The scope of this and forthcoming articles on IP Communications and MPLS will encompass various technologies and applications like: Multiprotocol Label Switching (MPLS), Quality of Service (QoS), Border Gateway Protocol (BGP), MPLS VPN, Traffic Engieering, and MPLS AToM (Any Transport over MPLS).
In all its mystery Multi-Protocol Label Switching was designed to be a data carrying mechanism. That is, MPLS can transport Ethernet, ATM, SONET, Frame Relay, PPP, among other protocols through an IP network. As the years have passed since its formal chartering as an IETF group in 1997, MPLS has evolved in to so much more than what it was intended to be. Many useful applications of MPLS have evolved. Some of the most popular applications are MPLS Virtual Private Networks, MPLS Traffic Engineering, and MPLS Any Transport over MPLS (AToM).
Essentially, MPLS creates a unique layer 2 (data link layer) identifier for layer 3 (network layer) network information. MPLS places this identifier (a “label”) in a packet that allows it to be forwarded at the Layer 2 level in layer 3 switches or routers. It does this by use of a Shim header. This is why MPLS is often referred to as switching at layer 2.5. The “network information” mentioned are often referred to as a prefixes, nothing more than the IP networks that connect to and from the MPLS switch or router.
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