1. What is IEEE 802.x? 2. Explain what is the difference between persistent, non
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1. What is IEEE 802.x? 2. Explain what is the difference between persistent, non-persistent and p-persistent CSMA. 3. What is the purpose of the soF start of frame field in the Ethernet frame? 4. What is the purpose of virtual LANs? Why not use just the physical LAN topology? 5. The figure below shows a small Ethernet LAN. Answer the following questions. (a) What kind of network topology is used? (b) Assume stations are connected through a hub. Station A sends a frame to the server while Station B sends a frame to Station D. ls there any frame collision? (c) Assume stations are connected through a switch. Station A sends a frame to the server while Station B sends a frame to Station D. Is there any frame collision? (d) Now assume that stations connected through a switch and all ports are full-duplex. Station A sends a frame to the server while the server sends a frame to Station B. ls there any frame collision? (e) Show one situation where a collision could happen with stations connected through a switch and full-duplex ports. 6. Is the CSMA protocol used in wireless networks? Why? 7. List at least two types of frames used in wireless networks. 8. Enumerate all fields in the UDP header. 9. UDP provides a service for error checking. Does that mean that data sent through UDP is guaranteed to correctly arrive to the destination? Explain.Explanation / Answer
1. IEEE 802.x is a group of standard networking protocol defined by IEEE. It mainly deals with local and metro-politan area networks. These networks are restricted to networks which carry variable size data packets. The corresponding layers which map to the protocol are physical and data link layer.
2.
A station that has frames to send, senses the channel and if station is idle, it sends immediately.
3. The start of frame (SOF) field gives a predictable signal to synchronize the data sampling clock with an incoming message.The clock is extracted through the signal because ethernet is a self clocked digital protocol. It consists of 56-bit i.e a 7 byte pattern consisting of 1 and 0 bits. It also allows devices to synchronize their own receiver clocks on the same network.
4. Virtuals Lans (V-LAN) are group of connected devices which may be on the same or different LAN's connected over networks. They communicate with each other as if they were on the same local area network.
Benefits over traditional LAN's :
7. Authentication frame - Used for authetication process where access point accepts or rejects the identit of a radio NIC.
Beacon frame : Sent by access point to broadcast its SSID, timestamp and other parameters.
Persistent Non-Persistent p - persistent Station that wants to send data continuously, checks if the channel is busy or idle. If the channel is busy, station waits for a fixed amount of time to send the data. Used when channel has fixed time-slots. If in case channel is busy, then the station waits until it is idle again Checks again. It the channel is free, it transmits the frames. Whenever station is ready to transmit, it senses the channel. As soon as the station detects a channel, it delivers in the frame immediately with probability 1.A station that has frames to send, senses the channel and if station is idle, it sends immediately.
If in case the channel is busy, it waits until the time of the next slot or else it transmits frames with probability p.Related Questions
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