Set TTL for RREQ Packet

[Khairul Azmi]

Hi,
I'm using INETMANET and want to simulate DSR routing protocol in OMNET. I want to limit the number of hop the RREQ packet should traverse. I look at the parameter of TTL_START in function dsr_rreq_route_discovery at file dsr-rreq.cc and change it from 10 to 1. Unfortunately it is not working. The control packet is still be rebroadcasted by the next node. Is there a way to solve this? Thanks in advance. 

[Alfonso Ariza]

TTL_START is the initial TTL not the maximum TTL, DSR double the TTL if the node doesn't receive a RREP

 

You should modify the MAXTTL label in the dsr-rreq.cc file

[Khairul Azmi]

Thanks for the reply,
Correct me if I'm wrong. DSR double the TTL only when there is timeout for the RREQ and if MaxMaintRexmt greater than 1. I want the RREQ control packet be broadcasted up to only one hop. But I could not see any where in the codes the TTL is been monitored and the packet is dropped when TTL is 0. Cheers.

[Khairul Azmi]

My mistake. The code is in function dsr_ack_req_send in file dsr-ack.cc. I've been looking in file dsr-rreq.cc. Cheers.

[Alfonso Ariza]

In the method

void

DSRUU::omnet_xmit(struct dsr_pkt *dp)

 

/* If TTL = 0, drop packet */

if (p->getTimeToLive() <= 0) {

DEBUG(

"Dropping packet with TTL = 0.");

drop(p,

ICMP_TIME_EXCEEDED);

dp->

payload = NULL;

dsr_pkt_free(dp);

return;

}

 

[Shaikha Al-Khuder]

drop(msg)

Does it drop the message(discards it the same way the function you wrote does)??

[Alfonso Ariza Quintana]

the method drop deletes the packet

---

Date: Mon, 8 Feb 2016 09:09:09 -0800
From: cpe....@gmail.com
To: omn...@googlegroups.com
Subject: Re: [Omnetpp-l] Re: Set TTL for RREQ Packet

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[Shaikha Al-Khuder]

Where does a node decides if this msg is for it or for another node (forwards it to other node)? in which class?

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[Alfonso Ariza Quintana]

It is DSR, the DSR is special because the packet has a header with all the nodes that the packet must cross
there is a dsr_srt file that contains all the functions used to process this header

---

From: cpe....@gmail.com

Subject: Re: [Omnetpp-l] Re: Set TTL for RREQ Packet

Date: Tue, 9 Feb 2016 13:03:23 +0300
To: omn...@googlegroups.com

[Shaikha Al-Khuder]

So I cannot do this in AODV ? It is only possible in DSR?

[Alfonso Ariza Quintana]

you can check also the ttl in aodv. Aodv also uses the ttl field to control the propagation of a packet.

---

From: cpe....@gmail.com
Subject: Re: [Omnetpp-l] Re: Set TTL for RREQ Packet

Date: Tue, 9 Feb 2016 13:16:35 +0300
To: omn...@googlegroups.com

[Shaikha Al-Khuder]

I did. It was useful for hopCount, thank you. But, now, I need to know where can I see the function that inspects the forwarded packets, so I can add the extra filtering step (maybe extra tag) to the forwarded message/packet.

I don’t want to use DSR...