MPLS and VPN services - Basic Terms

Customer Edge Routers:

• Reside on customer permises
• Provides access to service provider network over a link or more Provider Edge Routers.
• End user typically owns and operates these devices.
• CE devices are unaware of tunneling protocols over VPN services provided by the service provider.
• Eg: Home networking router or wireless access point.

Provider Edge Router:

• Has at lease one interface that is directly connected to the CE device.
• PE device usually has at lease one interface that connects to the Service Provider Core devices.
• Must be able to connect to different CE devices over different access media, usually able to support many different interface types.
• Customer's gateway to the VPN services offered by the service provider.

Provider Router:

• Routers located in the Provider Core Network
• P router supports the service provider's bandwidth and switching requirements over a geographically dispersed area
• Does not connect directly to the customer equipement
• P routers does not care about the different types of services that are provided to individual customers and instead simply make forwarding decisions based on information attached to the IP packets by the PE devices.

Thus we can say that much of the intelligence in a service-based network is provided by the PE devices.It provides almost all of the critical setup and control that are needed to mark traffic and have it forwarded correctly throughout the rest of a service network.

Service Access Point(SAP): 

• Provides the logical entity that serves as the customer access to whatever services are provided by the PE.

Service Distribution Point(SDP):

This is the method that a service uses to connect to another router's services.

Important features of SDPs include:

• To provide the transport tunnel encapsulation that the service will be using such as MPLS/RSVP-TE/MPLS-LDP or IP/GRE
• SDP IDs are locally unique, the same SDP ID can be used on another router
• An SDP is not specific to one service. Many services can use the same SDP.