Changes between Version 20 and Version 21 of Internal/RunningDemos


Ignore:
Timestamp:
Dec 23, 2005, 6:28:33 PM (19 years ago)
Author:
kishore
Comment:

—

Legend:

Unmodified
Added
Removed
Modified

  • Internal/RunningDemos

    v20 v21  
    77
    88== Conference room demo ==
     9
     10=== Revision History ===
     11
     12|| Version || Date || Revised by || Changes
     13|| v0.1 || 2005-12-23 || Kishore Ramachandran || Initial version
    914
    1015=== Objective ===
    … …  
    3439On the display machine, point your Internet Explorer or Mozilla Firefox browser to http://sb9.orbit-lab.org. What you expect to see is a page with three frames - one showing the topology of the smaller grid, one showing a control interface to change the packet size and offered load and the third with a link to plot the cumulative throughput at the access point (AP).
    3540
    36 The frame showing the topology should initially display 64 yellow boxes representing the nodes on the grid. Once the nodes in the experiment turn ON, the corresponding yellow boxes will turn green. Once the sending and receiving applications start, the senders will turn blue and the receiver will turn red.
    37  
     41The frame showing the topology should initially display 64 yellow boxes representing the nodes on the grid. Once the nodes in the experiment turn ON, the corresponding yellow boxes will turn green. Once the sending and receiving applications start, the senders will turn blue and the receiver will turn red. 
     42
    3843Click the link for the cumulative throughput in the third frame -- the expected behavior for the curve is that initially, the throughput will rise as senders are added but beyond a certain number of senders, throughput will fall drastically. The explanation for this drop is that
     44
    3945a. the current implementation of CSMA/CA fails to prevent losses from occurring in a congested environment
     46
    4047b. the 802.11 bit-rate adaptation algorithm, which believes CSMA/CA to be perfect, infers these losses to be due to poor channel (SNR) conditions and drops the bit-rate accordingly. This in turn makes the situation worse given that the same frame will now take a much longer time on the medium -- all senders will drop their rate to 6Mbps and the cumulative throughput will reflect this (it should be equal to the saturation throughput at 6Mbps).
    4148