Summary; Figure 6: Quadrant Comparison - Juniper M10i Application Note

APPLICATION NOTE - Demystifying H-VPLS
If you analyze, under this framework, the different technologies a service provider can select to operate an Ethernet
network, you come to the following conclusions:
1. Although plain VLAN with STP has the least operational complexity among all of the technologies and is very
efficient in its use of network resources, the lack of reliability of its control plane clearly makes it non-carrier
class, not to mention its scalability limitations, which are not reflected in this diagram.
2. There are a set of trade-offs that play across all of the LDP VPLS/H-VPLS solutions. VPLS provided some
additional complexity and much more reliability for a service provider, but at the expense of losing network
efficiency. H-VPLS brings some more network efficiency than full mesh VPLS, but because it creates single
points of failure, it reduces its reliability while it increases its complexity. H-VPLS, combined with Spanning Tree
Protocol, brings a higher level of network efficiency, but at the expense of substantially increased operational
complexity and reduced reliability, as it introduces STP again into the equation. Therefore, there is a set of trade-
offs that does not allow this technology to enter into the Carrier-Class Quadrant.
3. The only way to break through this barrier is by working with the real driver of network efficiency, which is the
point-to-multipoint LSPs. BGP-based VPLS with point-to-multipoint LSPs is the only technology that offers
the service provider the highest network efficiency while at the same time maintaining network reliability. This
technology also decreases the operational complexity of LDP VPLS by adding autodiscovery on the network,
which allows not only the members of the VPLS instances to know each other, but also allows the automatic
establishment of the point-to-multipoint LSPs without additional provisioning overhead. You could also add to
this analysis the additional operational synergies that BGP-based VPLS offers as most service providers will also
be offering BGP-based IP-VPNs.

Summary

H-VPLS tries to address some of the scalability problems that have been described about VPLS. We believe that
there are better ways to address them than those defined by LDP-based H-VPLS.
Specifically, if we think about efficiently addressing multicast traffic in a reliable way, we are convinced that H-VPLS
does not offer the solution required by service providers.
We believe that H-VPLS is a small step, and not necessarily in the right direction, towards what we would call
scalable VPLS service: S-VPLS, which is the real goal for service providers. If we need to find a technology that can
really get service providers closer to S-VPLS, then that would be BGP-based VPLS with point-to-multipoint LSPs.
8
Highest
Vlans/QinQ + xSTP
Network
Efficiency
Lowest
Lowest
Operational complexity
CARRIER CLASS QUADRANT
LDP H-VPLS + xSTP
LDP H-VPLS
Reliability

Figure 6: Quadrant comparison

BGP VPLS +
P2MP LSP
LDP VPLS
Highest
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