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Pseudowires Solutions – Advanced

Pseudowires Solutions – Advanced. Presented by: Merav Shenkar E-mail: merav_s@rad.com. Agenda. Introduction PW protocols for different services The PW Challenges PSN QoS Throughput & Delay PW OAM- connectivity confirmation Fault propagation Clock. PW Protocols for different Services.

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Pseudowires Solutions – Advanced

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  1. Pseudowires Solutions – Advanced Presented by: Merav Shenkar E-mail: merav_s@rad.com

  2. Agenda • Introduction • PW protocols for different services • The PW Challenges • PSN QoS • Throughput & Delay • PW OAM- connectivity confirmation • Fault propagation • Clock

  3. PW Protocols for different Services

  4. ETH/IP/ MPLS Network TDM PWServices • UnframedTDMoIP or SAToP over PSN • E1/T1 line is a 2.048/1.544 Mbps bit stream • Full transparency to the TDM traffic • No Multi-Bundling • End-to-End framing sync • TDMoIP standard: IETF – ietf-pwe3-tdmoip • SAToP standard: draft-ietf-pwe3-satop.txt- Structure-Agnostic TDM over Packet PBX PBX PW-GW PW-GW ETH ETH

  5. ETH/IP/ MPLS Network TDM PW Services cont. • Framed TDMoIP or CESoPSN • Framed E1/T1 • Multi-Bundling • TS0/Fbit Termination • Local framing sync • TDMoIP standard: IETF – ietf-pwe3-tdmoip • CESoPSN: draft-ietf-pwe3-cesopsn.txt - Structure-Aware TDM Circuit Emulation Service over PSN PBX PBX PW-GW PW-GW ETH ETH Framing Sync Framing Sync

  6. MPLS type8847 (2) ETH (12) IP type0800 (2) PW label (4) PW label (4) ETH (12) IP Header(20) CRC TDM/HDLC Payload ETH type0800 (2) IP Header (20) ETH (12) TDM PW Encapsulation Format Tunnel Label (4) • Overhead size: • IP: 46 bytes • MPLS: 30 bytes • UDP: 50 bytes *HDLC encapsulation is done according to IP/MPLS: RFC 4618 MPLS TDMCW (4) IP UDP UDP Header (8)

  7. TDM/HDLC Payload ETH IP CRC UDP CW TDMoIP Payload Size • TDMoIP Unframed/Framed payload size: is between 48-1440 bytesnx48 bytes (where n=1,2,3,……,30) • CESoPSN & SAToP payload size: is between 32-512 bytesaccording to the number of TS in a bundle(configurable) Payload configuration:N – Number of Time Slots in a bundle L– Packet payload size in bytes • L should be multiple integer (m) of number of Time Slots in the bundle (N) L = m x N • HDLCoIP mechanism monitors the data stream until a frame (data) is detected (flag)

  8. 3G ATM Based Services • ATMoPSN • Mapping of ATM cells to packets • Transparent backhaul of lub over packet based network • End-to-End QoS is maintained • 1:1 & n:1 mapping modes • Standard: draft-IETF-PWE3-atm-encap Node B ATMoPSN GW ATMoPSN GW RNC n × E1 IMA/ STM-1 PSN ATM Node B

  9. PW Label(4) IP Header(20) IP Type(2) CRC(4) ATM Payload ETH(12) ATMoPSN • Overhead size: • IP: 45 bytes • MPLS: 29 bytes Cell Header* MPLS Type(2) TunnelLabel(4) PW Label (4) ATM* CW (3) ETH(12) ATM Payload CRC(4) ATM* CW(3) CellHeader* *Cell Header – In VCC mode – 1 byte per cell, In VPC mode – 3 bytes per cell Control word – Has a different format for each PW type (optional for some PW types)

  10. Cell Header Cell Header* Cell Header Cell Header ATM CW ATM CW PW Label TunnelLabel MPLS Type CRC ATM Payload ATM Payload ATM Payload ATM Payload ETH Multiple Cells Concatenation Format ATM Payload size • Up to 29 cells in a single frame • Cell concatenation reduces overhead

  11. Pseudowire Standards

  12. The PW Challenges

  13. PSN QoS

  14. QoS over PSN Challenge: • Traffic coming from the native services ports (ATM/TDM) contains a certain QoS which should be kept across the PSN Solution: • The PSN GW scheduler should decide which packet will be sent first towards the PSN network • “Convert” the native service priority into priority over PSN PSN GW UBR VCC CBR PSN VCC E1

  15. ETH Scheduling TX Queue Assignment • User traffic priority should be also prioritized internally by the PW GW when transmitted to the PSN • The internal prioritization will be done using ETH Tx queues with different priority levels • The user should decide which service will get the highest priority within the PW-GW. for example: • Clock traffic – highest priority Tx queue • ETH data traffic – lowest priority queue

  16. PSN QoS • TDM/ATM QoS are mapped to PSN QoS: • Ethernet networks • VLAN ID or VLAN priority • VLAN can be optionally added to every encapsulation mode for CoS differentiation and QoS marking • MPLS networks • EXP bits of the MPLS label on both inner and outer label • IP networks • ToS/DSCP • ToS bit marking per PW

  17. Throughput & Delay

  18. Throughput & Delay Challenge: • Encapsulating the native service payload over PSN transparently adds an overhead and delay Solution: • Provide a mechanism to control PW bandwidth utilization and delay

  19. Header PSN Bandwidth Utilization • The output BW of the PW GW is governed by setting the PW frame’s payload size. • Typically the PW overhead introduced by the PW protocol has a fixed size, while the payload size is user configurable. • Increasing the payload size would reduce the ratio between the overhead and the frame size. • The larger the payload size the better smaller the BW utilization over the PSN. Header Header PW Frame Payload Payload PW Frame Payload PW Frame

  20. Payload Payload Packetization Delay • Packetization Delay (PD): The time it takes the PSN-GW to fill the payload with the incoming TDM/ATM traffic • The larger the payload, the longer it will take to fill up and transmit the PW frame. • The PD is the interval between two consecutive PW frames Overhead PW Frame Overhead PW Frame

  21. Triggers for Packet Transmission • A PW frame will be sent towards the PSN under the following conditions: • TDMoIP/CESoPSN/SAToP • The configurable payload size is filled with TDM frames. • ATMoPSN • Payload is filled with ATM cells (1-29 cells per frame) • The timeout mechanism expires (between 100 – 5000000 mSec) • Detection of AAL5 SDU bit=1 triggers packet transmission

  22. TDMoIP Calculator

  23. CESoPSN & SAToP Calculator

  24. ATMoPSN Calculator

  25. PW OAM-Connectivity Verification

  26. Connectivity Verification Challenge: PSN networks have no inherent connectivity verification mechanism between two end points. Solution: • Provide path fault detection for an emulated PW over PSN • Allow detecting faults occur on the remote end, in order to prevent IP/ETH network flooding • Enable the use of redundancy

  27. Failure Wait 10 sec TDM PWs* • TDM PWs generate constant traffic over the PSN (regardless of the TDM traffic) • Therefore, there is no need for “keep-alive” messages during steady state • During device failure condition, we need to stop traffic transmission in order to prevent PSN flooding. • The PW GW will initiate a “keep alive” messages based on TDMoIP OAM protocol, just in case a failure was detected 5 OAM messages PW PSN PW-GW PW-GW Wait 2 sec for an answer and then stop transmission * TDMoIP OAM – RAD’s proprietary Operation Administration and Maintenance protocol

  28. Declares state=down Declares state= down PW ATM PWs • Since ATM PWs based on a statistical network, a keep alive messages are required in order to verify the PW connectivity. • PW-GWs sends BFD messages messages periodically between PW, based on VCCV-BFD (Bidirectional Forwarding Detection)* BFD BFD state = down PW PSN PW-GW PW-GW * Complies with draft-ietf-pwe3-vccv

  29. Help!!! Fault Propagation

  30. Fault Propagation Challenges: • Alarms on the legacy services network should be propagated over the PSN transparently. • Impairments on the PSN network should be forwarded to the legacy services network. Solution: Provide alarm forwarding mechanism between the native ATM/TDM network to the PSN and vise versa.

  31. PSN TDM/ATM • PSN impairments (marked with ) can be: • TDM-PW Packet loss,Jitter buffer underflow/overflows • ATM-PW ETH Link down or BFD control message is not received • As a result the PW GW 2 will generate alarms on the Attachment Circuit (AC): • TDM PW: AIS/Trunk condition • ATM PW: AIS OAM • In addition PW GW 2 will signal the remote PW GW 1 on the local PSN fault Trunk condition/ AIS PW-GW 1 PW-GW 2 PSN TDM/ATM CE TDM/ATM CE

  32. Report on local TDM/ATM Failure Generate Failure Condition TDM/ATM failure State TDM/ATM to PSN • The local PW-GW enters a forward defects state when one of the below are detected on the TDM/ATM network: • LOS/ LOF/ AIS/ RDI • The PW-GW 1 reports on local failure to the remote PW-GW 2 • PW GW 2 propagate the relevant alarm on the Attachment Circuit PW-GW 1 PW-GW 2 PSN TDM/ATM CE TDM/ATM CE

  33. Synchronization and Clock Distribution

  34. 2G BSC TDM TDM PSN-GW PSN-GW Packet Switched Network Radio Stations ETH ETH 3G RNC ATM ATM Synchronization and Clock Distribution Challenge: • PSN networks are by nature asynchronous with statistical behavior, thus, can not provide the clock source. Solution: • Develop a mechanism which can recover synchronous clock over PSN networks.

  35. Synchronization and Clock Distribution Clock distributed over the PSN • Central unit distributes local clock source through the PSN • Remote device recovers the clock and distributes to the radio stations • Clock recovery performance • Complies to G.823/4 Traffic interface & G.8261 • Frequency Accuracy better than 16 ppb • Hold over mechanism in case of clock stream failure 3G RNC C.STM-1 ATM E1/T1 PSN-GW Node B PSN-GW Packet Switched Network Clock FE GbE 2G BSC E1/T1 TDM E1/T1 BTS

  36. thank you for your attention Merav Shenkar BroadBand Access team Email: merav_s@rad.com www.rad.com

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