2,5 and 5GBASE-T A Study of Development and Deployment. White Paper January 2017

Transcription

1 2,5 and 5GBASE-T A Study of Development and Deployment White Paper January 2017

2 For more than fifteen years, Category 5e cabling has provided a robust channel for 100BASE-TX and 1000BASE-T to operate. Last year, a new IEEE Standard 802.3bz 2.5/5GBASE-T was published which defines the requirements of new applications to provide more capacity for Category 5e and Category 6 cabling. While this may seem like promising way for some network managers to extend the life of their existing infrastructure, many will find deployment problematic when trying to maximize speeds in a densely-populated, multi-application environment. However, for those deploying new cabling, these new technologies will justify the performance benefits of premium cabling.

3 Increasing Capacity The explosion of wireless bandwidth consumption has driven speeds at the access point beyond 1 Gbps and the expectations are to exceed 5 Gbps by GBASE-T, as the available next step based on copper cable would meet this bandwidth requirement but also requires new Cat6A copper cable and does not operate over the installed base of cabling. The new standard now defines 2 new middle steps in between 1 and 10 Gbps and maybe more importantly, promises to work with the old cabling, the installed base of Cat5 and Cat6 cabling. To achieve this, it reuses 10 Gbps chip sets at reduced clock rates. This technic of Underclocking 10G was chosen as it promised the fastest way to implemention and was combinable with PoE support. A large benefit of adopting 10GBASE-T technology was also that it allows for the possibility of multiple-rate chips that would service 1/2.5/5 and 10 Gbps helping to further increase the industry s return on investment. 10GBASE-T has a Nyquist frequency of 400 MHz, meaning most of the transmitted data or information is contained below this frequency (Figure 1). Reducing the speed by half to 5 Gbps reduces the Nyquist frequency to 200 MHz, falling within Category 6 specified bandwidth. Cutting the speed in half again reduces the speed to 2.5 Gbps with a Nyquist frequency of 100 MHz, the specified bandwidth of Category 5e. Cat 5e (100 MHz) Cat 6 (250 MHz) Cat 6A (500 MHz) Encoding: bits/sec/hz (per pair) G BASE-T 1000 BASE-T 5GBASE-T 10GBASE-T Nyquist Frequency (MHz) for Ethernet Data Rates Figure 1: Application bandwidth based upon 10GBase-T encoding Concerns Although much thought has been given to the best route of product development, larger concerns exist over how the product will be deployed. Designing a system to work over new cabling infrastructure is a relatively simple process with minimal risk and a high degree of expected success. Designing for system operation over cabling infrastructure that was developed in the late 1990 s is risky and may require troubleshooting and vendor interaction to assure system performance.

4 Alien Crosstalk Alien Crosstalk was an issue during the development of 10GBASE-T technology and, as a result, Category 6A was ratified with specified limits on channel Alien Crosstalk performance. With the reuse of 10GBASE-T technology, Alien Crosstalk is expected to be a limiting factor in 2.5GBASE-T and 5GBASE-T system performance. However, near-end and far-end Alien Crosstalk limits were never specified for Category 5e and 6. Consequently, almost the entirety of the installed base of Category 5e and Category 6 cabling was never qualified for Alien Crosstalk performance, and very little reliable data exists about the performance of these systems. 10GBase-T technology employs power back-off as a power-saving and noise-reduction process, by which 10GBASE-T reduces the Signal Strength on short links by decreasing the amplitude of the operating voltage to reduce crosstalk onto longer, adjacent links. Although network integrity is improved through power back-off, it remains heavily dependent upon the built-in alien crosstalk isolation of Category 6A cabling. 2.5GBASE-T and 5GBASE-T will utilize power backoff as well, but it creates issues when deployed with 1000BASE-T on cabling not designed for Alien Crosstalk isolation. Unlike 10GBASE-T, 1000BASE-T does not vary the signal strength based upon the length of the channel, so it is likely that a short 1000BASE-T link at full volume will be adjacent to a 2.5GBASE-T or 5GBASE-T link that is quieter either due to length attenuation or power back-off. This may reduce the 2.5GBASE-T and 5GBASE-T system signal to noise ratios (SNR) to the point that errors are created due to the interference from the adjacent 1000BASE-T links. Cabling systems with poor Alien Crosstalk isolation will be particularly vulnerable to this scenario. But Alien Crosstalk performance is not the only concern, also the frequency range for 5G needs some thoughts before deployment. 2.5G uses 100MHz and is within the range Cat5 and Cat 6. 5G though uses 200MHz, fits into Cat6 cabling but is a stretch for Cat5 installed base. Some electronic manufacturers are indicating that Category 5e will be suitable for the transmission of 5 Gbps and example testing has shown that in some cases, it works for reduced lengths. However, using 100 MHz Category 5e channel for a 200 MHz application with minimal alien crosstalk isolation combined with other factors such as heat from PoE and the operating environment, as well as adjacent cable interference will lead to significant issues with system reliability. Therefore the IEEE standard defines explicitely additional requirements for Cat5 cabling from 100MHz to 200MHz and advises to re-test the installed base before deploying 5G. Table1: New Requirements for installed base / Parameters to verify Frequency Alien Crosstalk 2.5G over Cat5 OK To be checked 5G over Cat5 To be checked To be checked 2.5G over Cat6 OK To be checked 5G over Cat6 OK To be checked IEEE802.3bz defines a full new test method to assess the Alien Crosstalk performance of installed cabling base. This new method is called ALSNR Testing: Alien Limited Signal to Noise Ratio testing.

5 How fast am I really going? One key to technology acceptance is to make adoption as easy as possible. The box vendors are working towards this goal by developing system components that automatically configure to the highest operational speed that meets the 802.3bz bit error objective. In the past, auto-negotiation was a method for equipment to advertise its transmission speeds and attempt to establish a link at the fastest common rate. If the link was unable to be established, the equipment would not connect unless mitigation was performed or a lower speed was manually selected. Discussions are underway to mandate a process that, if unable to communicate at the highest common rate with minimal errors, the equipment would reduce the transmission speed and try again until an acceptable bit error rate is achieved. On the surface this sounds like a good thing, making link establishment the most critical aspect. However, since the purpose of the 2.5 Gbps and 5 Gbps initiative is to deploy higher speed capacity, this approach could result in some troublesome scenarios. For example a system s link light could be indicating a successful link, yet give no indication of the actual link speed, leaving the end user to assume the maximum equipment speed is being utilized. In the case of retrofitting existing links, a network manager may deploy 2.5GBASE-T and 5GBASE-T on a limited as needed basis. These systems may operate at a higher speed when just a few links are energized. However, as more links are added or converted to higher speeds, the additional noise from adjacent links may start to generate errors resulting in a drop to a lower bit rate. This does provide the benefit of keeping the network up and running, but it may cause reduced client performance, confusing the network manager that has added capacity but is not aware of the reduced link speeds. In order to establish a comfort level related to network integrity, various installation scenarios will have to be investigated and qualified by the network manager. TEK Center Testing Nexans TEK Center has used the new ALSNR method to measure system margins with respect to length. It examined several 100m seven-cable bundles of Category 6 cabling, including LANmark-6 brand, a competitor s premium Category 6 cable, Berk-Tek s premium LANmark -2000, and also some higher grades for 10G+, LANmark-6A and LANmark-7A. All channels were identically configured as shown in Figure 2 below. Figure 2: Channel configuration under test

6 Test Results As depicted in Figure 3, a fully bundled solution of LANmark-2000 achieved positive margins up to the full 100m length target when operating at 5Gbps. Other Cat6 U/UTP solutions were not able to reach the 100m and would require to be either shortened or unbundled to support 5Gbps. Figure 3: 5GBase-T system margin Note: Stair Steps are caused by power backoff schemes Table 2 compares the system margins when the bundled segment was 100m. Also here we see some significant variation from -6dB to almost +6dB. A Premium Cat 6 brand like LANmark-2000 achieved a positive margin. Otherwise, only higher grade cabling like Cat6A and Cat 7A reaches the 100m with significant headroom. Table 2: System Margin and Maximum Reach at 5 Gbps Cable Type Bundled System SNR Margin Maximum Reach Length (100m Channel) to 0dB Margin LANmark-7A 100m LANmark-6A 100m LANmark m LANmark-6 100m Competitive m * Maximum reach beyond 100m is not guaranteed for system operation. It is provided for comparative purposes only When evaluated for 2.5 Gbps performance (Table 2), all Cat6 U/UTP were able to achieve the 100m target.

7 Table 3: System Margin and Maximum Reach at 2.5 Gbps Cable Type Bundled System SNR Margin Maximum Reach Length (100m Channel) to 0dB Margin LANmark-7A 100m LANmark-6A 100m LANmark m LANmark-6 100m Competitive m * Maximum reach beyond 100m is not guaranteed for system operation. It is provided for comparative purposes only Additional testing to measure the impact of elevated temperatures in adverse environments was performed on the bundled samples. Testing at 40 C revealed a reach reduction of approximate 5 meters, while 60 C reduced the reach by approximately 11 meters. As cables are frequently installed in environments with temperatures higher than 20 C and high power PoE is expected in the near future, this reduction in length is a factor that should be considered in deployment. Based upon the above results, it becomes apparent that choosing premium cable brands like LANmark-2000 or higher graded 10G ready cabling like LANmark-6A and LANmark-7A can help maximize the system reach and avoid issues related to bundling and elevated temperatures. Nexans development of proprietary insulation and jacketing materials, in combination with Tek Twist technology to minimize crosstalk coupling or advanced double screened connectivity, helps to ensure system operation in adverse conditions. Deployment Recommendations Data consumption continues to grow at a staggering pace, placing a burden upon the existing infrastructure. Technology is being developed to incrementally increase network speed in a cost effective manner by utilizing existing electronic and cabling technologies. However, the end user should be aware of the possible complications he or she faces when attempting to deploy faster speeds on aged infrastructure. Special considerations have to be made when fast speed and PoE support in larger bundles and distances above 50m shall be combined.

8 Deployment over shielded cabling Although Alien Noise is not specified for Cat5 nor Cat6, all shielded Cat5 and Cat6 cabling are significantly less sensitive to Alien Crosstalk. This is caused simply by the presence of a shield. Shielded systems have at least one shield in cable, connectors and cords that provide protection against external noise. When the second parameters under question, the frequency range, is respected and stays within its nominal range, it can be assumed that full length of 100m bundles will operate at the desired speed level (see Table 5). For the European Market, which is to 40% a shielded market and also Nexans Cat5 and Cat6 customers around the globe, who to deployed shielded systems to 35%, this is an important note. Table 5: New Requirements for installed base / Parameters to verify Frequency Alien Crosstalk 2.5G over shielded Cat5 OK To be checked 5G over shielded Cat5 To be checked To be checked 2.5G over shielded Cat6 OK To be checked 5G over shielded Cat6 OK To be checked

9 Deployment over new cable At Nexans, we believe that often the installed cable is installed not at the right place in order to be used as a Wireless Access Points (WAP). Some form of new cable deployment is required. The placement of WAP s follow an own logic; it needs to ensure that sufficient coverage is provided to the end user. Very often this is not close to installed cable for passive outlets, for ex. laying in cable ducts or floor tanks etc, but somewhere else, for ex. under the ceiling. These cases require that some new cable is deployed. What is the right cable choice for this case? For shorter term deployments looking to 5 Gbps, a premium Category 6 cabling solution utilizing LANmark-2000 will help mitigate the impacts of bundling and elevated temperatures. This approach provides assurance that future deployment of next generation 2.5 and 5GBASE-T will operate at their advertised speeds with minimal impacts from alien crosstalk and elevated temperatures. The most effective solution for a trouble-free next generation BASE-T deployment is to use a shielded or isolated Category 6A solution, where alien crosstalk is specified and the insertion loss allows for robust system operation in harsh environments. This path ensures the easiest migration from 1000BASE-T to 5GBASE-T, but also provides a path one step ahead to eventually 10GBASE-T. For new constructions and cases with building lifetime expectations of >12 years it should be considered to already deploy the next cabling grade, Cat7A, which offers speeds even beyond 10G. If Wireless technology goes one step further it is not unlikely that also the uplinks will require more than today s and cross the 10G barrier. Table 6: New Cable Deployment for MultiG Minimum One Step Ahead 1G Cat 6 Cat6A 2.5G Cat 6 Cat6A 5G Cat 6 Premium UTP Cat6A Cat6 Shielded 10G Cat 6A Cat7A

10 OFFICES Nexans Cabling Solutions Alsembergsesteenweg 2, b3 B-1501 Buizingen Belgium Tel: +32 (0) Faraday Office Park Faraday Road - Basingstoke Hampshire RG24 8QQ UK Tel: +44 (0) Bonnenbroicher Str Monchengladbach Germany Tel: Office # 1703 Jumeirah Bay Tower - X3 PO Box # Dubai - UAE Tel: Nexans Cabling Solutions. All rights reserved. LANmark, LANsense and GG45 are registered trademarks of Nexans. Release date: January info.ncs@nexans.com