- Recall:
- The DSR algorithm
assumes that:
- Wireless links are asymmetric !!!
- The DSR algorithm
assumes that:
- Starting scenario:
- The ROUTE REQUEST has been
received by the
destination node:
- The ROUTE REQUEST has been
received by the
destination node:
- Simple scenario:
- The destination node D has (know) a source route back to the source node S
Solution:
- The destination D will return the ROUTE REPLY message using source routing
Example:
- Suppose D has
a source route to
A
- Node D will
return the
ROUTE REPLY using
source routing:
- Starting scenario:
- The ROUTE REQUEST has been
received by the
destination node:
- The ROUTE REQUEST has been
received by the
destination node:
- Difficult scenario:
- The destination node D does not have any source route back to the source node S
Solution:
- The destination D will piggy-back the ROUTE REPLY inside a ROUTE REQUEST message
Example:
- Suppose D does
not have any
source route to
A
- Node D will
send the
source route
inside a
ROUTE REQUEST message:
- The ROUTE REQUEST will be
forwarded to
B and D:
- Then 2 ROUTE REQUESTs will
be
forwarded to
A:
- When A receives the
2 ROUTE REQUESTs
(containing the same source route):
Node A will cache the (same) source route to D:
And A will send a ROUTE REPLY back to D --- using source routing:
(Because the node A has a source route to D !!!!)
- Note:
- Node A's
ROUTE REPLY will arrive at
node D later.
- The ROUTE REPLY message will provide node D with a source route...
- Node A's
ROUTE REPLY will arrive at
node D later.