Ethernet White Papers

MPLS Based Transparent LAN Services

• Tags:
• ethernet,
• atm,
• bandwidth,
• ethernet

Overview Traditional metropolitan services are based upon TDM technologies, like SONET, and are optimized for voice services. But with data traffic becoming prominent, new Metro Service Providers (MSPs), also known as IP CLECs, now offer data services based upon Ethernet and IP technologies. The drive to use Ethernet as an communications technology comes from the economic benefits and flexibility that Ethernet offers. MSPs offering Ethernet access can typically offer customers much more bandwidth for much less money.

But a serious challenge faces Ethernet-based MSPs: offering business customers the advanced services already available on ATM or frame relay networks. Today, MSPs rely on VLAN technology and IP networks to offer Virtual Leased Line (VLL) and Transparent LAN Services (TLS). Unfortunately, this is clearly a short term solution. VLANs were never designed for this usage. The IEEE 802.1Q specification allows a maximum of 4096 unique VLANs; as soon as more than 4096 customers need to be supported, MSPs will need new technologies. Furthermore, IP tunnels do not offer the kind of QoS guarantees available with ATM VCs, nor the level of protection that SONET offers. To truly compete with TDM technologies, new mechanisms are required.

MPLS-based TLS and VLL offer an attractive answer. Using MPLS-TLS and VLL allows MSPs to offer security, traffic engineering and QoS services to customers across the Metro network and into the core network. TLS allows MSPs to create a VPN tunnel for every customer through the network. Each VPN tunnel can be provisioned to a customer specified bandwidth and delay. VLL services, in turn, allow MSPs to compete with traditional LECs by offering a bandwidth provisioning point-to-point circuit within the metro. Instead of connecting metro buildings with traditional T1 circuits from a LEC, customers can obtain an Ethernet VLL from an MSP to perform the same service, for far less money.

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