Question

Discuss the benefits of MPLS LSP (multiprotocol label switching label switched path) to support high availability of service with illustration of use for Push, Swap and Pop.

Answer 1

Multiprotocol Label Switching (MPLS)

Multiprotocol Label Switching (MPLS) is a protocol-agnostic routing technique designed to speed up and shape traffic flows across enterprise wide area and service provider networks

Service providers and enterprises can use MPLS to implement QoS by defining LSPs that can meet specific service-level agreements (SLAs) on traffic latency, jitter, packet loss and downtime. For example, a network might have three service levels that prioritize different types of traffic -- e.g., one level for voice, one level for time-sensitive traffic and one level for best effort traffic.

Other benefits of MPLS include the following:

• It's good for real-time applications that can't tolerate latency, such as video, voice and mission-critical data.
• Data and voice apps can all be run on the same MPLS network.
• Different types of data can be preprogrammed with different priorities and classes of service.
• Organizations can assign different percentages of their bandwidth to various types of data.
• MPLS networks are scalable. Companies only have to provision and pay for the bandwidth they need until their requirements change.

How an MPLS network works

In an MPLS network, each packet gets labeled on entry into the service provider's network by the ingress router, also known as the label edge router (LER). This is also the router that decides the LSP the packet will take until it reaches its destination address.

All the subsequent label-switching routers (LSRs) perform packet forwarding based only on those MPLS labels -- they never look as far as the IP header. Finally, the egress router removes the labels and forwards the original IP packet toward its final destination.

When an LSR receives a packet, it performs one or more of the following actions:

• Push: Adds a label. This is typically performed by the ingress router.
• Swap: Replaces a label. This is usually performed by LSRs between the ingress and egress routers.
• Pop: Removes a label. This is most often done by the egress router.