1. CPSC 441 Tutorial - Network Tools 1 Network Tools CPSC 441 – Computer Communications Tutorial

2. CPSC 441 Tutorial - Network Tools 2 ICMP Internet Control Message Protocol ICMP messages are IP packets Used by network hosts to announce – Network errors – Network congestion – Network timeouts Not used directly by user except – ICMP Echo Request/Reply messages used in Ping – Traceroute

3. CPSC 441 Tutorial - Network Tools 3 ICMP Header ICMP Header starts after IP Header

4. CPSC 441 Tutorial - Network Tools 4 ICMP Messages Destination network/host/port unreachable Source Quench Message Echo Request/Reply (ping) Time Exceeded/TTL Expiry (traceroute)

5. CPSC 441 Tutorial - Network Tools 5 Ping Check if target host is alive – Troubleshoot network connectivity problems Check RTT ICMP Echo Request – 64 byte packet – Host replies with ICMP Echo Reply

6. CPSC 441 Tutorial - Network Tools 6 Ping - Example $>ping www.ucalgary.ca Pinging www.ucalgary.ca [136.159.x.x] with 32 bytes of data: Reply from 136.159.34.17: bytes=32 time=1ms TTL=62 Reply from 136.159.34.17: bytes=32 time=43ms TTL=62 Reply from 136.159.34.17: bytes=32 time=1ms TTL=62 Reply from 136.159.34.17: bytes=32 time=33ms TTL=62 Ping statistics for 136.159.34.17: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 43ms, Average = 19ms

7. CPSC 441 Tutorial - Network Tools 7 Traceroute Trace route of packets across the network Command line tools – Traceroute – Tracepath – Tracert (Windows) – Pathping (Win NT based systems)

8. CPSC 441 Tutorial - Network Tools 8 Traceroute Time to Live (TTL) – 8 bit field in IP header – Specifies the time a packet is allowed to “live” in the network – At each hop, router or host decrements TTL value of packet by 1 – When TTL = 1 Packet discarded “ICMP Time Exceeded” error datagram sent back to source host

9. CPSC 441 Tutorial - Network Tools 9 Traceroute Sends out a batch of packets – First three packets have TTL = 1 – Second three packets have TTL = 2 – and so on…. Each host along the way sees packet with TTL = 1 – Sends ICMP Time Exceeded packet – Source host uses these messages to build list of all hosts in the route

10. CPSC 441 Tutorial - Network Tools 10 References http://www.ping127001.com/pingpage.htm http://en.wikipedia.org/wiki/Internet_Control_Message_Protocol http://www.erg.abdn.ac.uk/users/gorry/course/inet- pages/icmp.html http://www.erg.abdn.ac.uk/users/gorry/course/inet- pages/icmp.html

11. CPSC 441 Tutorial - Network Tools 11 The end… Questions?