nx.os.and.cisco.nexus.switching.2nd.edition.1587143046

network receive these labeled packets, they can make a forwarding decision based only on
the label of the packet without regard to source, destination, or type of traffic contained
within the packet.
The core of MPLS is decoupled and consists of two primary areas:
• Control plane: Leverages protocols to construct the Forwarding Table, whereas the
forwarding plane forwards packets to the appropriate destination.
• Forwarding table: Lists label values, which are each associated with determining the
outgoing interface for every network prefix. Cisco NX-OS Software supports two
signaling mechanisms to distribute labels: Label Distribution Protocol (LDP) and
Resource Reservation Protocol/Traffic Engineering (RSVP / TE).
MPLS is composed of the following major components:
• MPLS Virtual Private Networks (Layer 3 VPN): Provides secure segmentation of
different traffic types and classes, shared services, and route import/export between
VPNs
• MPLS Traffic Engineering (TE): Enables on-demand bandwidth for applications,
optimized link sharing and protection, fast convergence, and capacity planning
• MPLS quality of service (QoS): Supports classification and prioritization of traffic
flows, ability to preserve or remark traffic flows, and ability to police and to conform
to service-level agreements (SLAs)
Integration of MPLS application components, including Layer 3 VPNs, Traffic Engineering,
QoS, and mVPN, enables the development of highly efficient, scalable, and secure networks
that guarantee SLAs.
MPLS Terminology
Before understanding and learning MPLS configurations and operations, the MPLS
terminology needs to be defined and understood:
• Label: An MPLS label is a 4-byte header placed on a data packet, which contains
basic information about how to forward the packet. The label contains a value, which
identifies the packet, traffic class for QoS purposes, and Time-To-Live (TTL). A
packet can be marked with multiple labels, for example, an outer label, which contains
forwarding information about the packet, and an inner label, which identifies a
specific customer VPN that the packet is destined for. The label also contains a bit,
which signifies whether it is the last or if subsequent labels are contained within the
packet. Labels can also be aggregated so that many different packets may be assigned
the same label; for example, packets going to the same destination network or
belonging to the same VPN. These packets are part of the same forwarding
equivalency class (FEC) and are treated the same throughout the MPLS network.
• Label Distribution Protocol (LDP): Each device determines the unique label that it
uses for a particular FEC. For end-to-end label switching to occur, the Label
Switching Router (LSR) must disseminate its local label bindings to adjacent devices.
LDP is the standard protocol used to propagate this information.