Nokia 7705 - Page 46

QoS and QoS Policies
46
Quality of Service Guide
3HE 11014 AAAC TQZZA Edition: 01
3.1.8.3.2 VLAN Shapers for Aggregation Site
Another typical use of per-VLAN shapers at network egress is shown in Figure 7. The
figure shows a hub-and-spoke mobile backhaul network where EVCs leased from a
transport provider are groomed to a single port, typically a 10-Gigabit Ethernet or a
1-Gigabit Ethernet port, at the hand-off point at the hub site. Traffic from different cell
sites is handed off to the aggregation node over a single port, where each cell site is
uniquely identified by the VLAN assigned to it.
In the network egress direction of the aggregation node, per-VLAN shaping is
required to ensure traffic to different cell sites is shaped at the EVC rate. The EVC
for each cell site would typically have a different rate. Therefore, every VLAN feeding
into a particular EVC needs to be shaped at its own rate. For example, compare a
relatively small cell site (Cell Site-1) at 20 Mb/s rate with a relatively large cell site
(Cell Site-2) at 200 Mb/s rate. Without the granularity of per-VLAN shaping, shaping
only at the per-port level cannot ensure that an individual EVC does not exceed its
capacity.
Figure 7 VLAN Shapers in Aggregation Site Scenario
Cell Site-1
Aggregation Site
7705 SAR(version 2)
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Cell Site-2
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Cell Site-3
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Cell Site-N
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Ethernet port
(10 port 1GigE)
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