Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - QUALITY OF SERVICE CONFIGURATION GUIDE 2010-09-22 Configuration Manual page 329

Copyright © 2010, Juniper Networks, Inc.
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:
host1#show qos queue-thresholds egress-slot 9 region 7
region 7 (28MB - 32MB) oversubscription 80%
exceeded
queue-profile length
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
conformed committed queue
length length count
total
committed
memory
---------
279296000
279296000
279296000
279296000
total
committed
memory
---------
8448000
8448000
8448000
8448000
total
committed
memory
299