Tag Archives: 2.3c

2.3.c Describe WAN rate-based ethernet circuits

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.




2.3.c Describe WAN rate-based ethernet circuits

2.3.c [i] Metro and WAN Ethernet topologies

Familiar network domains are likely to exist regardless of the transport technology chosen to implement Metropolitan area networks: Access, aggregation/ distribution, and core

● Access devices normally exist at a customer’s premises, unit, or wireless base station. This is the network that connects customer equipment, and may include ONT and/ or Residential gateway, or office router.

● Aggregation occurs on a distribution network such as an ODN segment. Often Passive Optical Network , microwave or Digital Subscriber Line technologies are employed, but some using point-to-point Ethernet over “home-run” direct fibre. This part of the network includes nodes such as Multi Tenanted Unit switches, Optical line terminals in an outside plant or central office cabinet, Ethernet in the First Mile equipment, or provider bridges.

● A MAN may include the transport technologies MPLS, PBB-TE and T-MPLS, each with its own resiliency and management solutions.

● A core network often uses IP-MPLS to connect different MANs together.

Much of the functionality of Ethernet MANs such as virtual private lines or virtual private networks is implemented by the use of Ethernet VLAN tags that allow differentiation of each part of the network. Logical differentiation of the physical network helps to identify the rights that the traffic has and to ease the management of host access rights with respect to other users and networks.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2182-2186).  . Kindle Edition.




2.3.c Describe WAN rate-based ethernet circuits

A metropolitan -area Ethernet, Ethernet MAN, or metro Ethernet network is a metropolitan area network (MAN ) that is based on Ethernet standards. It is commonly used to connect subscribers to a larger service network or the Internet. Businesses can also use Ethernet-based MAN to connect their own offices to each other.

Ethernet on the MAN can be used as pure Ethernet, Ethernet over SDH, Ethernet over MPLS, or Ethernet over DWDM. Pure Ethernet-based deployments are cheaper but less reliable and scalable and thus are usually limited to small scale deployments. SDH-based deployments are useful when there is an existing SDH infrastructure already in place, its main shortcoming being the loss of flexibility in bandwidth management due to the rigid hierarchy imposed by the SDH network. MPLS-based deployments are costly but highly reliable and scalable and are typically used by large service providers.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 2160-2167).  . Kindle Edition.