Tuesday, June 28, 2005


DNS - IP address - Produces IOR
Since there is no MG, hence at time of birth there is no need to produce IOR.
MH produces original IOR and ukey or Hash and distributes to all neighbour MHs to make an entry in their tables.
On movement Birth MH might not be connected to the old set of MH and might be connected to the new set of MH.
Birth MH notifies new set of MH not the old set of MH.
How old set of MH would be notified about the IOR getting dirty?
On movement of MH, devices which are immediate neighbour would get notified about device demise.
Request can be received from MH or FC.
In CORBA, a request can only be launched if a client has IOR.
1. An IOR can be distributed to the connected consumes(FC or MH).
2. A request of search can be issued by consumer (FH or MH) to connected MH by giving some search attributes, so that the receiving MH can do:
2a. Forwards the request attributes to it's connected MH if can't be answered.
2b. Replies back to the client with the modified or swapped IOR.

In approach 1, as IOR gets dirty it becomes difficult to trace. There would a heavy overhead of the distribution of the new IOR, I think this would need to be distributed to almost all.
In appraoch 2, a search request would be forwarded and it need to return the latest IOR or IOR information.
In appraoch 2, a category of identifying parameter needs to be passed by the servant to the birth MH and then by birth MH to connected MH, so that searching of the servant based on attributes can be done.

On movement the search attribute related entry in registers of neighbour MH is modified, so that the latest entry remains.

Monday, June 27, 2005

AODV (Ad Hoc On Demand Distance Vector)

combination of DSR and DSDV.
Route discovery and maintainatance from DSR.
Hop-by-hop, sequence number and periodic updates from DSDV.
Rreq packets contains last known sequence number for destination.
When a node recives a Rreq for a destination it has a route to, it generates a Rrep with the updated sequence number and number of hops.
Each node that forwards the reply back to the originator creates a forward path to the destination.

Wednesday, June 22, 2005

DSR (Dynamic Source Routing)

1. Source routing (full routing information)
2. On demand routing updates
3. Route Discovery and Maintainance
4. Bidirectional routing information updates by reversing the route request path.
5. Source initiates the Rreq (having Vs,Vd,Lsd).
6. Destination receives Rreq (may be more than one over the period of time), then sends a Rrep (a reverse mesaage) from the path which has shortest Lsd listing.
7. Intermediate nodes (Vi-Vj) also communicates bidirectionally to update their information. If fails then, Vi informs the Vj about Rerr and Vs initiates a new Rreq with a different route.

About DSDV (Destination Sequences Distance Vector)

Each node maintains a set of distance or cost vectors for each possible destination.
Each node periodically broadcasts its routing table to all neighbours.
The routing is hop by hop.
Predicated table structure tuple can be like this:

{Destination Mobile Node Identifier,Sequence Number, Next Neighbour hop information in direction of deestination}

Routes have sequence number.
Routes with higher sequence number are more favorable.

1. Periodic updates should be send and received from whom ?
Each node periodically broadcasts its routing table to all neighbours.

2. Route decisiveness based on what matric ? weight or latest or other factor ?Latest is a must as the use of sequence number shows.

Advantage Factors:
1. Guarantees loop-free routes.
2. Simple logic. (Should not be considered as adv. point)

Disadvantage Factors:
1. Hop by hop routing instead of Source routing.
2. Periodical updates.
3. Heavy overhead of exchange of routing information between neighbours.