DLSw Tuning 539
Initial window sizes are set during connection establishment and usually do not change during
the transfer of data.
NOTE
If the window size changes to 0, this means the sender should stop sending data.
Explorer Queue Depth
The explorer queue depth is important because it allows explorers to be handled on a queue
separate from real data. Explorers are used to find resources in DLSw+ and on LANs. This
helps reduce broadcast storms with Token Ring environments. The problems are that when
there is an excessive amount of broadcast traffic, the explorers arrive at a rate faster than
DLSw+ can process them.
Using the explorer queue depth in DLSw+ configuration helps control this activity. It also does
the following:
·
Sets up a queue specific to explorer traffic. This is where you configure limits on explorer
traffic.
·
Minimizes the risk of broadcast storms.
·
Dropping explorer packets is better than dropping user data. Another advantage is that
CPU utilization is minimized.
Idle Time
You should implement a larger LLC2 idle timer value when there is a large number of LLC2
sessions. Increasing the LLC2 idle time when supporting a large number (thousands) of
sessions significantly decreases router CPU utilization.
Router Startup
The input hold queue can be used to hold off input frames from LAN interfaces (Token, Ethernet)
that are waiting to be placed in a system buffer. Protocols such as DLSw+ that are traffic-intensive
at startup might require that the input hold queue be increased. Increasing this timer lets the router
buy some time, so to speak, and allocate system buffers in a more favorable manner.
Typically, APPN would fall into this type of category. Many small packets are involved with
APPN startup, and it is not uncommon to see a buildup in the input hold queue.
NOTE
If there are many constant drops in the input hold queue, increasing the input hold queue will
not make much difference. There might be a problem in the network, however.
87200333.book Page 539 Wednesday, August 22, 2001 1:41 PM