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History of MPLS
MPLS was originally proposed by a group of engineers from Ipsilon Networks, but their "IP Switching" technology, which was defined only to work over ATM, did not achieve market dominance. Cisco Systems, Inc., introduced a related proposal, not restricted to ATM transmission, called "Tag Switching". It was a Cisco proprietary proposal, and was renamed "Label Switching". It washanded over to the IETF for open standardization. The IETF work involved proposals from other vendors, and development of a consensus protocol that combined features from several vendors' work.One original motivation was to allow the creation of simple high-speed switches, since for a significant length of time it was impossible to forward IP packets entirely in hardware. However, advances in VLSIhave made such devices possible. Therefore the advantages of MPLS primarily revolve around the ability to support multiple service models and perform traffic management. MPLS also offers a robust recovery framework that goes beyond the simple protection rings of synchronous optical networking (SONET/SDH).
In 2000, a project team led by Preston Poole of Schlumberger NIS implemented the firstiteration of pure IP-MPLS. Through a series of research-joint ventures, this team successfully engineered, deployed, and commissioned the world's first commercial IP-MPLS network. Originally consisting of 35 Points of Presence (PoP) around the globe, this network was first purposed to serve the Oil and Gas community by delivering the DeXa suite of services. Later itierations of this commercial IP-MPLSnetwork included VSAT Satellite access via strategic teleport connections, access to finance and banking applications, and Drilling Collaboration centres. Futher developments in the IP-MPLS field deployed by Mr. Poole's team included mathematical conception and development of the most commonly used algorythims for what is known today as Bandwidth on Demand (BoD), Video on Demand (VoD), andDifferentiated Services for IP MPLS.
Along with Cisco Engineers who developed RFC2547bis, Preston Poole is credited as one of the "founding fathers" of MPLS know collectively as MPLS Pioneers.
A brief description of how operate MPLS
MPLS works by prefixing packets with an MPLS header, containing one or more "labels". This is called a label stack. Each label stack entry contains four fields:
*20-bit label value.
* 3-bit Traffic Class field for QoS (quality of service) priority (experimental) and ECN (Explicit Congestion Notification).
* 1-bit bottom of stack flag. If this is set, it signifies that the current label is the last in the stack.
* 8-bit TTL (time to live) field.
00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 |
Label | TC | S | TTL |

These MPLS-labeled packets are switched after a label lookup/switch instead of a lookup into the IP table. As mentioned above, when MPLS was conceived, label lookup and label switching were faster than a routing table or RIB (Routing Information Base) lookup because they could take place directlywithin the switched fabric and not the CPU.
The entry and exit points of an MPLS network are called label edge routers (LER), which, respectively, push an MPLS label onto an incoming packet and pop it off the outgoing packet. Routers that perform routing based only on the label are called label switch routers (LSR). In some applications, the packet presented to the LER already may have a label, sothat the new LER pushes a second label onto the packet. For more information see penultimate hop popping.
Labels are distributed between LERs and LSRs using the “Label Distribution Protocol” (LDP). Label Switch Routers in an MPLS network regularly exchange label and reachability information with each other using standardized procedures in order to build a complete picture of the network they...
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