An e-market, or electronic market, is a virtual marketplace where buyers and sellers can engage in transactions through the use of digital platforms, such as websites, mobile apps, or social media. E-markets have become increasingly popular in recent years due to their convenience, accessibility, and global reach. E-markets differ from traditional markets in several ways: Global reach: E-markets have a global reach, allowing buyers and sellers to connect from anywhere in the world. This means that businesses can access new markets and reach customers that they may not have been able to reach through traditional channels. Convenience: E-markets offer a high degree of convenience, allowing customers to shop from the comfort of their homes or on the go using mobile devices. This convenience factor can lead to higher customer satisfaction and loyalty. Lower overhead costs: E-markets typically have lower overhead costs than traditional markets, as they do not require physical storefronts, inventory storage, or other infrastructure. This can result in lower prices for customers and higher profit margins for businesses. 24/7 availability: E-markets are available 24/7, allowing customers to shop at any time of the day or night. This can be particularly advantageous for businesses that operate in multiple time zones or that cater to customers with varying schedules. Greater competition: E-markets can be highly competitive, with many businesses vying for the attention and loyalty of customers. This can result in lower prices, higher quality products, and better customer service as businesses compete for market share.

1. CARRIER SENSE MULTIPLE ACCESS
Presented by : SANDIP PRADHAN
BWU/DCS/20/013
BRAINWARE UNIVERSITY

3. CSMA Protocol
 CSMA : It is a carrier sense multiple access based on media access
protocol to sense the traffic on a channel (idle or busy) before
transmitting the data. It means that if the channel is idle, the station
can send data to the channel. Otherwise, it must wait until the
channel becomes idle. Hence, it reduces the chances of a collision on
a transmission medium.
 CSMA/CD: improves CSMA performance by terminating transmission as soon
as a collision is detected.
 CSMA/CA: improves CSMA performance by reducing the incidence of collision.

5. CSMA/CD : CSMA with Collision Detection
CSMA Procedure Collision Detected Procedure

6. CSMA/CD Applications
 Modern Ethernet networks, built with switches and full-duplex
connections, no longer need to utilize CSMA/CD because each collision
domain is now isolated.
CSMA/CD is still supported for
backwards compatibility and for
half-duplex connections.

7. CSMA/CD Applications
 CSMA/CD was used in now obsolete shared media Ethernet variants and in
the early versions of twisted-pair Ethernet which used repeater hubs.
10BASE2

8. CSMA with Collision Avoidance
Collisions are avoided by three
strategies:
 Inter-frame space
 The contention window
 Acknowledgments

9. CSMA/CA Applications
 GNET -
 Apple's LocalTalk
 802.11 RTS/CTS
 IEEE 802.15.4 (Wireless PAN)
 NCR WaveLAN
 HomePNA
 Bus networks
 ITU-T G.hn standards ( G.9960)

10. CSMA Access Modes
1-Persistent: In the 1-Persistent mode of CSMA that defines each node, first sense the shared channel and if the
channel is idle, it immediately sends the data. Else it must wait and keep track of the status of the channel to be idle
and broadcast the frame unconditionally as soon as the channel is idle.
Non-Persistent: It is the access mode of CSMA that defines before transmitting the data, each node must sense
the channel, and if the channel is inactive, it immediately sends the data. Otherwise, the station must wait for a
random time (not continuously), and when the channel is found to be idle, it transmits the frames.
P-Persistent: It is the combination of 1-Persistent and Non-persistent modes. The P-Persistent mode defines
that each node senses the channel, and if the channel is inactive, it sends a frame with a P probability. If the data is
not transmitted, it waits for a (q = 1-p probability) random time and resumes the frame with the next time slot.