615 PAPER 19 CEDAR: a Core-Extraction Distributed Ad hoc Routing algorithm

The paper has as a goal to design and present a QoS routing algorithm for 
ad hoc networks. But, I believe, it falls far short of its goals: the 
design seems lacking, the presentation poor, and the "ad hoc network" part 
appears to be an afterthought. On the bright side, I do see some 
contributions. Among them:
- Traditional broadcast is replaced with unicast along a tree structure. 
Unicast is an order of magnitude more reliable than broadcast in mobile 
networks, so it is probably the case that their approach is not only more 
efficient and perhaps faster, but more reliable as well.
- Routing updates are classified as either "increases" or "decreases". Each 
type of message is flooded (using the multicast tree) to the netowork at a 
different rate, so that "decrease" messages can overtake prior "increase" 
messages.
- An attempt is made to spread routing information a distance proportional 
to the usefulness of the information: better links are advertised further.

Aside from the numerous and typical complaints ("updations" is not really a 
word, poor evaluation, less than thorough simulation, etc.) are some 
serious ones:
- They appear to use a reservation system, but this is not presented or 
even mentioned.
- The simulation is poorly presented, and as it stands seems downright 
bizarre. Why is average node degree always a whole number? Why no mobility 
in the evaluation? Is there a reason for using a square transmission range? 
And is there really no transmission model, congestion, or collisions, or 
was that just left unmentioned?
- The results, presented in table format, are meaningless to me (perhaps I 
did not invest the time to understand them properly, though).
- As in another paper, the authors attempt to redefine "minimum" to be 
"what we implemented", when in fact they present no compelling reasons or 
evidence that their routes will be even close to minimal in realistic 
settings. Also, a "shortest path" is not defined as the path taken by the 
fastest message delivery.
- In my view, the most glaring and problematic assumption is buried in 
section V, subsection B: "The bandwidth that can be provided on a path is 
the minimum of the individual available link bandwidths on the path." In a 
shared medium, is this really the case? In a path A-B-C where both links 
are 10mbit, the A-C path will have only 5mbit available, since B must 
transmit each message twice. Worse, assuming bidirectional flow, it might 
have as little as 2.5mbit in each direction.

