1. Increase the network system
. The need for network growth:
1. Unlimited transmission distance
2. No conflict at all-all nodes can send and receive data at the same time
3.
Equipment to realize one-to-one unicast : bridge-later Replacement of switches
:
1. Increase of nodes—add hubs (HUB);
2. Increase of distance—
hidden dangers caused by the use of repeaters (also called amplifiers) :
1. 1. Security 2. Address 3. Delay 4. Conflict
2. Cannot be extended indefinitely.
Address: MAC address, serial number of the network card chip, 48-bit binary composition, and the only hexadecimal display in the world.
Conflict: CSMA/CD carrier sense multiple access/conflict detection-queuing
switch is two Layer equipment;
full-duplex (similar to mobile phones), half-duplex (similar to walkie-talkies)
switch operation mode: when a data frame enters the switch, the switch first checks the source MAC address in the data, and then maps it with the corresponding interface Record (MAC address table); then check the target MAC in the data, and then check the lower MAC address table to find the corresponding interface;
summary: 1. Find the record—only forward to this interface (unicast) 2. If not The record will flood the traffic. Flooding: the traffic enters the interface from the current low, a copy of all other interfaces;
flooding: the traffic enters the interface from the local, and all other interfaces copy the
IPV4 address-32 bits Binary composition
ARP-address resolution protocol-through an address of the opposite end to obtain another address to the short end to
increase the network-unlimited distance, no conflict, unicast-switch-MAC-flooding-flooding range-router- IP—ARP—Broadcast—Broadcast domain (flooding domain)
2. OSI open system interconnection reference model-seven-layer model: set by the ISO organization
1. Application layer : realize various services through human-computer interaction
2. Presentation layer : encoding, decoding, encryption, decryption
3. Session layer : distinguish the session of application equipment, provide session layer address, process data for application program-application
4. Transport layer : play the role of segmentation (limited by MTU) and provide port number. Commonly used protocols are TCP Protocol with UDP
Port number: The port number is 0–65535, of which 1–1023 are the indicated ports (also known as static ports), and 1024–65535 are dynamic ports (also known as high ports).
Dynamic ports are generally randomly allocated to terminal devices Applications started on the computer;
static port—fixed to various frequently used services;
HTTP server—generally displayed as 80;
port number: used to distinguish the various program processes of the terminal device and the various services provided by the server device;
UDP : User Data Message Protocol—Protocols that only complete the basic work of transmission—segmentation, port number
Non-connection-oriented unreliable transmission protocol
TCP: Transmission Control Protocol—In addition to completing the basic work of the transport layer, it is also necessary to ensure the reliability of data transmission. Reliable transmission protocol
for connection Connection-oriented-3-way handshake to establish an end-to-end virtual link
Reliable transmission-4 mechanisms 1. Confirmation 2. Retransmission 3. Sequencing 4. Flow control (sliding window) 
5. Network layer : Yes Network address for forwarding data packets and routing, IP protocol
6, data link layer : actually includes LLC logical link control + MAC media access layer control, MAC address, verification and control physical layer
HTTP: Hypertext Transfer Protocol
HTTPS: Secure Hypertext Transfer Protocol
DNS: Domain Name Resolution Service
FTP: File Transfer Protocol
TFTP: Simple File Transfer Protocol
MTU: The default maximum transmission unit is 1500 bytes
7. Physical layer : Mainly for hardware settings (Important devices include hubs (HUB) and repeaters)
3. Comparison of OSI seven-layer reference model and TCP/IP protocol stack
1. Similarities : Both are model-based and hierarchical; the lower layer provides service support to the upper layer; each layer is independent of each other
2. Differences : OSI has a model before a protocol TCP/IP has a protocol before a model; TCP/ IP protocol stack is only applicable to TCP / IP networks; different layers
four terms related supplementary
1, packaged - from top to bottom of the data processing process, the process will continue to become larger data
2, decapsulating - from the bottom to the data A high-level reading process; data keeps getting smaller
3. PDU -the unit of the protocol data unit to each layer of data. In the
4th and 7th layer model , the upper three layers = message, transmission layer = data packet, data link layer = Frame, physical layer = bit stream
5. DNS : domain name resolution service finds the corresponding ip address through domain name
6. ARP : address resolution protocol, known counterparty IP, obtain MAC
7, forward ARP : all the way to the IP address of the opposite end, pass Broadcast query the MAC address
of the opposite end 8. Reverse ARP : always local or opposite MAC address, query the ip address through MAC
9. Gratuitous ARP : In the process of using the ip address, forward ARP is performed outwards, but the target ip of the query Address is the low IP address conflict detection
10, MTU : Maximum transmission unit
11. Flooding : The communication behavior of the switch to the broadcast, all interfaces except the flow entrance are copied and transferred out
12. TCP : Transmission Control Protocol-connection-oriented reliable transmission Protocol
13, UDP: Non-connection-oriented unreliable transmission protocol
14. IPV4 : Internet Protocol version 4
15. OSI : Open System Internet Reference Mode—7-layer model set by the ISO organization;
16. TCP/IP protocol path : the actual network is true The model used, the 7-layer model is only used as a reference model