table of Contents
Computer Network Reference Model
1.3 OSI seven-layer model----》TCP/IP five-layer protocol cluster
Second, the data transmission process
2.1 Data encapsulation and decapsulation process
Five-layer protocol device association diagram:
Composition of TCP/IP protocol family
Install Packet Tracer emulator
Computer Network Reference Model
1. Hierarchical model
1.1 Stratification
that means you do not know the ftp protocol, you will not be able to access the server. So any two people, two points of communication must reach an agreement.
(in this layered protocol, each layer performs its own duties, but there are relationships between layers, and the relationship is that the next layer provides services for the upper layer. )
Switches provide services for firewalls, firewalls provide services for routers, routers provide services for computers, and computers provide services for grandma
in the figure above protocol used is the same with the layer (lowermost layer is the transport sector)
1.2 OSI seven-layer model
1.3 OSI seven-layer model----》TCP/IP five-layer protocol cluster
Our newly generated architecture is to commemorate the importance of TCP and IP, the new new architecture is named after these two protocols, called "TCP/IP five-layer protocol stack (or protocol cluster)"
Which model of the OSI seven-layer model or the TCP/IP five-layer protocol suite was born first?
Answer: It was born at the same time, but OSI first had the model, and TCP/IP first had the protocol.
Later, people have streamlined this protocol (but it has not been promoted). Some scientists believe that the "data link layer and physical layer" should be merged into the "network interface layer" ---- it has become TCP/IP four layers Model (see less).
When we used to configure the network card, we chose Internet Protocol Version 4 (TCP/IPv4) "——It means that my network card is based on the TCP/IP five-layer protocol, so my network card can be in line with the world (v4 is The version of the IP address in this model is 4)
Second, the data transmission process
2.1 Data encapsulation and decapsulation process
Data encapsulation process:
Data decapsulation process:
OSI model vs TCP/IP model
In the TCP/IP5 layer model, the upper three layers are the core, the lower two layers are called network cards and network cables (the lower two layers are the interfaces that connect your upper three layers of data with the world, called the network interface layer ), computer Work at the application layer. The mobile phone also satisfies the TCP/IP5 layer model.
Routers do some essential work for IP addresses, so the key object of routers is IP addresses, and IP addresses are in the IP header of the network layer, so routers work at the network layer (it also has to know the two layers below).
The firewall can operate on the IP address (some firewalls can only operate on the IP), and a data stream comes from the firewall [the data transmitted on the Internet is ultimately a frame, and the data running on the network line in the future is absolutely impossible. A small data must be a complete frame, so we will say that a data stream is composed of several frames]. The firewall can filter according to MAC address and ip address. This kind of firewall is called network layer firewall. Our firewall does not have the ability to check TCP and IP headers, and it does not have the ability to check Hello messages. It is an ancient firewall [the oldest firewall in the world can only work at the network layer]. Later, the firewall was upgraded, and it can also check TCP/UDP headers. You can filter based on the port number (called a transport layer firewall). The most powerful firewalls can also check application layer data (such as pornography), called application layer firewalls. The upper layer is compatible with the lower layer (except for application layer data filtering) It can also filter the port number, IP address, and MAC address), and the application layer firewall is the mainstream.
Five-layer protocol device association diagram:
Composition of TCP/IP protocol family
ICMP: (Internet Control Message Protocol) Internet Control Message Protocol
ARP: (Address Resolution Protocol) address resolution protocol
Although the computer has 5 layers, the most important function of the computer is the function of the application layer, and the functions of other layers are weakened.
Physical layer
The computer doesn’t care about the line sequence problem. When you plug the T568A or T568B network head into the computer, the computer only recognizes the pins (each channel inside is called a pin), and the computer only recognizes me when sending out from 1 , send out pin 2, from only the 3,6
means that if the head to do T568A plugged into the computer, the computer sends data when you white green, green for transmitting, white orange, orange to receive
to do line sequence by B, then white and green, green to receive, white orange, orange to transmit
by use of the network cable classification
1, intersecting lines : one end is a class a (T568A), one end of a class B (T568B) [both sides of the line sequence Different】. The crossover cable is used between the same kind of equipment ! (For example, two devices are routers, two devices are switches, and two devices are computers...)
Special circumstances: computers and routers with three or more layers are all regarded as the same type of equipment (with three layers and three layers) Devices with above functions will be regarded as the same kind of equipment in the future: for example, a computer and a router are connected with a crossover cable)
2. Straight line : both ends are A or B. The straight-through cable is used between heterogeneous devices (for example, the PC and the switch use the straight-through cable, and the switch and the router directly use the straight-through cable)! [Currently the straight-through lines we see on the market are in B line sequence]
Some manufacturers sell equipment with automatic reversal function to avoid you using the wrong line3. All-reverse cable: one end is type A, the other end is reverse A, also called console line [this line needs to be made by professional equipment] (console line will be brought to you every time a company sells a router switch or firewall Root console line. The enterprise switch router configures this device for the first time only through the console line to connect the switch router to configure it)
One side is the crystal head and the other is USB
One end is the com port and the other is crystal head
If there is no com port on the computer, buy a com to USB
com to USB
5. About the switch/PC interface:
| Interface name | rate | Shorthand |
|---|---|---|
| Ethernet (10M interface) | 10Mb/s | E |
| FastEthernet (100M interface) | 100Mb/s | F |
| GigabitEthernet (Gigabit interface) | 1000Mb/s | G |
| TenGigabitEthernet (10 Gigabit interface) | 10000Mb/s | TG |
In the future, I will see the network port called Ethernet on the switch or PC. Generally speaking, it means that the bandwidth of this interface is 10Mb/s.
For example, in Ethernet0/3, 0 is the module number and 3 is the interface number of the module
Example: f0/1 (F means this is a 100M interface, 0 means the module number, and the module is numbered from 0; 1 means the first interface on module 0) ----》On the first module of 100M The first interface
f1/4 ---> the fourth interface on the 100M 1 module (or the fourth interface on the second module)
g0/3---> the fourth interface on the Gigabit 0 module 3 interface numberThe interface of the router is numbered starting from 0: f 0/0
Only enterprise-level manageable switches have console ports (called initial management ports)
6. The "router" generally used at home is actually a hybrid product of a switch and a router. The real name is "Layer 3 switch" (4 ports are called Layer 2 ports, and 1 port is called Layer 3 ports)
Install Packet Tracer emulator
Software name : Cisco Packet Tracer 6.2 for Windows Student Version
Download link: http://pan.baidu.com/s/1bn2WRmR Password: j6jw
The necessary software for network interconnection learning, this is version 6.2 which is more fluent and easy to use, and can realize functions such as virtual network topology and structure.
Too strong! ! !
The ones starting with 1 and 2 are generally Layer 2 switches, and those with 3+ are Layer 3 switches.
Select the device and drag it
(Draw a meter in the square) represents a three-layer switch (24PS means that this switch has 24 ports) [Core switch] When 
buying a switch in the future, don’t buy another model, buy 2960
Buy routers can buy 2811 and 2901 models
The cable is straight line and cross line
The event is
not adaptive
gone too chat
Now our computers are usually gigabit adaptive
The switch cannot isolate the network segment (the switch is used to component the same local area network, so everyone connected to the switch, including the gateway)
router is specifically used to isolate the network segment (in other words, the router is specially used To connect to different network segments, and must connect to different network segments !) The
router does not allow its two interfaces to be on the same network segment! Routers are specially used to connect different network segments, and different network segments must be connected!
Small experiment:
Ping: Desktop---Command promot
