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Total Access 1240 Installation and Maintenance Practice
2-4 61179605L5-5B
• Network – Egress
– Every packet is forwarded.
• Subscriber - Egress
– The VLAN tag is removed.
– The packet is forwarded to the VC corresponding to the original VLAN Tag.
A diagram depicting the Total Access 1240 Ingress/Egress points is provided in Figure 2-2.
Figure 2-2. Total Access 1240 Ingress and Egress Points
TRAFFIC PRIORITIZATION
The Total Access 1240 supports four traffic priority classifications per VLAN:
•High = CBR
•MidH = VBRrt
• MidL = VBR
•Low = UBR
There are no rate settings for the CBR, VBRrt, and VBR configurations, therefore, these ATM
COS priorities have been redefined, in descending order of priority, as follows:
1. High
2. MidH
3. MidL
4. Low
Traffic prioritization applies to the data that is forwarded to the egress of the subscriber ports.
Any packets that cannot be serviced due to bandwidth limitations are discarded.
In the upstream path (subscriber to network), the Total Access 1240 can optionally set the
VLAN User Priority Bits from 0-7 for untagged traffic causing the data to be tagged with a
VLAN ID and Priority Bits.
Ingress
Egress
Network
Ingress
Egress
Subscriber
Total Access 1240