The letters mpls are short for Multiprotocol Label Switching, an
IETF initiative that integrates Layer 2 information about network
links within an ISP. The purpose of this is to simplify and improve
IP-packet exchange.
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Tutorials and more information on Multiprotocol label switching
or often known as MPLS can be found online on networking website or
PDF files based on networking. Also, the Cisco website has a
detailed tutorial for MPLS.