Re: [ns] RTS/CTS Handshaking in 802.11

[Vikram Kanodia <kanodia@ece.rice.edu>]

***from mac-802_11.cc

static MAC_MIB MMIB =
{
	0 /* MAC_RTSThreshold */, MAC_ShortRetryLimit,
	MAC_LongRetryLimit, MAC_FragmentationThreshold,
	MAC_MaxTransmitMSDULifetime, MAC_MaxReceiveLifetime,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};


as can be seens rts threshold is set to 0...that is its never used...set
it to a value that you need for your experiments and recompile...

-Vikram


> Hi,
> 
> If you look inside the function Mac802_11::sendRTS(int dst) you will see
> the following lines of code:
> 
>   if( (u_int32_t) HDR_CMN(pktTx_)->size() < macmib_->RTSThreshold ||
>       (u_int32_t) dst == MAC_BROADCAST) {
>     Packet::free(p);
>     //p = 0;
>     return;
>   }
> 
> Meaning that is the size of the packet to be sent is less than the
> RTSThreshold (or if the destination is broadcast), RTS/CTS should not be
> used, so the packet is deallocated, and the function returns without doing
> anything else. 
> It does however sound strange that it doesn't affect the performance in
> your simulations (low load could lead to no change in throughput, but as
> you say the delay should be higher...). What metrics are you looking at,
> and how do you measure them?
> 
> /Anders
> 
> On Wed, 31 Jan 2001, Al-kahtani wrote:
> 
> > Hi Everyone, In IEEE802.11, I tried to change RTSThresholed value
> > (mac-802_11.h) to see RTS/CTS handshaking effect on the performance.
> > My packet size was 512 bytes and the RTSThresholed default value was
> > 3000. When I change it to 300, nothing has changed in the performance
> > and as u already know it will affect at least the delay of the packet.
> > When I go through mac-502_11.cc source code I found RTS/CTS is used
> > regardless the RTSThresholed, eventhough this idea is mentioned in the
> > comment .  Am I right?. Have anyone checked that before?
> > 
> > 
> > Regards,
> > Mohammed Al-kahtani
> > 
> > 
> 
> 


Department of ECE, Rice University | 713 348 3786 (O)| 713 664 5650(H)
http://www.ece.rice.edu/~kanodia