Carrier Ethernet Transport (CET)

Another technology being discussed nowadays is Carrier Ethernet Transport (CET). Though this is not a wireless technology as such, it would still be very important as (can be seen from the diagram) the user data will be carried over this to the core.

A simple and straightforward explanation was not as easy to find but here are some more details which will give you a good idea.

Good source of introduction is this article from Meriton Networks:

Carriers around the world are increasingly being pressured to provide new services while reducing their costs to remain competitive with changing regulations and new, non-traditional entrants into the marketplace. As carriers migrate to next-generation networks (NGNs) to reduce their costs and improve their ability to support high bandwidth-intensive services with guaranteed SLAs, they need a flexible, scalable optical transport
infrastructure – especially in the metro network – that efficiently supports
Ethernet and minimizes operational complexities.

Carrier Ethernet Transport (CET) is an architectural approach to building scalable transport infrastructure for supporting Ethernet and the evolution to NGNs

* Carrier Ethernet Transport integrates intelligent WDM (ability to do multi-degree switching at wavelength and sub wavelength levels) with
Ethernet Tunnels, such as PBB-TE and T-MPLS .
* Carrier Ethernet Transport (CET) provides the simplicity and cost-effectiveness of native Ethernet with the reliability and power of WDM to deliver unparalleled flexibility, efficiency and cost savings
* Note that “Carrier Ethernet” comprises two distinct sub-segments: “Carrier Ethernet Services” and “Carrier Ethernet Transport”

Carrier Ethernet Transport is an architecture for NGNs based on wavelength networking. Services from both wireless and wireline access networks are simultaneously carried on a single network infrastructure. Three levels of embedded transport networking switching capabilities (wavelength, sub-wavelength, and Ethernet tunnels) provide a cost-effective transport network that can support services with guaranteed service level agreements (SLAs).

A good introduction is an article in Lightwave titled, "Carrier Ethernet transport: No longer 'if,' but 'how'". There are some very good diagrams explaining the concept and its difficult to reproduce them here.

Another article in Converge! Network Digest suggests that CET is not the only way and there are alternative technologies available. The main advantage with CET is that it can reduce complexity compared to its main rivals.

CET offers the following direct benefits to carriers as they migrate to NGN:

• Maximizing the amount of Ethernet traffic that can be switched and routed without leaving the optical transport layer
• Reducing the load on expensive MPLS systems and precious LSPs
• Reducing the number of expensive optical ports required at metro/core hub points
• Providing a circuit-orientated transport model similar to SDH/SONET – which has great benefits from an OSS and operational perspective
  

Additionally, CET provides an architecture that clearly separates the service and transport layers. Separation is an important attribute to allow the independent and efficient scaling of the service and transport layers. Separation also allows the transport layer to focus on its main task in the network – to provide to the access and service networks a large volume of circuit-orientated point-to-point paths that are deterministic and reliable.

Finally the article that made me curious about this subject was this article from Telecommunications Online (Part1 Part2) which is an interview of a Nokia-Siemens manager. Some interesting points as follows:

Telecommunications: You mentioned CET. Although it’s still an early concept, how are service providers responding to the idea at this time?

Bar-on: The perspective is very positive. CET is optimized transport Layer-2 carrier packet traffic. Traffic is growing tremendously. Sometimes you hear a number of 100 percent per-year growth in some carriers, but the average number would be about 70 percent. Everyone realizes the infrastructure needs to be packet-optimized. The way we present CET is it’s a combination of Ethernet and WDM. This has been positively received when looked at by carriers. You can have an argument as to what protocols to use, but CET is the next transport layer. Many carriers are looking for a migration from the current TDM- based infrastructure to a packet
optical-based infrastructure.

Telecommunications: Outside of traditional enterprise services, there’s a lot of talk about using Ethernet for wireless backhaul. Albeit it’s still early, are your carrier customers investigating Ethernet for that application?

Bar-on: We do see a strong requirement from carriers doing wireless backhaul over Ethernet. It’s driven by two elements happening in the market:

1. Base Station Migration: The base stations themselves are migrating from TDM/ATM to 4G or Ethernet. We have the luxury in that we manufacture both the base station and the transmission equipment. We have a dedicated solution because we understand both ends of the market. It’s quite clear that Ethernet will play a role in 4G deployments.

2. Pseudowires: On the other side, carriers are looking to reuse their opex to carry 2G and 3G over Ethernet with Pseudowire rather than SONET/SDH networks. We see it mainly coming from competitive carriers that are trying to fight on the backhaul business to fight with traditional ILECs and PTTs. Having said that we at Nokia Siemens are providing a solution that addresses the current scenario where you have 2G, 3G, and a migration for 4G. What you see in both cases is this metro Ethernet network not only has to address not only Ethernet traffic, but also highly sensitive voice traffic over TDM. For that we believe that concepts like connection-oriented Ethernet can provide five-9s reliability for this kind of service. It’s no longer just about Ethernet access.

Telecommunications: Earlier you mentioned Carrier Ethernet Transport (CET). One of the emerging debates to come out of the CET concept is the use of Provider Backbone Transport (PBT)/Provider Backbone Bridging-Transport Engineering (PBB-TE). How are these concepts resonating with the service provider community?

Bar-on: We’re seeing that everyone is interested in that and want to see if it’s real. Major carriers in the U.S. are very interested in the technology and are in a position to see that it’s real and it’s working. If you look at the cycle of technology, we are probably in the early beginning of the deployment of this technology at least in the U.S. market. We see other groups in Europe going quicker and are leading the camp here, but no one can really ignore this thing. Even if I look at the RFPs by major U.S. carrier out in the market some of them are including requirements for PBT/PBB-TE. If you think about this now and where we were a year ago that’s a major step.