1. The transmission medium
1.1 coaxial cable:
mainly used in domestic cable television, surveillance video cable, network effective bandwidth 10M, has been rarely used on the network.
1.2 UTP (cable):
1) UTP most widely used, the maximum theoretical value of the effective transmission distance is generally not advisable to exceed 80 to 90 meters.
2) Ethernet standard 10,100,1000 front refers to the rate, in units of M. It represents a base baseband transmission.
3) is divided into a twisted pair
shielded / unshielded twisted pair
two kinds of shielded twisted pair has a metal sheath in the gray pellicle, to prevent electromagnetic interference (e.g., twisted pair cable together when the circuit ).
4) Ethernet cable is divided into two line sequence:
568A:
white and green white orange blue orange blue brown white brown
568B: orange and white orange blue green white green white brown white brown
The wire cable head ends crystal different sequence, divided into
straight line
and
cross-line
two kinds.
Straight line:
line-sequentially are the same at both ends, as well as 568A or 568B.
Cross lines:
one end of the sequence lines 568A, 568B wire end sequence.
Using a crossover cable or straight line before there is a principle: different kind of equipment to use straight lines (PC-connect switch), the same kind of cross-line equipment (such as a PC connected PC). With the development of card technology, and now most of the communication between devices have auto-negotiation function, all using straight-through cable.
1.3 fiber:
fiber optical link is an optical communication trunk lines to be used, typically a plurality of packages, sandwiching a wire or fixing to improve strength. Generally can not do it yourself, you need to buy. A transmission medium for which glass fiber line, to transmit data by light, it is not crimped too, can damage the fiber.
1) pigtail:
pigtail just another form of fiber, typically at the end portion for optical communication, an optical device connected to, so called pigtail. The upper left corner as shown in FIG. FIG.
2) Module Interface:
optical interface to a variety of devices, the upper right corner ST, FC, SC, LC interfaces, to be noted that different interfaces connected to different network devices are shown below.
Example family: the broadband fiber handling, the ISP Internet Service Providers for construction, a very coarse fiber to the home through an optical fiber in the melt and cartridge, an optical cartridge fusible joint which connects pigtail the other end of the above, the pigtail to the network device will then draw a line to connect to the network cable our personal wireless router fine.
3）
Single-mode fibers:
mainly used for long-distance transmission. FIG left as
a pale yellow
to is the
single mode fiber
. There are transmission distance of tens of kilometers.
Multimode fibers:
mainly used for short distance transmission. Right below
the orange
of is the
multimode fiber
. There are transmission distance up to several kilometers away.
1.4 serial cable:
transmission distance and the rate is very low, only some will be used under special circumstances.
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2. collision domain:
refers to the
shared network
signal collision phenomenon may occur.
1) Solution:
use
CSMA / CD (Carrier Sense Multiple Access)
technology. For example, A wants to send data to the D, the following principles:
① first hear hair:
if there is data being transmitted on the first monitor line, not only sent.
② suspended conflict:
still listening link during transmission, such as found in conflict remains suspended (such as two devices simultaneously transmit).
③ random delay:
retransmission after a random delay after suspended.
④ hair while listening to the side:
the side sending side listening.
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3. duplex mode:
1) Half Duplex:
typically intercom, in the same collision domain, while only one transmission, a reception.
2) Full-duplex:
Now devices are full duplex network,
can transmit and receive simultaneously at both ends,
such as a telephone.
