Summary
An understanding of the following key points should have been achieved:
This page summarizes the topics discussed in this module.
Ethernet is the most common LAN architecture and it is used to transport data between devices on a network. Originally Ethernet was a half-duplex technology. Using half-duplex, a host could either transmit or receive at one time, but not both. When two or more Ethernet hosts transmit at the same time on a shared medium, the result is a collision. The time a frame or a packet takes to travel from the source station to the final destination is known as latency or delay. The three sources of latency include NIC delay, actual propagation delay, and delay due to specific network devices.
Bit or slot time is the basic unit of time in which ONE bit can be sent. there must be some minimum duration during which the bit is on or off in order for the device to recognize a binary one or zero.
Attenuation means that a signal will weaken at it travels through the network. This limits the distance that a LAN can cover. A repeater can extend the distance of a LAN but it also has a negative effect on the overall performance of a LAN.
Full-duplex transmission between stations is achieved by using point-to-point Ethernet connections. Full-duplex transmission provides a collision-free transmission environment. Both stations can transmit and receive at the same time, and there are no negotiations for bandwidth. The existing cable infrastructure can be utilized as long as the medium meets the minimum Ethernet standards.
Segmentation divides a network into smaller units to reduce network congestion and enhance security. The CSMA/CD access method on each segment maintains traffic between users. Segmentation with a Layer 2 bridge is transparent to other network devices but latency is increased significantly. The more work done by a network device, the more latency the device will introduce into the network. Routers provide segmentation of networks but can add a latency factor of 20% to 30% over a switched network. This increased latency is because a router operates at the network layer and uses the IP address to determine the best path to the destination node. A switch can segment a LAN into microsegments which decreases the size of collision domains. However all hosts connected to the switch are still in the same broadcast domain.
Switching is a technology that decreases congestion in Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) LANs. Switching is the process of receiving an incoming frame on one interface and delivering that frame out another interface. Routers use Layer 3 switching to route a packet. Switches use Layer 2 switching to forward frames. A symmetric switch provides switched connections between ports with the same bandwidth. An asymmetric LAN switch provides switched connections between ports of unlike bandwidth, such as a combination of 10-Mbps and 100-Mbps ports.
A memory buffer is an area of memory where a switch stores data. It can use two methods for forwarding frames including port-based memory buffering and shared memory buffering.
There are two modes used to forward frames. Store-and-forward receives the entire frame before forwarding while cut-through forwards the frame as it is received decreasing latency. Fast-forward and fragment-free are two types of cut-through forwarding.
An understanding of the following key points should have been achieved:
- The history and
function of shared, half-duplex Ethernet
- Collisions in an
Ethernet network
- Microsegmentation
- CSMA/CD
- Elements
affecting network performance
- The function of
repeaters
- Network latency
- Transmission
time
- The basic
function of Fast Ethernet
- Network
segmentation using routers, switches, and bridges
- The basic
operations of a switch
- Ethernet switch
latency
- The differences
between Layer 2 and Layer 3 switching
- Symmetric and
asymmetric switching
- Memory buffering
- Store-and-forward
and cut-through switching modes
- The differences
between hubs, bridges, and switches
- The main
functions of switches
- Major switch
frame transmission modes
- The process by
which switches learn addresses
- The
frame-filtering process
- LAN segmentation
- Microsegmentation
using switching
- The process a
switch uses to learn addresses
- Forwarding modes
- Collision and
broadcast domains
- The cables
needed to connect switches to workstations
- The cables needed to connect switches to switches
This page summarizes the topics discussed in this module.
Ethernet is the most common LAN architecture and it is used to transport data between devices on a network. Originally Ethernet was a half-duplex technology. Using half-duplex, a host could either transmit or receive at one time, but not both. When two or more Ethernet hosts transmit at the same time on a shared medium, the result is a collision. The time a frame or a packet takes to travel from the source station to the final destination is known as latency or delay. The three sources of latency include NIC delay, actual propagation delay, and delay due to specific network devices.
Bit or slot time is the basic unit of time in which ONE bit can be sent. there must be some minimum duration during which the bit is on or off in order for the device to recognize a binary one or zero.
Attenuation means that a signal will weaken at it travels through the network. This limits the distance that a LAN can cover. A repeater can extend the distance of a LAN but it also has a negative effect on the overall performance of a LAN.
Full-duplex transmission between stations is achieved by using point-to-point Ethernet connections. Full-duplex transmission provides a collision-free transmission environment. Both stations can transmit and receive at the same time, and there are no negotiations for bandwidth. The existing cable infrastructure can be utilized as long as the medium meets the minimum Ethernet standards.
Segmentation divides a network into smaller units to reduce network congestion and enhance security. The CSMA/CD access method on each segment maintains traffic between users. Segmentation with a Layer 2 bridge is transparent to other network devices but latency is increased significantly. The more work done by a network device, the more latency the device will introduce into the network. Routers provide segmentation of networks but can add a latency factor of 20% to 30% over a switched network. This increased latency is because a router operates at the network layer and uses the IP address to determine the best path to the destination node. A switch can segment a LAN into microsegments which decreases the size of collision domains. However all hosts connected to the switch are still in the same broadcast domain.
Switching is a technology that decreases congestion in Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) LANs. Switching is the process of receiving an incoming frame on one interface and delivering that frame out another interface. Routers use Layer 3 switching to route a packet. Switches use Layer 2 switching to forward frames. A symmetric switch provides switched connections between ports with the same bandwidth. An asymmetric LAN switch provides switched connections between ports of unlike bandwidth, such as a combination of 10-Mbps and 100-Mbps ports.
A memory buffer is an area of memory where a switch stores data. It can use two methods for forwarding frames including port-based memory buffering and shared memory buffering.
There are two modes used to forward frames. Store-and-forward receives the entire frame before forwarding while cut-through forwards the frame as it is received decreasing latency. Fast-forward and fragment-free are two types of cut-through forwarding.
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