What is 25gbase-t?
In recent years, 25gbase-t (that is, 25g twisted pair Ethernet) technology has become a popular technology in cloud computing data center due to its high port density, low power consumption and network deployment cost. 25gbase-t can achieve 25gbps transmission on a single channel, and can support higher bandwidth Ethernet upgrade. It is suitable for data center and server room. This article will give a comprehensive introduction to 25gbase-t.
25g Ethernet adopts 25gb / s single channel physical layer technology, which can realize 100g transmission based on four 25gbps fiber channels. Since the sfp28 package is developed based on the SFP + package, and their sizes are similar, the 25g sfp28 port can be compatible with the 10g SFP + port, but the bandwidth of the 25g sfp28 optical module is 2.5 times that of the 10g SFP + optical module. Compared with 40g Ethernet, 25g Ethernet has significant performance advantages, which can provide higher port density and lower bandwidth cost. In recent years, 25g products (such as 25g switch, optical module, DAC, AOC, etc.) have been widely used in cloud data center and 5g network.
25g is mainly used for the access between tor switch and server (the server access of next generation data center), and 100g or higher rate network upgrade. 40g is mainly used for the connection between switches in the data center to help break the bottleneck of the connection between access switches and distribution switches. If 25g can be widely used in switch interconnection, it will promote the further development of 25g Ethernet. At the same time, with the arrival of 5g network, the demand of 5g forward transmission for 25g WDM optical module will make 25g Ethernet usher in a new peak of development. For 40g, because its efficiency is higher than 10g and cost is lower than 100g, it is still the best choice for high bandwidth.
25gbase-t standard and technology
25gbase-t standard was developed by IEEE in 2016. It can realize 25gbps data transmission through twisted pair.
Name | Standard | Transmission media | Number of media | Gigabaud per channel | Maximum transmission distance | RS-FEC (802.3by CL 108) |
25GBASE-T | 802.3bq(CL 113) | Cat8 Copper twisted pair | 4 pairs | 2.000 | m30 | Unsupported |
25gbase-t technology is based on 10Base-T technology and can be compatible with 10gbase-t. after continuous development, it can be compatible with 40gbase-t. The parameter comparison of 10G / 25g / 40gbase-t technology is shown in the table below. By comparison, it can be found that the complexity of 25gbase-t technology is similar to that of 10GBASE-T technology. Meanwhile, 25gbase-t follows the 40gbase-t technology developed earlier, which will effectively reduce the complexity of 25gbase-t equipment and shorten the time to market. In addition, 25gbase-t uses SerDes technology, and Gigabit connection unit interface specification and sfp28 protocol are also reused by 25gbase-t.
Parameter | 10GBAES-T | 40GBASE-T | 25GBASE-T |
Passageway | 100m,CL 55.7 | 30m,CL98 7d1.0 | 30m,CL98 7d1.0 |
Baud rate (MHz) | 800 | 3200 | 2000 |
Receive significant bits | 9.5-10 | 7.8 | 6.5-7.5 |
Channel IL (DB) | 46.9 | 29.4 | 22.6 |
Channel round trip (baud) | 880 | 1056 | 660 |
Echo cancellation (DB) | 55 | 47(-6dB)~55 | 43(-12dB)~55 |
Next elimination (DB) | 40 | 34(-6dB)~40 | 28(-12dB)~40 |
FEXT elimination (DB)) | 25 | 22(-3dB)~25 | 19(-6dB)~25 |
Relative SNR margin (DB) | 0 | +2.7dB~0.2 dB | +8.7 Db~+4 dB |
What are the advantages of 25gbase-t?
Why is 25gbase-t so popular in a short time? The main reasons are as follows:
Excellent output / input ability and structure ability
25gbase-t can cost effectively expand the bandwidth capacity, and can meet the requirements of cloud data center and the next generation of data center servers and storage devices. 25gbase-t can achieve 25gbps transmission with a single channel. Compared with 10GBASE-T, it improves the network bandwidth performance by 2.5 times. At the same time, 25gbase-t can provide 4 times of switching port density for each switching chip. Compared with 40gbase-t, 25gbase-t has higher port density and better scalability.
Use automatic negotiation and high compatibility
According to the 25gbase-t standard, the port of the switch can automatically identify the transmission rate and create links at the same rate. Through the industry standard interoperability specification, the network upgrade is greatly simplified and the connection cost is effectively reduced. At present, the commonly used interoperability specifications are 10GBASE-T, 40gbase-t, 50gbase-t and 100gbase-t. 25gbase-t can not only be backward compatible with 10GBASE-T, but also provide forward compatible capability (such as 100g Ethernet) through automatic negotiation, which undoubtedly improves the connection efficiency and effectively saves the cost.
Flexible topology
It can be seen from the above that 25gbase-t can realize 30 meter data transmission with cat8 network jumper. Compared with 25G DAC high-speed cable, 25gbase-t has a long transmission distance, so 25gbase-t can support more topology cabling, such as the connection between cabinets or between EOR switch and server, MOR cabling, etc. For this reason, 25gbase-t is regarded by most large cloud data centers as an effective solution to manage switches in hundreds of cabinets.
Application of 25gbase-t
As mentioned above, the application of 25gbase-t is similar to that of 40gbase-t. its biggest advantage is that cat8 network jumper can be used to realize the transmission distance up to 30m, which fills the gap of short distance transmission, especially suitable for mor and EOR wiring. Therefore, 25gbase-t is widely used in the connection between switch and server in cloud data center.
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