Think about the streets you travel every day. What would happen if the traffic engineers who designed these roadways didn’t take into account the numbers of cars traveling on them, road width and the number of lanes? They wouldn’t be able to accommodate a certain amount of traffic at a certain average speed. Traffic would be a mess, there would be bottlenecks and delays, and it would be hard to get where you needed to go.
The same holds true for your network – it’s only as good as the planning that goes into it. Different types of applications require different network bandwidth levels. Each task completed using your network takes up network bandwidth, with many bits per second traveling across the network. Knowing and how much bandwidth each application uses is key to ensuring the functionality, reliability and speed of your network.
The data rate supported by your network bandwidth is typically expressed in “bps” (bits per second) or “Bps” (bytes per second). Your network bandwidth determines your network’s capacity to support what you do, and is impacted by the design principles of your structured cabling system.
As data rates increase, so do our bandwidth requirements. For speeds of 1 Gbps, Category 5e and Category 6 cabling were sufficient; when 10 Gbps came along, Category 6A cabling addressed bandwidth and external noise requirements. But now with 2.5 Gbps and 5 Gbps on the scene, which cabling system should you choose? Here are some factors to take into consideration.
What will your users be doing on the network? Streaming high-definition audio? Just sending emails? Creating and sending huge medical imaging files? Using online software to edit hours of video footage? Knowing your applications and the number of bytes per second they each send across the network makes a difference: even though it may seem counterintuitive, 500 people who send email all day may not require as much network bandwidth as 50 users who stream and download video and conduct videoconferencing calls.
Once you know your application bandwidth, you need to know the bandwidth capabilities of your cabling infrastructure. For example, if users regularly interact with bandwidth-intensive technology, such as 4K content, the cable needs to be able to support it. Category 6A cabling, for example, can handle the performance demands of 10G Ethernet (10GBASE-T) up to 500 MHz over a maximum distance of 100m.
2. Near-End Crosstalk Concerns for Speeds Above 1 Gbps
Near-end crosstalk (NEXT) is a measure of unwanted signal coupling from one pair to another at the near (closest) end of the cabling. NEXT is measured at the same end of the link/channel where the signal is sourced. Measured in decibels (dB), the higher the NEXT in dB, the greater the cable’s ability to reject crosstalk at its local connection.
Category 6A provides a higher margin above minimum requirements of 1 Gbps Ethernet for alien crosstalk parameters and performance of in-channel test parameters above 250 MHz. With higher frequencies required to support 2.5GBASE-T, 5GBASE-T and 10GBASE-T applications, crosstalk between cables – not just within them – is now a concern. Your NEXT levels might be okay above 250 MHz, but alien crosstalk will negatively impact cable performance – which is why Category 5e and Category 6 cabling can’t be used for data rates above 1 Gbps without worry.
To control noise and crosstalk at higher frequencies while providing adequate network bandwidth initially meant that Category 6A cables (with frequencies of 500 MHz) had to be up to 50% larger than Category 6 cables to accommodate twists that minimize crosstalk. This large size limited the number of cables that fit into a cable trays or runways. Today’s newer Category 6A cables, however, have reduced cable diameter closer to that of Category 6 cables.
3. Far-End Crosstalk Concerns for Speeds Above 1 Gbps
Very similar to NEXT, far-end crosstalk (FEXT) is also measured within a channel. Instead of being measured at the closest end of the cabling, it’s measured at the far end of the channel. FEXT isn’t typically talked about much on its own; because signals decrease in strength over distance, it doesn’t provide very helpful information.
From FEXT, however, information like equal-level far-end crosstalk (ELFEXT) or attenuation to crosstalk ratio far-end (ACRF) can be extracted to measure characteristics like power sum ACRF (PSACRF). As with near-end crosstalk, far-end crosstalk between cables at higher frequencies – not just within them – is now a concern. Similar to NEXT performance, your FEXT levels might be okay above 250 MHz, but alien crosstalk will negatively impact cable performance – which is why Category 5e and Category 6 cabling can’t be used for data rates above 1 Gbps without worry.
The same rules apply here – Category 6A cabling is designed to better control noise and crosstalk, but initially had to be bigger in diameter to do so. Newer cabling systems have reduced this problem, opening up the opportunity for LANs to improve network bandwidth through Category 6A cable.
4. Cable Balance for UTP Cables
Improper cable balance can limit your network bandwidth potential.
Cable balance isn’t defined for Category 5e UTP or Category 6 UTP cabling. Cable “balance” ensures that cabling systems offer appropriate electromagnetic compatibility (EMC) performance and eliminate interference. Cabling balance is directly related to alien crosstalk. Without proper balance, alien crosstalk will negatively impact cable performance – which is why Category 5e and Category 6 UTP cabling can’t be used for data rates above 1 Gbps without worry.
To be well balanced, voltage and current on each conductor of the pair must be equal in magnitude and opposite in phase. To obtain this balance, the cable’s two insulated conductors must be physically identical in terms of diameter, concentricity and dielectric material, and must be uniformly twisted. This requires precise design and manufacturing processes.
If you need help determining your network bandwidth, or need to improve your network to accommodate increasing bandwidth levels, contact us. Our LAN experts can help.
Ron joined Belden in 2016 to help define the roadmap of technology and applications in the enterprise. Prior to this, he developed cables and connectivity for Panduit and Andrew Corp. Ron Tellas is a SME in RF design and Electromagnetic Propagation and has BSEE from Purdue University, a MSEE from IIT, and a MBA from Purdue University.