User's Manual

Version 3.03 SPEEDLAN 9000 Series Installation and Operation User Guide
4-6 Using the Configurator to Set Up Special Parameters for a Base Station
CPE router is allowed to transmit during each poll. Note that determining the
"single busy CPE" router is dynamic. And, as soon as other CPE routers
respond to a poll with queued data, the network is deemed to have multiple
busy CPE routers.
• Poll Timeout Interval (expressed in units of 10 milliseconds)
The base station waits for each CPE router to respond to each poll. If a
response never arrives, the base station must continue polling other CPE
routers (or the same router again). This parameter governs how much time the
base station is willing to wait for a response to a given CPE poll. Note that this
value is strictly a timeout value in the case of no CPE response, and is not the
amount of time between polls. The range is from 1-30. The default value is
20.
Click Apply after making changes.
Notes:
• The Max Frames Per Base/CPE parameters should be optimized for each
individual network topology, environment, and requirement set. For example,
in networks where high throughput is desired, higher values for maximum
frames per base/ CPE timeslot are often desirable. On the other hand, in a
network that needs to be optimized for low latency, these parameters can be
set to lower values.
• The network administrator must take several points into consideration when
setting the poll timeout interval. It should be set high enough to allow any CPE
router to send its queued data (with retries taken into account). For example, if
Maxi Frames Per CPE Timeslot=4 and the CPE retry limit = 6 for that CPE, in
the extreme case one could encounter the following: The CPE router transmits
7 (original frame + 6 retries) frames for each allowed frame per timeslot (4) =
28 frames. The time to do this depends on the signaling rate being used and
the length of each frame, which are network and application specific. The tim-
eout interval is reset after each successful received frame, but if (due to noise),
all frames where lost, you would need to wait the full 28 frame period before
moving on to the next CPE router. If you poll the next CPE router before the
previous CPE router is finished transmitting, collisions (and more loss) will
result.
• It is not necessary to reboot the system after changing these
parameters because these changes immediately become active.