Transcript CCNA 3 Module 5 Switching Concepts

CCNA 3 Chapter 5
Switching Concepts
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Your Name
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Objectives
• Introduction to Ethernet 802.3 LANs
• Introduction to LAN switching
• Switch operation
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802.3 LAN Development
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Factors that Impact
Network Performance
• Network traffic (congestion).
• Multitasking desktop
operating systems
(Windows, UNIX, and Mac)
allow simultaneous network
transactions.
• Faster desktop operating
systems (Windows, UNIX,
and Mac) can initiate faster
network activity.
• Increased number of
client/server applications
using shared network data.
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Ethernet 802.3
• Performance of a shared-medium Ethernet/802.3
LANs is negatively affected by factors such as the
following:
– The broadcast delivery nature of Ethernet.
– Carrier sense multiple access collision detect (CSMA/CD)
access method allows only one host to transmit at a time.
– Multimedia applications with higher bandwidth demand such
as video and the Internet.
– The latency of additional devices added by the extension of
LANs by using repeaters.
– The distance added by using Layer 1 repeaters.
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Half-Duplex Ethernet
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Network Congestion
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Network Latency
Latency, or delay, is the time a frame or a packet
takes to travel from the source station to the final
destination.
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Ethernet 10BASE-T
Transmission Times
• Bit time (or slot time) — The basic unit of time in which 1 bit can
be sent. For electronic or optical devices to recognize a binary 1 or
0, there is a minimum duration during which the bit is "on" or "off. "
• Transmission time — Equals the number of bits being sent times
the bit time for a given technology. Another way to think about
transmission time is as the time it takes a frame to actually be
transmitted. (Small frames take a shorter amount of time, large
frames take a longer amount of time to be transmitted.)
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Benefits of Using Repeaters
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Full-Duplex Transmitting
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Introduction to LAN Switching
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LAN Segmentation
Segmentation allows network congestion to be
significantly reduced within each segment.
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LAN Segmentation with Bridges
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LAN Segmentation with Routers
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LAN Segmentation with Switches
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LAN Switch Operation
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Ethernet Switch Latency
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Layer 2 and Layer 3 Switching
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Symmetric and Asymmetric
Switching
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Memory Buffering
• Port-based memory buffering
– Packets are stored in queues that are linked to
specific incoming ports.
– It is possible for a single packet to block all other
packets because its destination port is busy (even
if the other packets could be delivered).
• Shared-memory buffering
– All packets use a common memory buffer.
– Packets in the buffer are then linked (mapped)
dynamically to the appropriate destination port.
– Helps balance between 10- and 100-Mbps ports.
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Two Switching Methods
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Store and Forward
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Cut Through
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Switch Operation
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Function of Ethernet Switches
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Frame Transmission Modes
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How Switches and
Bridges Learn Addresses
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LAN Segmentation Using
Bridging
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Microsegmentation
A switch employs “microsegmentation” to reduce the
collision domain on a LAN. The switch does this by
creating dedicated network segments, or point-to-point
connections.
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Switches and Collision Domains
The network area where frames originate and collide is
called the collision domain. All shared media
environments are collision domains.
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Switches and Broadcast
Domains
• Broadcasting is when
one transmitter tries to
reach all the receivers
in the network. The
server station sends out
one message, and
everyone on that
segment receives the
message.
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Communication Between
Switches and Workstations
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