[ns] MAC layer ?

[Luigi Iannone]

>
> Message: 1
> Date: Mon, 12 Jan 2004 09:35:53 -0800 (PST)
> From: Rohan S <syphy8@yahoo.com>
> To: ns-users@ISI.EDU
> Subject: [ns] MAC layer ?
>
> HI, I had a post earlier but wasn't clear. So here I
> go again. Sorry about that!
>
> I have run some simulations for the MAC layer protocol
> with the following topology. I have one multicast
> sender and 8 multicast receivers, also I have a 8
> unicast sender/receiver pair. The unicast receivers
> are in the range of the the multlicast sender. As the
> multicast sender is in the range of the unicast rx'r,
> it will not transmit as it senses the CTS. NOdes are
> stationary. Multicast sender and unicast sender are
> not in each other's range.
>
> Problem: I ran a couple of simulations and am getting
> a very minimal packet loss for the unicast session.
> After the RTS/CTS, the unicast sender transmits and
> the packet is being dropped at the MAC layer.
> I tried varying the buffer size, 5 <= ifqlen <=30000,
> but I get the same result.
> Would anyone know why this may be happening as there
> shouldnt be any packet loss?
>
> Here is a trace for packet id 1499 being sent from
> 21->22.
>
> s 144.533399808 _21_ MAC  --- 0 RTS 44 [426 16 15 0]
> r 144.533571530 _10_ MAC  --- 33602 cbr 1 [13a a 9
> 800] ------- [9:0 10:0 64 0] [1510] 1 0
> s 144.533581530 _10_ MAC  --- 0 ACK 38 [0 9 0 0]
> r 144.533751855 _22_ MAC  --- 0 RTS 44 [426 16 15 0]
> s 144.533761855 _22_ MAC  --- 0 CTS 38 [2ec 15 0 0]
> r 144.533885577 _9_ MAC  --- 0 ACK 38 [0 9 0 0]
> r 144.534065902 _21_ MAC  --- 0 CTS 38 [2ec 15 0 0]
> s 144.534075902 _21_ MAC  --- 33601 cbr 53 [13a 16 15
> 800] ------- [21:0 22:0 64 0] [1499] 0 0
> s 144.534499901 _0_ MAC  --- 33600 cbr 552 [0 ffffffff
> 0 800] ------- [0:0 -1:0 64 0] [21872] 0 0
> D 144.534499947 _22_ MAC  --- 33601 cbr 53 [13a 16 15
> 800] ------- [21:0 22:0 64 0] [1499] 0 0

I would investigate why node 0 starts a broadcast before packet 1499 has
been received. From your topology description node 22(unicast receiver) is
in the transmission range of node 0 (multicast transmiter).
May be I'm worg but that's my feeling.
ciao
                                     Luigi


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