About CX4

2012-12-11 11:38:12

What is CX4?
CX4, also known by its IEEE designation, 802.3ak, supports 10-Gigabit Ethernet data transfer over 4-lanes of copper cabling in each direction (8-lanes total). In order to rapidly bring this technology to market, the IEEE workgroup designed CX4 to utilize field-proven InfiniBand type cabling and connectors. Nearly one quarter of the world's Top 500 super computers utilize InfiniBand interconnects for mission-critical applications, making it an ideal choice for CX4 use. While InfiniBand is more proprietary in nature and requires licensing fees, CX4 is based on an Open Source MSA (Multi-Source-Agreement), allowing any manufacturer to develop CX4 products at significantly lower costs.

What is CX4 Used For?
CX4 is primarily used as a 10-Gigabit Ethernet interconnect for backbone applications. With the rapid rise of Gigabit Ethernet at the desktop level (1000BASE-T), a broader data pipeline is required on the back-end to aggregate data between servers. Therefore, it is not uncommon to see CX4 capable switches installed in nearly any environment, including data centers, enterprise networks, or even HD video distribution hubs.

Are there any Limitations to CX4?
CX4 interconnects offer the advantages of low-cost, low-latency, and low-power consumption at the expense of range. The length limitation for CX4 is 15m (49ft) when using passive cable assemblies. Some novel solutions exist which use active signal boosters or fiber optics to achieve lengths beyond 15m, but these solutions negate the cost, latency, and power benefits inherent to CX4 technology. Fortunately, lengths beyond 15m are rarely needed, since most switches reside in close proximity within a wiring closet.

What do I Need to Integrate CX4 into my Network?
Depending upon your particular requirements, several upgrade paths exist to integrate CX4 into your network. Many switches from companies such as HP, Cisco, and Intel can be upgraded with a CX4 plug-in module. These CX4 modules are available in XENPAK, X2, and XFP configurations. Another option is to purchase a new CX4 capable switch. These high performance switches often feature a combination of CX4 ports and standard RJ45 ports for Gigabit Ethernet. Nearly all servers with PCI-Express slots can be upgraded with a CX4 enabled PCI-E NIC card. Finally, you will need quality CX4 Cables to connect to your gear.

What Types of Connectors are used on CX4 Cables?
A properly designed CX4 cable should feature die-cast SFF-8470 InfiniBand type latching connectors. These connectors are easy to engage and will maintain continuity even if significant strain or vibration exists along the body of the cable. SFF-8470 thumbscrew style (i.e. SAS) connectors should be avoided since most equipment does not support them. Amphenol CX4 cables utilize the best connector on the market today, the Fujitsu microGiGaCN. The microGiGaCN is the market original high-speed, differential-signal, copper interconnect for high-performance (data I/O) applications.

How Does CX4 Compare with 10GBase-R & 10GBase-T?
CX4 has numerous advantages over 10GBase-R (Fiber) and 10GBase-T (Cat-6). An optical connection would require (2) 10-Gig optical modules and a fiber patch cord to function. This has significant cost and power budget implications. Running 10-Gigabit Ethernet over UTP cabling like Cat-6 may sound promising, but it is plagued by power consumption and latency issues. Today's 10GBase-T chipsets are power hogs, as they require several Watts just to separate out signal noise. Here's a comparison of how CX4 stacks up in terms of power-consumption in a 50-server datacenter. Essentially, CX4 consumes 6x-20x less power.