The debate whether there is a market for 100G direct detection systems which are essentially Non Coherent is interesting. ADVA is on one side while the rest of industry on the other side. ADVA has been strongly advocating the need for 100G direct detection trasnponders that can cater to the need of what they call 40 KM to 500 KM market segment. This segment is essentially the metro market where cost matters and that is where the DD (Direct Detection) systems cost wise are much better than the Coherent systems. Coherent systems also generate more heat and need more power – A point highlighted by ADVA.

ADVA is almost alone in the camp that is advocating the DD systems, while the rest of the market is on the other side. Coherent market thinks that there is an ecosystem for 100G coherent system which will be affected if a competing technology comes in. The whole idea of having one technology is to have economy of scale; once everyone is developing same technology the costs will bring down automatically. That there is no need for a competing technology specially when Coherent systems can give you some low-cost Metro flavours though not at a cost at which DD system sells.

As an operator, I do have concerns about the cost of Coherent 100g but then there are larger industry interests and that is creating an ecosystem for Coherent 100g components; without the industry focusing on a single technology, there would be a  competition for the market in the metro area between the direct detection and Coherent technologies. This of course does not augur well for the industry in the long-term. I am a firm believer that the cost of coherent will go down in future, if all of us focus on it.  So what do you think about the Coherent versus DD debate, let me know !

Ideally VLAN ID Preservation should be preserved ( CE-VLAN ID = Yes). After all, why it should matter, changing VLAN IDs. Having same VLANs IDs make it operationally efficient for both operator and customer. Operator can trace the circuit well, so can the end customer by just knowing the VLAN IDs. Not to forget that it would be easy to setup such an EVC  since the VLAN ID to EVC map will be much simple in this case.

In this post I will explain that why it is needed to set VLAN Preservation ID = NO

Let’s see the example of setting VLAN Preservation ID = YES and its advantages. See the diagram 1 below, customer has two campuses with the same VLAN number 14. Obviously this situation demands that VLAN Preservation ID should be set to YES. Why asking the end customer to change VLAN IDs in the first place ?

Lets see a second scenario in which two campuses of the same customer are connected to each other but both have different VLANs. The obvious advantage here for using VLAN Preservation ID= No is to let the service provider do the switch and hence in that case the service provider will switch the VLAN ID from 15 to 14  before handing the traffic to B while the converse will be true when handing the traffic to A. This is shown in diagram 2 below.

The three types of  Carrier Ethernet Services are following:

Carrier Ethernet has five essential attributes that must be met as shown in the following diagramImage