Ethernet LAN (E-LAN) is a multipoint Carrier Ethernet service type that connects multiple sites, two or more, so that each can send traffic directly to any other, as if they were plugged into the same local area network. It is one of the service types defined by MEF, the industry body that standardizes Carrier Ethernet, alongside point-to-point E-Line. Providers deliver E-LAN using various technologies, such as Virtual Private LAN Service (VPLS), but the buyer sees a single Layer 2 network spanning its sites.
At a glance
- E-LAN is multipoint-to-multipoint: every site can reach every other site without traffic passing through a hub.
- It runs at Layer 2, so sites can share a subnet and IP addressing is under your control.
- MEF defines two flavors: a port-based version (one service per port) and a VLAN-aware version (a port can carry several services).
- Providers commonly deliver it over MPLS with VPLS or EVPN, but the delivery technology varies.
- Bandwidth, number of sites and MAC address limits are set per service and vary by provider.
What problem it solves
Connecting many sites with point-to-point circuits grows quickly in cost and complexity: a full mesh between ten sites needs dozens of circuits. A hub-and-spoke design is cheaper but forces site-to-site traffic through headquarters, adding latency and a single point of failure.
E-LAN gives each site one connection into a shared provider network that forwards traffic directly between sites. Adding a site means adding one port, not a new circuit to every other location. Because it works at Layer 2, it also suits applications or systems that expect devices to be on the same network segment, such as some data center, storage and building systems.
How it works
Ports and service. Each site gets an Ethernet port, the user-network interface (UNI), on the provider’s equipment. All sites in the service belong to one Ethernet virtual connection that the provider’s network treats as a private LAN.
Port-based or VLAN-based. In the port-based version, often called EP-LAN, the whole port belongs to one E-LAN. In the VLAN-based version, often called EVP-LAN, the port can carry several services, each identified by VLAN tags, so one physical connection can join an E-LAN and other services such as Ethernet Virtual Private Line (EVPL) circuits.
Forwarding. The provider’s network learns which MAC addresses sit behind which site and forwards frames accordingly, flooding unknown or broadcast traffic to all sites. Providers usually cap how many MAC addresses each service can learn and may rate-limit broadcast traffic.
Delivery technology. Within the provider’s network, E-LAN is commonly built with VPLS or EVPN over MPLS, or with provider bridging in metro networks. These choices affect scale and resilience but not what the customer plugs into.
Bandwidth profiles. A port or service may have a bandwidth profile with a committed rate and an excess, best-effort rate; how commitments, bursting and oversubscription work varies by provider. Because any site can send to any other, sizing ports for peak traffic matters more than in hub-and-spoke designs.
For help choosing between Layer 2 services, routed VPNs and SD-WAN, see our private networking page.
When it matters for buyers
- Several main sites exchange heavy traffic. Data centers, campuses or regional offices that replicate data between each other benefit from direct paths.
- Layer 2 is a requirement. Some applications, migrations and clustered systems expect a shared segment across locations.
- Replacing a mesh of private lines. Consolidating point-to-point circuits into one multipoint service can simplify management.
- Considering Layer 3 alternatives. If you would rather the provider handle routing, an MPLS IP VPN or SD-WAN may fit better.
Questions to ask vendors
- Is this port-based or VLAN-based E-LAN, and can other services share the port?
- Which technology delivers the service in your network, and how does it handle failures?
- What are the limits on sites, MAC addresses and VLANs per service?
- How do you control broadcast storms and loops?
- What committed rate, burst and class-of-service options apply per port?
- Which sites are on-net, and how are off-net sites connected?
- What do the SLA’s latency, loss and availability targets cover, and between which points?
How it differs from VPLS
E-LAN is the service; VPLS is one way to build it. VPLS is a technology that emulates a LAN over an MPLS network, and many providers use it to deliver E-LAN. Others use EVPN or provider bridging instead. When you buy, compare the E-LAN service terms: ports, limits, performance and SLA. Ask about the delivery technology mainly to understand scale and how failures are handled.