9.4 Multiprotocol Label Switching (MPLS)
Multiprotocol Label Switching (MPLS) functions similarly to IP, but the infrastructure switches based on a predetermined path instead of calculating paths hop-to-hop. MPLS can also operate on a variety of Layer 2 infrastructures.
For an MPLS or IP interconnect between data centers, the design changes from the fiber model. Because the interconnect between the data centers is a Layer 2.5 or Layer 3 link, Layer 2 connectivity is not available beyond the data center boundary. However, because long distance vSphere vMotion is a design goal for the sample use case, to perform the same actions as a fiber link, with cross-site Layer 2 adjacency (routed over a Layer 3 network) when using an IP-based WAN, a tunnel must be established between the two sites and the Ethernet data encapsulated within that tunnel structure.
Figure 7. Multiprotocol Label Switching (MPLS)
In summary, MPLS has the following key design considerations:
• Layer 2.5 protocol
• Used over short or long distances
• Used when dark fibre is not available
• Links might be shared
• Operates over a variety of Layer 2 infrastructures
• Switches based on label
• Uses predefined paths, reducing delays from dynamically calculated paths
• MPLS performance (which affects delay, jitter, failover, and so on) is dependant of Service Provider SLAs
