Shulou(Shulou.com)06/01 Report--

OSI seven-layer model

Application layer

Presentation layer

Session layer

Transport layer core layer

Network layer aggregation layer

Data link layer access layer

Physical layer

I. physical layer

1. Transmission unit: bit bitstream

two。 Device network card, hub hub, transmission media

Professional term broadcast: one-to-all multicast: one-to-many unicast: one-to-one full duplex: receive and transmit simultaneously

Half-duplex: receive and send one of the two

Broadcast domain: a pair of all within a certain range

Collision domain: the collision domain generated by sending or receiving packets to a certain extent.

Division of broadcast domains: a network segment

VLAN

Router

RJ-45: the crystal head on the twisted pair

RJ-11: the head on the phone line

Each port of the switch is a separate collision domain.

All interfaces on the hub hub are in the same collision domain

4. Transmission medium: optical fiber type: indoor and outdoor

Function: single film (gold) multiple film (orange)

Tail fiber: round head, square head

Effective transmission distance: 1000 meters

Without electronic signal interference, the bending radius can not be less than 15cm.

Coaxial cable 10base2 thin cable 30 crystal head effective transmission distance: 185m

10base5 thick cable 100 crystal head effective transmission distance: 500m

10 refers to the transmission rate-M / s calculation.

Effective distance of twisted pair 10baseT: 100m

5. The network is divided into wide area network, local area network and metropolitan area network by region.

The wide area network is composed of local area network and good metropolitan area network.

6. According to the topology type, the network is divided into bus, star, ring, tree and network.

The most frequently used are: stars and trees.

II. Data link layer

1. Transmission unit: data frame

The starting field reminder frame of A data is coming.

Address field of frame B destination address and source address

C length type controls the length and type of field frames

D data field raw data

E frame check sequence field check frame integrity

2. LLC logical link control sublayer

MAC encapsulation

3. The first 24 digits of the 48-bit hexadecimal number of the MAC address are the manufacturer's logo.

The last 24 digits are the device number.

4. Features: only know MAC but not IP

5. Concept: 1 > the data link layer provides the physical transmission of data, which will mean that in the local area network where hardware addresses are used, the data link layer ensures that the information is transmitted to the correct device. the information from the network layer is converted into a bit stream to facilitate transmission by the physical layer.

2 > encapsulate the information into a frame and add a custom header that contains the destination address and source address in hardware form, which surrounds the original information and plans to Apollo.

6. The difference between network layer and data link layer

Routers work at the network layer, they only care about the best path to these networks and the location of the network, the router does not care about the interior of the network, the data link layer is responsible for the unique identification that resides in the local network.

7. Functions of the data link layer

Physical address definition

Physical media access

Link parameters

Error verification

Network topology

Flow control

8.LLC sublayer function

Responsible for identifying the network protocol, the fire encapsulates the door, and the LLC header tells the data link layer what to do with the packet once the frame is accepted.

9. Limitations of physical layer and solutions of data link layer

The first layer cannot communicate with the high layer and the second layer can communicate with the high layer through the LLC sublayer.

The first layer cannot identify the computer the second layer uses the MAC addressing scheme to identify the computer

The first layer can only describe the organization or grouping of bitstream layer 2 with frame comparison.

10. Device switch, bridge

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