Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations strongm on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!
Pathping
- Thread starter deeze6
- Start date
- Thread starter
- #3
Utility Ping: How dose PING work?
A Ping utility is essentially a system administrator's tool that is used to see if a computer is operating and also to see if network connections are intact.
Ping uses the Internet Control Message Protocol (ICMP) Echo function which is detailed in RFC 792. A small packet of information containing an ICMP ECHO_REQUEST is sent through the network to either a particular IP address or a domain name. This packet contains 64 bytes - 56 data bytes and 8 bytes of protocol reader information.
The computer that sent the packet then waits (or 'listens') for a ECHO_REPLY packet from the specified IP address. The ping program then evaluates this reply, and a report is shown. You can check several things with the ping program: can you reach another computer, how long does it take to bounce a packet off of another site. The time taken to Send and Receive a Data Packet is calculated in Milliseconds.
But it is the "LISTENING" activity that is the key to the answer to your question. At some point ping has to realize that a response is not going to be forthcoming, and the error report is issued. This specific sequence: send to IP an echo request; open and wait for a response for a set period of time; close connection and report the results is what allows it to report what were for each IP in the pingpath what results obtained.
A Ping utility is essentially a system administrator's tool that is used to see if a computer is operating and also to see if network connections are intact.
Ping uses the Internet Control Message Protocol (ICMP) Echo function which is detailed in RFC 792. A small packet of information containing an ICMP ECHO_REQUEST is sent through the network to either a particular IP address or a domain name. This packet contains 64 bytes - 56 data bytes and 8 bytes of protocol reader information.
The computer that sent the packet then waits (or 'listens') for a ECHO_REPLY packet from the specified IP address. The ping program then evaluates this reply, and a report is shown. You can check several things with the ping program: can you reach another computer, how long does it take to bounce a packet off of another site. The time taken to Send and Receive a Data Packet is calculated in Milliseconds.
But it is the "LISTENING" activity that is the key to the answer to your question. At some point ping has to realize that a response is not going to be forthcoming, and the error report is issued. This specific sequence: send to IP an echo request; open and wait for a response for a set period of time; close connection and report the results is what allows it to report what were for each IP in the pingpath what results obtained.
- Thread starter
- #5
Yes but how can the sending host differentiate between a ping packet being:
1. Dropped by the outbound interface of the sending router.
2. Corrupted on the dirty wan circuit.
3. Dropped by the inbound interface of the receiving router.
All three would by shown by traceroute to be dropped in the same hop.
1. Dropped by the outbound interface of the sending router.
2. Corrupted on the dirty wan circuit.
3. Dropped by the inbound interface of the receiving router.
All three would by shown by traceroute to be dropped in the same hop.
It sends multiple requests and averages the results. Any link failure affects the average, whatever the cause.
You might consider watching the ICMP traffic yourself. Freeware:
- Status