2.3.c [ii] Use of rate-limited WAN ethernet services
The Native Ethernet service is comprised of Layer 2 end to end native Ethernet signaling over the Metro Ethernet network where available. There is no transition of packets to any other WAN protocol and no VLAN encapsulation required. The use of native Ethernet services is mostly available for metropolitan connectivity. As the distance between offices increases, the use of a WAN transport such as SONET must be used. Traffic shaping or rate limiting of packets to the CIR should be done at the customer edge Ethernet interface to make sure packets are not dropped by the service provider.
Ethernet Private Line (EPL)
The Ethernet Private Line service is used to deploy private line WAN connectivity across the Metro network. Typically the Ethernet service will forward packets to a long haul SONET network where Ethernet packets are encapsulated in SONET frames. The Ethernet packets are stripped off (de-encapsulated) at the SONET Provider Edge (PE) equipment and forwarded to thelocal Metro service provider network. The Ethernet private line is similar to any WAN link where VLAN information isn’t sent between routers . The service provider does the rate limiting of traffic based on the CIR selected by the customer. The CIR is the guaranteed data rate service level agreement with the ISP. Traffic shaping or rate limiting of packets should be done at the Customer Edge (CE) on the CPE Ethernet interface to make sure packets are not dropped by the service provider.
Ethernet Virtual Private Line (EVPL)
The Ethernet virtual private line service is deployed for trunking of multiple VLANs across a Metro network (i.e. multiplexing multiple point to point EVCs). The 802.1q encapsulation protocol is the new standard that works with Cisco and other vendor equipment. The customer edge device uses 802.1q protocol to tag each Ethernet packet with VLAN membership before forwarding it across the virtual point to point Metrolink . QoS is applied at the Customer Edge (CE) Ethernet interface using per VLAN or per Class per VLAN traffic shaping.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2200-2205). . Kindle Edition.