[OLSR-users] Maximum message size

Andreas T√łnnesen (spam-protected)
Tue Jul 27 10:57:33 CEST 2004


Hi,

The OLSR packet buffer is of 512 bytes - so if you do not want to
change code in olsrd(or provide your own packet buffer and emission functions)
you should never create messages bigger than (512 bytes - sizeof(OLSR 
packet header)) which equals to 508 bytes.

To avoid fragmentation of packets you must know the MTU in the
network. As far as I can remember a typical MTU on Ethernet links is
1500 bytes - on 802.11 this is suposed to be bigger, but RFC3580
states that some 802.11 stations cannot handle frames larger than 1500
bytes. Please correct me if I'm wrong on this.

Anyways - you can get away with sending OLSR messages of 508 bytes if
you desperatly need to :)

- Andreas


On Mon, 26 Jul 2004, Toan Hoang wrote:

> 
> Thank you for the reply...
> 
> I need to send alot of data (alot = more then 32Kb)...
> In OLSR-plugin, I can see a place where I can set the size of the my own
> packets to what ever I want(I think, the default is 512 though)....
> 
> What I wonder is if I set my own packets to, let's say, 4096 bytes... will
> OLSR fragment it before it sends? I could also try to change the OLSR
> packet size to 1024 (or more) and then use that as my own packet size...
> 
> Another solution is to set my packets to OLSR max size (512), but then it
> will give ALOT of traffic... (64 packets flooding the whole net) :-(
> 
> Do anybody have any clue how to best solve my problem?
> 
> Toan
> 
> 
> 
> Matteo Martincigh said:
> > The maximum size of an OLSR packet (not message!) is 512 bytes
> >
> > ----- Original Message -----
> > From: "Toan Hoang" <(spam-protected)>
> > To: <(spam-protected)>
> > Sent: Monday, July 26, 2004 11:50 AM
> > Subject: [OLSR-users] Maximum message size
> >
> >
> >> Hi all!
> >>
> >> I just wonder if anybody knew how big an OLSR message can be, I'm
> trying to send alot of data, and want to avoid fragmantation...
> >>
> >> Toan
> >>
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-- 
Andreas T√łnnesen((spam-protected))
UniK University Graduation Center
University of Oslo
http://www.olsr.org



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