PACE-IT: Basic Network Concepts (part 2)

Basic network concepts II.

Instructor, PACE-IT Program – Edmonds Community College

Areas of expertise Industry Certifications

PC Hardware

Network Administration

IT Project Management

Network Design

User Training

IT Troubleshooting

Qualifications Summary

Education

M.B.A., IT Management, Western Governor’s University

B.S., IT Security, Western Governor’s University

Entrepreneur, executive leader, and proven manger with 10+ years of experience turning complex issues into efficient and effective solutions.

Strengths include developing and mentoring diverse workforces, improving processes, analyzing business needs and creating the solutions required— with a focus on technology.

Brian K. Ferrill, M.B.A.

Basic network concepts II.PACE-IT.

– Network transmission concepts.

– CSMA/CD and CSMA/CA.

Network transmission concepts.Basic network concepts II.


– Wavelength.» A measurement of the distance between peaks in the

wave patterns emitted by electromagnetic radiation (e.g., light, radio, and microwave).

• Each type of electromagnetic radiation falls into a specific range of wavelengths. By modifying a wavelength, data can be encoded into the wavelength and transmitted to a receiving device, which then decodes the transmission.

– Baud rate and bit rate.» The baud rate was originally used to measure the

speed of a telegraph transmission. It is a measure of the number of state changes in a given period of time.

• The usual state change that was measured was electricity (e.g., the number of times the state changed from .5 volts to 1.5 volts).

» The bit rate is a measure of the number of zeros and ones that can be transmitted across a medium in a given period of time (usually measured in bits per second, or bps).

• The bit rate is a more accurate measure of transmission throughput than the baud rate.


– Sampling size.» When converting from an analog audio signal to a

digital signal, a computer (or other device) captures the analog audio waveform and mathematically converts the captured sample into different wavelengths (which is how we get the discrete sounds). This occurs over a specific period of time, which is called the size of the sample.

– Carrier detect and carrier sense.» Carrier detect is when a device can only tell when a

carrier signal or channel is present by the reception of a control signal.

• The presence of the control signal signifies that transmissions can occur.

• The control signal controls the order of transmissions, so data collisions are not possible.

• The control signal can also be used to establish the maximum speed of the transmission that can be used.

» Carrier sense is when a device uses feedback from a receiver to determine if a carrier channel is present.

• If a carrier signal is detected, the device can send transmissions.

• Data transmission collisions are possible with carrier sense.

CSMA/CD and CSMA/CA.Basic network concepts II.

The carrier detect method of network transmission works well when there are just a few nodes that need to be connected together.

However, as the number of nodes that need to transmit increases, the efficiency of carrier detect begins to decrease to the point where it can become unmanageable.

Although the carrier sense method of network transmission is not as efficient when the scale of the network is small, as the number of nodes increases, it becomes more efficient than the carrier detect method.



– CSMA/CD (Carrier Sense Multiple Access with Collision Detection).

» Uses the carrier sense method of network transmission.• Every device on the network uses feedback from a

receiver to determine if a carrier channel is present.» Every device connected to the network has an equal

opportunity to place a transmission on the carrier channel (the multiple access part of the name).

» Before placing a transmission on the carrier channel, a device will listen to the channel to determine if another node is transmitting.

• If it detects a signal on the carrier signal, the node will wait before attempting to transmit.

• If no signal is detected, the node is free to send.» If two devices send a transmission at the same time, a

collision between the transmissions is possible.• Sending devices listen for transmission collisions. If a

collision is detected, a jamming signal is sent informing all nodes that a collision has taken place.

• All devices that receive the jamming signal, will wait for a random amount of time before attempting to transmit.


– CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance).

» Operates in the same manner as CSMA/CD with one exception, it uses a collision avoidance scheme through the use of a controlling device.

• Before attempting to send data, a device will place a specific signal on the network called a request to send (RTS) packet.

• If no other device is utilizing the network, the controlling device will respond with another specific signal called a clear to send (CTS) packet.

• Once the sending device receives the CTS, it knows it can send a transmission without a collision occurring.

– CSMA/CD vs. CSMA/CA.» CSMA/CD is better suited for high speed, high throughput

networks and is the specified network transmission standard for the 802.3 Ethernet networking standard, as it has a low amount of network overhead.

» CSMA/CA is better suited for lower speed, lower throughput types of networks where the possibility of data collisions is higher. It is the specified standard for 802.3 wireless (Wi-Fi) networks.

What was covered.Basic network concepts II.

Wavelength is a measure of distance between the peaks of a waveform; transmissions can be encoded into a wavelength. Baud rate is a measure of the number of state changes over time. Bit rate is a measure of the number of bits transmitted over time. Sampling size is used in the process of turning analog sound into a digital signal. With carrier detect, a control signal is used to denote the presence of a carrier signal. With carrier sense, a device uses feedback from a receiver to detect the presence of a carrier signal.

Topic

Network transmission concepts.

Summary

The carrier detect method is efficient as long as the number of nodes is small. Carrier sense becomes the more effective method as more devices need to send network traffic. With CSMA/CD, all devices have an equal opportunity to place transmissions on the network. If a collision occurs, it is detected and, after a random length back off period, devices will resend the data. With CSMA/CA, all devices have an equal opportunity to place transmissions on the network, but they must first get permission from a controlling device. CSMA/CD is used in Ethernet networks, while CSMA/CA is used in wireless networks.

CSMA/CD and CSMA/CA.

THANK YOU!

This workforce solution was 100 percent funded by a $3 million grant awarded by the U.S. Department of Labor's Employment and Training Administration. The solution was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor. The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability or ownership. Funded by the Department of Labor, Employment and Training Administration, Grant #TC-23745-12-60-A-53.

PACE-IT is an equal opportunity employer/program and auxiliary aids and services are available upon request to individuals with disabilities. For those that are hearing impaired, a video phone is available at the Services for Students with Disabilities (SSD) office in Mountlake Terrace Hall 159. Check www.edcc.edu/ssd for office hours. Call 425.354.3113 on a video phone for more information about the PACE-IT program. For any additional special accommodations needed, call the SSD office at 425.640.1814. Edmonds Community College does not discriminate on the basis of race; color; religion; national origin; sex; disability; sexual orientation; age; citizenship, marital, or veteran status; or genetic information in its programs and activities.

PACE-IT: Basic Network Concepts (part 2)

Education

Transcript of PACE-IT: Basic Network Concepts (part 2)