The central idea of Juniper router design is separation of the control (Routing Engine) and forwarding (Packet forwarding Engine) planes.

 

RE ------------- PFE

 

Routing Engine Overview

  1. RE Controls the system.
  2. All routing intelligence lies here.
  3. All JUNOS software lies here. That’s where all software upgrades are performed.
  4. When we telnet into the router, we are telneting into RE.
  5. All routing protocols and tools such as OSPF, RIP, BGP, Ping, trace-route etc operated from within RE.
  6. RE places best paths in forwarding-table and copies that same data into forwarding-table on the PFE. Forwarding-table in PFE allows the router to actually forward data packets.
  7. RE is just like a PC.
    1. RAM in RE stores routing tables, Link state DB, JUNOS running software.
    2. Flash memory/drive stores the JUNOS software and configuration files for the router.
    3. Hard disk is used to store backup copy of JUNOS, log files, traceoptions or debug output and any type of files you want.

 

PFE Overview

 

Main job is to forward packets.

PFE = PIC + FPC + Switching Control Board

 

Switch Control Board:

SCB contains a PowerPC CPU and 64MB of RAM that controls the other components of the Circuit board. Another set of RAM carries the Forwarding Table.

 

The “Internet Process ASIC” is located on the control board and accesses the forwarding table for route lookups. The control board also contains ASIC for packet storage memory mgmt.

 

Each router model uses a different name for the control board functionality.

Forwarding Engine Board (FEB): M5 and M10. No more than one FEB. Circuit board is integrated with the FPC

On M5:

user@ Router > show chassis feb

FEB status:

  Temperature                        34 degrees C / 93 degrees F

  CPU utilization                    14 percent

  Interrupt utilization               1 percent

  Heap utilization                   65 percent

  Buffer utilization                 45 percent

  Total CPU DRAM                     64 MB

  Internet Processor II                 Version 1, Foundry IBM, Part number 9

  Start time:                           2005-01-23 00:38:45 MST

  Uptime:                              336 days, 7 hours, 46 minutes, 49 seconds

 

For M10i:

user@Router> show chassis cfeb

CFEB status:

Slot 0 information:

  State                                 Master

  Intake temperature                 29 degrees C / 84 degrees F

  Exhaust temperature                36 degrees C / 96 degrees F

  CPU utilization                    22 percent

  Interrupt utilization              11 percent

  Heap utilization                   31 percent

  Buffer utilization                 23 percent

  Total CPU DRAM                    128 MB

  Internet Processor II                 Version 2, Foundry IBM, Part number 164

  Start time:                           2005-01-23 04:34:04 EST

  Uptime:                              336 days, 5 hours, 52 minutes, 26 seconds

Slot 1 information:

  State                                 Backup

 

System Switching Board (SSB): M20. Can hold dual SSB but one is operational at a time.

user@Router> show chassis ssb

SSB status:

Slot 0 information:

  State                                 Master

  Temperature                        29 degrees C / 84 degrees F

  CPU utilization                     9 percent

  Interrupt utilization               0 percent

  Heap utilization                   57 percent

  Buffer utilization                 45 percent

  Total CPU DRAM                     64 MB

  Internet Processor II                 Version 1, Foundry IBM, Part number 9

  Start time:                           2005-12-10 12:03:34 GMT

  Uptime:                              15 days, 3 hours, 25 minutes, 57 seconds

Slot 1 information:

  State                                 Backup

 

System Control Board (SCB): M40. No more than one SCB

user@Router> show chassis scb

SCB status:

  Temperature                        24 degrees C / 75 degrees F

  CPU utilization                    24 percent

  Interrupt utilization               2 percent

  Heap utilization                   78 percent

  Buffer utilization                 56 percent

  Total CPU DRAM                     64 MB

  Internet Processor II                 Version 1, Foundry IBM, Part number 9

  Start time:                           2005-07-20 04:04:29 EDT

  Uptime:                              158 days, 7 hours, 18 minutes, 34 seconds

 

Switching and Forwarding Module (SFM): M40e/M160. M40e has two SFMs with only one operating at a time. M160 has four working in parallel.

 

user@Router> show chassis sfm

 

Temp

CPU Utilization (%)  

Memory

Utilization (%)

Slot State           

(C) 

Total 

Interrupt    

DRAM (MB)

Heap 

Buffer

0  Online           

38

14                              

1

64  

62

50

1  Online - Standby 

40

11     

0

64

62   

48

                       

 

user@Router> show chassis sfm detail

Slot 0 information:

  State                                 Online

  SPP temperature                    38 degrees C / 100 degrees F

  SPR temperature                    38 degrees C / 100 degrees F

  Total CPU DRAM                     64 MB

  Total SSRAM                         8 MB

  Internet Processor II                 Version 1, Foundry IBM, Part number 9

  Start time:                           2005-09-21 02:04:42 EDT

  Uptime:                              95 days, 9 hours, 6 minutes, 17 seconds

Slot 1 information:

  State                                 Online - Standby

  SPP temperature                    40 degrees C / 104 degrees F

  SPR temperature                    43 degrees C / 109 degrees F

  Total CPU DRAM                     64 MB

  Total SSRAM                         8 MB

  Internet Processor II                 Version 1, Foundry IBM, Part number 9

 

Memory Mezzanine Board (MMB): T320. MMB is located on FPC itself.

 

ASICs on SCB:

The Internet Process ASIC is located on the control board and accesses the forwarding table for route lookups. This ASIC is the heart of PFE as it is the only ASIC that:

·        accesses the FT,

·        performs route lookups,

·        makes forwarding decisions,

·        performs firewall packet filtering,

·        enforces policy controls on data packets,

·        Collects exception packets for transmission to the RE.

·        Receives notification cells from the inbound distributed buffer manager ASIC and transforms them into result cells after performing a route lookup.

 

Each Control Board contains two Distributed Buffer Manager ASICs. They connect to the IO manager ASIC on the FPC and to IP ASIC, which is also on control board. The ASIC is logically separated into two components, Inbound DBM _ handles inbound J-Cells, Outbound DBM _ handles outbound J-Cells.

 

The two ASICs store and retrieve J-cells in the shared packet buffer pool. Inbound DBM generates special J-cell cells called the notification cells. The notification cell contains the vital signs of each packet e.g. source and destination IP, port numbers, QoS, TTL etc. The ASIC sends the notification cells to IP ASIC.

 

   Flexible PIC Concentrator (FPC):

FPC connects to both the SCB and the router’s interfaces (ge-0/0/0, so-1/1/0, at-1/1/1, etc) within the PFE. A PowerPC CPU controls the FPC but doesn’t participate in packet forwarding. Other ASICs forward packets.

 

Physical Interface Card (PIC):

All Ethernet, GE etc. media connect to PIC. There could be up to 4 PICs on each FPC. Each PIC contains its own PIC I/O Manager ASIC. ASICs on PICs are media (GE, atm, sonnet etc) specific. PIC I/O Manager ASIC is responsible for removing data packets from physical media and placing them back onto media. It verifies data-link framing, detects link-level errors and generates link-level alarms.