Carrier Ethernet is an attempt to expand Ethernet beyond the borders of Local Area Network (LAN), into the Wide Area Networks (WAN).
With Carrier Ethernet, customer sites are connected through the Wide Area Network. Carriers have connected the customers with ATM (Asynchronous Transfer Mode) and Frame Relay interfaces in the past. (User to Network Interface/UNI).
Carrier Ethernet is not about the Ethernet within the Local Area Networks.
Driver of Carrier Ethernet is; since Ethernet is the de-facto protocol on the Local Area Network, why not to use Ethernet everywhere, and not only within LAN. When any other Wide Area Network protocol is used such as ATM, customer Ethernet frame is encapsulated into another protocol.
This reduces the overall efficiency of customer service, consumes more network bandwidth, makes troubleshooting harder and many other drawbacks.
Carrier Ethernet is also known as Carrier Class Ethernet and Carrier Grade Ethernet.
Another reason for Carrier Ethernet is; Ethernet interfaces and the devices are cheaper compare to the other technologies. This result cheaper service to the customers.
CARRIER ETHERNET REQUIREMENTS
Traditional Ethernet lacks many features which are required to transport critical services, time sensitive applications and voice services.
These are:
- Traffic Engineering
- Bandwidth Guarantee
- Quality of Service
- OAM
- Decoupling of Providing and Customer Networks
- Resilience, High Availability, Fast Convergence
Metro Ethernet Forum (MEF) is a standard body which defines the Carrier Ethernet, its services and all the extensions.
CARRIER ETHERNET SERVICE TYPES
MEF has been defined three service types for Carrier Ethernet:
- E-LINE (Point-to-Point)
- E-LAN (Multipoint-to-Multipoint)
- E-TREE (Hub and Spoke)
E-LINE, E-LAN and E-TREE are the MEF terms. They are used as below in the IETF standards. They are exactly the same things.
- E-LINE = VPWS
- E-LAN = VPLS
- E-TREE = VPMS
Very important point in Carrier Ethernet is Service Provider transport protocol doesn’t have to be Ethernet. If it is Ethernet, then the solution is called Carrier Ethernet Transport. So in this case, Customer’s Ethernet frame is carried over Provider’s Ethernet infrastructure with the Resiliency, OAM, Bandwidth guarantee, Traffic Engineering, QoS and other Carrier Ethernet feature supports.
ETHERNET over NON-ETHERNET TRANSPORT
As I stated above, Customer Ethernet service can be carried over Non-Ethernet Service Provider transport infrastructure, so different technologies can be used. These are:
- SONET/SDH
- Ethernet over MPLS (E-LINE, E-LAN , E-TREE)
- MPLS-TP (MPLS Transport Profile)
- PBB-TE (Provider Backbone Bridge – Traffic Engineering)
- Synchronous Ethernet
- OTN (Optical Transport Network)
This is not the full list but the common ones. Still many networks uses SONET/SDH as a transport mechanism.
Recently there are many debates in the Carrier community around MPLS-TP, OTN and Ethernet. I will cover the pros and cons of these technologies in the separate articles.
In this high level overview post, I just wanted to introduce you the Carrier Ethernet, definition , service types and how Customer Ethernet frames are carried over the Non-Ethernet carrier backbone.
Carrier Ethernet and the transport technologies are still evolving. Some standards are completed and others are still being developed.
