Re: Collision using Mac-802_3 and retransmission

[Ya Xu <yaxu@ISI.EDU>]

Paul,

the code you pointed out is only for collision for receiving packets. It
does not need retransmisson for the receiver. see send(p,h) for the
sender's behavior.

-Ya

On Tue, 24 Aug 1999, Paul Ghobril wrote:

> Hi,
> 
> While working with LAN on ns I have noticed that there is no
> retransmission after collision. I made some change to the code because I
> found that ETHER_ADDR(mh->mh_da) in mac-802_3.cc is always 0. The
> following change is made to Mac802_3::discard(Packet *p,const char*):
> 
>         // Added by PAUL
>         char* mha = (char*)p->access(hdr_mac::offset_);
>         int dst = this->hdr_dst(mha);
>         if (dst == index_)
>           {
>             //if (drop_ !=0) printf("do recv(p)");
>           drop(p);
>           }
>         else      
>           Packet::free(p);
>           
>         // End Added by PAUL
> 
> 
>           //Commented by PAUL
>           /*    
>                 hdr_mac802_3* mh = (hdr_mac802_3*)p->access(off_mac_);
>                 if((u_int32_t)ETHER_ADDR(mh->mh_da) ==
> (u_int32_t)index_)
>                 drop(p);
>                 else
>                 Packet::free(p);
>           */
>           //End Commented by PAUL
> 
> Is this right??
> 
> Now drop(p) is called when it is necessary but in the drop(p) drop_ is
> also 0. 
>         1- How to change drop_ with the ns script using drop-target?
>         2- Anyway drop doesn't retransmit. How to retransmit? and what
> drop stands for?
>         3- Can I forget about drop and redirect the packet whith a
> backoff and how?
> 
> Thanks.
>