[OLSR-users] WLAN and Broadcasts (e.g. OLSR)

Joerg Pommnitz (spam-protected)
Tue Apr 25 10:46:03 CEST 2006

Hello all,
I have stumbled accross a problem with olsrd. It seems that HELLO-Messages are only visible over a very short distance. Other protocols (ICMP-Echo, ssh, iperf) work fine, however. The difference is, that these protocols are unicast while olsr HELLO-messages are sent to the broadcast address of the subnet. I have verified that a broadcast ping has the same problems, so its not really OLSR-specific.

This got me thinking. My understanding is, that 802.11 modifies the over-the-air coding of the data packets according to the error rate when talking to the peer. It trades bandwidth for reliability when the error rate goes up. However, this is a point-to-point concept. In AdHoc-Mode where you talk to all the nodes in a cell, this is not applicable. My suspiction is, that the 802.11 card sends the broadcast packets in whatever coding is the default for the current mode which might not be optimal for nodes that are further away. Has anybody seen something like this? Am I on the right track? Is there a solution? Something I could try?
--  Thanks in advance

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