Introducing to Modern SP networks (VPN)

Traditional Router-Based networks

  • traditional router-based networks connect customer sites through routers connected via dedicated POINT-TO-POINT links (leased lines)

Leased lines advantages

  • complete secure, high bandwidth, superior quality, reliable

Leased lines disadvantages

  • Expensive
  • Permanent physical connection
  • not scalable – it is very difficult for SP to provide separate physical connection for every customer sites.

VPN networks

  • VPNs replaced dedicated point-to-point links with emulated point-to-point links that share common infrastructure. Customers use VPNs primarily to reduce their operational costs. Note we are speaking about VPN in general so this include also technologies like frame relay.
  • Example of VPN netwoks are: X.25, Frame relay, ATM, GRE, DMVPN, IPSec, MPLS, L2TPv3
  • you connect your sites to SP but now SP will not create for you physical point-to-point connection but virtual point-to-point connection via physical links shared among more SP customers.
  • this is very good cost effective, scalable solution

Advantages of VPNs

  • cost savings – much cheaper than leased lines
  • scalable – adding a new branch office is very fast and simple
  • similar security – you can use encryption and authentication. This will ensure you that it is as secure as leased lines
  • similar performance  – performance is equivalent to leased lines

VPN Basic Terminology

  • Provider network – the service provider infrastructure used to provide VPN services
  • Customer network – the part of the network still under customer control
  • Customer site – part of the customer network
  • P device – the device in the provider network with no customer connectivity (SP CORE devices)
  • PE device – the device in the provider network to which the customer devices are connected. It can be connected to multiple customers
  • CE device – the device int the customer network that links to the provider network (sometimes called CPE)
  • PE-CE link – a link between a PE router and a CE router