PING
Definition
- Is it an acronym for Packet InterNet Developer?
- Or is it just a sonar anlogy for echoing signals
from a target?
Whatever it may be, it does the following
:
- It sents packets of data to a target machine.
It receives back the packets echoed by the target. The roundabout time,
loss of any packets are caculated to measure the
network connecion.
- Ping is used for network testing, measurement
and management. It is used to check communication links, or to check
whether a particular host exists or is running.
Probing...
- The following appears in the man pages
of ping, which I have to figure out:
"The maximum possible value of the TTL field of ICMP ECHO_REQUEST packets
is 255. Most of the unix systems sets it to 255. That is
why you can ping some hosts
but cannot reach them via ftp or telnet. "
New words found : TTL and ICMP.
Need to find what they are.
TTL is time to live. This field
in packet header sets the maximum number of hops that the packet can take
to reach the target. Each router on the
route, reduces the count by one.
Test Results
- I used ping on my school sebsite (www.sskzm.org)and
got the following results.
Ping sskzm.org (216.83.162.27)
4 packets transmitted, 4 packets received, 0% packet loss
Host reachable, average round-trip time: 22.857 ms
- I used the same on SERC server (144.16.79.58) and the
reults were more elaborate
64 bytes from
144.16.79.58: icmp_seq=0 ttl=255 time=9.955 msec
64 bytes from
144.16.79.58: icmp_seq=1 ttl=255 time=253 usec
64 bytes from
144.16.79.58: icmp_seq=2 ttl=255 time=232 usec
64 bytes from
144.16.79.58: icmp_seq=3 ttl=255 time=236 usec
64 bytes from
144.16.79.58: icmp_seq=4 ttl=255 time=229 usec
64 bytes from
144.16.79.58: icmp_seq=5 ttl=255 time=229 usec
64 bytes from
144.16.79.58: icmp_seq=6 ttl=255 time=234 usec
64 bytes from
144.16.79.58: icmp_seq=7 ttl=255 time=252 usec
64 bytes from
144.16.79.58: icmp_seq=8 ttl=255 time=235 usec
64 bytes from
144.16.79.58: icmp_seq=9 ttl=255 time=238 usec
64 bytes from
144.16.79.58: icmp_seq=10 ttl=255 time=267 usec
64 bytes from
144.16.79.58: icmp_seq=11 ttl=255 time=219 usec
64 bytes from
144.16.79.58: icmp_seq=12 ttl=255 time=227 usec
64 bytes from
144.16.79.58: icmp_seq=13 ttl=255 time=224 usec
64 bytes from
144.16.79.58: icmp_seq=14 ttl=255 time=235 usec
64 bytes from
144.16.79.58: icmp_seq=15 ttl=255 time=232 usec
Note
: The stream kept on going . When will it end ? After how many icmp_seq?
After some time ...
64 bytes from 144.16.79.58: icmp_seq=1713 ttl=255
time=223 usec
Still it has not ended. Why can't the server such traffic
automatically once the testing is over?
I interrupted and got the message
:
1851 packets transmitted, 1851 packets received, 0% packet loss
round-trip min/avg/max/mdev = 0.213/0.322/21.505/0.856
ms
Probing...
- The following appears in the
man pages of ping, which I have to figure out:
"The maximum
possible value of the TTL field of ICMP ECHO_REQUEST packets is 255. Most
of the unix systems sets it to 255. That is
why you can ping some hosts but cannot reach
them via ftp or telnet. "
- New words found : TTL and
ICMP. Need to find what they are.
- TTL is time to live. This
field in packet header sets the maximum number of hops that the packet
can take to reach the target. Each router on the route, reduces the
count by one.
- While looking around for ping, I found another
tool called traceroute.