IPv6 Provider Edge (6PE) is a technology that facilitates IPv4-to-IPv6 transition based on Multiprotocol Label Switching (MPLS). 6PE enables isolated IPv6 networks to communicate using MPLS LSPs on an IPv4 MPLS backbone network. It improves the utilization of MPLS network resources without affecting existing services.
Why Do We Need 6PE?
Various solutions, such as tunneling and dual-stack technologies, are proposed to facilitate network evolution from IPv4 to IPv6, enabling IPv6 traffic to be carried on the original IPv4 network. 6PE is a transitional IPv6 over IPv4 technology that uses MPLS tunnels to carry services. If the original bearer network is based on MPLS, 6PE can be used to facilitate IPv4-to-IPv6 evolution.
IPv6-oriented MPLS Network Evolution
During the early stage of IPv6 network development, such networks carry few services and are like isolated islands in an ocean of IPv4 networks. When evolving an IPv4 network toward IPv6, use easy, simple, and cost-effective methods to achieve smooth evolution. Ensure that the existing IPv4 services can run properly during this process.
No mature IPv6 label distribution protocol is available for MPLS networks. As a result, directly allocating labels to IPv6 prefixes for IPv6 data forwarding is difficult. Against this backdrop, the transitional 6PE solution is proposed.
6PE uses one protocol to carry the services of another protocol, enabling service interworking across different domains. 6PE is widely used during the evolution of backbone and metro networks. Metro networks differ from backbone networks in that IPv4 MPLS networks may span multiple ASs during 6PE deployment.
Benefits of 6PE
6PE offers the following benefits:
Easy maintenance: All configurations are performed on PEs connected to user-side devices, and the IPv6 networks are unaware of the IPv4 network. Using an existing IPv4 network to carry IPv6 services simplifies maintenance and facilitates progressive network deployment.
Low network construction costs: 6PE fully utilizes existing IPv4 MPLS tunnels to provide IPv6 services for users, eliminating the need to upgrade the network. 6PE devices can provide multiple types of services, such as IPv6 VPN and IPv4 VPN.
What Types of 6PE Exist?
In real-world situations, different metro networks of a carrier or backbone networks of collaborative carriers often span multiple ASs. 6PE is classified as either intra-AS 6PE or inter-AS 6PE, depending on whether separate IPv6 networks connect to the same AS. The following describes 6PE networking.
6PE Networking
Intra-AS 6PE is used to connect separate IPv6 networks to the same AS, whereas inter-AS 6PE is used to connect separate IPv6 networks to different ASs. Inter-AS 6PE can be further classified as inter-AS 6PE Option B or inter-AS 6PE Option C. Each type of 6PE has its own advantages and application scenarios. The following describes the basic types of 6PE.
Intra-AS 6PE
As shown in the following figure, separate IPv6 networks connect to the same AS. PEs in the AS exchange IPv6 routes through MP-IBGP peer relationships.
PEs and CEs use the IPv6 routing protocol to exchange IPv6 routing information. On a 6PE network, three types of devices exist: provider (P), provider edge (PE), and customer edge (CE).
PEs exchange IPv6 routing information through Multiprotocol Extensions for Border Gateway Protocol (MP-BGP) and add two MPLS labels to IPv6 packets. The inner label (L2) corresponds to the IPv6 prefix, and the outer label (L1) corresponds to the LSP between 6PE devices.
PEs and Ps use the IPv4 routing protocol to exchange routing information, and PEs use MPLS to establish LSPs with each other. IPv6 traffic is transmitted over the IPv4 MPLS core network based on MPLS label
Ps are backbone devices on the 6PE network. Generally, Ps are the backbone devices of a service provider. They do not connect to any CE and must have basic MPLS forwarding capabilities.
PEs are edge devices on a 6PE network. Generally, PEs are edge devices on the backbone network of a service provider. PEs connect to both CEs and Ps and are important network devices.
CEs are edge devices on the customer network. These devices directly connect to a service provider network through interfaces. CEs can be routers, switches, or hosts. Generally, CEs do not need to support MPLS.
