Re: [ns] Addressing structure

[Felix Ko <felix.ko@mchp.siemens.de>]

Hi!

You have written, that packet headers ARE NOT simulated in ns2.

Is this also true for wireless simulations?
After careful examination of the sourcecode, it seems to me that
the transmission of packet headers ARE simulated when simulating
wireless networks!

Please tell me, if the observations below are correct!

1) Whoever creates a packet (CBR-sources or routing-agents like AODV)
or adds a header to a packet (like MAC-802.11) sets or adjusts the
size-field of the common-header to reflect the actual size of the packet
(i.e. payload and used headers)

2) when the first bit of a packet is received by the MAC-Layer, it
calculates the timeout for the the receive-timer by dividing the size-field
of the common-header by the bandwidth. When this receive-timeout
occurs, the complete packet has been received.

Doesn't this mean, that packet headers ARE simulated???

Please tell me, if this is correct!

Bye

Felix



>
> We don't have an 'overhead' struct that keeps count of all the structs
> used and the space they'd take up. Things like one-way TCP - where
> headers are neglected entirely and packetSize_ equates to segment
> size, which is more-or-less fine for large serial packets, but... show
> this deficiency quite well.
>
> header overhead computation is basically at the mercy of whatever
> decides to tweak the payload size field to add some header overhead.
> If they don't bother, header overhead isn't included.
>
> Considering such overheads wasn't in ns's original design goals. Now
> ns is being used in simulation of multiple layers (especially in
> wireless), it's becoming more important.