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Multiprotocol Label Switching
Published in Goff Hill, The Cable and Telecommunications Professionals' Reference, 2012
The forwarding summary described in this section matches the description in RFC 3031. In practice the breaking up of tasks into various tables (or maps) is somewhat arbitrary, and router vendors often have their own internal architectures that perform tasks by a method that matches their implementation. For example, Cisco has a mechanism termed Cisco Express Forwarding (CEF) that is used to perform IP forwarding in an ASIC (De Ghein, 2006). It turns out that CEF is also ideally suited to perform the FEC-to-NHLFE mapping, and hence this latter term is replaced by CEF in most Cisco documentation.
Avaya P580 and P882 Routing Switch Architecture with 80-Series Media Module
Published in James Aweya, Switch/Router Architectures, 2019
Using a forwarding engine directly with a full topology based forwarding table (not a route/flow cache) provides a much more powerful and efficient architecture for the design of networks that aim to deliver improved availability, performance, and scalability. Such networks also enable important services that include: Multiprotocol Label Switching (MPLS) with sophisticated network traffic engineering that allows for the creation of services such IP Virtual Private Networks (VPNs)Network monitoring and collection tools such as NetFlow and sFlow [RFC3176] that allow for gathering network statistics. sFlow and NetFlow are tools that can be used to generate detailed information on traffic flows in a network to help network operators analyze their traffic patterns and accurately plan network capacity.Quality of service (QoS) functions such as traffic policing, traffic shaping, WFQ, WRED and other traffic management mechanisms that help prevent one application (particularly, one generating best-effort traffic) from hogging network bandwidth and starving out other applications (particularly, ones generating real-time traffic).The approach of using a forwarding engine with both optimized lookup mechanism and topology based forwarding table (referred to as Cisco Express Forwarding (CEF) by Cisco Systems) can be implemented in a distributed architecture where processing tasks are spread across the line cards—distributed forwarding engines (with associated forwarding tables). In the distributed forwarding architecture, the line cards maintain an identical copy of the forwarding table and adjacency information. The line cards perform local forwarding of packets, thus relieving the route processor (control plane) of direct involvement in the forwarding process.
A Survey on Packet Switching Networks
Published in IETE Journal of Research, 2022
The first and foremost thing is that the Cisco Express Forwarding (CEF) table must be enabled on the Cisco router to use MPLS technology. The CEF table is used to create the Forwarding Information Base (FIB) table, an optimized form of the routing table or Routing Information Base (RIB). The FIB table is not much different from the RIB table as both tables contain the information (next hop and outgoing interfaces) of some specific routes. Nevertheless, the advantage of the FIB table is that more packets are sent per second because the router finds the correct entry in no time. Another table named Label Forwarding Information Base (LFIB) table performs a significant role in forwarding the packets in the MPLS network. This table is created from the FIB table and Label Information Base (LIB) table. The LIB contains all labels and information used by Label Switch Router (LSR) in forwarding the packets. The LSR is the router that knows about the MPLS technology, and these are providers (Ps) in the MPLS domain, while the first and the last PEs in the MPLS domain are known as Label Edge Routers (LERs). All LSRs and LERs assign the labels to the packets independently. They also exchange the information of labels to one another using the Label Distributing Protocol. After establishing the LDP, all routers in the MPLS domain build their MPLS forwarding tables, which are LFIB tables and the LSRs/LERs use these tables to perform three types of forwarding on the incoming packets: IP-to-Label forwarding, Label-to-Label forwarding, and Label-to-IP forwarding. These types of forwarding depend on the information saved in the LFIB tables. IP-to-Label forwarding means that the label is injected into the incoming packet by the first LER in the MPLS domain. This injection of the label is also called pushing the label. Label-to-Label forwarding is also known as swapping/switching the label, performed by the LSRs. When a labelled packet reaches an LSR, it sends the packet to the following related node, but before that, it swaps the current label with its own assigned label. The last forwarding type is Label-to-IP forwarding which is also called removing the label. In this popping label operation, the last P receives a labelled packet from the previous P and removes the label from the packet, and forwards the packet as a regular IP packet to the LER.