1. We have a laptop user transmitting at 1 Mbps with no loss. The packets, inclu
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Question
1. We have a laptop user transmitting at 1 Mbps with no loss. The packets, including payload and all headers, are 100 bytes long and the average CSMA backoff is 32 microseconds. Assuming RTS/CTS induces an extra amortized load of 160 microseconds per data packet, how much faster (in percent) is the CSMA/CA protocol in this situation?
2. Suppose you are transmitting a 1500 byte WiFi frame at 600Mbps. If the physical and link layer overhead is 92% (only 8% of packet time is spent transmitting the 1500-byte WiFi frame), how long is this overhead, in microseconds?
3. What is the theoretical maximum length for cable segments using the original 10Mb/s Ethernet standard (in meters)? You should assume the minimum length packet is 72 bytes, and a propagation speed of 2 * 10^8 m/s.
Explanation / Answer
Size L=1500 bytes = 1500*8 bits = 12000 bits
Bandwidth B=600 Mbps = 600*106 bps
Transmisition time (Ttransmistion) = L/B
=(12000) bits/( 600*106 bps)
=20 * 10-6 sec =20 us
we know In Ethernet
(Ttransmistion) >=2* (Tpropagation)
(20 us)>=2(Tpropagation)
(Tpropagation)<=10 us
(0.08T) =10 us
T=10*100 us
=1000 us
=1 ms
3)
Bandwidth B = 10Mb/s = 10*106bits/sec=107 bits/sec
Size L=72bytes = 72*8 bits = 576 bits
Propagration speed V=2*10^8 m/sex
Length of cable=D meters
Transmisition time (Ttransmistion) = L/B = (576 bits)/(107 bits/sec) = (576*10-7)sec
Propagrtion time (Tpropagation) =D/V=D/(2*108) sec
We Know in ethernet
(Ttransmistion) >=2* (Tpropagation)
576*10-7>= (2)*(D/2*108)
576*10-7>= D/108
D<=(576*10-7)*108
(5760)>=D
maximum lenght is 5760meters
Size L=1500 bytes = 1500*8 bits = 12000 bits
Bandwidth B=600 Mbps = 600*106 bps
Transmisition time (Ttransmistion) = L/B
=(12000) bits/( 600*106 bps)
=20 * 10-6 sec =20 us
we know In Ethernet
(Ttransmistion) >=2* (Tpropagation)
(20 us)>=2(Tpropagation)
(Tpropagation)<=10 us
only 8% of packet time is spent transmitting the(0.08T) =10 us
T=10*100 us
=1000 us
=1 ms
3)
Bandwidth B = 10Mb/s = 10*106bits/sec=107 bits/sec
Size L=72bytes = 72*8 bits = 576 bits
Propagration speed V=2*10^8 m/sex
Length of cable=D meters
Transmisition time (Ttransmistion) = L/B = (576 bits)/(107 bits/sec) = (576*10-7)sec
Propagrtion time (Tpropagation) =D/V=D/(2*108) sec
We Know in ethernet
(Ttransmistion) >=2* (Tpropagation)
576*10-7>= (2)*(D/2*108)
576*10-7>= D/108
D<=(576*10-7)*108
(5760)>=D
maximum lenght is 5760meters
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