Significance of TTL value

TTL = 32 Windows 9x/me
TTL = 64 Linux
TTL = 128 windows x/XP
TTL = 255 Unix

TTL)
TTL is a value in the IP protocol package. It tells the network router package whether the time in the network is too long and should be discarded. There are many reasons that the package cannot be delivered to the destination within a certain period of time. For example, an incorrect route table may cause an infinite loop of packets. One solution is to discard the packet after a period of time and then send a message to the sender, which determines whether to resend the packet. The initial value of TTL is usually the default value of the system, which is the 8-bit domain in the header. The original assumption of TTL is to determine a time range and discard the package after this time. Since each vro must at least reduce the TTL domain by one, TTL usually indicates the maximum number of vrouters that can pass the packet before it is discarded. When the Count reaches 0, the router decides to discard the packet and send an ICMP packet to the original sender.

In Windows 95/98, the default value of TTL is 32. It is recommended that you set the value to 128 when it is difficult to reach a node. Ping and tracerouter both use the TTL value to try to reach the specified host or track the route to that host. Traceroute sets the packet's TTL value to a small value so that it is discarded continuously by each vro on the way to the destination. The time between the packet sent and the returned ICMP message is used to calculate the time from one vro to another.

The multiplexing IP protocol is used. The TTL value indicates the range of a packet forwarding. There are the following conversions: 0, limited to the same host 1, limited to 32 in the same subnet, limited to 64 on the same node, limited to 128 in the same region (region), limited to the same mainland (continent) 255,

because the default TTL values of different operating systems are different, therefore, in the Article , you can use the returned TTL value to determine the type of the target system. This is correct, but it is not a TTL function, only an application that understands TTL. The TTL value can be modified. Some special TTL values are defined by the system (such as NIDs) to deny unauthorized access to data. When executing the ping command, we can use the-I parameter to specify the TTL value. If you can set TTL to 0, the packet will be discarded immediately. Sometimes we run a ping command, but the other address is busy in the busy hours, with a prompt in English (the approximate meaning is that TTL is invalid ), it indicates that the TTL of the packet is 0 or smaller than the TTL value allowed by the next network segment before the packet reaches the target (that is, when the returned IP address is reached, the package has been discarded by the route.