VPN Models

VPN : This term is very popular in service provider industry which is used in industry as a product or service integrating with many other services.Basically they are offering same thing. They are offering you a virtual private tunnel in public network(shared network).

Currently in Industry there are two VPN models to offer service as per business requirement

•  Overlay VPN
•  Peer to Peer VPN

Overlay VPN: In this Service provider will establish physical connectivity between customer sites and customer is responsible for all higher layers. Service provider is not responsible for any routing.They are just providing a Circuit. For all other things customer is responsible.

The overlay VPN is deployed via private trunks across a service provider’s shared infrastructure. These VPNs can be implemented as below.

• At layer-1 using leased/dialup lines (E1, T1, SDH, SONET, ISDN, etc.)
• At layer-2 using X.25/frame relay/ATM Virtual Circuits.
• At layer-3 using IP (GRE) tunneling.

The service provider has no knowledge of the customer routes and is simply responsible for providing point-to-point transport of data between the customer sites.

Service Provider infrastructure appears as point to point links to customer routes. The provider network is invisible to customer.

 Routing protocols are directly between customer routers.

Peer to Peer VPN: Here Service provider participates in customer routing.

Routing information is exchanged between CE & PE routers.

PE routers exchange customer routers though the core network

Finally the routes propagated through the PE network are sent to other CE routers.

Peer to Peer implementation: Commonly PE router is shared router for Customers and Packet filters isolate the customers, Due to packet filters the CPU utilization increases which results in performance issue.

  

Dedicated PE router Model: In this model for every customer service provider use a dedicated PE router to reduce the complications but it results in high cost.

MPLS VPNs is combination of best features of both Overlay and Peer to Peer Model.