Administrator Handbook | TOC |
The Ping program de LoriotPro allows you to check in one click if a host is reachable when it is connected to an IP network (Internet). Ping uses a simple exchange of messages between two hosts, the first one sending a « Are you there ? » , the second one answering « Yes I am ». Ping provides also a measurement of the round trip time required for packets to travel between two hosts.
The Loriotpro ping windows:
The term Ping was taken from the sonar operation for locating objects. The Ping program was initially written by Mike Muuss in 1983 and it is become since an indispensable tool that all network administrators use.
The Ping program some of the ICMP protocol features to operate. A ping consist of sending an ICMP echo request packet to an IP address and wait for an ICMP echo reply packet.
What could be the reasons for a non response to a Ping ?
The Ping program is very easy to use,
select first a host in the directory and click on the Ping icon .
You can also
use the contextual menu of that host and chose the Tools option then the Ping
option.
You can also launch the Ping form the main Menu of LoriotPro, option Tool and Ping. The Ping is launched on the directory selected host.
Once the Ping Window is opened you can change manually the Ping destination. Enter either a host name or an IP address and click on the Start Ping Button. By default 4 ping packets will be sent at one second interval.
If you enter a Host name you should first click on the Resolve button to get the IP address of the host. The Resolve button performs a DNS request to your default DNS server for name resolution.
If the host has multiple entries in the DNS a list is displayed asking you to choose one of them. Double click on your selection.
If you want to choose afterward another host from the LoriotPro Directory you can click on the wizard button. The Directory Picker Wizard is displayed then chose a host.
When you have selected an IP address, click on the Start Ping button to launch it.
The results of the Ping requests are displayed in the upper table of the LoriotPro Ping dialog box.
The upper entry in this table is always the latest request performed.
The Time column gives the time at which the request has been sent.
The IP address column gives the IP address to which the PING is sent
The Round Trip Time column gives the time in milliseconds elapsed between the ICMP echo request and the ICMP echo reply.
The packet size column gives the size of the packet used by the Ping.
The Ping options allows you to change some of the characteristic of the Ping ICMP echo request packets
Packet Size (bytes) | Specify the size of the packet in bytes, available choices are 32,64,128,256,512,1024 (Default value is 64 bytes). |
Time Out (seconds) | Specify the maximum time that the LoriotPro Ping software wait before considering that there is no response. (Default value is 2 seconds). |
Time to live (hop count) | Specify the maximum number of hops (IP router) that the packet can go through. |
Ping Interval (Milliseconds) | Specify the time interval between 2 consecutive Ping (Default value is 1 second) |
Repeat (-1 continuous) | Specify the number of Ping that will be sent (default value is 4). A value of -1 sends Ping continuously. In that case a click on the stop button is mandatory to stop the Ping. |
Interpreting the result of the Ping test is not so easy. At least, when they is no response , you can bet that something is not working fine and look into the destination host configuration, the intermediate router, etc. Remember that the most common error that we know is the lack of default gateway in the destination host.
What about the response time RTT and how to qualify it?
The theoretical round trip time should be first estimated
The packet size is a key point in the calculation. If you choose a packet size of 64 Bytes, add 20 bytes for the IP header and 8 bytes for the ICMP header. That gives a total of 92 bytes.
To be perfect you should add the few bytes overhead of the under layer protocol (hdlc, SLIP, PPP, ATM etc.).
If there is a simple 64 Kbps line between the source and the destination of the ping, the minimum theoretical round trip time (RTT) will be at least to 92 x 1 / (64000 / 8) x 2 = 23 milliseconds.
This time doesn’t include the time needed by intermediate router to forward IP packets and the time needed by the destination host to process the incoming ping packet and forge an answer.
The following table gives the minimum theoretical round trip time (RTT) for each type of link speed and ping packet size.
RTT in milliseconds | Ping Packet size (bytes) | |||||||
---|---|---|---|---|---|---|---|---|
32 |
64 |
128 |
256 |
512 |
1024 |
|||
Link speed | ||||||||
1200 |
bps | 800 |
1227 |
2080 |
3787 |
7200 |
14027 |
|
9600 |
bps | 100 |
153 |
260 |
473 |
900 |
1753 |
|
57600 |
bps | 17 |
26 |
43 |
79 |
150 |
292 |
|
64000 |
bps | 15 |
23 |
39 |
71 |
135 |
263 |
|
128 |
Kbps | 8 |
12 |
20 |
36 |
68 |
132 |
|
256 |
Kbps | 4 |
6 |
10 |
18 |
34 |
66 |
|
512 |
Kbps | 2 |
3 |
5 |
9 |
17 |
33 |
|
1024 |
Kbps | 1 |
1 |
2 |
4 |
8 |
16 |
|
2048 |
Kbps | 0 |
1 |
1 |
2 |
4 |
8 |
|
4 |
Mbps | 0,24 |
0,37 |
0,62 |
1,14 |
2,16 |
4,21 |
|
8 |
Mbps | 0,12 |
0,18 |
0,31 |
0,57 |
1,08 |
2,10 |
Remark: The first ping packet of a ping test can be slower than the successive ones.
There are many possible explanations to this.
On the destination host, it is possible to check that ping packets are received and that answers are sent. To check that, use the MIB browser of LoriotPro and search the icmpinechos and icmpoutechosreps SNMP objects.
Icmpinechos object counts the number or received ping and icmpoutechoreps counts the numbers of replies. If the host works fine both values should be identical.
Keywords for this page : ping,icmp protocol,rtt,round trip time,echo request,echo reply,ping packets,ping packet size
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