When Virtual Private Network ( VPN ) constructed by Multiprotocol Label Switching ( MPLS ) and Border Gateway Protocol( BGP) is used in crossing domain platform,the label path can not be found and boundary devices are overloaded. Aiming at these problems,this paper analyses the fundamental reasons on the basis of label distribution and data forwarding plane. It brings forward two schemes,namely back to back project and single hop scheme based on EBGP to solve the problem of label distribution. However,the problem of overloading remains to be unsolved. Then this paper further proposes load-separation VPN solution based on multi-hop EBGP. In detail,the scheme improves the traditional VPN scheme by extending the existing protocols and modifying the systematic framework and brings forward specific configuration according to different network environment. This paper evaluates the performance of the schemes by comparing the different solutions through many indexes and the results indicate that load-separation VPN scheme is effective in realizing crossing-domain VPN and can solve both label distribution and overloading.%利用多协议标签交换和边界网关协议构建的虚拟专用网( VPN)，在跨域平台中存在无法生成标签路径和边界设备负载过重的问题。为此，从标签分配原理和数据转发层面分析产生上述问题的根源，并提出背靠背方案和基于单跳EBGP的方案处理承载标签转发问题，但这些方案无法解决边界设备负载过重问题。进而基于多跳EBGP提出负载分离的VPN解决方案。通过扩展现有协议和修改系统架构，对传统VPN方案进行改进，并针对不同的网络环境给出具体配置方案。为评估方案性能，通过多项指标对比不同的解决方案。分析结果表明，基于负载分离的VPN解决方案能够解决标签问题和负载问题，是实现跨域VPN的有效方案。
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