Network Tapping at 100G

The Ethernet market has grown tremendously in recent years. Data center speed and capacity are just a few factors that are contributing to this trend. Did you know that by 2019, 100 Gbps Ethernet will account for over 50% of the data center fiber optic transceivers alone? Since 2014, revenue in this industry has increased by 21% to nearly $1.4 billion. Other factors contributing to this trend are the low cost of network cards and/or devices to support 100G speeds.

Nowadays, IT managers and data center architects are looking for ways to change their existing infrastructure to adapt to faster speeds. The benefits of higher bandwidth can solve common network problems such as minimizing network congestion and latency issues that could negatively impact the end user.

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Considerations of Network Tapping 100G

When it comes down to upgrading the infrastructure, there are several important aspects to consider. For example, new transceivers, new cabling and new taps may be required to monitor and support these upgrades. Before making any significant changes, we need to decide on what taps to use and if we can reuse existing 1/10G or 40G taps and fibers.

The 40/100 Gigabit Ethernet standards include several different Ethernet physical layer (PHY) specifications. It’s important to note that optical modules (specifically 100G optical modules) are not standardized by any official standards body, but are in multi-source agreements (MSAs).

There are a number of different port types as well as optical or electrical interfaces which cover short distances (typically a few meters for the electrical interfaces) and up to 40 km for fiber connections. Figure 1 below shows examples of various optical transmission modes by distance and their relevant transceivers.

Figure 1: Various optical transmissions modes by distance with relevant transceivers

Multi-mode Optical Fiber

To simplify, single mode (SM) means the fiber enables one type of light mode to be propagated at a time. Multimode (MM) on the other hand, means the fiber can propagate multiple modes. The difference between the two mainly lies in fiber core diameter, wavelength, light source and bandwidth.

Single mode fiber is generally suitable for long distance applications and widely deployed in carrier networks, while multimode optical fiber is designed for shorter distances and most often deployed in data centers, enterprise and local area networks. Because of the high dispersion and attenuation rate with multimode fibers, the quality of the signal is reduced over long distances.

Achieving 100G Speeds

To achieve 1G or 10G speeds, the most common used fiber connections require two fibers: one for receive (Rx) and one for transmit (Tx). However, as speeds increase from 40G onward, the increasing number of multiple fibers per direction is needed to obtain the desired speed using parallel transmission.

Standards like the SR4 (short range 4 lanes) use four fibers to achieve 40G speeds in 4x10G or 100G in 4x25G. As a result, they require additional connectors and cable bundles in packages consisting of more fibers. Because of the multi-lane nature of these optics, both 40G and 100G multimode optics use a different style of fiber cabling known as MTP/MPO cabling. MTP/MPO cables bring 8, 12 or 24 fibers in a single interface.

Identified by the ISO 11801 standard, multimode fiber optic cables can be classified into OM1 fiber, OM2 fiber, OM3 fiber, OM4 fiber and OM5 fiber. Each “OM” has a minimum Modal Bandwidth (MBW) requirement. The distinction between these multimode fibers rests on physical difference. Accordingly, this physical difference leads to different transmission data rate and distance.

Optimized 100GBASE-SR10

100GBASE-SR10 optics use laser optimized multimode fiber (OM3/OM4) for transmission and use a 2×12-fiber or 24-fiber strand MPO/MTP cable for connectivity: ten strands to transmit and ten strands to receive. Figure 2 below shows several examples of different 100G taps.

Figure 2: Examples of various 100G TAPs

Network Taps versus SPAN ports

With so many different types of taps available on the market today, how we do choose the right one? For starters, let’s compare some key differences between Network Taps and a Switch Port Analyzer (SPAN). TAPS (sometimes referred to as plug and play) are completely passive devices that transmit both the send and receive data streams simultaneously on separate dedicated channels to ensure that all data arrives at the monitoring or security device in real time.

SPAN ports will send a copy of network packets on one port to another port for analysis. Historically, SPAN ports were a viable monitoring technology for monitoring at lower speeds such as 10 Mbps. This is no longer the case since the trend is quickly moving to higher speed networks of 100G, which will soon become the new standard for higher bandwidth in today’s enterprises.

Choosing the right network TAP

TAPS are a critical part of any complex infrastructure. They provide security and analysis of network traffic and are the basic building block of any visibility solution. It’s important to note that not all TAPS are made the same. TAPs differ from materials to speed to functional capabilities, so choosing the right TAP can be challenging. To decide which TAP best suits your infrastructure needs, let’s consider some key factors.

First, we need to examine which type of standard (i.e. 100GBASE-SR4 or SR10) through which transceiver the network device is using. Second, consider the type of connector that is needed: LC, MTO/MTP8, 12 or 24. Third, it’s important to choose the right cabling and the correct split ratio that’s required to drive sufficient light to the monitoring tool without reducing too much of the signal on the network path. If low light levels occur on the monitor link, this can often lead to false conclusions of data errors on the network link.

Network TAP Vendor Questions To Ask

Network taps offer many benefits such as increased flexibility, little to no configuration involved, are less costly than SPAN ports and reduce points of failure and/or bottlenecks in the network. But choosing the right network tap is equally as important as choosing a vendor that will provide you with all features and functionalities you need. Below are a few questions to consider before committing to any vendor:

  1. Does the vendor carry a large range of network taps?
  2. Can the vendor’s taps handle traffic speeds from 1G to 100G?
  3. Do they offer Single mode and Multimode fiber types and optical split ratios?

Clearly, choosing the right vendor that can offer the best network TAPs will not only provide the visibility, security, and pervasive monitoring you need, but will yield the greatest cost savings to help you achieve your long-term business outcome.

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