how to set and get the TTL value from a packet?

[Victor]

Dear all,

Suppose I have two nodes, says node A and node B. Node A has been assigned an Ipv4address says "10.0.0.1" and node B has also got an Ipv4address as well, which is "10.0.0.2". Now, I would like to send a packet from node A to node B. Specifically, before sending the packet from node A, I would like to set an initial TTL value of this packet and whenever node B receive this packet, it will be able to get this TTL value from the packet. I have actually found some functions that are capable to do that, i.e. SetTtl and GetTtl. However, I cannot code correctly as what I expected. Just wondering is there any simple example codes in NS3 that can help? 

Thanks for the help.

Regards,

Victor

[Konstantinos]

TTL is an element of Ipv4Header. In order to access it you have to be in the correct layer. 

If you study the documentation you can find this http://www.nsnam.org/docs/models/html/internet-stack.html#example-path-of-a-packet
Step 4 in the outgoing path adds the Ipv4Header (the Ipv4L3Protocol or Ipv6). This is the correct place to "SetTTL" and similarly in the incoming path Ipv4L3Protocol (or Ipv6) will remove the header.