Juniper JUNOSE 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010 Configuration Manual page 349

fills beyond the last region, all frames are dropped except control traffic, until the
queues are drained and memory usage falls back into one of the regions.
To display the router's memory management:
host1#show qos queue-thresholds egress-slot 9 region 0
region 0 (0MB - 4MB) oversubscription 3330%
exceeded
queue-profile length
------------- --------
default 34944
video 34944
multicast 34944
internet 34944
Static and dynamic oversubscription determines that when 8000 queues are
configured and 0–4 MB of egress buffer memory is in use, memory is oversubscribed
by 3330 percent. If significantly fewer queues are configured, there is less
oversubscription. This example illustrates static oversubscription.
Because all of the queues in Example 2 use default queue profiles, all queues have
the same lengths. Each queue is allocated 139,648 bytes of committed buffer memory
when operating within this region. This allocation allows active queues to burst traffic
by using memory that is unused by quiescent queues. This example illustrates
dynamic oversubscription, which is based on the assumption that when a large
number of queues is configured, only a fraction of the queues is active at a given
time. While more queues become active, memory fills and spills into another region.
When this occurs, queues are given progressively smaller queue limits.
In memory regions 1 through 5, queue limits are progressively reduced. In region 6,
memory is strictly partitioned among queues.
To display oversubscription in region 6:
host1#show qos queue-thresholds egress-slot 9 region 6
region 6 (24MB - 28MB) oversubscription 100%
exceeded
queue-profile length
------------- --------
default 1152
video 1152
multicast 1152
internet 1152
Oversubscription is 100 percent. When 24–28 MB of the memory is in use, there is
no oversubscription of egress buffer memory; 32 MB of the 32-MB memory is
allocated. In Example 3, each of the 8000 egress queues is given a queue of 4224
bytes, for a total of 16 MB.
If memory continues to fill into region 7, egress buffer memory is undersubscribed,
allowing control traffic to flow within the router. As shown in Example 4, when
operating in region 7, only 80 percent of the 32-MB memory is allocated.
To display oversubscription in region 7:
Chapter 31: Monitoring QoS on E Series Routers
conformed committed queue
length length count
--------- --------- -----
69888 139648 2000
69888 139648 2000
69888 139648 2000
69888 139648 2000
conformed committed queue
length length count
--------- --------- -----
2176 4224 2000
2176 4224 2000
2176 4224 2000
2176 4224 2000
Monitoring Queue Thresholds
total
committed
memory
---------
279296000
279296000
279296000
279296000
total
committed
memory
---------
8448000
8448000
8448000
8448000
317