The SPU-Hitless board provides packet-level Hitless Switching capability to any type of signal streams handled by an MD8000 series system. Although all MD8000 line cards (UVTX, J2K, etc.) natively support Hitless Switching, there are two cases where line card sourced Hitless Switching is inadequate. In case one, an MD8000 chassis may only have a single trunk connection to the wide area network, so it is impossible to protect video or data signals by using diverse routes across the network (see Figure 1, Hitless Transmission Mode). In this instance, a SPU-Hitless module can be installed in an intermediate MD8000 chassis to replicate the incoming stream and create a redundant or backup stream in the network. This backup stream can take its own unique route over the network, ensuring some signal protection in the case of an intermediate MD8000 node outage.
Case two is almost a mirror image of case one, except that the destination MD8000 chassis (in contrast to the source chassis) is the one equipped with a single trunk card (see Figure 2, Hitless Reception Mode). Here again, an intermediate chassis containing an SPU-Hitless board is used, but in this case, it accepts hitless Line 1 and Line 2 streams coming over two different trunk cards and sends these two Line 1 and Line 2 streams over a single trunk to the destination chassis and line card.
The SPU-Hitless module is capable of protecting up to 16 streams, replicating them to 32 streams (16 redundant pairs) on the network. The module can operate in either Tunnelling Mode (RTP encapsulation) or Header Translation Mode. SPU-Hitless module has an aggregate bandwidth capacity of 10Gbps in both directions, Flow-in (for input and reception) and Flow-out (for transmission and output).