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Network Timing

Network Timing. ATM Switch. Objectives. Explain the purpose of network synchronization Identify the meaning of the Stratum clocking grades Identify the internal and external timing components associated with the CEC-Plus and ASX-4000 Series TCM

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Network Timing

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  1. Network Timing ATM Switch

  2. Objectives • Explain the purpose of network synchronization • Identify the meaning of the Stratum clocking grades • Identify the internal and external timing components associated with the CEC-Plus and ASX-4000 Series TCM • Describe the basic distribution of timing architecture for line timing and external timing sources • Configure the IP interfaces on the CEC-Plus • Configure and verify timing (external timing example) on the CEC-Plus and the ASX-4000 Series TCM

  3. Overview Reference Source In Primary Reference Source (PRS) Port Distributed to all ports Used for transmission Physical Links

  4. Timing Fundamentals • A timing element (a.k.a., clocking) is a pulse pattern • A timing element can be seen from two perspectives: • Receive timing is derived from the incoming frame rate • Transmit timing controls the outgoing frame rate • Frame rates are universal, even on different interface speeds InterfaceBit rateFrame rate DS1 1.544 Mbps 8,000 fps E1 2.048 Mbps 8,000 fps DS3 44.736 Mbps 8,000 fps E3 34.368 Mbps 8,000 fps OC-3 155.52 Mbps 8,000 fps

  5. Timing Precision • The integrity of a timing pulse can be classified by quality • The goal is to have all the devices follow the same reference; hence they are synchronized • Normally the timing signal is derived from the most accurate of clocks (referred to as a Stratum 1 traceable clock)

  6. Impact of Timing Problems • When sending and receiving devices use different reference sources, bit slips and frame slips can result • The underlying problem is either buffer overrun or underrun • Synchronized networks minimize these problems ~8,000 fps(8,150 fps) ~8,000 fps(7,920 fps) Framer buffer Overrun example ~8,000 fps(7,885 fps) ~8,000 fps(8,215 fps) Framer buffer Underrun example

  7. Timing Structure Stratum1 SRS PRS Primary Reference Stratum1 Secondary Reference S2 S2 S3 S3 S3 S4 S4 S4 Voice or VideoApplication Voice or VideoApplication

  8. ASX-1000/1200 and TNX-1100 Dual TCMs comprise the CEC-Plus Supports network timing subsystem and alarm relays Runs with or without switch fabrics installed ASX-4000 Series TCM is a daughter card to the SCP Supports timing functions and alarm relays TCM Types Daughtercard

  9. TCM Features • Hot-swappable • ASX-4000 version is integral to SCP; must remove SCP • Redundant • BITS inputs • Line timing inputs • Hitless reference switching and failover • Timing holdover • Stratum 3 or 4 oscillator and digital phase lock loop • Configurable alarm relay contacts

  10. CEC-Plus: TCM Front Panel • 25 pin D-sub: Alarm relay connections • Normal open or normal closed wiring • Alarm LEDs: Alarm relay is normal or energized • Ethernet connection to SCPs • Serial port • Status LED • Solid: Active • Flashing: Standby • Amber: Error • External timing signal ports (TX and RX) • Reset button

  11. ASX-4000 Series: TCM Front Panel SCP front panel includes: • 25 pin D-sub: Alarm relay connections • Normal open or normal closed wiring • Alarm reset button • Returns relays to normal state • Alarm LEDs: Alarm relay is normal or energized Alarm Relay LEDs

  12. Timing Distribution Architecture TCM X BITS-X PLL P S P S P S P S P S Fabric/Port card Fabric/Port card Fabric/Port card Fabric/Port card TCM Y BITS-Y PLL S P

  13. Line Timing Example TCM X BITS-X PLL P S P S P S P S P S Fabric/Port card Fabric/Port card Fabric/Port card Fabric/Port card TCM Y BITS-Y PLL S P

  14. BITS Timing Example TCM X BITS-X PLL P S P S P S P S P S Fabric/Port card Fabric/Port card Fabric/Port card Fabric/Port card TCM Y BITS-Y PLL S P

  15. Modes of Operation for TCM Hitless modes move between available clock sources • Line timing – references a network port • CEC-Plus: Automatic mode • ASX-4000 Series: Line mode • BITS timing references an external source • CEC-Plus: BITS mode • ASX-4000 Series: External mode Manual modes do not change sources • FreeRun (internal oscillator) • Primary (CEC-Plus only) • Secondary (CEC-Plus only)

  16. CEC-Plus Address Configuration ASX-1000/1200/TNX-1100 1 2 3 4 TCM Interface IP Addressing ie0 192.168.20.1 ie1 192.168.20.2 ie0 192.168.20.3 ie1 192.168.20.4 TCM X X A C X A C X A C X A C B D B D B D B D TCM Y Y Y Y Y Fabric 1ie0 192.168.20.5 Fabric 2ie0 192.168.20.6 Fabric 3ie0 192.168.20.7 Fabric 4ie0 192.168.20.8 SCP Addressing

  17. CEC-Plus Management Interface - EMI • Extended Management Interface (EMI) • Used to configure the IP addresses for the TCM interfaces (ie0 and ie1) • ATM Management Interface (AMI) • Controls the CEC-Plus after IP addresses are configured on the Timing Control Modules (TCMs) • The syntax used for EMI is different than AMI

  18. Configure the TCM’s IP Interfaces localhost::> configuration localhost::configuration> ip localhost::configuration ip>address ie0 192.168.20.1 localhost::configuration ip>address ie1 192.168.20.2 localhost::configuration ip> adminie0 up localhost::configuration ip> adminie1 up localhost::configuration ip> show interface state address netmask broadcast ie0 up 192.168.20.1255.255.255.0 192.168.20.255ie1 up 192.168.20.2 255.255.255.0 192.168.20.255lo0 up 127.0.0.1 255.0.0.0 N/A

  19. Addressing the SCPs of the Switch ATM SWITCH:interfaces ip-> mod ie0 192.168.20.5 -state up ATM SWITCH:interfaces ip-> show Interface State Address Netmask Neighbor Bcast MTU Address Setting lo0 up 127.0.0.1 255.0.0.0 N/A N/A 32768 asx0 down N/A N/A N/A N/A N/A qaa0 down N/A N/A N/A N/A N/A qaa1 down N/A N/A N/A N/A N/A qaa2 down N/A N/A N/A N/A N/A qaa3 down N/A N/A N/A N/A N/A ie0 up 192.168.20.5 255.255.255.0 N/A 1 1500

  20. Configure BITS Reference Source (BITS) Verify Reference Sources Timing Configuration BITS Configure each fabric to listen to the TCM Bus(CEC-Plus only) Line Timing Configure the Primary and Secondary Line Timing Sources Configure the TCM to listen to the PRS and SRS Configure Automatic Reference Source Configure each fabric to listen to the TCM Bus

  21. BITS: Configure Fabrics to Use the TCM Switch Fabric 1:system timing-> modify –timingmode tcmmode Switch Fabric 1:system timing-> show Timing Mode: tcmModePrimary Clock: noneSecondary Clock: noneClock Status: tcm (Repeat for each additional fabric) CEC-Plus This is the default for an ASX-4000 Series switch (no action needed)

  22. Verify Reference Sources Switch Fabric 2:hardware cecplus timing-> references show Reference Source Status Admin RefQual fabric1_Primary 1 (Down) unavailable up ok fabric1_Secondary 1 (Down) unavailable up ok : fabric4_Primary 4 (Down) unavailable up ok fabric4_Secondary 4 (Down) unavailable up ok tcmX_bits1 BITS1 available up ok tcmY_bits2 BITS2 unavailable up ok CEC-Plus ASX-4000:hardware tcm references-> show Reference Source Status Admin RefQual freerun freerun available up ok bits1 BITS1 available up ok bits2 BITS2 unavailable up N/A switchPrimary none unavailable up N/A switchSecondary none unavailable up N/A ASX-4000 Series

  23. Configure Timing Mode Switch Fabric 1:hardware cecplus timing-> modify –mode bits Switch Fabric 1:hardware cecplus timing-> show : BITS interface framing esf line coding b8zs , output level 0.6dB PLL Status: acquiring Current Timing Reference: BITS2 Requested Timing Reference: bits : BITS1 Reference available BITS2 Reference available : CEC-Plus ASX-4000:hardware tcm-> show Operational Status: disabled TCM Type: DS1_Stratum_3K TCM Version: 0 TCM PLL Status: acquiring Requested Timing Mode: external Operational Timing Mode: external Primary Timing Reference: bits1 Secondary Timing Reference: bits2 Current Timing Reference: primary : ASX-4000 Series * This is the default for an ASX-4000 (verify with display)

  24. Summary • Explained the purpose of network synchronization • Identified the meaning of the Stratum clocking grades • Listed the internal and external timing components associated with the CEC-Plus and ASX-4000 Series TCM • Described the basic distribution of timing architecture for line timing and external timing sources • Configured the IP interfaces on the CEC-Plus • Configured and verify timing (external timing example) on the CEC-Plus and the ASX-4000 Series TCM

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