Design and investigation of scalable multicast recursive protocols for wired and wireless ad hoc networks

smooth roaming process. To implement these messages in MoSReM, there are two
proposed ways as follows:

■ First, the old Local Multicast Router (oLMR) will treat this roaming out message
as an ordinary leave message and the new Local Multicast Router (nLMR) will
treat the roaming in message as an ordinary joining message. This is done by
sending a RqM message towards the upstream BNR, the BNR receiving this
message should be able to distinguish between the ordinary join/leave messages
and the join/leave messages because of roaming. This is done by adding a field as
a flag (R) to the RqM message, this field is set to 1 (R=1) if this message
regarding a roaming process and the message will not be forwarded to the source,
otherwise (R=0) regarding an ordinary joining/leaving messages. One of
advantages of using this way is: the control message traffic due to receivers’
roaming is greatly reduced because roaming messages never traverse within the
multicast tree. Another advantage is that these messages use similar format as
JoinM/LeavM with minor modification. However, the disadvantage of this way is
that a modification with respect to join/leave and registration messages is needed
for the compatibility between MoSReM and its original version SReM.

■ Second way by treating the roaming messages as a new type of messages. The
designated LMR just forwards the roaming message towards its up-level BNR.
Upon receiving these messages, the up-level BNR updates its MFT and decides if
it is still a BNR or not. If yes, this BNR will stop forwarding these messages and
there is no more impact on the remaining DBT. Otherwise, these messages will be
forwarded to the next up-level BNR, say Y, which start a DBT update process just
like join/leave process in SReM. Note that forwarding these messages will be
terminated at Y. The advantage of this way is that it is fully compatible with
SReM and there is no need to modify the join/leave and registration messages.
The disadvantage is that it requires a fully new message format to be used, might
quite different from JoinM/LeavM or RqM. Using new format messages will
cause more complexity in roaming process, esp., at the time when leaving and

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