Chapter 10 network protocol and management configuration

1.1 network concept

Computer network is a collection of computers or network devices connected by tangible cables or intangible media such as wireless, and communicating according to certain rules.

Network functions and benefits

  • Data and Applications
  • resources
  • Network storage
  • Backup device

Scope classification

  • Wide area network (WAN)
  • Man (metropolitan area network)
  • Local area network (LAN)

1.2 common network physical components

1.3 network applications

1.3.1 various network applications

  • Web browser (Chrome, IE, Firefox, etc.)
  • Instant messaging (QQ, wechat, nailing, etc.)
  • E-mail (Outlook, foxmail, etc.)
  • Collaboration (video conferencing, VNC, Netmeeting, WebEx, etc.)
  • web services (apache, nginx, IIS)
  • File network service (ftp, nfs, samba)
  • Database services (MySQL, MariaDB, MongoDB)
  • Middleware services (Tomcat, JBoss)
  • Security services (Netfilter)

1.3.2 application requirements for network

  • batch application

    • FTP, TFTP, inventory update
    • No direct human interaction is required
    • Bandwidth is important, but not critical
  • Interactive Applications

    • Inventory query and database update
    • human-computer interaction
    • Because users need to wait for a response, response time is important, but not critical, unless it takes a long time
  • Real time applications

    • VoIP, video
    • Human interaction
    • End to end delay is critical

1.4 characteristics of network

  • speed
  • cost
  • Security
  • usability
  • Scalability
  • reliability
  • topology

1.4.1 speed (bandwidth)

1.4.2 network topology

Topology generally refers to the geometric figure arranged by points and lines

The topology of computer network refers to the geometric figure formed by the interconnection of communication links and computer nodes of a network

Topological classification

  • Physical topology describes the routing of physical devices
  • Logical topology describes how information flows in the network

Topology classification

  • Bus topology: all devices can receive signals
  • Star topology: transmission through central point, single fault point
  • Extended star topology: more resilient than star topology
  • Ring topology: signal loop transmission, single fault point
  • Dual loop topology: the signal is transmitted in the opposite direction, which is more resilient than a single loop
  • Full mesh topology: strong fault tolerance and high implementation cost
  • Partial mesh topology: balance between fault tolerance and cost

1.5 network standards

1.5.1 network standards and layering

Old model: proprietary products, applications and embedded software controlled by one vendor

Standards based model: multi vendor software, layered approach

Necessity of hierarchy
Computer network is a complex system intertwined by many hardware, software and protocols. Due to the complexity of network design, how to design, organize and implement computer network is a challenge, and scientific and effective methods must be adopted

Hierarchical method

  • The first layer of the network should have relatively independent functions
    Sort out the relationship between functions, so that one function can provide necessary services for the realization of another function, so as to form the hierarchical structure of the system
  • In order to improve the work efficiency of the system, the same or similar functions are realized only in one level, and as far as possible in a higher level. Each layer only provides services for the adjacent upper layer

Advantages of hierarchy

  • Each layer is independent of each other, and each layer only realizes a relatively independent function, which reduces the complexity of the problem
  • Good flexibility, and the operation inside each layer will not affect other layers
  • The structure can be separated, and the most appropriate technology can be used between each layer
  • It is easy to implement and maintain because the whole system has been decomposed into relatively independent subsystems
  • It can promote standardization because the functions of each layer and the services they provide are accurately described

1.5.2 open system interconnection OSI

OSI seven layer memory formula

All People Seem To Need Data Process
 Data transmission table

The two major international organizations that play an important role in formulating computer network standards are the Telecommunications Standardization Department of the International Telecommunication Union and the international standards organization (ISO) , although they work in different fields, with the development of science and technology, the boundary between communication and information processing began to become blurred, which has become a common concern of the Telecommunication Standardization Department of the International Telecommunication Union and ISO. In 1984, ISO released the famous OSI(Open System Interconnection) Standard, which defines the 7-layer framework of network interconnection (physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer), that is, OSI Open Systems Interconnection Reference model

Seven layer structure of OSI model


Layer 7 application layer

The Application Layer provides an interface for application software to set up communication with another application software. For example: HTTP, HTTPS, FTP, TELNET, SSH, SMTP, POP3, MySQL, etc

Layer 6 represents layer

Main entry: the Presentation Layer converts data into a format compatible with the receiver's system format and suitable for transmission

Layer 5 session layer

The Session Layer is responsible for setting and maintaining the communication connection between two computers in the computer network during data transmission.

Layer 4 transport layer

The Transport Layer adds the transport header (TH) to the data to form a packet. The transmission header contains the transmission information such as the protocol used. For example: transmission control protocol (TCP), etc.

Layer 3 network layer

The Network Layer determines the path selection and forwarding of data, and adds the network header (NH) to the data packet to form a message.
The network header contains network data. For example: Internet Protocol (IP), etc.

Layer 2 data link layer

The Data Link Layer is responsible for network addressing, error detection and error correction. When the header and footer are added to the data packet, a Data Frame will be formed. Data link header (DLH) contains physical address and error detection and correction methods. The end of a data link list (DLT) is a string indicating the end of a packet. For example, Ethernet, wireless local area network (Wi Fi) and general packet radio service (GPRS), etc. It is divided into two sublayers: logical link control (LLC) sublayer and Media access control (MAC) sublayer

Layer 1 physical layer

The Physical Layer transmits Data Frame on the local LAN, which is responsible for managing the interworking between computer communication equipment and network media. Including pin, voltage, cable specification, hub, repeater, network card, host interface card, etc

1.5.3 network communication process

1.5.3.1 data encapsulation and data unpacking



1.5.3.2 protocol data unit PDU


PDU: Protocol Data Unit refers to the data unit transmitted between peer-to-peer layers

  • The PDU of the physical layer is a data bit
  • The PDU of the data link layer is the data frame
  • The PDU of the network layer is packet
  • The PDU of the transport layer is the data segment
  • The other higher-level PDU is message

1.5.3.3 three communication modes

  • unicast
  • broadcast
  • multicast

1.5.3.4 conflict domain and broadcast domain

Conflict domain: two network devices send data at the same time. If a conflict occurs, the two devices are in the same conflict domain, otherwise, they are in different conflict domains

Broadcast domain: if one network device sends a broadcast and the other device receives it, the two devices are in the same broadcast domain, otherwise, they are in different broadcast domains

1.5.3.5 three communication mechanisms

  • Simplex communication: Communication in only one direction, such as radio
  • Half duplex communication: both sides of communication can send and receive information, but they cannot send or receive information at the same time, such as walkie talkie
  • Full duplex communication: both sides of communication can send and receive at the same time, such as mobile phone

Example: viewing duplex and speed

[root@rocky8 ~]# mii-tool eth0
-bash: mii-tool: command not found
[root@rocky8 ~]# dnf -y install net-tools
[root@rocky8 ~]# mii-tool eth0
eth0: negotiated 1000baseT-FD flow-control, link ok
#FD is full duplex

[root@rocky8 ~]# mii-tool -v eth0
eth0: negotiated 1000baseT-FD flow-control, link ok
  product info: Yukon 88E1011 rev 3
  basic mode:   autonegotiation enabled
  basic status: autonegotiation complete, link ok
  capabilities: 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  advertising:  1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  link partner: 1000baseT-HD 1000baseT-FD 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD

[root@rocky8 ~]# ethtool -i eth0
driver: e1000
version: 7.3.21-k8-NAPI
firmware-version: 
expansion-rom-version: 
bus-info: 0000:02:01.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no

[root@rocky8 ~]# ethtool eth0
Settings for eth0:
	Supported ports: [ TP ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                        100baseT/Half 100baseT/Full
	                        1000baseT/Full  #Half: half duplex, Full: Full duplex, T: twisted pair
	Supported pause frame use: No
	Supports auto-negotiation: Yes
	Supported FEC modes: Not reported
	Advertised link modes:  10baseT/Half 10baseT/Full
	                        100baseT/Half 100baseT/Full
	                        1000baseT/Full
	Advertised pause frame use: No
	Advertised auto-negotiation: Yes
	Advertised FEC modes: Not reported
	Speed: 1000Mb/s
	Duplex: Full #Duplex: duplex, Full: Full duplex
	Auto-negotiation: on
	Port: Twisted Pair #Twisted Pair: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: off (auto)
	Supports Wake-on: d
	Wake-on: d
        Current message level: 0x00000007 (7)
                               drv probe link
	Link detected: yes

#Status of network disconnection
[root@rocky8 ~]# mii-tool -v eth1
SIOCGMIIPHY on 'eth1' failed: Operation not supported #This is when the network cable is not connected
[root@rocky8 ~]# ethtool eth1
Settings for eth1:
	Supported ports: [ TP ]
	Supported link modes:   1000baseT/Full
	                        10000baseT/Full
	Supported pause frame use: No
	Supports auto-negotiation: No
	Supported FEC modes: Not reported
	Advertised link modes:  Not reported
	Advertised pause frame use: No
	Advertised auto-negotiation: No
	Advertised FEC modes: Not reported
	Speed: Unknown!
	Duplex: Unknown! (255)
	Auto-negotiation: off
	Port: Twisted Pair
	PHYAD: 0
	Transceiver: internal
	MDI-X: Unknown
	Supports Wake-on: uag
	Wake-on: d
	Link detected: no #This is when the network cable is not connected
[root@rocky8 ~]# ip link show eth1
3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:f9:6a:db brd ff:ff:ff:ff:ff:ff

Tags: Linux architecture DevOps Cloud Native

Posted on Wed, 10 Nov 2021 18:39:53 -0500 by droms