ZyXEL Communications IES-708-22A - Manual (Page 122)

Chapter 14 xDSL Profiles Setup
IES-708-22A User’s Guide
122
Figure 53 TAT, CDVT and BT in Traffic Shaping
14.6 Upstream Policing
Upstream policing is an agreement between the carrier and the subscriber to regulate the
average rate and fluctuations of data transmission coming from the subscriber's device to the
IES-708-22A.
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Upstream policing controls incoming (upstream) traffic, not outgoing
(downstream).
The ATM traffic classes and parameters are identical with downstream shaping.
Upstream policing can control the upstream incoming traffic rate on specific PVCs. Upstream
ATM cell traffic that violates the policing profile will be discarded. Traffic shaping must also
be enabled on the subscriber's device in order to use upstream policing. If a subscriber
attempts to enlarge his device's PVC shaping parameters in order to get more upstream traffic
bandwidth, it will violate the IES-708-22A's upstream policing profile and the traffic will be
discarded. Operators can use this feature to prevent subscribers from changing their device
settings.
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Traffic shaping must also be enabled on the subscriber's device in order to use
upstream policing.
Note that since the IES-708-22A uses ATM QoS, if the subscriber device's upstream shaping
rate is larger than the IES-708-22A's upstream policing rate, some ATM cells will be
discarded. In the worst case, none of the Ethernet packets from the CPE will be able to be
reassembled from AAL5, so no packets from the subscriber's device can be received by the
IES-708-22A.
The upstream policing feature can be enabled/disabled per PVC. No matter which ATM traffic
class is used for the PVC's upstream traffic (CBR, VBR, or UBR), the IES-708-22A will drop
any upstream traffic that violates the specified ATM VC profile.