Theory C_Gtobcast
theory %invisible C_Gtobcast
imports "../../Aodv_Basic"
begin
chapter "Variant C: From Groupcast to Broadcast"
text ‹
Explanation~\<^cite>‹‹\textsection 10.4› in "FehnkerEtAl:AWN:2013"›:
A node maintains a set of `precursor nodes' for each of its valid routes.
If the link to a route's next hop is lost, an error message is groupcast
to the associated precursor nodes. The idea is to reduce the number of
messages received and handled. However, precursor lists are incomplete.
They are updated only when a RREP message is sent. This can lead to packet
loss. A possible solution is to abandon precursors and to replace every
groupcast by a broadcast. At first glance this strategy seems to need more
bandwidth, but this is not the case. Sending error messages to a set of
precursors is implemented at the link layer by broadcasting the message
anyway; a node receiving such a message then checks the header to
determine whether it is one of the intended recipients. Instead of
analysing the header only, a node can just as well read the message and
decide whether the information contained in the message is of use. To be
more precise: an error message is useful for a node if the node has
established a route to one of the nodes listed in the message, and the
next hop to a listed node is the sender of the error message. In case a
node finds useful information inside the message, it should update its
routing table and distribute another error message.
›
end %invisible