ccna 3 v3.0 module 4 - switching concepts

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CCNA 3 v3.0 Module 4Switching Concepts


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• This PowerPoint primarily consists of the Target Indicators (TIs) of this module in CCNA version 3.0.

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NOT a study guide for the module final assessment.

NOT a study guide for the CCNA certification exam.

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Objectives

• Introduction to Ethernet 802.3 LANs

• Introduction to LAN switching

• Switch operation


802.3 LAN Development: Today’s LANs


Devices Function at Layers


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.


Typical Causes of Network Congestion


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.


Half-Duplex Ethernet Design


Network Congestion


Network Latency

Latency, or delay, is the time a frame or a packet takes to travel from the source station to the final destination.


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.)


Benefits of Using Repeaters


Full-Duplex Transmitting


LAN Segmentation

Segmentation allows network congestion to be significantly reduced within each segment.


LAN Segmentation with Bridges


LAN Segmentation with Routers


LAN Segmentation with Switches


LAN Switch Operation


Ethernet Switch Latency


Layer 2 Switching


Layer 3 Switching


Symmetric Switching


Asymmetric Switching


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.


Two Switching Methods


Store and Forward


Cut Through


Functions of Ethernet Switches


Frame Transmission Modes


Network Switch Using CAM


How Switches and Bridges Filter Frames

• Bridges and switches only forward frames, which need to travel from one LAN segment to another.

• To accomplish this task, they must learn which devices are connected to which LAN segment.

• Bridges are capable of filtering frames based on any Layer 2 fields.


LAN Segmentation Using Bridges


Microsegmentation of the Network

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.


Switches and Collision Domains

The network area where frames originate and collide is called the collision domain. All shared media environments are collision domains.


Three Methods of Communication


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.


Communication Between Switches and Workstations

ccna 3 v3.0 module 4 - switching concepts

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