Various computer communication protocols

 

Various computer communication protocols:

L Protocol: behavior and specification in Network Communication

L protocol three elements:

1. Syntax: the sender sends data according to certain rules

2. Semantics: the recipient's computer can read the received information.

3. timed relationship: After receiving the message, you must send a response to the recipient.

Common network protocols:

1. netbeui (Microsoft): Enhanced interface protocol

L support all network protocols

L small size and fast speed

L simple configuration

L cannot be routed (cannot be connected to the Internet)

2. IPX/SPX protocol set (novlle ):

L used by the NetWare host

L fast

L routerable, but it does not work well when the network is large

3. nwlink (Microsoft ):

L compatible with IPX/SPX Protocol sets

L fast

L routable, poor performance when the network is large

4. Apple Talk: the protocol used by the operating system of the Apple Computer. The proprietary protocol of the vendor, which can be routed.

5. TCP/IP protocol set:

L the only accepted protocol on the Internet

L large size and slow speed

L routable, especially when the network is highly effective

 

Protocol selection:

1. The communication host must select the same compatible protocol for communication.

2. Recommended netbeui protocol for small offices (not on the Internet)

3. If you connect to the Internet, you must select the TCP/IP protocol.

4. The protocols are relatively small and can be installed at 30-50 m, but the speed is slow.

5. If a Netware host exists in the network, the nwlink protocol must be installed.

 

Note: There are two types of Protocols: Router Protocol and non-Router Protocol.

1] routable Protocol: data transmitted based on this protocol can be transmitted through a router. It can be transmitted between networks. Protocols used in large networks. TCP/IP, IPX/SPX, and Apple Talk.

2] non-Routing Protocol: data transmitted based on this Protocol cannot pass through the router. The protocol used in a small network. NetBIOS/netbeui.

 

Other communication modes: Win2000 supports other communication protocols and technologies (ATM and IrDA infrared data protocols)

 

ATM is developed for the high-speed and connection-oriented transmission of multimedia content. It transmits various types of communication traffic over the network. Use an ATM switch.

Features: it provides a single network connection for reliable mixing of sound, video, and data

High-speed connection

Effectively allocate network bandwidth (ensure that there is no single type of data over-using line)

 

The infrared data protocol is developed for wireless connections. Defines short-distance, high-speed, two-way wireless infrared connection protocol.

Features: world standard for wireless infrared connection

Easy to implement and use

No electromagnetic noise

 

Remote AccessProtocol

Dial-Up Protocol: In a dial-up connection, you can use the slip protocol (Serial Line Internet Protocol) or the PPP protocol (Point-to-Point Protocol). Win2000 does not provide the SLIP Server, because it is not secure and effective. However, you can use a Unix-running server as the SLIP Server.

Slip restrictions: Only TCP/IP is supported.

Static IP addresses are required

Transmit the authentication password in plaintext

PPP: supports encrypted password verification and allows clients to use netbeui, TCP/IP, and IPX/SPX network transmission protocols.

 

VPN Protocol

It protects data packets by placing normal data packets in encrypted PPP data packets. The PPP packet encapsulates netbeui, TCP/IP, and IPX/SPX packets.

VPN usePPTP(Point-to-Point Tunneling Protocol)OrL2TP(Layer 2 tunnel protocol)To establish a connection

 

PPTP: encapsulates PPP frames in the form of TCPIP packets on the network. This encapsulation allows you to use all PPP features in the PPTP virtual private network, including netbeui, TCP/IP, IPX/SPX, and Microsoft point-to-point encryption (MPPE)

Win2000 supports PPTP and can be used in a dedicated Lan-to-lan network

L2TP: basically the same mechanism as PPTP. The difference is that L2TP does not use MPPE to encrypt PPP frames, but uses ipsec (Internet Protocol Security) to provide encryption services. IPSec provides data integrity and encryption. This is more advanced than the MPPE encryption used by PPTP.

How to install the Protocol:

1] Right-click "Network Neighbor"-"properties-" right-click "Local Connection"-"properties-" Install-"protocol-" and select the protocol to be installed.

2] Note: local connection refers to the connection of the network card in the computer.

 

TCP/IPProtocol hierarchy and functions

The TCP/IP protocol also adopts a hierarchical structure, which includesNetwork Interface Layer, Internet layer, transmission layer, and Application Layer

TCP/IP communication process: Send mail

TCP/IP protocol:

1. TCP/IP is a protocol set, including two protocols, TCP is called Transmission Control Protocol, IP is called Internet protocol, and TCP/IP is a combination of multiple protocols. TCP/IP is generally regarded as a layer-4 protocol system.

L TCP/IP layer:

Layer 5-7 of OSI corresponding to Application Layer telnet, FTP, SMTP, etc.

 

Transport Layer TCP and UDP correspond to OSI model layer 4th

 

The Network Layer IP, ICMP, and IGMP correspond to layer 3rd of the OSI model.

 

The network interface layer interface card and Device Driver correspond to layer 1-2 of the OSI model

1) Network Interface Layer

The TCP/IP protocol rarely describes this layer. Generally, the network interface layer provides TCP/IP protocol and interfaces of various physical networks, which provides the possibility of transmitting and verifying data packets.

Responsible for placing data on the network media or receiving data from the network media.

2) Internet layer (Network Layer)

Corresponds to the OSI network layer, which effectively solves the problem of interconnection between heterogeneous networks,

Function:Connectionless and unreliable Transfer Service

Responsible for allocating addresses

Packet segmentation and reorganization

Route Data

This layer includes four core protocols:

InternetProtocol(IP)

Allocates IP addresses for the data to be transmitted and provides simple data stream transmission services. In intenet, data transmission between networks mainly depends on the IP protocol (Internet Protocol) in the Internet layer ).

IP functions include the following:

① Manage addresses in the Internet (IP address Division)

② Routing selection

③ Data sharding and reorganization

ICMPProtocol: The Internet Control Message Protocol Ping is used to detect network connectivity.

Each ICMP message type is encapsulated in an IP group. Only errors can be reported and cannot be corrected.

ARPProtocol: Forward Address Resolution Protocol:

This protocol is used to convert the IP address of a computer connected to the same physical network to the physical address of the computer. Converts an IP address to a physical address.

Working principle: each node saves a ing table between IP addresses of all nodes on the physical network and physical addresses. When a node is started, this table is empty. When address translation is required without ing information, ARP broadcasts a special ARP packet to all other nodes to ask about the IP address of the target address. A node with a matched IP address will respond, and its IP address and physical address are described in the ARP packet. After receiving the information, the source node immediately updates the address ing table (stored in memory)

RARP:Reverse Address Resolution Protocol:

It is used to convert known physical addresses to IP addresses. Generally used in diskless workstation, diskless workstation only has a physical address, no storage IP address, when the workstation starts, read the physical address from the network card, then send a RARP broadcast, ask their own IP address, A computer that provides the RARP service (with a storage IP address) responds.

IGMP:Internet Group Management Protocol: responsible for managing multiple deliveries.

 

3) Transport Layer

It corresponds to the OSI transmission layer and provides end-to-end connections, mainly using the following two Protocols:

Connection-oriented Transmission Control Protocol (TCP) is suitable for applications that transmit a large number of packets at a time.

A reliable and connection-oriented data transmission service is provided between two computers. Such communication is called spof.

Because TCP is a reliable transmission protocol, two computers must establish a connection before data communication. This connection is a virtual connection called a session. The two computers establish a TCP session through the three-way handshake process. This process synchronizes the serial number and provides other information.

Three-way handshake: 1. The source computer initiates a connection by passing session information, including the serial number and the packet size.

2. the target computer uses its session information to reflect

3. The source computer agrees and confirms the received information

The connectionless User Datagram Protocol (UDP) is applicable to applications that transmit a small number of packets at a time, such as database queries.

It provides a non-connection data packet delivery service, which is fast but unreliable. It delivers the data as much as possible, and does not require confirmation of the received data, and does not intend to re-transmit the lost data.

 

A port is an application in a computer.Program. The port is associated with the TCP or UDP Transport layer protocol, which is called the TCP port or UDP port. Any number between 0 and 65535, less than 1024 is reserved by common ports. ViewWinnt/system32/Drivers/etcDirectoryProtoclAndServeisFile to view more protocol ports

 

A socket is a combination of an IP address and a TCP port or a UDP port. The IP address component of the socket helps identify and locate the target computer. The port determines the specific application to which data is delivered.

4) Application Layer

It contains many complex protocols and is the most complex layer. it is necessary not only to provide the careful exchange and remote operations required by the application process, but also to act as the user agent of the Interaction application process to complete some functions necessary for semantic meaningful information exchange.

The layered model of the Protocol corresponds to the top three layers of OSI.

Web browsing (HTTP 80) based on TCP

File Transfer (FTP 20 21, TFTP 65) FTP is the most widely used File Transfer Protocol on iternet. it provides interactive access. In the early days of iternet, ftp-based file transfer accounted for 1/3 of the total iternet traffic, but in 1995, the WWW communication volume exceeded the ftp

FTP is based on TCP; TFTP is based on udp ftp (file transfer protocol) 21 is the transmission port number, 20 is the control port number, the biggest characteristic is the breakpoint resume

TFTP (simple File Transfer Protocol) uses UDP for transmission. resumable data transfer is not supported.

E-Mail (SMTP 25) Simple Mail transmission protocol based on TCP

Remote Logon (Telnet 23) based on TCP

The Domain Name Service (DNS 53) domain name system is a typical customer/server interaction system. The domain name system is a multi-level, domain-based naming system, the distributed database is used to implement this naming mechanism based on TCP and UDP.

Network Management (SNMP 161) based on UDP