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Disadvantages of 10G-T SFP transceiver

Disadvantages of 10G-T SFP transceiver

The 10G-T SFP copper transceiver, which originally enables the SFP + port transceivers to be connected to the 2.5G / 5G-T, which has been increasing in recently and large orders have been received. If you have a lot of UTP connections in the first place, you will probably arrange an Ethernet switch with a UTP port at the beginning, so it is natural that there are no large necessary of 10G-T SFP optics.

It's a good idea to plug it into the last port of a switch that has an SFP + port, or put it together with a USB 2.5G-T adapter for your notebook PC. It is a very easy-to-use transceiver.

However, there is a drawback because it is a "deception" implementation on the switch side if it is 10GBASE-SR.

  1. In IEEE802.3an, which supports only 30m at 10Gbps, the maximum 100m of UTP of Cat 6a is the specification of 10GBASE-T. However, this product only supports up to 30m, which is called the short reach mode. The main reason is power consumption, which exceeds 3.3V 700mA (2.3W), maximum 900mA (3.0W), which is equivalent to the optical transceiver, and SFP + (SFF-8472) power level 3 (2.0W) even with a limit of 30m.
    But the future model currently under development is expected to consume less power.
    Regarding the distance limit, it is 2.5G or 5G when connecting a wifi AP etc. But it is a server when connecting with 10G and it fits in the wiring in the rack, so it seems that there is not much operational problem.
  2. Now many 10G-T switches equipped with an RJ-45 port can determine which link speed is linked by the blinking pattern or color of the LED.
    You can also check the link speed using the CLI or GUI.
    In Rate Match, the switch side is fixed at 10 Gbps, so on the switch side, it is not possible to know at what speed the link is unless that additional implementation is performed by referring to the register inside the transceiver. In addition, the transceiver does not have a display function such as an LED.
  3. It has a buffer internally because there is a bandwidth difference inside the transceiver that cannot recognize the overflow of the internal buffer. This buffer will not overflow if the traffic flow has a flow control such as TCP, but if broadband data such as audio or video flows through UDP, the buffer may overflow. 
    However, the overflowing information cannot be recognized by the switch, so it is not reflected in the buffer overflow counter provided on the switch interface. It becomes an obstacle when tracking which stage of the route the packet loss is occurring.
    The buffer size is 16Kbytes.

After all, the SFP + port is essentially a specification for optical transceivers, and UTP is also incidental to use outside of 10Gbps and has various restrictions.

SFF-8472 Power Level

  • Power level 1: 1.0W max
  • Power level 2: 1.5W max
  • Power level 3: 2.0W max
  • Power level 4 (3+)

Powr class III was added to SFF-8431 in rev 4.1 (2013-06-20)

Power level 3 added in SFF-8419 Rev 1.0 (2015-03-31), a replacement for SFF-8431

Power level 3 plus added in SFF-8472 Rev 11.9 (2014-08-14)

At the IEEE802.3an meeting, it was rejected in November 2005 to adopt the short read mode, but the mounting technology at that time required 10W of power consumption to achieve a full spec of 100m. IEEE803.an-2006 includes a short reach mode.

http://www.ethernetalliance.org/wp-content/uploads/2011/10/static_page_files_127_10GBASE_T2.pdf

The outlook for 2005 is 7.0W at 100m for a chip with a 65nm process. 5.0W for the next 40 nm process. In 2020, the actual product will be 2.5W for 28nm process and 1.5W for 30m.

The next generation 12nm process will be below 2.0W even at 100m,

As a real product, Marvell announced the 88X3580 in December 2020, which supports 8-port 10GBASE-T on a 12nm process. Since it is for 8 ports, it cannot be used for transceivers, but by using this product on the switch side equipped with multiple 10GBASE-T, power consumption of less than 2.0W per port can be expected even at 80m link.

Vendor PN Process technology Year of announcement PHY ID
broadcom BCM8481 65 nm May 2008  
Broadcom BCM84821 65 nm 2009  
Broadcom BCM84831 40 nm May 2011  
Broadcom BCM84851 28 nm    
Broadcom BCM84861 28nm December 2014  
broadcom BCM84881     0xae025150
broadcom BCM84891 28 nm   0x35905080
Aquantia AQR113     0x31c31c12
Marvell 88X3310 28 nm 2015? 0x002b09a0

Aquantia was acquired by Marvell in 2019

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