User Manual
Product information and planning
9500 MPR Rel. 3.1
3DB18809AAAA Issue 1 185/980
Table 31. 802.1p mapping
[4] Packet Dropper
The packets marked with yellow are discarded in case of congestion, when the buffer in the Modem
unit exceed a specific threshold.
Dropping mechanism:
• if a configurable queue fill level is overcame, then ATM PW packets that have been marked by
ASAP as out of profile (within 802.1p bits) are discarded.
The dropping mechanism applyies to queues with guaranteed Traffic:
• It applies to queue 7 and 6.
• To avoid delay on queue 7, shared among TDM2ETH, ATM CBR, the fill level to start descarding
is configured according to max acceptable delay (about 1 ms).
[5] Shared Tx queues
The packet according to its service category is send to one of the output queues.
[6] Rx Queues
Flows of the same type are reassembled in different queues.
[7] Packet to cells
The ATM cells are extracted from the PWE3 packet.
[8] ATM Egress Shaping
• A four-queue scheduling is used for for ATM traffic egressing MPR system.
• The higher priority queues are reserved for ATM shaped traffic, while the lowest one is reserved
to not shaped traffic.
• Cell-based ATM Shaping is applied for a VP/VC that has been configured with CBR and VBR
Service Category on the basis of its configured egress ATM Traffic Descriptor, general refer
-
ence for this feature is ATM standards.
• A Weighted Round Robin is instead applied for all VPs/VCs that are not shaped. The weights
are based on the value of configured MDCR in the egress ATM Traffic Descriptor value accord
-
ing to below table:
802.1p bits Usage Color
000 Best Effort, Out-of-Profile YELLOW
001 unused -
010 Expedited, Out-of-Profile YELLOW
011 unused -
100 Best Effort, In-Profile GREEN
101 unused -
110 Expedited, In-Profile GREEN
111 Contro - egress only -
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