icmp monitoring

ICMP Internet Control Message Protocolis generally considered an integral part of the IP layer and is generally used by the IP layer or higher (TCP, UDP).The ICMP message is transmitted inside the IP datagram.The format of the ICMP message is as follows:The first 4 bytes of the message are the same: 8bit type, 8bit code, 16bit test and.The

(i) ICMPIP is an unreliable protocol, and IP does not provide error control (if the data is in error during propagation), this time ICMP is working.ICMP provides two functions: Error reporting, querying.ICMP ICMP packets are divided into two categories, one is error message, and the other is query message.ICMP target unreachable: That is, there is no way to send IP packets to the corresponding destination a

field is MF (more Fragment) Mf=1 indicates "There are shards" later. Mf=0 represents the Last Shard Df The one in the middle of the Flag field is DF (Don ' t Fragment) Shards are allowed only when df=0 Chip Offset:Occupies 12 bits, which refers to the relative position of a piece in the original group after the Shard. Slice offset in 8-byte offset unitsSurvival time:The maximum number of routers that are recorded as TTL (Time to Live) datagrams in th

MTUIdentity:Occupies 16 bits, it is a counter that is used to generate the identity of the datagramLogo (flag):3-bit, currently only the first two bits have meaning Mf The lowest bit of the Flag field is MF (more Fragment) Mf=1 indicates "There are shards" later. Mf=0 represents the Last Shard Df The one in the middle of the Flag field is DF (Don ' t Fragment) Shards are allowed only when df=0 Chip Offset:Occupies 12 bits, which

It is necessary to prohibit the use of PING commands in Linux systems by using specialized hacking programs to steal information that is transmitted over a network line and to use stolen information to attack a specified server or system. In Linux, if you want the ping to be unresponsive and to ignore the ICMP package, we can enter the following command on the Linux command line: disabling ICMP protocol ac

These two days in an experiment need to construct their own IP header, encountered a lot of problems, a day finally fix.Introduction to the socket on the internet a lot of, I only record the construction of the IP header when I encountered problems. Because did not play the socket constructs the IP header, looked for the paragraph code research on the net, helpless code to run, all sorts of problems, the net collects the data to have no fruit, from the foundation study, adds own brain hole final

TCP/IP Note 2. Network Layer (2) -- ICMP, RIP, OSPF, BGP 1. ICMPICMP (Internet Control Message Protocol): improves the chances of successful IP datagram delivery. 1.1 features ICMP allows the host or router to report errors and reports exceptions. ICMP is not a high-level protocol, but an IP layer protocol. An ICMP pac

TCP will not cause IP sharding, while UDP and ICMP will cause IP sharding. Why does TCP not cause IP sharding? The reason is that TCP itself supports segmentation: when TCP needs to transmit data with a length greater than the MSS (Maxitum Segment Size), it first segments the data. Normally, the MSS is smaller than the MTU. Therefore, TCP generally does not cause IP fragmentation. UDP and ICMP do not suppor

ICMP Protocol (Internet Control Message Protocol) 1.1. Definition: A protocol used by a host or router to send error or query information to a source point.1.2. Message structure IP Header ( up to four bytes)Note: TheICMP message is encapsulated in the IP packet, so include the IP header Type of message (2 bytes) Report Text field (2 bytes) Checksum (4 bytes)

Internet Control Message protocol,icmp is one of the core protocols of the network protocol family. It is used for sending control messages in TCP/IP networks, providing feedback on various issues that may occur in the communication environment, through which the manager can diagnose the problems that occur and then take appropriate action to resolve them.ICMP is typically used to return an error message or to parse a route. The

For the ICMP protocol, we are more concerned with its security issues. In many ways, its security concerns are even more worrying. Here we will explain in detail the main methods to prevent ICMP attacks. Using system defects for various intrusions has always been an important way for hackers. Especially for family users with low awareness, hackers are more likely to gain access, readers who know about compu

Document directory Significance of ICMP Message Type Error Report Query The meaning of the existence of icmp ip provides unreliable connectionless datagram transmission. In this way, the IP protocol is designed to effectively use resources and provide a service that is best transmitted, it transmits a datagram from its original source end to the final destination end. However, it has two disadvantages

A gateway is essentially an IP address of a network to another network. For example, network A and network B, network A's IP address range is "192.168.1.1~192." 168.1.254 ", the subnet mask is 255.255.255.0; The IP address range for Network B is" 192.168.2.1~192.168.2.254 "and the subnet mask is 255.255.255.0. In the absence of a router, TCP/IP communication between the two networks is not possible, even if the two network connections on the same switch (or hub), the TCP/IP protocol will determi

Construct IP and ICMP headers for Python socket programming, pythonicmp In the past two days, an experiment requires you to construct your own IP Address Header. If you encounter many problems, you have finally completed the experiment in one day. There are a lot of questions about socket on the Internet. I only record the problems I encountered when constructing an IP header. Because I have never played the socket to construct the IP Address Header,

Using system defects for various intrusions has always been an important way for hackers. Especially for family users with low awareness, hackers are more likely to gain access, readers who know about computer networks know that Ping commands are often used to check whether the network is smooth. However, this command can also cause serious consequences for Windows systems, namely Ping intrusion, or ICMP attacks. The

Python sends icmp echo requesy requestCopy codeThe Code is as follows:Import socketImport struct Def checksum (source_string ):Sum = 0Countid = (len (source_string)/2) * 2Count = 0While count ThisVal = ord (source_string [count + 1]) * 256 + ord (source_string [count])Sum = sum + thisValSum = sum 0 xffffffffCount = count + 2If countTo Sum = sum + ord (source_string [len (source_string)-1])Sum = sum 0 xffffffffSum = (sum> 16) + (sum 0 xffff)Sum = su

Once in a firewall configuration policy see the following code:Iptables-A INPUT-P ICMP--Icmp-Type8 -J Acceptiptables-A FORWARD-p ICMP --icmp-type 8 -j acceptiptables -a INPUT -p ICMP -- icmp-type 11-j acceptiptables -a FORWARD -p

ICMP is often considered an integral part of the IP layer. It transmits error messages and other information that requires attention. ICMP packets are usually used by the IP layer or higher layer protocol (TCP or UDP. Some ICMP messages return error messages to the user process.ICMP packets are transmitted within the IP datagram, as shown in Figure 6-1. For more

ICMP protocol ICMP (Internet Control Message protocol,internet) is a connectionless protocol that is a child protocol of the TCP/IP protocol family and belongs to the Network layer protocol for IP host, Transfer control messages between routers (network access, host availability, routing is available, etc.). ICMP messages are automatically sent when an IP data u

discovery: The value of the Protocol field in the message that hosts the ICMP IP is 0x01 As the principle of the ping command, itself by pinging the same dorm computer but the scene of the failed message: The return message in the echo request or reply message in the ICMP Inquiry packet: A B C D E F G H I J K L M N O P