Bandwidth demand in data centers and campus networks is increasing due to growing virtualization. In data centers, this has a particular impact at aggregation points of top-of-rack switches, i.e., from leaf to spine in modern architectures. But in campus networks, too, the load on the uplinks to the core and distribution levels is rising due to the increase in digitization and the increased quantity of networked end devices.

Network managers are trying to meet these increasing demands with 40G and 100G connections. The passive network infrastructure in the form of fiber optic cabling is one of the cost drivers in such projects. In addition, expansions and changes need an extended project lead time. Therefore, the responsible parties prefer to use technologies that can build on the existing base.

BiDi Module approach

To efficiently migrate from 10G to 40G or 100G over short distances on a fiber pair and existing OM3 and OM4 multimode connections with LC connectors, bidirectional (or "BiDi") modules are available. 

These increase the cost efficiency while shortening the project time: with classic solutions, eight fibers would be required instead of only two with BiDi. The functionality of these modules is based on a passive WDM (Wavelength Division Multiplexing) technology with 850nm and 910nm on both sides. In the 40G variant, each module transmits and receives 20G on each fiber. In contrast, at 100G, each module transmits and receives 50G on each fiber. The two channels are also separated via WDM. 

Challenges of tapping BiDi

Despite all the advantages of the BiDi modules, monitoring these links poses a problem: the modules do not support Rx-only reception. This means that the connected analysis solution automatically injects packets back into the network, as this connection is also bidirectional.

Profitap Rx only 100GBASE-SR BiDi QSFP28

To enable tapping bidirectional connections, Profitap has developed a pure Rx based 100G BiDi transceiver (or receiver in this case). This is the first 100G Rx-only transceiver solution for Cisco’s BiDi 40/100G standard on the market. It offers the possibility of secure monitoring of 100G BiDi links, as they do not inject light in the reverse direction. 

Figure 1: Application of the new 100G Rx-only BiDi transceivers. A TAP in the top center routes traffic to the BiDi Rx transceivers located in the bottom right of an X2-Series Packet Broker.

The Profitap ecosystem

Profitap has a diverse portfolio of network monitoring solutions to provide end-to-end network visibility. These solutions are divided into three main categories:

Traffic access
Network analysis starts with getting actionable data reliably and securely. Profitap manufactures purpose-built network TAPs for Copper, Fiber, and virtual networks. We pay extra attention to the secure deployment with Secure TAPs and the Rx-only QSFP for BiDi networks mentioned in this article.

Data flow management & optimization
With TAPs placed at key capture points throughout the network, the number of connections and data volume forwarded to monitoring and security tools can grow exponentially. A Network Packet Broker can be used to manage this traffic efficiently. By aggregating TAP connections and streamlining data for monitoring and security tools with advanced filtering capabilities, tools are utilized to their maximum.

Traffic Capture & Analysis
With a steady flow of traffic to security and monitoring tools in the data center, it can be valuable to look into traffic capture and analysis tools to monitor remote locations, such as branch offices. Profitap IOTA brings a complete network analysis and troubleshooting solution, combining TAP, storage, and analysis capabilities in a single portable device. ProfiSharks are portable traffic capture devices that provide quick packet-level insight anywhere they are deployed.