How Many Media Options Do We Have for 10 Gigabit Ethernet?
As the added complexity, power needs and cost of additional GbE adapters will not allow customers to scale to meet current and future I/O demands, it is necessary to migrate to 10GbE. Moving to 10GbE addresses the increased bandwidth needs while greatly simplifying the network and lowering power consumption by replacing multiple GbE connections with a single or dual-port 10GbE connection. Generally, there are three main media options for 10 Gigabit Ethernet: 10GBase-CX4, 10G SFP+, and 10GBase-T. The following text will briefly introduce these three options, including their advantages, disadvantages and applications, to help you better understand them.
10 Gigabit Ethernet, defined by IEEE 802.3ae-2002 standard, is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabit per second. Unlike previous Ethernet standards, 10G Ethernet defines only full duplex point-to-point links which are generally connected by network switches. Like previous Ethernet standards, 10G Ethernet can use either fiber or copper cabling, but higher-grade copper cables are required, such as cat6a or cat7 cables for links up to 100 m. Since it can support higher bandwidth and provide better performance than previous Ethernet networks, 10G Ethernet has been ubiquitous in most data centers.
10GBase-CX4 is the first 10G copper standard published by 802.3 (as 802.3ak-2004). Using Infiniband 4×cabling with each lane carrying 3.125 GBd of signaling bandwidth, CX4 can have a maximum distance of 15 meters. 10GBase-CX4 offers the advantages of low power, low cost and low latency, but it has a bigger form factor and more bulky cables than the newer single lane SFP+ standard and a much shorter reach than fiber or 10GBase-T. The applications of 10GBase-CX4 today are very rare, although some network vendors offer CX-4 interfaces which can be used for either 10GBase or for stacking of switches at slightly lower latency.
SFP+’s support for both fiber optic cables and DAC makes it a more flexible solution than CX4. Here will introduce SFP+ fiber optic cable and SFP+ DAC cable respectively.
There are various of SFP+ modules available on the market which can be cabled with fiber, providing low latency and long transmission distance, such as 10GBase-SR, 10GBase-LR and 10GBase-ER. Take Finisar FTLX8571D3BCL as an example, it can work through a multimode optical cable to support the link length of up to 300 m, achieving the maximum data rate of 10.51875Gbps. Generally, fiber cabling coupled with SFP+ transceivers offers the best power consumption footprint, however it is more expensive than other 10G media types.
10G SFP+ DAC (shown in the following picture) is a lower cost alternative to fiber, but its reach for passive cables is limited to 7 meters, and it is not backward-compatible with existing GbE switches. Since DAC requires the purchase of an add-in adapter and uses a new top-of-rack (ToR) switch topology, it is much more expensive than structured copper channels and cannot be field-terminated. Besides, with the deployment of ToR, it is very difficult to use all the switch ports purchased due to the generally lower number of server adapter ports and the limited reach of the cables. The unused ports carry an initial cost outlay and require maintenance costs, making them expensive on an ongoing basis.
10GBase-T, or IEEE 802.3an-2006, is a standard released in 2006 to provide 10G connections over unshielded or shielded twisted pair cable, which can support the distances up to 100 meters. With backward-compatibility, 10GBase-T, cabled with cat6a or great cabling, can be used in existing 1GbE switch infrastructures, which helps IT managers to keep costs down while offering an easy migration path to 10GbE. The main drawback to 10GBase-T is the very high power consumption per port, around 6 w per port for current devices. However, since it retains the incredibly simple cabling of other -T standards, 10GBase-T has gained increasing popularity in recent years.
10G Ethernet has become a common choice for enterprise, metropolitan and wide area networks. Three 10G media options have been introduced above—10GBase-CX4, 10G SFP+ and 10GBase-T. If you want to choose the right one for your 10G infrastructure, you should take many factors into consideration, like power consumption, cost, transmission distance, etc.
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