The need for WAN technology has increased over time, and as technology has progressed (alongside its reliability) more offerings for WAN links appeared. Circuit switched lease lines have started to fall out of favour and are being replaced by packet switched virtual circuits which is not as expensive.
3.5.a MPLS (Multiprotocol Label Switching)
This is modern packet switch technology, the latest and greatest. It allows service providers to put tags on their interfaces. PVC’s (Permanent Virtual Circuits) are often defined, and each of those circuits would have a CIR (committed information rate).
The customer usually will not know if they are getting a leased line, or an MPLS circuit. The handoff (i.e. ethernet or fibre or DSL) doesn’t mean anything in this sense. The underlying technology will be something like MPLS.
MetroEthernet was, at one point, metropolitan areas only. Instead of running copper cable – bundles of fiber cable would be run to POP’s. Providers would put in way more fiber than they need and then let other people use this fiber. – sometimes this is called Dark Fiber.
3.5.c Broadband PPPoE
PPPOE Point to Point Protocol over Ethernet – Used to provide a level of Authentication to DSL (and increasingly Fiber) connections.
3.5.d Internet VPN (DMVPN, site-to-site VPN, client VPN)
Internet VPN’s are all about using the Internet as the backbone, as opposed to private WAN links. They are becoming much more popular as they are low cost.
That said the big drawback is that there is no gurantee of bandwidth, you could be impacted by someone’s network in the middle having trouble. QoS is also not guranteed, there is absolutely no prioritisation.
There are three main types of VPN that are in use today.
Site-to-site VPNs involve creating a permanant tunnel using routing and firewall rules.
Client VPNs and to a lesser extent SSLVPNs require a client portal such as ovpn to be installed on the connecting users device, which introduces issues around making sure they are kept up to date.
DMVPN (dynamic multipoint VPN): As you increase the number of sites that you want to connect using a VPN it becomes very difficult to manage using just site to site VPNs. It makes the system of connecting lots of sites together a little more easy to manage. It uses GRE to achieve this.