WAN) Services
To connect one network to a remote network
Provide different connection methods
Different cabling standards from those of LANs