Convergence Services


The business case for L3 IP/MPLS VPNs is not limited to IP connectivity. Rather, the VPN service is a solid foundation on which service providers can offer many other services. Because the enterprise network's IP routing table is shared with the service provider network, adding a service can be as simple as injecting additional routes into the enterprise's VPN.

Internet Access

One of the simplest services to deploy in an L3 IP/VPN is Internet access. A service provider can deploy this service fairly easily, especially if it already hosts its Internet connectivity across its IP/MPLS backbone. A default route to the Internet can be injected into the VPN, drawing traffic that does not go to a specific location on the enterprise's network. A managed firewall then screens traffic and may provide Network Address Translation (NAT) if required. By using this service, the enterprise can eliminate the need to carry Internet-bound traffic back to its regional HQ sites and send that traffic on its external Internet connectivity.

Security is a very common concern with Internet access service. Chapter 9, "Off-Net Access to the VPN," discusses Internet access services on L3 IP/MPLS VPN services, common enterprise requirements, and security concerns.

Mobile Access and Teleworker Access

Another service that most service providers are considering for deployment in conjunction with their VPN services is remote access for teleworkers. By coupling the L3 IP/MPLS VPN service with an IPSec VPN service, service providers can offer direct access to the enterprise network for travelers or telecommuters, eliminating the need for the enterprise to operate its own remote access infrastructure. To implement this service, service provider VPN concentrators terminate the IPSec VPN tunnels, and traffic for authenticated users from a particular enterprise customer is directed into the enterprise's L3 IP/MPLS VPN. We will look at this service in more depth in Chapter 9.

Voice Services: Service Provider Hosted PSTN Gateway

Beyond basic connectivity services, the first area that service providers are focusing on for expansion of IP/VPN capabilities is integrating their voice networks with the PSTN. Today, IP telephony installations in enterprise networks consist of an IP call agent server, such as Cisco CallManager, IP telephony endpoints (typically telephone handsets and a PC-based software phone application), and IP telephony gateways that connect to the PSTN through plain old telephone service (POTS) or ISDN PRI. Outsourcing the IP/PSTN gateway functionality to the VPN service provider removes the need for the enterprise to connect multiple PRIs or POTS lines at the branch office and allows the traffic to be hosted in the IP/MPLS VPN service instead.

Voice Services: Service Provider Hosted IP Telephony

Expanding on PSTN gateway service, hosted IP telephony takes the outsourcing of IP telephony one step further by outsourcing the call agent server and its operations to the service provider, leaving only IP-based telephones and a basic POTS gateway functionality for emergency calling. This removes the need for enterprises to manage call agent servers in branch offices. Instead, it only requires users to plug in an IP telephone to the IP network they are already accustomed to for their data connectivity.




Selecting MPLS VPN Services
Selecting MPLS VPN Services
ISBN: 1587051915
EAN: 2147483647
Year: 2004
Pages: 136

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