packet catcher

Most recent tasks are related to the network, so we often need to deal with packet capture tools. Here is a brief introduction for future reference. There are still many network packet capture tools, such as ethereal, Wireshark in windows and tcpdump in Linux. However, these tools depend on the pcap library. The pcap library encapsulates many network packet cap

Hierarchical structure of the network stack:We're going to start at the bottom and trace the delivery flow of a packet.1. Network interface layer* The hardware listens to the physical medium, carries on the data reception, when the received data fills the buffer, the hardware will produce the interruption, after the interruption produces, the system will turn to the interrupt service subroutine.* In the Interrupt service subroutine, the data is copied

Tcpdump: Get time-stamp from libpcap, and libpcap get time stamp from OS KernelWhen is a packet time-stamped? How accurate are the time stamps? Q: When is a packet time-stamped? How accurate are the time stamps? Tcpdump gets time stamps from libpcap, and libpcap gets them from the OSKernel,So tcpdump-and any other program using libpcap, suchEthereal or snoop-is at the mercy of the time stamping code in t

Lab Environment:650) this.width=650; Tracer of "alt=" Cisco Packet EtherChannel increases link bandwidth and redundancy-Ibm.chick-mingkang.zhou "src=" http://img0.ph. 126.net/1inyhgrqquafdjfzpjjgsw==/6630808280955124494.jpg "style=" border:0px;height:auto;margin:0px 10px 0px 0px; "/ >Experimental Purpose:1. Observe the STP status of the two switches.2. Configure the EtherChannel, and add the physical port to the channel.3. Then check the STP status of

Blockchain Enthusiast (qq:53016353) The data packet of the cottage is very large (more than 10G), and the cottage coin wallet will default to the packet to the C drive, our C disk space is often not enough, this time, we can move the packet to the D drive. Take a look at the method provided by the bit-age gadget.First step: Find the counterfeit currency

be combined with diagrams to understand And look at the head data for the packet. The front is the frame header, IP header, the front of the UDP is introduced, it will not be expanded. The following includes the TCP header and data. Because the TCP header has a fixed length of 20 bytes, the variable length is 40 bytes, mainly during the link establishment phase. So look at the TCP header data again. Source port number: 52173, corresponding CBCD D

1. Circuit Switching Technology The network switching technology has gone through four stages: Circuit Switching Technology, packet switching technology, group switching technology and ATM technology. Both the Public Telephone Network (PSTN) and the mobile network (including the GSM network and CDMA network) Adopt the circuit switching technology. Its basic feature is that the connection-oriented approach is adopted before both parties can communicate

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Http://acm.pku.edu.cn/JudgeOnline/problem? Id = 1887 The topic description is complex. In fact, it is to find the longest descent subsequence, which is also a typical topic of dynamic planning. There are two algorithms for this type of problem: T

Basic use of the packet capture tool EtherealThis is a tutorial written by enthusiastic people on the Internet. I have put it into practice and it is very simple, but the basic work is enough. I will organize it for the moment.You can perform basic packet capture according to the steps. 1. Use the prefix parameter settings -- capture option settings Interface: Specifies the interface (NIC) on which the

The protocol number for OSPF is 89, and when OSPF packet multicasting occurs, their TTL is set to 1,1. Packet headerAll OSPF packets are started by a 24-byte eight-bit group header650) this.width=650; "Style=" Background:url ("/e/u261/lang/zh-cn/images/localimage.png") no-repeat Center;border : 1px solid #ddd; "src="/e/u261/themes/default/images/spacer.gif "alt=" Spacer.gif "/>650) this.width=650; "Style="

this This paper mainly introduces the realization of WEBRTC in Nack, Weizhenwei, the article was first published in the Wind network , Id:befoioSupport original, reprint must indicate the source, welcome attention to my public number blacker (Id:blackerteam or WEBRTCORGCN).In WEBRTC, forward error correction (FEC) and packet loss retransmission (NACK) are important methods to resist network errors. FEC adds a redundant error-correcting code to the

This article mainly uses an example to explain in detail how to solve the packet loss problem caused by CISCO router faults? The following article gives me a detailed answer. Recently, some people in my department (Department A) reported that they could not access the network of the higher-level department (Department B. I use the ping command from the computer A1 (IP Address: 10.20.12.11/24) used by this person to send the ping command to the compute

let's start by understanding the following basic concepts :1. Forwarding: represents the process of selecting a path for a group2,IP forwarding: Its traditional method is IP routing (IP routing), IP forwarding it is to send the datagram to select the path.3, Group:(most computer networks can not continuously transmit arbitrary long data, so the network system actually divides the data into small pieces, and then block-by-piece, this small block is called the grouping (

We have introduced the basic content of DHCP. Here we will discuss in detail the knowledge and problems related to the DHCP packet format. DHCP packet format Let's introduce the DHCP packet format, 1 OP (1) Htype (1) Hlen (1) Hops (1) Transaction ID (4) Seconds (2)

H264 video packet loss is inevitable during transmission in the group network, especially when the network environment is poor, transmission of h264 code streams, packet loss will lead to the decoding terminal screen, mosaic is serious, this cutting-edge technology is FEC, NACK, the former is the forward correction technology, and the latter is the retransmission. The two can work well to solve the visual e

Programming Requirements: Capture the IP packet of the native network card to resolve the captured IP packet. The following fields must be output: Version number, total length, flag bit, slice offset, protocol, source address, and destination address. The TCP/IP protocol defines a packet that is transmitted over the Internet, called an IP datagram (IP Datagram).

Transferred from: http://blog.csdn.net/wanggp_2007/article/details/5136609Packet loss compensation (Packet Loss CONCEALMENT--PLC) is a very important technology in ILBC codec, and it is an indispensable part of VoIP codec applications. The ILBC PLC only handles packet compensation at the decoding end. In the decoding end according to receive the bitstream frame by the process of decoding, ILBC decoder first