Just as large enterprises settle into 10G networking, bandwidth intensive applications and big data demands are forcing companies to adopt 40G network speeds. However, the shift from 10G to 40G requires a major investment in a new cabling infrastructure, leaving architects in a difficult position when trying to make upgrades.
To make 40G more accessible, Cisco, a Garland Technology partner, created bidirectional (BiDi) 40G fiber connectivity. But the technology is not without its challenges.
Boosting bandwidth 10G to 40G so quickly introduces significant monitoring challenges. However, network TAPs that support 40G BiDi technology, such as Garland Technology’s multi-mode 40G-SR-BiDi passive fiber TAPs, can help organizations achieve 40G speeds without dropping packets even in environments with the highest utilization.
Large enterprises that have functioned with 1G fiber from servers to tops-of-racks (TOR) and 10G fiber from TORs to an aggregator, are now upgrading to avoid oversubscription. However, introducing 10G off servers and moving to 40G from TORs would typically require network managers to replace the entire cable infrastructure.
Typically, the 10G traffic from TORs to aggregators requires two strands of OM3 or OM4 multi-mode fiber, according to IEEE standards for SF4. Using this aging standard for 40G would require four 10G links for the receive connections, four 10G links for the transmit connections and essentially four unused links as MPO 12 connectors are implemented.
Purchasing new MPO 12 connectors and supporting cabling is an undertaking that many companies can’t afford to handle; so Cisco developed 40G BiDi technology, using two parallel multi-mode fiber strands to transmit the signal bidirectionally rather than unidirectionally.
The Cisco QSFP 40-Gbps BiDi transceiver has two 20-Gbps channels, each transmitted and received simultaneously on two wavelengths when connected to a duplex MMF. The result is an aggregated 40-Gbps lnk over a duplex MMF.
Rather than implementing 8 brand-new fiber cables, BiDi allows network managers to achieve 40G traffic over their existing cable infrastructure.
As a Cisco technology partner, Garland Technology developed the BiDI Passive Fiber Network TAPs to ensure all data—every bit, byte and packet®—is copied to the Cisco solution.
Even though BiDi technology unifies 10G simplex cables to create bidirectional 20G links, traffic must still be treated as if it comes from four different links. That’s why network TAPs must support four cable connections to monitoring appliances in BiDi environments.
Consider the following features of the 40G-SR BiDi TAP that help you ensure visibility in your BiDi environment:
Any time you’re migrating from one network speed to another, you must ensure the network design is prepared to support greater traffic demands without losing visibility.
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If the inline security tool goes off-line, the TAP will bypass the tool and automatically keep the link flowing. The Bypass TAP does this by sending heartbeat packets to the inline security tool. As long as the inline security tool is on-line, the heartbeat packets will be returned to the TAP, and the link traffic will continue to flow through the inline security tool.
If the heartbeat packets are not returned to the TAP (indicating that the inline security tool has gone off-line), the TAP will automatically 'bypass' the inline security tool and keep the link traffic flowing. The TAP also removes the heartbeat packets before sending the network traffic back onto the critical link.
While the TAP is in bypass mode, it continues to send heartbeat packets out to the inline security tool so that once the tool is back on-line, it will begin returning the heartbeat packets back to the TAP indicating that the tool is ready to go back to work. The TAP will then direct the network traffic back through the inline security tool along with the heartbeat packets placing the tool back inline.
Some of you may have noticed a flaw in the logic behind this solution! You say, “What if the TAP should fail because it is also in-line? Then the link will also fail!” The TAP would now be considered a point of failure. That is a good catch – but in our blog on Bypass vs. Failsafe, I explained that if a TAP were to fail or lose power, it must provide failsafe protection to the link it is attached to. So our network TAP will go into Failsafe mode keeping the link flowing.
Single point of failure: a risk to an IT network if one part of the system brings down a larger part of the entire system.
Heartbeat packet: a soft detection technology that monitors the health of inline appliances. Read the heartbeat packet blog here.
Critical link: the connection between two or more network devices or appliances that if the connection fails then the network is disrupted.