netflow packet

Ps:tcpdump is a tool for intercepting network groupings and outputting grouped content, which is simply the packet capture tool. With its powerful capabilities and flexible interception strategy, tcpdump is the preferred tool for network analysis and troubleshooting in Linux systems.Tcpdump provides source code, exposes interfaces, and is therefore highly extensible, and is a useful tool for network maintenance and intruders. Tcpdump exists in the bas

1. Packet forwarding rate of the switch The packet forwarding rate of the switch marks the size of the switch forwarding packet capability. Unit General bit BPS (packet per second), the packet forwarding rate for general switches ranged from dozens of kpps to hundreds of MP

Next I will introduce a very practical method based on the characteristics of network viruses scanning network addresses: Use the packet capture tool to find the virus source. Are you a network administrator? Have you ever experienced a sudden decline in network performance, failure to provide network services, slow server access, or even access, the network switch port indicator lights are flashing like crazy, the router at the network exit is alrea

Dynamic Host Configuration Protocol (DHCP) is a protocol designed by IETF to achieve automatic IP configuration, it can automatically assign IP addresses, subnet masks, default gateways, DNS Server IP addresses, and other TCP/IP parameters to the client. Understanding the DHCP process can help us eliminate problems related to the DHCP service. DHCP is an application based on the UDP layer (that is to say, only UDP packets can be viewed during the Snort detection process). DHCP uses UDP to carry

connection requires a "three-time handshake":First handshake: The client sends a SYN packet (SYN=J) to the server and enters the Syn_send state, waiting for the server to confirm;(That is, make a connection request packet: "I want to send you data, OK?" ”）Second handshake: The server receives the SYN packet, it must confirm the customer's SYN (ACK=J+1), and also

# Description ------------- maindump. sh (the main program for packet capturing) uses the endless loop detection every one minute to allow the program to continuously capture packets. considering that the packet capturing results may be too large, the analysis tool cannot open the analysis, therefore, the size of each packet is limited to about 100 MB. the

TCP requires ACK, but for efficiency, instead of waiting for ACK every time a piece of data is sent, it tries its best to use the window mechanism to accumulate ack sending, of course, in some special circumstances, Ack still needs to be sent immediately, for example, when unordered data is received, although the receiving end can temporarily store unordered data packets, however, the receiver must send an ACK with the expected serial number in order to the sender. In addition, the receiver must

Keywords TCP IP Packet Structure Detailed network protocol In general, network programming we only need to call some of the encapsulated functions or components can do most of the work, but some special circumstances, it requires in-depth understanding Network packet structure, and protocol analysis. such as: network monitoring, troubleshooting, etc... IP packet

"Package" (Packet) is a data unit in TCP/IP protocol communication transmission and is generally referred to as "packet". Some people say that the LAN transmission is not "frame" (frames)? Yes, but the TCP/IP protocol is working on the third layer of the OSI model (the network layer), the fourth layer (the Transport layer), and the frame is working on the second layer (data link layer). The contents of the

In general, for network programming, we only need to call encapsulated functions or components to complete most of the work, but in some special cases, we need to have a deep understanding. Network Packet structure and protocol analysis. Such as network monitoring and troubleshooting ...... The IP package is insecure, but it is the foundation of the Internet and widely used in various aspects. More than 10 protocol families (as far as I know) derived

outputs a slightly detailed information. For example, the IP package can contain TTL and service type information;-VV: Output detailed message information;-C. After receiving the specified number of packages, tcpdump stops;-F Read the expression from the specified file and ignore other expressions;-I indicates the network interface of the listener;-R reads packets from a specified file (these packets are generally generated using the-W option );-W directly writes the package into the file and d

ptcl ;????????? // Protocol typeUshort Plen ;??????? // Length of TCP/UDP packets (that is, the length unit from the calculation of the TCP/UDP header to the end of the packet: bytes)} Psd_header;?? This process is a very tedious process. After several computations, I can no longer endure such repetitive work. So I wrote a general computing function. I feel very convenient to use this function: encapsulate your data

Wireshark data packet capture tutorialWireshark data packet capture tutorial understanding capture analysis data packet understanding Wireshark capture data packet when we understand the role of the main Wireshark window, learn to capture data, then we should understand these captured data packets. Wireshark displays t

outputs a slightly detailed information. For example, the IP package can contain TTL and service type information;-VV: Output detailed message information;-C. After receiving the specified number of packages, tcpdump stops;-F Read the expression from the specified file and ignore other expressions;-I indicates the network interface of the listener;-R reads packets from a specified file (these packets are generally generated using the-W option );-W directly writes the package into the file and d

The preceding section analyzes the initialization process of the ARP protocol. This section is primarily an ARP packet processing process that, when ARP is initialized, adds the receive handler function of the ARP protocol to the hash list associated with the three-layer protocol packet processing function by calling Dev_add_pack Ptype_ In base (for a hash list related to the three-layer protocol

Understanding of the IP packet header validation field the IP packet format and the first field:Www.2cto.comThe data items in the table above are not explained in detail. Here we focus on the following data items:1. 4-bit Header Length: The length here refers to the number of 4-Bytes units. For example, if the "option" field does not exist, the header of the IP package is 20 Bytes, the header length field s

Function description: dumping network transmission data. Syntax: tcpdump [-adeflnNOpqStvx] [-c packet count] [-dd] [-ddd] [-F expression file] [-I network interface] [-r packet file] [-s data packet size] [-tt] [-T data packet type] [-vv] [-w data packet file] [output data c

Design of TCP packet capture segmentation and reorganization Function-------The TCP packet segment is out of order, repeated, and packet loss occurs in packet capture.Before analyzing the upper layer protocol, you need to reorganize the TCP packets.Segment reorganization re-sorts TCP data, drops duplicated data in ord

This article comes mainly from the manual of the man Packet Linux comes in:Http://man7.org/linux/man-pages/man7/packet.7.htmlUsually used in the inet socket provides a 7-layer grasp of the ability to grab the data is directly TCP or UDP payload, do not care about L3 and L4 header information.Packet socket provides the ability of L2, also known as raw socket, meaning is not through the operating system TCP/I

Introduction to three exchange technologies1. Circuit Switching TechnologyThe network switching technology has gone through four stages: Circuit Switching Technology, packet switching technology, group switching technology and ATM technology. Public Telephone Network (PSTN) and mobile network (includingBoth GSM and CDMA networks use circuit switching technology. The basic feature of this technology is connection-oriented.For a fixed-bandwidth communic