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This article mainly introduces the relevant knowledge of what the concept of ping, time,TTL is, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe that after reading this ping, the concept of time,TTL will gain something. Let's take a look at it.

First, what is ping?

PING (Packet Internet Grope), an Internet packet explorer, is a program used to test the number of network connections. Ping sends an ICMP echo request message to the destination and reports whether it has received the desired ICMP echo reply. How does he work? look at the picture below.

Ping request description

Second, what is TTl?

TTL: time to live, which specifies the number of network segments allowed before the packet is discarded by the router. The TTL is set by the sending host to prevent packets from looping endlessly over the IP Internet. When forwarding IP packets, the router is required to reduce the TTL by at least 1. The type of ICMP message involved when using PING: one for ICMR request echo (ICMP Echo Request) and one for ICMP echo reply (ICMP Echo Reply) TTL field value can help us identify the operating system type. The TTL field value of ICMP echo reply for UNIX and UNIX-like operating systems is 255,

Compaq Tru64 5.0The TTL field value of ICMP echo reply is 64

The TTL field value of Microsoft Windows NT/2K operating system ICMP echo reply is 128,

The TTL field value of Microsoft Windows 95 operating system ICMP echo reply is 32.

Of course, the TTL values returned are the same, but in some cases there are special LINUX Kernel 2.2.x & 2.4.x ICMP echo reply TTL field values of 64 FreeBSD 4.1,4.0,3.4; Sun Solaris 2.5.1,2.6,2.7,2.8 OpenBSD 2.6,2.7, NetBSD HP UX 10.20 ICMP Echo reply TTL field value is 255Windows 95/98/98SE Windows ME ICMP Echo reply TTL field value is 32 Windows NT4 WRKS Windows NT4 Server Windows 2000 Windows XP ICMP Echo reply TTL field value is 128. so we can identify the operating system in this way.

three, For example, C:\ Documents and Settings > ping blog.51yip.comPinging blog.51yip.com [173.201.152.6] with 32 bytes of data:Reply from 173.201.152.6: bytes=32 time=257ms TTL=45Reply from 173.201.152.6: bytes=32 time=256ms TTL=45Reply from 173.201.152.6: bytes=32 time=262ms TTL=45Reply from 173.201.152.6: bytes=32 time=258ms TTL=45Ping statistics for 173.201.152.6:Packets: Sent = 4, Received = 4, Lost = 0 (0 loss), Approximate round trip times in milli-seconds:Minimum = 256ms, Maximum = 262ms Average = 258ms

From this, we can conclude that blog.51yip.com is a linux host. After 64-450019 transfers, it arrives at the local machine, time=257ms. This time is the time of a request. The smaller the time, the faster the speed, the greater the speed, the slower the speed.

C:\ Documents and Settings > ping 127.0.0.1Pinging 127.0.0.1 with 32 bytes of data:Reply from 127.0.0.1: bytes=32 timefor 127.0.0.1:Packets: Sent = 4, Received = 4, Lost = 0 (0% loss) Approximate round trip times in milli-seconds:Minimum = 0ms, Maximum = 0ms, Average = 0ms

The TTL=128 here means two things:

1. The requesting host is a computer with WINDOWS system.

2, and there is no routing, that is, the request is the local machine. The time of each request is less than one-millionth of a second.

This is the end of the article on "what is the concept of ping, time,TTL". Thank you for reading! I believe you all have a certain understanding of "what is the concept of ping, time,TTL". If you want to learn more, you are welcome to follow the industry information channel.

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