Hardware ComponentsEach Juniper Networks router consists of a chassis and a set of components, including FPCs, PICs, Routing Engines, power supplies , cooling system, and cable management system. Many of the components are field replaceable units. Each major component is discussed in this section. Chassis
Each Juniper Networks router features a rigid sheet metal chassis that houses all the router components. The chassis are designed to install into a variety of racks, including standard 19-inch equipment racks, telco center-mount racks, and four-post racks and cabinets . See Table 3.1 for the maximum number of each router that can be installed into a rack. Each chassis includes mounting ears or support posts to facilitate rack mounting, and one or more points for connecting an electrostatic discharge (ESD) wrist strap for use when servicing the router. Table 3.1. Maximum Number of Routers Per Rack
Each chassis includes a midplane (called the backplane on an M40 router). The major functions of the midplane include transferring data packets to and from the FPCs, distributing power to router components, and providing signal connectivity to the router components for monitoring and control of the system. Flexible PIC ConcentratorsThe Flexible PIC Concentrators (FPCs) house the PICs used in the router and connect them to other router components. FPCs install into the front of the router in either a vertical or horizontal orientation, depending on the router. A compatible FPC can be installed into any available FPC slot, regardless of the PICs it contains. If a slot is not occupied by an FPC, a blank FPC panel must be installed to shield the empty slot and to allow cooling air to circulate properly through the FPC card cage. Some routers support more than one type of FPC. The FPCs for each router are unique to that router. Physical Interface CardsJuniper Networks routers use Physical Interface Cards (PICs) to connect to a wide variety of network media. (See Table 3.2 for a list of PIC interfaces as of the time of publication.) PICs receive incoming packets from the network and transmit outgoing packets to the network, performing framing and line-speed signaling for their specific media type. Before transmitting outgoing data packets, the PICs encapsulate the packets received from the FPCs. Each PIC is equipped with an ASIC that performs control functions specific to the PIC's media type. Table 3.2. PIC Media Types
PICs install into the FPCs (on the M5 and M10 routers, into the FEB). Each FPC can accept up to four PICs. (Table 3.3 lists the number and type of PICs currently supported on each router.) The PICs for each router are unique to that router. Table 3.3. PICs Supported on Each Router
Routing EngineThe Routing Engine consists of an Intel-based PCI platform running the JUNOS software. The Routing Engine maintains the routing tables used by the router in which it is installed and controls the routing protocols on the router. The T640 routing node, T-320, and the M160, M40e, and M20 routers support up to two Routing Engines, while the M40, M10, and M5 routers support a single Routing Engine.
Each Routing Engine consists of a CPU; SDRAM for storage of the routing and forwarding tables and other processes; a compact flash disk (on some M40 routers, a floppy disk) for primary storage of software images, configuration files, and microcode ; a hard disk for secondary storage; a PC card slot for storage of software upgrades; and interfaces for out-of- band management access. Power SuppliesEach Juniper Networks router has two load-sharing power supplies. A single power supply can provide full power for as long as the router is operational. The power supplies are redundant: if one power supply is removed or fails, the other power supply automatically assumes the entire electrical load. The power supplies are connected to the router midplane (on an M40 router, the backplane), which distributes the different output voltages throughout the router and its components. Some routers can operate using either AC or DC power; others operate with DC power only. For information about the type of power used by each router, see the "Electrical Specifications" table for each router. Cooling SystemEach Juniper Networks router features a cooling system designed to keep all router components within recommended operating temperature limits. If one component of the cooling system fails or is removed, the system adjusts the speed of the remaining components automatically to keep the temperature within the acceptable range. The cooling system for each router is unique and can consist of fans, impellers, and air filters. For information about the cooling system components of each router, see the "Major Hardware Components" table for each router. Cable Management SystemEach Juniper Networks router includes a cable management system designed to maintain the proper bend radius for optical cables and to keep installed cables organized and securely in place. The cable management system evenly distributes the weight of the optical cables so that no individual cable is subjected to undue stress. Field-Replaceable UnitsComponents that can be replaced at the customer site are called field-replaceable units (FRUs). FRUs can be replaced with minimal loss of performance or router downtime. Most of the components previously discussed in this section ”including the FPCs, PICs, Routing Engine, power supplies, and cooling system components ”are FRUs. There are three types of FRUs: hot-insertable and hot-removable FRUs, which can be removed and replaced without powering down the router or disrupting router functions; hot-pluggable FRUs, which can be removed and replaced without powering down the router, but whose removal does cause an interruption to router performance; and FRUs whose removal requires powering down the router. For a list of which components are FRUs for each Juniper Networks router, see "Major Hardware Components" table for each router. |