# How to implement low latency 10GbE DWDM, cost-effectively

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Dense wavelength division multiplexing (DWDM) is a multiplexing technology that creates parallel data channels over a common fibre by sending each channel on a different wavelength of light. The capacity of a single fibre pair can be increased by a factor of at least 32. Almost 20 years old, DWDM is a staple for transmitting information over long distances.

DWDM is no longer just for telcos and service providers. With dark fibre drops widely available and network equipment manufacturers offering DWDM transceivers in their switches, multiplexing up to 40 x 10GbE channels (100 GHz spacing) using fixed-frequency transceivers and 96 x 10GbE channels (50 GHz spacing) using tunable transceivers down a single fibre is now possible using readily available DWDM transceivers.

#### Conventional Low-latency DWDM Implementations

A configuration such as the following is often adopted (DWDM components are in red):

The switches are each equipped with 24 x 10GBASE-ZR DWDM SFP+ transceivers, one per wavelength, on the WAN side.

Most of the major network equipment manufacturers selling low-latency switches mandate that their own transceivers be used with their devices. These can be rather pricey at over $20,000 (list) or ~$13,500 (street). Equipping a pair of switches with 24 DWDM transceivers would cost over \$600,000 (street).

#### Metamako DWDM Device Support

All current Metamako devices fully support a large range of off-the-shelf DWDM SFP+ transceivers from a number of leading vendors. These transceivers are significantly less costly than those sold by the major network equipment manufacturers.

For example:

#### Alternative Low-latency DWDM Implementation

A functionally identical, solution to the above could therefore be:

In this solution, each switch can use switch-vendor supported SR transceivers or even-more cost-effective switch-vendor supported TwinAx to connect to a MetaConnect 48 rather than DWDM transceivers. The MetaConnect 48 acts as a 24-port pass-through device converting each 10GBASE-SR or 10GBASE-CR to a DWDM wavelength via supported off-the-shelf DWDM SFP+ transceivers.

#### Doing the Maths - Cost Savings on implementing DWDM

Replacing one pair of the DWDM transceivers in the switches with a pair of MetaConnect 48 devices and the associated transceivers and cabling would save:

* Metamako promotional pricing valid until 31st July 2017

This represents a significant cost saving with the only penalty being a 4 ns latency increase through each MetaConnect 48, with an additional 5 ns latency for the 1 m copper cable between the MetaConnect 48 and the Layer 2/3 switch.

Cost savings quantified:

• A 23% saving replacing one wavelength
• A significant 75% saving, when increasing the number of wavelengths replaced to four
• An even more significant 98% saving when fully-populating a MetaConnect 48 with 24 wavelengths

#### Going beyond DWDM - additional benefits of MetaConnect 48

Adding the MetaConnect 48 devices also provides a number of supplementary benefits not generally available from switches:

• Each port on the device can be remotely re-patched to any other port with without the need for physical interaction by data center engineers or hot hands
• Ports may be replicated, multiple times if required, allowing ultra-low-latency fanout of data or allowing links to be monitored
• Full Layer 2 statistics are available on each physical port
• A per-port eye diagram can also be generated to facilitate troubleshooting physical connectivity

And, since all Metamako devices come with the same MetaConnect functionality built in, it's also possible to converge other functions into the same device – patching, tapping, timestamping, aggregating, filtering and more

#### In Summary

• Plugging switch-vendor-mandated DWDM transceivers into their devices can be costly;
• It is cost effective to purchase a pair of MetaConnect 48 devices with associated direct-attached-copper and DWDM optics and cabling to replace even a single pair of switch-vendor-mandated DWDM transceivers;
• As the number of DWDM wavelengths required increases, the savings become substantial;
• All the Metamako devices offer this functionality and more.