Tag: ttl

Traceroute works I

Posted on by lechuck park

From The Bard with some prompting
The image is a diagram of how a traceroute works. Traceroute is a tool that uses ICMP packets to determine the path that a packet takes from a source to a destination.

The image shows the following steps:

The source sends an ICMP packet with a TTL (time to live) of 1.
The first router that receives the packet decrements the TTL by 1 and sends it to the next router.
If the TTL reaches 0 before reaching the destination, the router sends an ICMP packet back to the source with an error message.
The source then sends an ICMP packet with a TTL of 2.
The process repeats until the destination is reached.
The text in the image provides additional information about each step. For example, the text for step 1 states that the source sends an ICMP packet with a TTL of 1. This means that the packet will be discarded by any router that receives it after it has traveled 1 hop.

The image also shows the following information:

  • The source IP address is 192.168.1.1.
  • The destination IP address is 203.0.113.5.
  • The RTT (round-trip time) for each hop is shown in milliseconds.

The image is a useful tool for understanding how traceroute works. It can be used to troubleshoot network problems by identifying the routers that are causing delays or errors.

Here is a more concise summary of the image:

Traceroute uses ICMP packets to determine the path that a packet takes from a source to a destination. The source sends an ICMP packet with a TTL of 1. If the TTL reaches 0 before reaching the destination, the router sends an ICMP packet back to the source with an error message. The source then sends an ICMP packet with a TTL of 2. The process repeats until the destination is reached.tunesharemore_vertadd_photo_alternate

TTL(time to live) in ip packets

Posted on by lechuck park

From DALL-E with some prompting
The image provides an educational visualization of how the “Time to Live” (TTL) value in the Internet Protocol (IP) is used to manage the life span of data packets during transmission. TTL is a crucial part of the IP header, which is decremented by each router the packet passes through. When the TTL value reaches zero, the packet is discarded, preventing it from circulating indefinitely.

The diagram outlines the following key points:

  1. ICMP Packets: It shows the process of sending ICMP (Internet Control Message Protocol) packets, specifically an Echo Request, which is a common method for pinging a destination IP address to test connectivity.
  2. TTL Decrement: Each hop in the network decreases the TTL value of the packet by one. This decrement process helps determine how many network hops the packet has passed through to reach its destination.
  3. TTL in Action: The sequence of routers illustrates the TTL value decreasing from 64 down to 57 as the packet travels across seven network hops.
  4. Command Usage: It includes a command line example # ping -t [ttl] (Dest ip address) that specifies how to ping with a defined TTL value.
  5. TTL Analysis: It suggests that analyzing TTL values can help detect anomalies in packets, changes of routes from the same peer IP address, among other uses. For example, receiving a packet with an unusually high TTL value like 500 could indicate an abnormality.
  6. Receiving and Responding: The final part of the image shows a receiving computer that gets the ICMP packet with a TTL of 57 and replies with an Echo Response.

This visual aid is likely used for educational purposes to teach about network packet management, routing, and network troubleshooting techniques.