The MSA devices run a limited set of MPLS features, whereas the MSE requires
a more complex feature set (including, for example, BGP). Per-flow QoS may either be
applied at the MSA, or at the MSE, depending on the feature sets of the two devices.
The benefits of using MPLS and pseudowires in this application are twofold:
?– MPLS provides rapid protection in the event of link or node failure.
?– Pseudowires provide adaptation of multiple services onto a common set of facilities.
Triple Play Aggregation
The first generation of DSL aggregation networks deployed by carriers were typically
based on ATM. This was dictated by the ATM uplinks available on early DSLAMs
(DSL Access Multiplexors). ATM switches were typically used to aggregate a number
of DSLAMs and then to feed traffic toward higher-layer ATM aggregation switches or
directly to ATM interfaces on Broadband Remote Access Servers (BRAS) devices.
A second generation of DSLAMs has emerged with Gigabit Ethernet uplinks and
with higher throughputs suitable for video services (these typically support ADSL2+
rather than the ASDL or ADSL2 of earlier DSLAMs and have high-speed backplanes).
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