This means that the label distribution across the interface is unsolicited downstream with independent label control. Figure provides an example of this type of connectivity. Figure illustrates two routers connected across a Frame Relay network. From this router's perspective, any routes learned from its routing protocol neighbor across this VC Paris in this case have a next-hop forwarding address pointing to the Paris router.
You can see the relevant configuration of the San Jose router in Example To confirm the TDP relationship between the two routers, use the show tag-switching tdp neighbor command, as shown in Example This command confirms that your TDP session is established across the Frame Relay interface and that unsolicited downstream label distribution is in effect. MPLS forwarding and control functions across either encapsulation. Figure shows the two encapsulation methods and how the MPLS information is added to the frame.
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Using the l2transport keyword specifies that the PVC is not a locally switched PVC, but is tunneled over the backbone network. The connection-name argument is a text string that you provide. The interface argument is the interface on which a PVC connection is defined. Step 11 xconnect peer-router-id vcid encapsulation l2tpv3 pw-class l2tpv3 Example: Device config-xconnect-conn-config xconnect The vcid or identifier of the virtual circuit VC between the PE devices should be the same on both devices that are being connected.
Step 4 encapsulation frame-relay [ cisco ietf ] Example: Device config-if encapsulation frame-relay ietf Specifies Frame Relay encapsulation for the interface. Step 5 pseudowire-class [ pw-class-name ] Example: Device config pseudowire-class l2tpv3 Specifies the name of a Layer 2 pseudowire class and enters pseudowire class configuration mode. Step 6 encapsulation l2tpv3 Example: Device config-pw encapsulation l2tpv3 Specifies the tunneling encapsulation as L2TPv3.
Step 7 ip local interface loopback loopback id Example: Device config-pw ip local interface Loopback0 Specifies the local loopback interface.
Step 9 xconnect peer-router-id vcid encapsulation l2tpv3 pw-class l2tpv3 Example: Device config-fr-pw-switching xconnect Step 3 class-map class-name Example: Device config class-map class1 Specifies the user-defined name of the traffic class and enters class map configuration mode. Step 4 match fr-dlci dlci-number Example: Device config-cmap match fr-dlci 50 Specifies the number of the Data-Link Connection Identifier DLCI associated with the packet as a match criterion in the class map.
Step 5 policy-map dlci dlci-number Example: Device config-cmap policy-map dlci 50 Specifies the type of policy map as DLCI and enters policy map configuration mode. Step 6 class class-name Example: Device config-pmap class class1 Specifies the name of a predefined traffic class, which was configured with the class-map command, used to classify traffic to the traffic policy and enters policy-map class configuration mode.
Step 7 set ip precedence tunnel precedence-value Example: Device config-pmap-c set ip precedence tunnel 2 Sets the precedence value in the header of the L2TPv3 tunneled packet for tunnel marking. Step 9 no ip address [ ip-address mask ] [ secondary ] Example: Device config-if no ip address Disables IP processing.
Step 10 encapsulation frame-relay [ cisco ietf ] Example: Device config-if encapsulation frame-relay ietf Specifies Frame Relay encapsulation for the interface.
Step 11 no keepalive Example: Device config-if no keepalive Disables the keepalive configuration. Step 12 service-policy input policy-name Example: Device config-if service-policy input policy1 Attaches a traffic policy to the interface. Step 14 pseudowire-class [ pw-class-name ] Example: Device config pseudowire-class l2tpv3 Specifies the name of a Layer 2 pseudowire class and enters pseudowire class configuration mode.
Step 15 encapsulation l2tpv3 Example: Device config-pw encapsulation l2tpv3 Specifies the tunneling encapsulation as L2TPv3. Step 16 ip local interface loopback loopback id Example: Device config-pw ip local interface Loopback0 Specifies the local loopback interface.
Step 18 xconnect peer-router-id vcid encapsulation l2tpv3 pw-class l2tpv3 Example: Device config-xconnect-conn-config xconnect Table 1. Was this Document Helpful? Yes No Feedback. MPLS is a key driver for next-generation multiservice provider networks. MPLS makes an excellent technology bridge. By dropping MPLS capability into the core layer of a network, you can reduce the complexity of Layer 2 redundancy design while adding new Layer 3 services opportunity.
Because of these attributes, MPLS has momentum as a unifying, common core network, as it more easily consolidates separate purpose-built networks for voice, Frame Relay, ATM, IP, and Ethernet than any methodology that has come before. In doing so, it portends significant cost savings in both provider capital expenditures CapEx and operational expenditures OpEx. MPLS is a method of accelerating the performance and management control of traditional IP routing networks by combining switching functionality that collectively and cooperatively swaps labels to move a packet from a source to a destination.
When moving data through a frame-based MPLS network, the data is managed at the frame level variable-length frames rather than at a fixed length such as in cell-based ATM. It is worthwhile to understand that a Layer 3 router is also capable of Layer 2 switching. Understanding frame-based MPLS terminology is challenging at first so the following review is offered:.
It is also helpful to understand common terms used to describe MPLS label switching. Table shows these terminology comparisons. MPLS fuses the intelligence of routing with the performance of switching. MPLS is a packet switching network methodology that makes connectionless networks like IP operate in a more connection-oriented way.
By decoupling the routing and the switching control planes, MPLS provides highly scalable routing and optimal use of resources. The use of labels facilitates faster switching through the core of the MPLS network and avoids routing complexity on core devices. Prior to the first packet being routed, the core LSRs P nodes have already predetermined their connectivity to each other and have shared label information via an LDP.
Figure shows the concept of frame-based MPLS label switching. This is the ultimate definition of next-generation multiservice networks—networks that are capable of supporting circuit-based Layer 2 and packet-based Layer 2 and Layer 3 services on the same physical network infrastructure.
In the discussion that follows, cell-based MPLS is presumed. This is accomplished through either external routers such as the Cisco or via a co-controller card essentially a router in a card form factor resident in the ATM switch. The egress eLSR is now responsible for reassembling all cells belonging to the original packet, for examining the Customer A-sourced Layer 3 IP header once again, searching its IP routing table for the destination port of customer site B, and routing the Customer A packet to the Customer B destination output interface.
Figure shows the concept of cell-based MPLS label switching. It is worthwhile to consult Cisco support for those features, hardware components, and software levels that are supported by cell-based MPLS platforms.
Table shows a summary of these MPLS realizations. You could draw the analogy that an MPLS label is a tunnel of sorts, invisibly shuttling packets or cells across the network core. The core LSRs, therefore, don't participate in customer routing awareness as a result, reducing the size and complexity of their software-based routing and forwarding tables. This blend of the best features of Layer 3 routing with Layer 2 switching allows MPLS core networks to scale very large, switch very fast, and converge Layer 2 and Layer 3 network services into a next-generation multiservice network.
In summary, both frame-based and cell-based MPLSs provide great control on the edges of the network by performing routing based on destination and source addresses, and then by switching, not routing, in the core of the network. MPLS eliminates routing's hop-by-hop packet processing overhead and facilitates explicit route computation on the edge. MPLS adds connection-oriented, path-switching capabilities and provides premium service-level capabilities such as differentiated levels of QoS, bandwidth optimization, and traffic engineering.
Ethernet is a broadcast technology, and simply extending Ethernet over classic Layer 2 networks merely extended all of these broadcasts, limiting scalability of such a service.
At Layer 2, AToM provides point-to-point and like-to-like connectivity between broadband access media types. Since IP routing always uses shortest path algorithms, longer paths connecting the same source and destination networks would generally go unused. MPLS TE simplifies the optimization of core backbone bandwidth, replacing the need to manually configure explicit routes in every device along a routing path. In other words, MPLS can be used to create forwarding tables for any underlying protocol.
Experimental: Experimental bits are used for Quality of Service QoS to set the priority that the labeled packet should have. This usually means the router is an egress router. Time-To-Live: This identifies how many hops the packet can make before it is discarded. The benefits of MPLS are scalability, performance, better bandwidth utilization, reduced network congestion and a better end-user experience.
MPLS itself does not provide encryption, but it is a virtual private network and, as such, is partitioned off from the public Internet. Therefore, MPLS is considered a secure transport mode. And it is not vulnerable to denial-of-service attacks, which might impact pure-IP-based networks. On the negative side, MPLS was designed for organizations that have multiple remote branch offices that are geographically dispersed across the country or the world where the majority of traffic was on-net to enterprise data centers.
It is more efficient to send traffic directly to the cloud. Also, the use of cloud services, video and mobile apps has driven up bandwidth requirements, and MPLS services are difficult to scale on demand.
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