- Overview
- Carrier Ethernet
- Coarse Wave Division Multiplexing Solution
- Commercial Services Solution
- IP Video Surveillance
- Layer 2 Virtual
Private Networks - Network Resiliency
- OAM
- Provider Backbone Bridging — Traffic Engineering
- Service Assurance
Hard QoS - Switched Ethernet vs. TDM-PON
- Wireless Backhaul Infrastructure
Layer 2 Virtual Private Networks (L2VPN)
Ethernet-based L2VPNs
The most popular, cost-effective technology utilized in access and metro-edge networks is Ethernet. In 1998, Ethernet was augmented to support multiple Virtual LANs (VLANs) on the same physical enterprise infrastructure. Internal departments within an enterprise such as finance, sales, and engineering could be logically separated by using VLANs. VLANs work well in a single administrative domain where all equipment configurations are planned and managed by a single entity. The IEEE 802.1Q standard supports up to 4,094 VLANs – an enormous number for even the largest enterprise, but a potentially limiting number for service providers.
Ethernet Q-in-Q L2VPN
Early Ethernet VLAN-based L2VPNs required customer and provider negotiation of available VLAN assignments. Often, customers were required to change equipment and network settings in order to fit within a provider’s 4K VLAN space. This proved too limiting and the industry quickly moved to adopt a technique known as Q-in-Q (e.g., IEEE 802.1Q VLAN tag stacking). Q-in-Q emerged as a de facto technique for preserving customer VLAN settings and providing transparency across a provider network.
World Wide Packets Ethernet Q-in-Q L2VPN solution supports the delivery of time critical services such as voice and video. In order to maintain acceptable service levels during topology changes, reconvergence must occur within 50 milliseconds or less, much more rapidly than what IEEE 802.1w RSTP alone was designed to support.
The LightningEdge solution has been optimized to enable RSTP reconvergence well below 50 milliseconds. These enhancements allow Ethernet service delivery networks based on LightningEdge products to support critical, time-sensitive applications with the same service level agreements and guarantees of SONET/SDH optical rings.
Ethernet Provider Bridges
Addressing the gap in the definition of Ethernet-based L2VPNs, a project known as IEEE 802.1ad Provider Bridges was created. IEEE 802.1ad formalizes the definition of Ethernet frames with multiple VLAN tags. It also formally labels Customer VLANs (C-VLANs) and Service VLANs (S-VLANs). Provider devices that interface to the customer and that add/remove S-VLANs are known as Provider Edge Bridges. A second class of device, known as Provider Bridges, interconnects Provider Edge Bridges to form IEEE 802.1ad-based L2VPN metro Ethernet networks.
The following figure shows a possible implementation using IEEE 802.1ad Provider Bridges and Provider Edge (PE) Bridges.
Within the service provider network, PE Bridges are used at the edge to interface with Customer Edge (CE) devices. Invisible to the CE devices, there is a mesh of Provider Bridges. Loops are avoided using IEEE 802.1w Rapid Spanning Tree Protocol, which disables redundant paths.
Metro Ethernet Forum
Building upon the constructs defined by IEEE 802 Local and Metropolitan Standards Committee, the Metro Ethernet Forum (MEF) created several Ethernet service definitions. The MEF uses reference points, such as the User-Network Interface (UNI) or Network-Network Interface (NNI), and specifies the observable behavior and characteristics of a given service at that interface.
The MEF defines two types of VPWS services: Ethernet Private Line (EPL) and Ethernet Virtual Private Line (EVPL). The EPL service supports a single Ethernet VC (EVC) between two customer sites (UNIs). Conversely, the EVPL service supports multiple EVCs between two UNIs. According to the MEF definitions in the area of VPLS, the Ethernet LAN (E-LAN) service supports multiple EVCs between multiple UNIs.
In addition, the MEF has created UNI implementation agreements and test suites to promote vendor interoperability and service provider adoption of Carrier Ethernet equipment. World Wide Packets was among the first in the industry to achieve certification of both CPE and metro edge platforms supporting EPL, E-LAN and EVPL services.
