Are 100GE transceivers suitable for an aggregation switch?

By the end of 2015, 100GE equipment will be widely deployed and will not only become a significant portion of telecom core routers, but will also be found in aggregation switches. It will perform in “bump in the wire” DPI (Deep Packet Inspection) applications as high-end firewalls, low full interception, and QoE  (Quality of Experience) service management.

As with new standards in general, we need to ask, “What will be the ultimate form factor of the optical transceiver that can deliver this new standard, and can it support a wide variety of technologies and not just at “cherry-picked” locations?”

Generally speaking, over time, network-equipment developers are motivated to create devices that consume as little real estate and power as possible, while achieving necessary price points and delivering superior performance.

Carrier Ethernet MPLS Aggregation Switch

As a good example of this trend, we can observe what happened with10GE devices in the not-too-distant past. At the outset, 10GE devices utilized an XFP form factor. Although not very impressive by today’s standards, it was massively deployed. But it was soon replaced by the SFP+ that offered the usual advantages of compactness, performance and cost savings.

The first optical transceivers that were shipped with 100GE optical transceivers were CFP 100 Gb/s, 10GE x 10 lane electrical interface as defined in 802.3ba. Adequate for a start, but CFP2 soon came along and achieved 5 x 25G (or 10 x 10G) lane electrical interface while it reduced the form factor by half from 82mm to 41mm. Even so, pricing was too expensive and the footprint too large to trigger mass deployment.

Today, two new form factors are competing to become the successor to CFP2: CFP4 and QSFP 28 (also known also as QSFP2). Which is better?

CFP4 is slightly wider and longer than QSFP28 while both are about four times smaller than the original CFP. Both support modules of less than 6W of power consumption. In fact, QSFP28 can even achieve 3.5W. Despite the size and performance advantages of QSFP28, stacking it is more difficult than belly-to-belly CFP4 due to heat, signal integrity and EMI considerations. But, if the manufacturer is willing and able to cope with the stacking challenge, QSFP28 is indeed the superior choice. The remaining mystery is: who will be first to achieve 40KM distances, if anybody.

Telco Systems’ next-generation 100GE ATCA switch, T-ATCA510, or next-gen Carrier Ethernet MPLS Aggregation Switch will utilize the best successor to the CFP2. For us, it’s the QSFP 28. The importance of power consumption and constrained front panel real-estate outweigh the difficulties involved in designing a high-capacity, 1U, rack-mount switch. We can cope with that challenge. Our customers will get the benefit of a superior solution.


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