An Investigation into Transport Protocols and Data Transport ...

9.2. Preferential Flow Handling Using DiffServ 218
give an indication of the bandwidth utilisation of the BE and AF classes.
Test Set-up
The experiments were performed on the DataTAG testbed (See Appendix C.3)
and DiffServ was enabled on the Juniper M10. This testbed is unique in
providing a DiffServ network with high propagation delay with Gigabit per
second bandwidth capacity.
The testbed PCs of DataTAG as shown in Table B.2 are used and results
are obtained for a TCP connections with congestion moderation turned on
- i.e. the code of moderate_cwnd() are left as per the Linux defaults. The
experiments were conducted by continuously running a 1Gb/sec UDP BE
flow running and by switching on and off different New-TCP algorithms for
different bandwidth allocation tuples.
The UDP flow was injected into the network using iperf and was set
to inject packets into the network at line rate, i.e. 1Gb/sec. As such, and
because the background BE UDP traffic does not back off in the event of
congestion, the BE class is always oversubscribed. Therefore, whenever AF
under utilises its allocated bandwidth, (i.e. QEF AF < 1) the BE throughput
should show a proportional gain (BE > 100%).
Calibration
The bandwidth scheduling and DiffServ systems of the Juniper router were
initially tested with UDP CBR in both the AF and BE classes in order ensure
correct calibration of the system. Figure 9.19 shows the achieved bandwidth
allocations of the BE and AF flows as the router configuration was changed
on-the-fly between the bandwidth allocations of 90:10, 70:30, 50:50, 30:70