Know-how

25. October 2016

Category 8

Milestone in information technology

The trend towards ever-higher transmission rates is holding steady. Ever more powerful mobile devices are transmitting and receiving ever more data. Users want to post and send images and video clips spontaneously and from anywhere. And soon autonomous, networked driving will produce an astounding amount of data that will have to be transmitted and processed. That puts more and more pressure on backbone networks and data centers to handle a literal flood of data. The data rates of ten gigabits per second offered by the 10GBASE-T variant of Ethernet are in many cases simply no longer sufficient. Faster alternatives will be essential but will have to be cost-effective.

40 Gigabit Ethernet (40GBASE-T) provides four times the data rate of the existing 10 Gigabit Ethernet standard, offering the high performance of fiber optics in proven, cost-effective copper cabling. Requirements for cable components go far beyond the performance capabilities of existing categories. The standards bodies have reacted, working out new specifications. As of now, there are three different versions of a new component Category 8, so in practice one encounters a wide variety of opinions and manufacturer statements.

Categories 8, 8.1 and 8.2

In the United States, the TR42.7 working group of the ANSI/TIA standards committee specifies cabling components in Category 8 that are backwards-compatible with Category 6A, 6 and 5e RJ45 connectors compliant with ANSI/TIA-568-C.2.

The international standards bodies ISO and IEC (JTC1 SC25 WG3) have simultaneously specified two globally valid variants: Categories 8.1 and 8.2.

ISO/IEC Category 8.1 components build a Class I link. They are backward-compatible with the RJ45 plug for Categories 6A, 6 and 5 specified by ISO/IEC 11801 and EN 50173.

ISO/IEC Category 8.2 components build a Class II link. The draft standard defines different plug types that are not compatible with one another. Category 8.2 components offer greater margins than Category 8.1 components and are backward-compatible with components in Category 7A and 7 with the appropriate plug. Category 8.2 plugs are not backwards-compatible with RJ45 connectors, and therefore cannot be used with the vast majority of existing cabling.

All three categories are specified up to a maximum frequency of 2 GHz. TIA and ISO/IEC are currently discussing harmonising the specifications on both ends, as well as including Category 8.2 components in the TIA standard.

The different component categories in Cat.8 in overview:

Component category Link class Max. frequency Standards body Validity 25GBASE-T 40GBASE-T Plug compatible
with RJ45 jacks
8 Cat.8 link 2 GHz ANSI/TIA USA yes yes yes
8.1 I 2 GHz ISO/IEC global yes yes yes
8.2 II 2 GHz ISO/IEC global yes yes no

Link models in practice

The maximum channel length of 40GBASE-T is 30 meters. It is divided into cable sections of up to 24 meters and at most 3 meters for patch cords on both ends.

A channel may contain at most two plug connections (2-connector channel). The direct connection of devices (Direct Connect, or end-to-end link) is also supported. In this case, the devices, for example a switch and a server, are connected directly by the cable, which is provided with locally assembled plugs at both ends.

mfp8-bg.jpgExample of a field-assembled RJ45 plug (Telegärtner MFP8) that can be used to connect devices such as switches and servers directly to the cabling (Direct Connect).

The manufacturers of active network components have spoken for an RJ45-compatible plug configuration, and therefore for the international use of Category 8.1. This solution is backward-compatible with the billions of RJ45 connections installed worldwide.

Naturally, Telegärtner has been active in the development of practical components in Category 8.1 right from the start.

Telegärtner: Your competent system supplier

As an innovative, competent system supplier, Telegärtner has their own leading test laboratory for the testing of development samples, prototypes and series products. Telegärtner test equipment far exceeds the requirements of applicable standards. Impressive examples include the Direct Probe used to measure RJ45 components directly without diversion through coaxial test leads, providing reliable precision measurements, or the world's first test adapter for Category 6A RJ45 patch cords. Many of the test adapters used by independent measurement and testing laboratories originated at Telegärtner.

For detailed information about 25/40GBASE-T and Category 8 please read our special topic.