The small form-factor pluggable (SFP) or Mini-GBIC is a compact, hot-pluggable transceiver used for both telecommunication and data communications applications. It interfaces a network device mother board (for a switch, router, media converter or similar device) to a fiber optic or copper networking cable. It is a popular industry format supported by many network component vendors. SFP transceivers are designed to support SONET, Gigabit Ethernet, Fibre Channel, and other communications standards.
InfiniBand is a switched fabric communications link used in high-performance computing and enterprise data centers. Its features include high throughput, low latency, quality of service and failover, and it is designed to be scalable. The InfiniBand architecture specification defines a connection between processor nodes and high performance I/O nodes such as storage devices.
The SDR serial connection's signalling rate is 2.5 gigabit per second (Gbit/s) in each direction per connection. DDR is 5 Gbit/s and QDR is 10 Gbit/s. FDR is 14.0625 Gbit/s and EDR is 25.78125Gbit/s per lane.
For SDR, DDR and QDR, links use 8B/10B encoding — every 10 bits sent carry 8bits of data — making the useful data transmission rate four-fifths the raw rate. Thus single, double, and quad data rates carry 2, 4, or 8 Gbit/s useful data, respectively. For FDR and EDR, links use 64B/66B encoding — every 66 bits sent carry 64bits of data. (Neither of these calculations take into account the additional physical layer overhead requirements for comma characters or protocol requirements such as StartOfFrame and EndOfFrame).
Implementers can aggregate links in units of 4 or 12, called 4X or 12X. A 12X QDR link therefore carries 120 Gbit/s raw, or 96 Gbit/s of useful data. As of 2009 most systems use a 4X aggregate, implying a 10 Gbit/s (SDR), 20 Gbit/s (DDR) or 40 Gbit/s (QDR) connection. Larger systems with 12X links are typically used for cluster and supercomputer interconnects and for inter-switch connections.
10GBASE-CX4 — was the first 10G copper standard published by 802.3 (as 802.3ak-2004). It uses the XAUI 4-lane PCS (Clause 48) and copper cabling similar to that used by InfiniBand technology. It is specified to work up to a distance of 15 m (49 ft). Each lane carries 3.125 G baud of signaling bandwidth.
10GBASE-CX4 offers the advantages of low power, low cost and low latency, but has a bigger form factor than the newer single lane SFP+ standard and a much shorter reach than fibre or 10GBASE-T.
SFP+ Direct Attach
Also known as 10GSFP+Cu or 10GBase-CR, this uses a passive twin-ax cable assembly and connects directly into an SFP+ housing. It has a range of 10 m and like 10GBASE-CX4 is low power, low cost and low latency with the added advantage of having the small form factor of SFP+. SFP+ Direct Attach is expected to be the optimum solution for reaches of 10 m
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