Next Generation Ethernet (NGBASE-T) Beyond Ethernet 10GBASE-T - What does the future hold?

Transcription

1 Next Generation Ethernet (NGBASE-T) Beyond Ethernet 10GBASE-T - What does the future hold? Contents: 1. Scope 2. Ethernet market potential 3. Improvement opportunities for NGBASE-T 4. TE Connectivity activities 5. Conclusions 1. Scope This technical paper provides an overview of the future of Ethernet networking technologies that use twisted pair copper cabling. It also covers the progress of the IEEE standard group that is responsible for defining requirements and also the compatibility of new standards with existing Ethernet services. Firstly, the document explains the necessity for increased network speeds in data center environments. Secondly, it reviews improvement opportunities for passive infrastructure transmission performance to help avoid IC design constraints that would otherwise increase the need for large and costly digital signal processing (DSP) cores to be used. The use of large DSP cores contributed to some of the delays witnessed in the take up of 10GbE. The document concludes by explaining how TE Connectivity is currently at the vanguard of the standards activity and using state of the art design to develop solutions for the transmission requirements to accommodate all current standard proposals.

2 2. Ethernet market potential: Ethernet has become the most widely implemented network physical layer data technology used to support the transfer, process and storage of data across local area networks. The main reason for its success has been the ability to keep the cost per bit at reasonable levels, while traffic has grown exponentially. Cost of installation, simplicity, upgradeability and ease of maintenance are other factors that have helped Ethernet consolidate its position as the preferred option for data transmission. Transmission speed rates have increased rapidly over the last three decades, but the arrival of new communication services like mobile 4G, video distribution, cloud services, storage backup, etc. with the associated huge demand for data transmission will be a real challenge for Ethernet to support, especially in data centers. Fig 1 CPU Performance Drives Network Speeds Networking Speed (Mbps) CPU Performance (MIPS) >8yrs Ethernet Speed CPU Performance 40Gb 3+yrs yrs yrs Time Figure 1 - The Market Need for 40G (Sun Microsystems presentation to IEEE 802.3ba Task Force) The main physical transmission media used are fiber optics and twisted pair copper cabling. Fiber optics technology has always led the way as higher baud rates have initially been deployed, but, historically, it has been matched soon afterwards by twisted pair copper cabling supporting the same speeds, but with more competitive installation costs driving wide market acceptance. Twisted pair copper cabling is the most adopted physical medium in LAN applications, especially for the horizontal distribution of Ethernet services; but it has also achieved significant penetration in data center networks due to its flexibility when implementing the Top of Rack, Middle of Row, and End of Row topologies that are widely deployed in data centers today. Page 2

3 3. Improvement opportunities for NGBASE-T: Currently, the maximum transmission speed that can be achieved with existing twisted pair copper cabling is 10Gbps. The supporting IEEE 802.3an standard, which defines the transmission parameters for 10Gbps Ethernet, was released in June 2006 after three years of work collecting the requirements for compatibility with previous Ethernet services and the accepted topologies. The topologies specified for 10Gbps were based on those that already existed for lower transmission rates and they were mainly designed with office cabling installations in mind, not data centers. As a result, 10Gbps Ethernet active equipment (switches, routers, etc.) had to deliver data transmission up to 10Gbps for a 100m channel configuration of four-connectors for both shielded and unshielded cabling. These requirements placed a constraint upon silicon device designs (referred to as PHY from now on) that, in turn, significantly delayed the uptake of 10Gbps Ethernet technology by the market. The IEEE 802.3bq standard group, which is responsible for defining Next Generation BASE-T, has highlighted some improvement opportunities for cabling infrastructure, with the aim of having the new digital communication service deployed quickly into the market. These improvement opportunities include the following: 1) Shorter network topologies: NGBASE-T (40GBASE-T) is being developed mainly for data centers where the distances between active equipment (switch to server or switch to storage device) are significantly shorter. Reducing channel lengths means higher signal-noise ratios are acceptable and this helps reduce power consumption, one of the most important issues to consider. Fig 2 ToR switches 3.5W/port EoR switches 6W/port Figure 2 - Table of per port power consumption required for typical DC topologies Source: IEEE 802.3bq standard group for 40GBASE-T 2) Support for shielded cabling only: minimizing Alien Crosstalk (noise crosstalk which occurs among adjacent cables) was an important requirement for ensuring the proper operation of Ethernet 10GBASE-T; therefore systems based on unshielded cabling were more vulnerable to this effect. Today, almost everybody accepts the need for shielded solutions to assure the required electromagnetic isolation for NGBASE-T (40GbE). As a result, even many of the cabling manufacturers that lobbied to keep the unshielded configuration for the 10GBASE-T standard have abandoned their position, supporting shielded configurations only for the new standard. Fig 3 Example of how noise crosstalk affects adjacent cables Page 3

4 3) Align the twisted pair copper cabling requirements from TIA and ISO/IEC: These are the two standard bodies that collect the transmission needs from the IEEE standard group for 40GBASE-T and define the cabling standards. Both have open working groups for defining the transmission requirements for the new Ethernet standard. TE Connectivity is contributing to the drafting of both documents with the desired aim of aligning the transmission requirements and avoiding some of the confusion that happens today in the market for 10GbE where TIA and ISO/IEC differs in some requirements. Fig 4 ISO vs TIA Cat. 6A Comp ISO Cat. 6A Comp TIA Cat. 6A Comp 50.0 NEXT in db db Frequency in MHz 1000 ISO/IEC nd Ed. Amd.2 vs TIA-568-C.2 Cat6A NEXT component requirement Example of requirement s divergence The cabling standard working groups are considering two scenarios; the first is called Class I or Cat.8 (depending of the standard body) based on Category 6A style components and the second is Class II based on Category 7A style components. Both scenarios extend the requirements up to 2GHz with the latter being the more demanding. 4) Include the internal layout of the active equipment for channel modelling: Taking the influence of the internal elements of the active equipment (magnetics, track layout, etc.) into consideration in the cabling model during the requirements definition stage, will help with the signal integrity requirements and consequently, reduce power consumption for data post-processing. Fig 5 Equipment Patch Panel Patch Panel Equipment PHY MDI Patch Cord Patch Cord Patch Cord MDI PHY Traditional Structured Cabling CHANNEL MDI connector magnetics and trace length PHY-2-PHY CHANNEL 2-connector Channel configuration for 40GBASE-T Including MDI and Internal layout Page 4

5 4. TE Connectivity activities At TE Connectivity, we are actively participating in the relevant standards groups and our engineers are currently working on innovative designs based on the well known RJ45 interface, achieving excellent results that meet the transmission requirements currently defined by TIA Cat.8 (draft 0.9 Aug 9th 2013) and ISO/IEC Class I (draft N2121 Apr 17th 2013) and take into consideration the backward compatibility with existing Ethernet services. Fig 6 TE Connectivity RJ45 prototype Transmission performance against ISO/IEC Class I (draft N2121 Apr 17th 2013) Even prior to this, we had anticipated the need to design a data connector for higher speed Ethernet applications by launching the AMP-TWIST 7AS SL Jack in The jack already offers premium performance above the Cat. 7A frequency limit of 1000MHz while keeping the well known features of our AMP-TWIST SL Jack family. This connector already meets the strongest requirements of ISO/IEC Class II (draft N2121 Apr 17th 2013) currently defined for 40GBASE-T. Fig 7 AMP-TWIST 7AS SL Jack Transmission performance against ISO/IEC Class II (draft N2121 Apr 17th 2013) Page 5

6 5. Conclusions 40Gb/s servers and switched ports are currently being shipped around the world, and the need to design the network in a data center for future upgrade to those transmission speeds is key. Today the only viable option for transmitting 40Gb/s packets further than 7m in a data center is fiber. The IEEE, TIA and ISO/IEC standards bodies have begun to define the electrical and physical characteristics for channels that will give customers the flexibility to use copper twisted pair technology to transmit 40Gb/s Ethernet traffic. However, there are no parameters currently specified that active equipment vendors can use to design equipment for 40GBASE-T. This in turn means that any designer of a data center network infrastructure cannot confidently design a copper network today for 40GBASE-T transmission, unless they chose to deploy a point to point direct attach network over limited distances. Some of the areas within the cabling standard that still require definition include: 1. Measurement methods at the higher frequencies required to support 40GBASE-T 2. Interoperability between the connectivity solutions of different manufacturers 3. Field verification methods of the installed cabling However, there are a number of areas of agreement that have emerged from the standards activities that give clear direction on the way that things are likely to develop: 1. RJ45 is preferred choice for the Media Device Interface (MDI) connector for 40GBASE-T because of its wide adoption within the industry and its familiar form factor. However, other connectors may be considered if they deliver superior performance. 2. Stronger performance requirements are needed for cabling compared to previous generations of Ethernet to help minimize PHY design complexity and decrease power consumption. 3. Screened products will be necessary to achieve, by design, the stronger electromagnetic immunity requirements that are anticipated. 4. Extending the channel modelling from chip-to-chip is likely with the aim of assuring the data signal integrity and reducing data post-processing. TE Connectivity is a driving force within the 40GBASE-T copper standards activities and is helping to give active vendors information on what is possible to achieve from the physical layer. As we move closer to the proposed publication date for a 40GBASE-T structured cabling standard, sometime in 2015, the physical and electrical parameters will become better defined and TE Connectivity will be part of ensuring customers are given the best possible cabling infrastructure solution available to meet those needs. It is currently too early in the process to make claims of 40GBASE-T performance for cabling solutions and everyone should be cautious when hearing such claims. We are committed to helping network designers, installers and end users to build new data centers ready for 40GBASE-T, while retaining the flexibility inherent within a structured cabling approach to deliver an agile data center.w Page 6

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