Operation and maintenance of network infrastructure
1. What is the network
It is a form of objects, allowing for communication between objects with objects
How two hosts communicate with each other
1. have a transmission medium (cable, optical fiber, WiFi)
2. have NIC device, an identifier, MAC address, physical address, globally unique, by hexadecimal data into an electric signal modulation process # wires Number into a data demodulation process # 3 negotiated transfer rate network unit: Mbps = 'bit. 1 / 8B B = 8bit
How to achieve multiple hosts to communicate
Switch
broadcast storm problem
to a hair cut into a number of small local area network LAN
switches
fool (tp-link, dlink, Mercury)
programmed (Configuration Management h3, Cisco, Huawei)
How to make multiple LANs to communicate
Routers
communicate between each LAN, the only way to go through a gateway.
Identity: IP address, network-bit + host bits 10.0.0.100 entire network, with the number in decimal notation
on the public network, the whole network the only similar passport
linux:
get curl cip.cc external network IP
curl ifconfig
Windows: Baidu search
the routing table: -n route
netstat -rn
private network
Network topology
Level of
the core layer: deployment of a routing device, a network connection is required redundancy
aggregation layer: Layer deployment switching equipment, the need for the routing function of
the access layer: deploying two switching equipment, terminal equipment connected to
one switch: the physical layer only supports
switcher: support physical layer and data link layer
three switches support physical layer and data link layer and the network layer
Network Type
LAN: Local private networks, local area networks called large, campus network.
MAN: Coverage reach a city
wide area network: national, global internet Internet
OSI model
Physical Layer: The network device
data link layer: a packet encapsulated in a frame; transit node to the offering node mode
network layer: IP protocol
transport layer: udp TCP transport protocol and
a session layer establishing, managing and terminating a session
presentation layer: data decoding the encoded
application and interface application layer sequence, a variety of protocols similar to the boss of http simplex: similar (radio), one as a receiver, the sender as one half-duplex intercom :() either as a sender, a recipient may be, can not be performed at the same time full-duplex telephone :() simultaneously at both ends
DOD model TCP
OSI TCP
Application Layer:
Presentation Layer:
Session Layer:
Transport Layer: host-to-host layer,
the network layer: Internet layer
a data link layer: The network access layer (two layers)
physical layer:
1565318406246](C:\Users\IBM\AppData\Roaming\Typora\typora-user-images\1565318406246.png)
Encapsulation and de-encapsulation of data
Package (buy similar courier package)
Top to bottom,
the three-tier PDU data
transport layer protocol TCP + packed
network layer segment + IP + TCP protocol protocol
data link layer of the TCP protocol is framed + IP address + mac protocol
physical layer bit electric signal, a bit stream
Unseal
From bottom to top
converting the electrical signal into a physical layer bit
data link layer protocol TCP + IP protocol
network layer protocol TCP
transport layer of
the three-tier data
cat / proc / sys / net / ipv4 / ip_local_port_range
Application layer protocol
ftp 21 File Transfer Protocol, is not encrypted
tftp 69 Trivial File Transfer Protocol, based
telnet 23 remote connection protocol, expressly
ssh 22 Secure Shell protocol, encrypted
SNMP 161/162 Simple Network protocol
SMTP 25 Simple Mail protocol
pop3 110 postal service agreement
http 80 simple request-response protocol
https 8080 hypertext link protocol
dns 53 domain protocol, based on UDP
dhcp 68/67546 dynamic host configuration protocol, 67 is a client server 68
DHCP principle
1. The client requests an IP address to the server
2. The server receives the request
3. Client IP address selection
4. service ip address assigned to the end client, the ip address pool to delete the IP
5. lease
DNS resolution process
DNS is the Domain Name System, a major role, the domain names into IP addresses, the opposite is reverse DNS
-based UDP53 port
1. Visit www. baidu.com domain name, looks up the local cache
1.ipconfig / displaydns
2. local hosts file
C: \ Windows \ System32 \ the Drivers \ etc \ hosts
2. LDNS request to the server, (local DNS), has a resolution records, returns to the client, if not to find the root name server
3. root name server resolves the root domain part, the top record domain name back to the server LDNS
4.LNDS request to the server for a domain name server, the second level domains return address
5.LNDS secondary domain name server server access request, find a. A record, record A will return LNDS
6.LNDS A received record cached locally, in the parsed information back to the client
7. The client receives the resolution records, local cache, performing the access request
parsing process there are two queries
recursive query
iterative queries
A recording
domain and ip address corresponding to
[the root M01 @ ~] # DIG www.increase93.com
[the root M01 ~ @] + # DIG @ 223.5.5.5 www.increase93.com the trace # View A detailed record information [root @ m01 ~] # nslookup www.increase93.com
[root@m01 ~]# host www.increase93.com
[root@m01 ~]# ping www.increase93.com
Host-to-host layer
TCP Transmission Control Protocol
features: connection-oriented, reliable, the transmission rate is slow
UDP User Datagram Protocol
Features: connectionless, reliable, fast transmission rate
Control field
1 indicates a successful connection request SYN 0 indicates a failure
ACK acknowledgment indicating successful connection 1 0 indicates a failure
FIN disconnected 1 0 indicates a failure indicating success
RST data represents data transmission with a real tcp packet contents represented bit is transmitted psh
seq. No: after the large data split marker sequence information, the receiver will facilitate assembling data information, +1 original sequence based on the replies. What to send data to inform the next time Send me is
TCP three-way handshake
1. The client sends a connection request (syn) to the server to define their own serial numbers A,
2, syn server receives a client request, response ack, a + 1, the server sends a request to the client syn, to define their own serial number B
3. server client receives ack and syn, will respond ack,. 1 A +, B +. 1
4. server receives ack, both connected state is established
!img](file:///C:\Users\IBM\Documents\Tencent Files\1643168583\Image\Group\LQ{9`$T]IZACRGN177TBX8D.png)
TCP four wave
1. The client sends a FIN disconnection request to the server, add the serial number A 2. Disconnect the server receives the client's request, replies the ACK, SEQ. 1 = A + 3. Layer upward reporting server transmits FIN request to the client, seq = a + 1, to add their own serial numbers B 4. client receives the server request FIN, ACK = A + replies. 1 the ACK, SEQ = B +. 1 5. The server received the ACK, the two sides disconnect
!(C:\Users\IBM\AppData\Roaming\Typora\typora-user-images\1565335999076.png)
