10G Ethernet (10GbE) is a very popular interconnect technology in today’s data center. It’s widely used for servers/storage devices connecting to top-of-rack (leaf) switches, as well as connecting those leaves to the aggregation (spine) switches. According to a Dell’Oro Ethernet Switch Market report published in 2014, 80% of server connections will be 10GbE-based by 2018.
In general, two types of physical media are used in 10GbE interconnects: fiber and copper. For intra-rack (server/storage to leaf switch) connections, most deployments use copper cabling as it is the most cost effective for short distances within the rack.
There are two copper cable types: twinax and twisted pair. Twinax is used in the 10GBASE-CR standard in the DAC (direct attached cable) format, which is a fixed length cable with SFP+ plugs integrated into both ends. Twisted pair, on the other hand, is something that should be very familiar to every IT person. Remember CAT cables and RJ-45? The 10GbE interconnect standard that uses twisted pair is 10GBASE-T, which is officially defined in the IEEE 802.3an standard.
10GBASE-CR with DAC is great and used in many deployments. However 10GBASE-T over twisted pair offers some unique benefits:
Distance & Interoperability
10GBASE-T over twisted pair has a range of up to 100 meters over CAT6A cable and about 50 meters over CAT6, while DACs are limited to much shorter distance. 10GBase-T is a good choice for the deployments where there are lots of existing CAT6 cables installed or many cross connects between the racks. Legacy vendors require proprietary SFP+ optics or cables, while there is no such limitation with twisted pair. It’s plug and play.
Simplicity & Customizability
Twisted pair cable, especially UTP (unshielded twisted pair), is cheap, simple to handle and quite familiar to any IT personnel. For example, it allows customers to use their existing toolsets to customize any length of cables. We have partners who create their whole rack with exact-length UTP cables to ensure a clean and tidy design. Another benefit is to use different colors of cable to indicate different connection types, as some of our customers and partners do, making it easy to maintain and troubleshoot. And it looks great too.
Incremental 1G to 10G Transition
UTP cables are predominantly used for 1GbE connections. 10GBASE-T is backwards compatible with 1GbE (1000BASE-T) and thus becomes the perfect choice for gradual transitioning from 1G deployment to 10G. Customers can pace their server upgrade without worrying if the network connection will work or not.
One of the major concerns on 10GBASE-T is power consumption. However with the latest PHY technologies and relative short distances for intra-rack use cases, the power delta between 10GBASE-T (over twisted pair) and 10GBASE-CR (over DAC) is quite small and pretty much negligible when compared to the overall power consumption of a rack.
The 10GBase-T ecosystem is mature today. The NIC cards and 10GBASE-T LOM (LAN-On-Motherboard) equipped servers are widely available, and with more open networking platforms now supporting 10GBASE-T and more customers transitioning their 1GbE deployments to 10GbE, we believe its deployment will accelerate, especially in enterprise data centers.
Check out the Ethernet Alliance FAQ page to learn more about 10GBASE-T.