Short answer questions for computer networks! I hope that teachers who understand the Internet will

I've read a book on the Internet, but it's not this profession now, so I'll talk about it casually, and you can identify it yourself.

1.To put it simply, it is to make a single network cable (transmission medium) that can be used by multiple users.

Probably it's frequency division multiplex and time division multiplex.

Frequency division multiplexing, dividing a network cable into different frequency ranges, and different signals take their own frequencies. Just like the highway is divided into sidewalks, car lanes, and expressways, all kinds of cars go their own ways, and it is a waste to let bicycles take the highway.

Time division multiplexing, time-by-time transmission. I suddenly remembered that when I was in high school, I ended at 8 o'clock in the first year of high school, 8:30 in the second year of high school, and 9 am in the third year of high school.

2.Wireless LAN, the advantages are the same, no network cable, no need to squat on the spider web office, in addition, the new equipment is also convenient.

I only know the previous four-segment 32-bit, and the current IPv6 I don't understand at all, because it's not the industry.

For example, this is a C-class address, its network number is the host bit, and the subnet mask, it is not difficult for you to find that the subnet mask is its network number, and there are also subnets and broadcasts, which are more.

4.The first type, commonly used by telecommunications, is to send broadband to about 100 per month. It's called ADSL, and its advantages are suitable for home use, and it is very convenient to use the ** network. The disadvantages, the speed can't go up, and the upload speed is very low.

The second type, broadband network, is transmitted by cable or fiber optic cable, which is more commonly used in this community, which is the kind of 20 yuan a year.

The third type, cable television networks, uses cable television networks.

Fourth, wireless networks, now 3G networks.

5.Viruses are malicious programs, like, like what. Just like the bad guys, they have their own boss and do bad things for their boss. Trojans and rogue software can also be classified as viruses. The characteristics are contagion, destruction, and lurking, I can't remember.

6.Firewall to prevent bad guy stuff. For example, the trenches used on the battlefield.

Of course, he does not take the initiative to attack the enemy, he only works if the enemy comes to the door, he just blocks the enemy, and cannot kill. So, there are no impermeable walls, and as long as the enemy is tough enough, it is only a matter of time before they enter the castle.

The formula for calculating the maximum information transfer rate c is c=h*log (1+s n) (bit s). In the formula:

h is the bandwidth of the limb circle, s is the signal power (watts), n is the noise power (watts) and s in the formula n is the ratio of the power of the signal to the noise, which is a dimensionless unit. For example, s n = 1000 (i.e., the signal power is 1000 times the noise power).

Here c=64kb s; h is the channel bandwidth, where h = 3khz, substituting the above formula, snr(s n) = 2641634, which is converted to db, that is, db.

This result illustrates that a very high signal-to-noise ratio is required to transmit 64 kbs of data in a 3kHz ** channel. In addition, the channel capacity is not only proportional to the bandwidth of the channel band, but also depends on the signal-to-noise ratio of the system and the type of coding technology.

The owner of the building is a student of Zhongkai.,I have this question in my homework tomorrow.。。

Let's give you an idea, and the specific answer will be calculated by yourself.

Message exchange is a good package to go all the way:

The latency time is Host A send time + 8 routers send time + 8 routers + 8 routers + link propagation time.

Packet switching method: It is a packet that follows 300KB into 150 packets of 2KB, and the last packet is sent from host A to the last router It is equivalent to 2KB packets sent 9 150 9 168 times delay time Sending time x168 8 router delay time Link propagation time.

(1) [(300*1024+60)*8 10000 ] 9+(100*1000) *7+8*1 is approximately equal to.

Finally approximately equal.

This is a bad math problem number, and the landlord is so dark、。。

This is the ...... of the Olympiad math questions in primary schools

Class B network network bits default 16 bits, host bits default 16 bits, 3 departments, borrowing 2 host bits is enough, that is, 18 bits, converted.

Let's look at the options in the question:

a:, the network bit is: 19 bits, borrow the host bit 19-16 = 3 bits, then it can be divided into 2 to the 3rd power = 8 subnets, the number of hosts available in each subnet is 32-19 = 13 bits, and the number of hosts is: 2 to the 13th power.

b: , the network bit is 18 bits, borrowing the host bit 18-16 = 2 bits, can be divided into 2 to the 2nd power = 4 subnets, the number of available host bits in each subnet is 32-18 = 14 bits, the host digit: 2 to the 14th power.

c:, the network bit is 27 bits, borrowing the host bit 27-16 = 11 bits, which can be divided into 2 to the 11th power = 2024 subnets, the number of available host bits in each subnet is 32-27 = 5, and the number of hosts is: 2 to the 5th power = 32

d:, the network bit is 25 bits, borrowing the host bit 25-16 = 9 bits, it can be divided into 2 to the 9th power = 512 subnets, the number of available hosts in each subnet is 32-25 = 7, and the number of hosts is: 2 to the 7th power = 128

1.The maximum frequency of the analog signal is 600Hz, and when the sampling frequency is taken as ( ), all the information of the original signal can be reconstructed. a 300hz how did you make this?

2.The answer is 1200hz

3.This is calculated according to the Nyquist sampling theorem, for the sampling of low signals, the sampling rate is greater than or equal to 2 times the highest frequency, and the original signal can be restored without distortion.