M20 Internet Router


The M20 Internet router (see Figure 3.33) has a maximum aggregate bandwidth of 20 Gbps. It accepts up to four FPCs. Table 3.24 shows the physical specifications of the M20 router, and Table 3.25 gives an overview of the major hardware components of the router.

Figure 3.33. M20 Internet Router Chassis and Components

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Table 3.24. M20 Router Physical Specifications
Category Value
Dimensions 14 in. (36 cm) high x 19 in. (48.3 cm) wide x 21 in. (54 cm) deep
Router weight

80 lb (36 kg) minimum configuration

134 lb (61 kg) maximum configuration

Required clearances 19 in. (48 cm) front and rear; 6 in. (15.2 cm) on each side
Table 3.25. M20 Internet Router Major Hardware Components
Component Quantity Function Redundant FRU Online/offline Button
Chassis (including midplane) 1 Houses router components
Flexible PIC Concentrators (FPCs) 1 “4 Connects PICs to other components, houses shared memory

Hot-removable

Hot-insertable

Yes
System and Switch Boards (SSBs) 1 “2 Performs route lookups, manages shared memory, transfers control packets Hot-pluggable
Physical Interface Cards (PICs) 1 “4 per FPC Interfaces to network media From removed FPC Yes
Routing Engines 1 “2 Maintains routing protocols, routing tables Hot-pluggable Yes
Power supplies 2 AC or 2 DC Distributes voltages to components Yes

Hot-removable

Hot-insertable

Cooling system 3 fan trays and 1 rear Routing Engine fan Cools router components Yes

Hot-removable

Hot-insertable

Craft interface 1 Displays status and troubleshooting information, provides control functions

Hot-removable

Hot-insertable

The router chassis includes two front-mounting metal ears, two optional rack-mounting ears for telco center-rack mounting, two optional front-mounting brackets, and two ESD points. The midplane forms the back of the card cage. The FPCs, SSB, and craft interface install into the midplane from the front of the chassis. Power supplies and the Routing Engine plug into the midplane from the back of the chassis. Fan trays plug into the midplane from both the front and rear of the chassis.

The M20 router can have up to four FPCs, which install horizontally in the front of the chassis (see Figure 3.34). The FPCs connect the PICs to the rest of the router so that incoming packets can be forwarded across the midplane to the appropriate destination port. FPCs contain shared memory, which is managed by the Distributed Buffer Manager ASIC on the SSB, for storing data packets. The I/O Manager ASIC on each FPC divides incoming data packets from the PICs into cells , which are stored in a shared memory buffer, and reassembles them into data packets when they are ready for transmission.

Figure 3.34. M20 FPCs in the Chassis

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For information about the PICs used in the router, see "Physical Interface Cards" on page 34.

FPCs are hot-insertable and hot-removable. When you bring an FPC online, the midplane flushes the entire system memory pool before the new card is brought online, a process that takes about 200 milliseconds . Then the Routing Engine downloads the FPC software, the FPC runs its diagnostics, and the PICs on the FPC slot are enabled. No interruption occurs to the routing functions.

The components of each FPC include two SDRAM modules used as shared memory by the Distributed Buffer Manager ASIC on the SSB, an SSRAM module, and a DRAM module used by the PowerPC processor. Each FPC has two LEDs, located on the craft interface, that indicate its status.

The System and Switch Board (SSB) (see Figure 3.35) occupies the top slot of the card cage, installing into the midplane from the front of the chassis. The SSB houses the Internet Processor II ASIC and the Distributed Buffer Manager ASICs. The SSB communicates with the Routing Engine using a high-speed internal link to transfer routing table data and nondata packets.

Figure 3.35. M20 SSB

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The SSB contains processing components, including a 200-MHz CPU, Internet Processor II ASIC, and Distributed Buffer Manager ASICs; storage components, including four slots of 2-MB RAM for forwarding tables associated with the ASICs, and 64-MB DRAM for the microkernel ; system interfaces, including a 19.44-MHz Stratum 3 reference clock for SONET/SDH PICs; and two LEDs.

For more information, see "Routing Engine" on page 37.

The M20 router has one or two Routing Engines. The Routing Engines install into the rear of the chassis above the power supplies. There is also a Routing Engine panel on the rear of the router that has LEDs indicating each Routing Engine's status and offline switches for removing the Routing Engines.

The craft interface (see Figure 3.36) is located below the SSB on the front of the chassis, and contains the alarm relay contacts, alarm LEDs, alarm cutoff button, Routing Engine ports, link and activity status lights, Routing Engine LEDs, and FPC online/offline buttons .

Figure 3.36. M20 Craft Interface

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The router has two redundant load-sharing power supplies. A single power supply can provide full power (up to 750 W) for as long as the system is operational. Redundancy is necessary only in case of power supply failure or removal.

The power supplies install into slots on the lower rear of the chassis. The power supplies are internally connected to the midplane, which distributes the different output voltages produced by the power supplies throughout the system and its components. Each power supply contains an integrated fan that cools the power assembly.

The router supports both AC and DC power supplies. Table 3.26 lists the specifications for both types. You cannot mix both types in a single router. An enable control signal on the output connector ensures that the power supply is fully seated into the router midplane before the power supply can be turned on. The enable pin prevents a user -accessible energy hazard , so there is no interlocking mechanism. The enable pin disables the voltage at the output connector if the power supply is not turned off before removal.

Table 3.26. M20 Router Power Supply Specifications
Item AC Specification DC Specification
Maximum power consumption 750 W 750 W
Input voltage 90 through 264 VAC operating range “40 through “72 VCD operating range
Input line frequency 47 “63 Hz, autoranging
Input current rating 13 A @ 90 V 24 A @ “48 V (typical)
Output voltages +3.3 V, +5 V, + 2.5 V, +12 V, +24 V +3.3 V, +5 V, + 2.5 V, +12 V, +24 V
Power and grounding cords and cables Country specific; see M20 Internet Router Hardware Guide 4 or 6 AWG wire cables with dual hole 20 UNC terminal studs @ 15.86 mm (0.625 in.) centers

AC power supply cords are country-specific . The AC inlet is oriented to allow a standard right-angle power cord to exit to the right of the power supply. A power cord latching mechanism is provided for the use of straight power cords. The DC power supply uses a cable lug and locking washers to attach the cables to the supply.

The M20 router cooling system consists of three front fan trays, located on the left front side of the chassis, that cool the FPCs and the SSB; one rear fan tray, located immediately to the right of the Routing Engine, that cools the Routing Engine; and a fan built into each power supply that cools the power supply. Each front fan tray contains three fans. The rear fan tray contains two fans. Both front and rear fan trays are hot-swappable. The four fan trays work together to provide side-to-side cooling (see Figure 3.37).

Figure 3.37. Air Flow through the M20 Chassis

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The cable management system is attached to the chassis and consists of a row of staggered metal hooks, each draped with a rounded plastic shield.

The router has LEDs that display the status of various router components. Table 3.27 lists the LEDs on the craft interface and the individual router components.

Table 3.27. M20 Internet Router LEDs
Component LED Location
FPCs

Green OK

Red FAIL

Craft interface
PICs

Tricolor: Red, green, amber

PIC faceplate
SSBs

Blue MASTER

Green ONLINE

Amber OFFLINE

2 Green STATUS

SSB faceplate
Routing Engines

Blue MASTER

Green ONLINE

Amber OFFLINE

Craft interface and Routing Engine panel
Power supplies

Green OK

Red FAIL

Power supply faceplate
Alarm LEDs
Red alarm Large, circular red Craft interface
Yellow alarm Large, triangular amber Craft interface


Juniper Networks Field Guide and Reference
Juniper Networks Field Guide and Reference
ISBN: 0321122445
EAN: 2147483647
Year: 2002
Pages: 185

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