Since the MPLS PEs are typically deployed in the core PoPs for each metro,
they can be easily connected to inter-city transport facilities, enabling the carrier to
link different city networks together. Likewise, the core PoPs are generally also concentration
points for metro TDM networks, making these good locations for bringing
Ethernet traffic groomed over the TDM network onto the MPLS network. Finally, the
MPLS PE devices generally support fine-grained QoS, which may be used to provide
differentiated service offerings and give carriers the option of connecting customers directly
to the PE device where the highest levels of QoS and availability are required.
Business Ethernet Services
In the few years immediately preceding the bursting of the dot-com bubble in 2001,
several startups in the U.S. and in Europe obtained funding to build Metro Ethernet
networks to offer business services. While some initially deployed enterprise-class
Ethernet switches, others deployed MPLS-enabled Ethernet switches and offered
service using Ethernet pseudowires. The service providers that deployed MPLS were
generally able to offer better SLAs than those that relied on Layer 2 switching and
were also able to make better use of leased facilities??”since MPLS enables use of all
available paths in contrast to spanning tree, which turns links off to break loops, and
gives operators the flexibility to traffic engineer their networks, placing specific traffic
demands on specific paths.
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