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each version of Ethernet has a maximum cable length limit (that is, the length without amplification). Signals within this range can propagate normally, and signals beyond this range cannot propagate
in order to allow the construction of a larger network, repeaters can be used to connect multiple cables. Repeater is a physical layer device, which can receive, amplify and retransmit signals in two directions
extended data
several common Ethernet interface types
1. SC optical fiber interface
SC optical fiber interface has been applied in the era of 100base TX Ethernet, so it was called 100base FX at that time (F is the abbreviation of optical fiber). However, at that time, because the performance was not more prominent than twisted pair, but the cost was higher, so it was not popularized. Now the instry vigorously promotes gigabit network, and SC optical fiber interface is re valued
2. RJ-45 interface
this kind of interface is the most common network equipment interface, commonly known as "crystal head", and the professional term is RJ-45 connector, which belongs to the type of twisted pair Ethernet interface. RJ-45 plug can only be inserted along the fixed direction, and a plastic spring piece is set to be stuck with RJ-45 slot to prevent it from falling off
3. FDDI interface
FDDI has the highest transmission rate among the mature LAN technologies. It has the characteristics of timed token protocol, supports a variety of topologies, and its transmission medium is optical fiber. Fiber distributed data interface (FDDI) is a set of protocols developed by American National Organization for Standardization (ANSI) to transmit digital signals on optical cables
reference source: Network Ethernet interface
mahjong is the earliest application of blockchain in China:
the idea that a wants to play mahjong is equivalent to creating a block:
a calls to inform B, C and D, which means "decentralization & quot; Point to point transmission of
ABCD has formed a consensus that the touch action is "mining", and four people are "miners"
mahjong is a hash value. The Hu card is to hit the correct hash value and get the corresponding chip reward, which is called bitcoin
each of the four recorded the first round of the game. In the whole blockchain, this is only one node. If 20 mahjong games were played that day, that is, 20 nodes (blocks), and 20 blocks were connected together to form a complete ledger, that is blockchain< According to historical records, China is the world's earliest application group in blockchain, so you can be proud to say that China is more than 1000 years ahead of the world in blockchain application
it's powerful. Our country is [strong] [strong] [strong]
Round table is also called lingtai. It is said that because all treasures have aura, ancient emperors and emperors used this furniture when they were resting in the backyard to enjoy the treasures from all over the world. The dining room of Chinese family is a place for family members to get together and exchange feelings, and the round table not only conforms to the diet habit of "sitting around" of the Chinese people's Congress family, but also contains the meaning of "Reunion"
traditional Chinese families are very particular about table and banquet etiquette:
1 family banquet, the chief is the most respected guest, the host is the last. If the chief is not seated, the rest can not be seated. If the chief is not eating with chopsticks, no one can eat with chopsticks. During the wine inspection, the chief of staff should respect the wine in order
2 if it is a round table, the one facing the gate is the host guest, the left side is 2, 4, 6, etc., the right side is 3, 5, 7, etc., until the meeting
3 if there is a seat facing the gate, the right seat facing the gate is the host guest. If it is not facing the gate, the left seat on the east side is the chief. Then the chief's left side is 2, 4, 6 and 8, and his right side is 3, 5 and 7
4 if it's a big banquet, the arrangement between tables should pay attention to that the chief should be in the front and the middle, with 2, 4 and 6 seats on the left and 3, 5 and 7 seats on the right, respectively
The times are changing, and the essence of round table culture is still well inherited. As an important part of Chinese traditional culture, round table reflects the brilliance of Chinese traditional culture and art, and is endowed with deeper significance. In the conference room of the unit and in all kinds of meetings from all walks of life, you can often see a huge oval round table. Although the diameter of the round table is different, it shows the meaning of equality for all. Obviously, the spirit of round table has penetrated into modern people's life, and has become the consensus of the public. The public to buy mahogany round table is not only to buy a proct, but also to buy a culture [Jiaxin big board] bahua round platform wooden table: bahua is a kind of wood name, also known as Brazil pear. Texture crisscross obviously, with light brown stripes, mainly distributed in tropical Africa, with luster; No special smell
round table
iptables - t NAT - a routing - I eth0 - s 192.16.0.0/24 - J drop
all translations from eth0, the IP address segment of the network card 192.16.0.0/24, are discarded
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