Cisco ASR 900 Series User Manual

•
Label Distribution Protocol (LDP)--enables peer LSRs in an MPLS network to exchange label binding
information for supporting hop-by-hop forwarding in an MPLS network
•
Tag Distribution Protocol (TDP)--Used to support MPLS forwarding along normally routed paths
•
Resource Reservation Protocol (RSVP)--Used to support MPLS traffic engineering
•
Border Gateway Protocol (BGP)--Used to support MPLS virtual private networks (VPNs)
When a labeled packet is being sent from LSR A to the neighboring LSR B, the label value carried by the IP
packet is the label value that LSR B assigned to represent the forwarding equivalence class of the packet.
Thus, the label value changes as the IP packet traverses the network.
Benefits of MPLS
MPLS provides the following major benefits to service provider networks:
Scalable support for Virtual Private Networks (VPNs)--MPLS enables VPN services to be supported in
service provider networks, thereby greatly accelerating Internet growth.
The use of MPLS for VPNs provides an attractive alternative to the building of VPNs by means of either
ATM or Frame Relay permanent virtual circuits (PVCs) or various forms of tunneling to interconnect routers
at customer sites.
Unlike the PVC VPN model, the MPLS VPN model is highly scalable and can accommodate increasing
numbers of sites and customers. The MPLS VPN model also supports “any-to-any” communication among
VPN sites without requiring a full mesh of PVCs or the backhauling (suboptimal routing) of traffic across the
service provider network. For each MPLS VPN user, the service provider’s network appears to function as a
private IP backbone over which the user can reach other sites within the VPN organization, but not the sites
of any other VPN organization.
From a user perspective, the MPLS VPN model enables network routing to be dramatically simplified. For
example, rather than having to manage routing over a topologically complex virtual backbone composed of
many PVCs, an MPLS VPN user can generally employ the service provider’s backbone as the default route
in communicating with all of the other VPN sites.
Explicit routing capabilities (also called constraint-based routing or traffic engineering)--Explicit routing
employs “constraint-based routing,” in which the path for a traffic flow is the shortest path that meets the
resource requirements (constraints) of the traffic flow.
In MPLS traffic engineering, factors such as bandwidth requirements, media requirements, and the priority
of one traffic flow versus another can be taken into account. These traffic engineering capabilities enable the
administrator of a service provider network to
•
Control traffic flow in the network
•
Reduce congestion in the network
•
Make best use of network resources
Thus, the network administrator can specify the amount of traffic expected to flow between various points in
the network (thereby establishing a traffic matrix), while relying on the routing system to
•
Calculate the best paths for network traffic
•
Set up the explicit paths to carry the traffic
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
3
Multiprotocol Label Switching (MPLS) on Cisco Routers
Benefits of MPLS

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English