6. Conclusion

Two technologies - IPSec and MPLS - seem to be the most popular for building cross-site VPNs today. IPSec technology provides classic security services (authentication, confidentiality, integrity, etc.) for each datagram transiting a transport network (e.g. the Internet). This technology can be implemented by the user company, or by a service provider in the context of outsourcing. There are two main limitations to this technology: (1) it cannot be used to manage quality of service at the core of the network; (2) it only transports IP datagrams.

MPLS technology enables quality-of-service management at the transport network level. It can transport any OSI level 2 or 3 datagram. It does not offer encryption of transported datagrams.

The combination of MPLS and IPSec can meet special needs where security and quality of service are essential....