Ethernet has now become a Metropolitan Area Network MAN and

Ethernet has now become a Metropolitan Area Network (MAN) and Wide Area Network (WAN) service. Answer the four parts below about Ethernet services.
Part 1: What is the purpose of the metro Ethernet forum?
Part 2: Describe the architecture of metro-Ethernet networks (MEN) and how it interfaces with other existing technologies?
Part 3: What is the importance of using Ethernet virtual connections (EVCs)?

Part 4: Explain how an Ethernet port can support several Ethernet virtual connections (EVCs) simultaneously.

Solution

Part 1:

The Metro Ethernet Forum (MEF) is a nonprofit organization that seeks to accelerate the use of carrier class Ethernet networks and services worldwide. It is made up of leading service providers, local exchange carriers, test equipment vendors, network equipment vendors and other networking companies that share an interest in the organization\'s goal.

The Metro Ethernet Forum was formed in 2001. The forum makes recommendations to existing standards bodies and also makes its own specifications.

Part 2:

A comparison of MPLS-based Metro Ethernet against a pure Ethernet MAN:

    Scalability: In a properly designed Ethernet VLAN network, each switched path can have 4094 single tag VLANs. Some aggregation and core switches can classify traffic by two VLANs using IEEE 802.1ad VLAN stacking, so with such aggregation devices properly placed in the center of a network, end segments and rings of single tag devices can receive only the traffic that they need. When using MPLS, Ethernet VLANs have local meaning only (like Frame Relay PVC). Same scalability considerations apply to the MAC addresses where in a pure Layer 2 Ethernet MAN all MAC addresses are being shared across the network, although this issue can be managed by smart network design and choosing switches with MAC tables sufficient for the size of network segments.

    Resiliency: pure Ethernet network resiliency relies on Spanning Tree Protocols STP, IEEE 802.1w RSTP or IEEE 802.1s MSTP (30 to sub 50 ms convergence depending on network design) while MPLS-based MANs use mechanisms such as MPLS Fast Reroute to achieve SDH-like (50 ms) convergence times. Metro Ethernet can also utilise Link aggregation or Resilient Packet Ring where appropriate to add link redundancy and recovery in distribution networks. Some Ethernet vendors\' RSTP convergence is also sub-50 ms, but this convergence time may vary from vendor to vendor. Ethernet protection switching is also standardized in ITU G.8031.

    Multiprotocol convergence: with the maturity on pseudowires standards (ATM Virtual Leased Line VLL, FR VLL, etc.) an MPLS-based Metro Ethernet can backhaul IP/Ethernet traffic together with virtually any type of traffic coming from customer or other access networks (i.e. ATM aggregation for UMTS or TDM aggregation for GSM), while this could be more challenging in a pure Ethernet scenario.

    End to End OAM: MPLS-based MAN offers a wide set of troubleshooting and OAM MPLS-based tools which enrich Service Providers ability to effectively troubleshoot and diagnose network problems. These include for example, MAC ping, MAC traceroute, LSP ping etc. However, there are now Ethernet OAM tools defined in IEEE 802.1ab, IEEE 802.1ag and Ethernet in the First Mile (IEEE 802.3ah) for monitoring and troubleshooting Ethernet networks. EOAM (Ethernet Operations, Administration, and Maintenance) is a protocol for installing, monitoring, and troubleshooting MANs and WANs.

Part3:

Ethernet Virtual Connection (EVC) is a Cisco carrier Ethernet equipment function dedicated to service providers and large enterprises. It provides a fine granularity to select and treat the inbound workflows known as service instances, under the same or different ports, based on flexible frame matching.

One of benefits of EVC is the ability to address independent Ethernet encapsulation on the same physical interface with a mix of different services such as dot1q trunk, dot1q tunneling, EoMPLS Xconnect, VPLS attachment circuit, routing, and Integrated Routing and Bridging (IRB). Each service instance can match a unique identifier or a range of identifiers (i.e. a VLAN tag deployed mainly in the context of DCI).

Another important feature is the ability to aggregate multiple service instances into the same transport virtual instance. For example, EVC can multiplex multiple VLANs into the same Bridge Domain (BD) connected to a Virtual Forwarding Instance (VFI) of a VPLS.