Cisco 10000 - Manual (Page 369)

C H A P T E R
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Cisco 10000 Series Router Software Configuration Guide
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18
Configuring L2 Virtual Private Networks
To improve profitability, service providers (SPs) introduce new services to reduce operational
expenditures. To reduce the number of managed networks, use network convergence, a multiphase
transition of the network. This affects both the core and edge/aggregation side. The technology is
predominantly Multiprotocol Label Switching (MPLS) based core networks. However, IP cores are the
service of choice in a number of large SPs. Both the IP and the MPLS cores carry multiservice traffic.
The edges of the network is constructed with network elements providing a single network element for
convergence between Layer 2 and Layer 3 services.
The following Layer 2 virtual private network (L2VPN) solutions enable existing or emerging Layer 2
transport technology to interwork through converged MPLS or IP core networks.
• Virtual Private Wire Services (VPWS)—A point-to-point service consisting of individual
point-to-point connections cross-connected to native interfaces.
• Virtual Private LAN Services (VPLS)—A service consisting of a set of point-to-multipoint
connections.
L2VPN features are of the VPWS type and are designed for the benefit of the carriers. L2VPN features
allow for a transparent use of network resources, and a way of reducing the number of networks that
need managing.
Cisco nonstop forwarding (NSF) with stateful switchover (SSO) is effective at increasing availability of
network services. Cisco NSF with SSO provides continuous packet forwarding, even during a network
processor hardware or software failure. In a redundant system, the secondary processor recovers control
plane service during a critical failure in the primary processor. SSO synchronizes network state
information between the primary and the secondary processor."
Any Transport over MPLS (AToM) uses NSF, SSO, and Graceful Restart to allow a route processor (RP)
to recover from a disruption in control plane service without losing the MPLS forwarding state. In
Cisco IOS Release 12.2(33) SB, the L2VPN features support NSF/SSO. See the
“NSF and
SSO—L2VPN” section on page 18-6 .
Cisco 10000 series routers also support the following two L2VPN technology solutions:
• Local Switching (LS)—The ordered duple <AC, AC>. This is the point-to-point interconnection of
two attachment circuits within a Cisco 10000 series router chassis. Also, two attachment circuits
(ACs) can be of:
– The same type—Creating a like-to-like LS connection.
– A distinct type—Creating an any-to-any LS connection.
• AToM—The ordered triple <AC, PW, AC>. This is the point-to-point interconnection of two
attachment circuits in separate Cisco 10000 series router chassis through a pseudowire (MPLS).
Also, two ACs can be of the same type in which case a like-to-like AToM connection exists. Or, two
ACs can be of a distinct type, in which case an any-to-any AToM connection exists.