The concept of virtual hardware routers, or Protected System Domains (PSDs), is an extension of the existing JUNOS software feature of logical systems. A logical system partitions a single, physical router into multiple logical devices that perform independent routing tasks. Logical systems reduce complexity by performing a subset of the actions of the main router and by having their own unique routing tables, interfaces, policies, and routing instances. A set of logical systems within a single router can handle the functions previously performed by several small routers.
In contrast, a PSD has its own control plane as well as forwarding plane. A PSD functions exactly as a separate physical router, running a separate configuration file, administering its own domain, and requiring unique authentication in order to access it. By providing a highly scalable control plane with a cost-efficient forwarding plane on a single platform, the JCS 1200 chassis interconnected with up to three T-series routing chassis obviates the need to deploy numerous physical routers.
A PSD is a redundant Routing Engine pair (or single Routing Engine) on the JCS 1200 platform matched with one or more FPCs on a T-series routing platform. Any number of FPCs can be assigned to a PSD. Only one redundant Routing Engine pair (or single Routing Engine) can be assigned to a PSD. In Figure 2, FPC1 and FPC2 and the Routing Engines in slots 1 and 2 belong to PSD1. In contrast, PSD2 is made up of the FPCs in slots 3 and 4 on the T-series routing platform and the Routing Engines in slots 3 and 4 on the JCS 1200 chassis.
Figure 2: Protected System Domain
A PSD detects and manages only its own Routing Engines in the JCS 1200 and the assigned FPCs and PICs in the T-series router. In addition, failures on one PSD do not affect other PSDs.
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