Cut Sheet

COTB02--WW-ENG, Rev.0, 10/2014 Page 2 of 2
©2014 Panduit Corp. All Rights Reserved.
40GBASE-T will Include 25GBASE-T and Use the Same Category 8 Channel Already Developed
Because the industry-wide view is that 40G to the server will be limited in scope, the development of the
40GBASE-T standard (IEEE 802.3bq) will expand to include 25GBASE-T to support 25G to the server
over twisted pair. The plan is to have a new Call for Interest in the IEEE to officially begin work on
25GBASE-T in November, 2014. It will then roll into 40GBASE-T to become the 25G/40GBASE-T
standard. The combined 25G/40GBASE-T standard is expected to reuse much of the work done for
40GBASE-T, such as using the same shielded, 2 connector, 30 meter Category 8 channel. This is
expected to help keep to the original timeline of being released in early 2016. Category 7/7A cabling and
connectors are not expected to work, due to the 2GHz bandwidth requirements of this standard (Cat 7 is
600MHz, Cat 7A is 1GHz).
Figure 2: Category 8 Channel Maximum Length Configuration
Retaining the 30 meter channel used for 40GBASE-T development limits the complexity of the
25GBASE-T equipment to minimize time to market. It also limits the power per port to under 3W on first
generation equipment, and provides a true upgrade path where the same 30 meter channel can be used
to support 25GBASE-T, 40GBASE-T, and 50GBASE-T.
25GBASE-T is Good News
The standards for 25GBASE-T and 25G DAC are both scheduled to be released at about the same time
in 2016. With a longer 30 meter reach and a cost effective price, 25GBASE-T presents a strong
alternative to the 3-5 meter 25G DAC. It will allow customers a more cost-effective alternative for 25G for
both Top of Rack (ToR) server connections using point-to-point patch cords, and enable End of Row
(EoR) or Middle of Row (MoR) by using the 30 meter structured cabling. This is all achieved with the
commonly used RJ45 plug and connector, which offer the familiar advantages of BASE-T:
Backwards compatibility
Auto-negotiation
Cost effective
Conclusion
The dominant next-generation server connection speed is going to be 25G at the server. This may limit
40G to the server, as the migration path from 25G would be to 50G or 100G. However, 40G between
switches is expected to remain and will not be affected by this development. A current IEEE study group,
driven by the needs of high density cloud computing, is working on 25G to the server using a breakout
100G QSFP28 to four 25G SFP28 copper cabling with the potential for 25G optical. An upcoming IEEE
study group will begin working on 25GBASE-T over twisted pair to provide a cost competitive longer reach
option for mainstream customers wanting to use EoR and MoR architectures.
Panduit recommends that data centers start planning for the 25G to the server, and will be glad to offer
our expertise in choosing the physical infrastructure that best meets your needs.