Author
Dave Tanis
With all of the buzz and excitement in the cabling industry around Category 8 and 40GBASE-T, one question that comes up is, “What does this mean for Category 7/7A systems?” For years these systems were touted by some as the future-proof solution to meet next generation requirements. Yet in both the TIA and ISO/IEC cabling standards groups, the consensus is that Category 8 is the way forward for 40GBASE-T in the data center. With Category 7/7A , the issue IT managers face quite often is figuring out which connector they should use. Multiple connector form factors have long been the thorn in the side of network designers planning fiber networks until the LC connector emerged as the de facto fiber connector. Having to choose from among multiple connector types was never an issue for those designing copper-structured cabling networks, as there was only one: the ubiquitous RJ-45. This connector can be found on nearly any Ethernet port.
This changed with the advent of the Category 7 standards in ISO/IEC. Still unrecognized by TIA, a full decade after standardization in ISO, the Category 7 standards officially recognize two different connector types; none of which are the RJ-45. The preferred Cat 7 connector is the IEC 60603-7-71and it has 12 contacts: eight on the top and four at the bottom with the key down. The alternative connector is the IEC 61076-3-104 and it is non-RJ-45 with eight contacts.Category 7A followed suit with the same recognized connector types. The industry came out with a printed wiring board (PWB) version of the Cat 7A connector, which is the IEC 61076-3-110 with 8 contacts--four on the top and four at the bottom with the key down.
One of the key objectives of the IEEE P802.3bq 40GBASE-T Task Force is to support auto-negotiation for 1G/10G/40G. However, the media-dependent interface for both 1000BASE-T and 10GBASE-T is based on the RJ-45 interface, which is incompatible with the PWB version of IEC 61076-3-110. This eliminates the auto-negotiation objective, which is unlikely to be accepted by the IEEE. Additionally, incompatibilities exist between some of these outlets and none of them can connect with an RJ-45 plug while maintaining their Category 7A channel rating. This leads to the need for special hybrid patch cords to connect with equipment that almost inevitably will have an RJ-45 port.
Ironically, the popularity and ubiquity of the RJ-45 remains so strong that many Category 7/7A cables end up being terminated on RJ-45 connectors. It is important to remember that a Category 7 or 7A cable terminated in a Category 6A connector becomes part of a Category 6A permanent link.
Category 8/8.1 brings simplicity back by offering the industry favorite RJ-45 as part of the 8/8.1 or Class I standard. In doing so, it provides the answer to the previous question IT managers want to hear regarding which connector they should use: the RJ-45.
With the RJ-45-based Category 6A standards addressing the 10GBASE-T application, and the RJ-45-based Category 8/8.1 addressing the future 40GBASE-T application, where does that leave Category 7/7A systems and their multiple connector form factors?
To learn more about NGBASE-T, download our latest white paper, “NGBASE-T Cabling Requirements,” by Dr. T.C. Tan.
