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Background: Know: traceroute Recognize:

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Path from UNSW to www.irtf.orgEdit

This slide is a practical example of the traceroute mechanism . Here, it shows the traceroute messages from UNSW to IRTF website. Several important aspects of this message makes it a meaningful measure about the path packets are taking from a linux machine in UNSW's network to the web server of IRTF. We can see at the beginning the traceroute, it declares few initial values, the IP address} to where the packets will travel (192.150.187.18), traceable maximum up to 30 hops and the probe packets will be 38 bytes in size.


Next, it shows the messages acquired per hop on the path to the destination using 18 rows and 6 columns. There are three main categories of the columns, first the hostname} of the router followed by its IP address and the round trip time (RTT)} for that particular probe packet. Generally, traceroute uses 3 probes on each router on the path, for example : in entry 5 (5th router on the path) has a hostname of "pos1-0.sccn1.seattle.aarnet.net.au" and IP address 192.231.212.34 along with three RTT's, which are 157ms, 157ms and 157ms.


Here we can see that the 5th router on the path is a router from UNSW's ISP Aarnet, probably is the edge router of the ISP as the next hop is a different domain name, moreover we can see from the domain name that, this POP} of Aarnet is probably situated in seattle, USA. The three delay measurements are taken for each hop which vary due to the congestion} state of the link.


Analyzing the data from the traceroute messages, we can identify different networks, across which the packet is routed to the IRTF web server. For example, in the slide we can observe the packet is passing through several major networks, namely aarnet.net.au, ucaid.edu, cenic.net and berkeley.edu before it reaches the destination. In addition, from the different RTT values we can have an idea about the distances of the path. If we look closely to the RTT values of entry 4 and 5 we can see a sudden increase in the delays, this is because the packets are passing over the Pacific Ocean accumulating the propagation delay} which depends on the distance of the link.



See alsoEdit

Corresponding TELE9752 lecture slide