Let’s now see in details what happened by using Wireshark. The last line (8) corresponds to the final destination itself.
In this example, the packet has reached the destination after 7 consecutive hops. You can see this through the 3 network latency values provided per line.
#Best trace rout application windows#
By default, a Windows traceroute sends three packets per hop. One line corresponds to a discovered router. These pictures show a Windows traceroute to. The standard Windows implementation of traceroute uses ICMP as protocol to send IP packets. They are typically transported in a upper transport layer protocol like UDP, or directly in ICMP packets. With traceroute, the IP packets are not sent as is.
The type of message this final destination will send to the source depends on the specific traceroute implementation used (see next topic). … and so on up until the packet reaches the final destination. Again an ICMP error message is sent back to the source, which discovers the second router in the path. The router drops it due to the TTL value of 1. The packet hits the second router in the path. The packet hits the first router, is routed normally, and the TTL values is decreased by 1 (new TTL value = 1). For this, it sends a packet with a TTL value of 2. The source has discovered the first router! So let’s go to the next one. The router drops the packet due to this TTL value and sends an ICMP error message back to the source. The packet hits the first router in the network path. The source sends a first IP packet with a TTL header field value of 1. When performing a traceroute, this is what happens: So traceroute relies on the fact that routers will send this ICMP error message back to the source in case of a TTL value reaching 1. It also informs the source about this by sending a specific ICMP error message back to the source (ICMP error message “TTL Exceeded In Transit”). So it drops the packet (to avoid potential looping problem). When a packet with a TTL value of 1 hits a router, this latter cannot route the packet anymore (it would mean a TTL=0). 
Each time the packet hits a router and must be routed, the TTL value decreases by 1. When a host sends a packet on a network, its initial TTL value is between generally 32 and 255, depending on the operating system used. This field is mainly used to avoid loops in networks, where packets could be routed indefinitely in a loop under certain circumstances. The whole traceroute principle is based on the TTL (Time To Live) field of the IP packet header. The main principle of traceroute is shown hereunder: It can also detect any network path variation that may occur through BGP peering/routing configuration changes. It is extremely useful to measure the network quality (congestions, …).
measure the network latency to reach each hop on the path. discover the network path between a source and a destination. Traceroute is a very useful tool for network monitoring and problems diagnostics. We also address the main limitations of such a tool that makes it unfit for accurate measurements. In this article, we explain the main concepts of Traceroute and how it can be used to measure network latency and packet loss.
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