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REPEATER
The term "repeater" originated
with telegraphy and referred to
an electromechanical device used by
the army to regenerate telegraph
signals.
Repeaters work against attenuationby repeating DIGITAL signals that
they receive on a network.
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HUBS
Hubs form the HE ART of a
network, with every separate
node of the network connected tothe hub through its ports.
All hubs can be uplinked together,
Performance will decrease as the
number of users is increased.
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1. Passive Hub
Also known as CONCENTRATOR
Does not rectify or enhance
Does not enhance the performance
of LAN
Simply passes the signal through
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2. Active Hub
Store and forward feature
High priority data over low priority
Acts as repeater and boosts signal
Rectifies, re-transmit packets
Helps in troubleshooting
Also called MULTIPORT
REPEATERS
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3. Intelligent Hubs
manages the network resources
Improves performance of LAN
Diagnoses problem
Packet destination
Controls and minimizes
traffic/collision
Recognition on device (speed)
Also called MANAGEABLE HUBS
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BASIC TYPES OF HUBS
1. ETHERNET HUB
Engineer Robert Metcalfe 1980
Also called as repeaters10 Mbps (initially)
Most affordable and readily available
manipulated to support SNMP2. NETWORK HUB
3. USB HUB
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5-4-3 Rule
The 5-4-3 is a design guideline
for Ethernet computer networks covering
the number of repeaters and segments on
shared-access
In collision domain there should be 5
segments -4 repeaters-subsegments
containing active senders Ethernet backbones in a TREE
TOPOLOGY.
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BRIDGES
A bridge is a LAN interconnectiondevice which operates at the DATA
LINK LAYER of the OSI reference
model.
forward frames according to their MAC(media access control) address.
Bridges can be eitherremote or local.
oTYPES OF BRIDGES:
(1) Transparent; (2) Source Route;
(3) Translational.
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TRANSPARENT BRIDGESAlso called as LE ARNING AND
ADAPTIVE BRIDGES
Used to bridge networks which
have the SAME TOPOLOGY.
records MAC addresses in a
table and evaluates that
information whenever a packet is
routed toward its location.
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The bridge makes a decision based on three
rules:
Source and destination
address are on the
same network:
Remove packet from
memory and do
nothing
Source and destination
address are not on the
same network:
Forward packet to the
right destination port
Destination address is
unknown:
Forward packet to all
output ports (flooding)
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SOURCE ROUTE BRIDGES
is part of the IEEE802.5
standardfound primarily in TOKEN RING
NETWORKS
the SOURCE DETERMINESTHE PATH it wants to take, not
the bridge.
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SOURCE ROUTE BRIDGES
2 FRAME TYPES:
o
SINGLE
ROUTE
(SR)
Framesmake up most of the network
traffic and have set destinations.
o ALL ROUTE (AR) Frames are
used to find routes.
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used to bridge data between
DIFFERENT MEDIA TYPES.This is typically used to go
betweenE
thernet and FDDIor Token Ring to Ethernet.
TRANSLATIONAL BRIDGES
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ADVANTAGES OF NETWORK
BRIDGES Have SIMPLE
CONFIGURATION MODES. SIMPLE TO USE
relatively INEXPENSIVE.
ALTERNATIVE TO
SWITCHES
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ROUTER
Routing occurs at the
NETWORK LAYER of the OSI
modelIt is used to ROUTE DATA
PACKETS between two
networksIt reads the information in each
packet to tell where it is going.
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They can connect networks WITH
DIFFERENT ARCHITECTURES
such as Token Ring and Ethernet.Routers DO NOT SEND broadcast
packets or CORRUPTED
PACKETS. If the routing table doesnot indicate the proper address of a
packet, the packet is discarded.
ROUTER
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ROUTING TABLE is a set of rules, often viewed in
table format
used to determine wheredata packets travelling over
an Internet Protocol (IP) network
will be directed.
All IP-enabled devices,
including routers and switches,
use routing tables.
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A BASIC ROUTING TABLE INCLUDES
THE FOLLOWING INFORMATION
Destination: The IP ADDRESS of the
packet's FINAL DESTINATION
Next hop: The IP address to which the
packet is forwarded, which SPECIFIESTHE NEXT CLOSEST/MOST OPTIMAL
ROUTER in its routing path.
Interface: This is a PORT NUMBER or
other type of logical identifier.
Metric: Assigns a COST to each available
route so that the most cost-effective path
can be chosen.
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STATIC VS DYNAMIC ROUTING
STATIC ROUTING DYNAMIC ROUTINGmanually sets up the
optimal paths
uses dynamic protocols to
update the routing table and
to find the optimal path
routers do not sense thefaulty computers routers can sense a faultyrouter in the network
suitable for very small
networks
used for larger networks
the simplest way of routingthe data packets uses complex algorithms forrouting the data packets
requires minimal memory have quite a few memory
overheads, depending on the
routing algorithms used