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
First, the physical layer
1. Transmission unit: bit bitstream
2. Device NIC, Hub hub, transfer media
Professional Terminology broadcast: A pair of all multicast: one to many Unicast: One to all full duplex: Receive and send simultaneously
Half Duplex: Receive and send two select one
Broadcast domain: A certain range of a pair of all
Conflict domains: Within a certain range, packets are generated by sending or receiving conflicting domains
Dividing broadcast domains: a network segment
Vlan
Router
RJ-45: Crystal head on twisted pair
RJ-11: The head on the phone line
Each port of the switch is a separate conflict domain
All interfaces on a hub hub are in the same conflict domain
4. Transmission media: Fiber Type: Indoor and outdoor
Function: Single Film (Gold * * *) Multi-Film (orange)
Pigtail: Round Head square head
Effective transmission distance: 1000 m
No electronic signal interference, can not bend radius less than 15cm
Coaxial cable 10base2 Thin cable 30 crystal head effective transmission distance: 185 m
10BASE5 thick cable 100 crystal head effective transmission distance: 500 meters
10 refers to the transfer rate of one m/s calculation
Twisted pair 10baseT effective distance: 100 m
5. Network by geographical division: WAN, LAN, metropolitan area network
Wan is made up of good metropolitan area network
6. The network is divided by topology type: Bus, star, ring, tree, net
The most used are: stars and trees
Second, Data link layer
1. Transmission Unit: Data frame
The Start field of the a data reminder frame comes up
Address field destination address and source address for B-frames
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 sub-layer
Mac Encapsulation
3. MAC address 48-bit hexadecimal number consisting of the first 24 bits is the manufacturer's identity
The rear 24 bits are the device number
4. Features: Only the Mac does not know IP
5. Concept: The 1> Data link layer provides physical transmission of data, which would mean that in a local area network using a hardware address, the data link layer ensures that the information is transmitted to the correct device, and the information from the network layer is converted into a bitstream form to facilitate the transfer of the physical layer.
2> encapsulates the information into frames and adds a custom header, which contains the destination address and source address in hardware form, which surrounds the original information to the Apollo program.
6. The difference between the network layer and the data link layer
Routers work at the network layer, they only care about the best path to reach these networks and the location of the network, the router does not care about the internal network, the data link layer is responsible for residing in the local networks unique identity.
7. Features of the data link layer
Physical Address definition
Physical media access
Link parameters
Error verification
Network topology structure
Flow control
8. LLC Sublayer Features
Responsible for identifying the network protocol, burning fire to its door encapsulation, the LLC header tells the data link layer, one but the frame is accepted should be how to handle the packet.
9. The limitation of physical layer and the solution of Data link layer
One layer can not communicate with high-level communication Layer Two through the LLC sublayer
One layer does not identify the computer two layer identifies the computer with a Mac addressing scheme
The first layer can only describe the bit stream layer two to organize or group bits with frames
10. Device switches, bridges,
This article is from the "Kay Sky" blog, please make sure to keep this source http://1349787063.blog.51cto.com/9459104/1678367
CCNA Notes--osi--Physical layer, Data link layer