Download - Pseudowires Solutions – Advanced
RAD International Technical Seminar
Tel-Aviv,May 2007
Pseudowires Solutions – Advanced
Presented by:
Merav Shenkar
E-mail: [email protected]
PW Solutions Advanced TS2007 Slide 2
Agenda
• Introduction
• PW protocols for different services
• The PW Challenges
• PSN QoS
• Throughput & Delay
• PW OAM- connectivity confirmation
• Fault propagation
• Clock
PW Solutions Advanced TS2007 Slide 3
PW Solutions Advanced TS2007 Slide 4
TDM PW Services
• Unframed TDMoIP 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
ETHETH
PW-GWPW-GWPBX PBX
ETH/IP/ MPLS
Network
PW Solutions Advanced TS2007 Slide 5
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
ETHETH
PW-GWPW-GWPBX
Framing Sync Framing Sync
PBX
ETH/IP/ MPLS
Network
PW Solutions Advanced TS2007 Slide 6
ETH (12)ETH (12) ETH type
0800 (2)
ETH type0800 (2) IP Header (20)
IP Header (20) UDP Header (8)
UDP Header (8)
ETH (12)ETH (12) IP type
0800 (2)
IP type0800 (2) IP Header(20)
IP Header(20)
ETH (12)ETH (12) MPLS type
8847 (2)
MPLS type8847 (2) Tunnel
Label (4)
TunnelLabel (4)
TDM PW Encapsulation Format
• Overhead size: • IP: 46 bytes
• MPLS: 30 bytes
• UDP: 50 bytes
*HDLC encapsulation is done according to IP/MPLS: RFC 4618
PW label (4)
PW label (4)
TDMCW (4)
TDMCW (4)
PW label (4)
PW label (4)
IP
MPLS
UDP
TDM/HDLC PayloadTDM/HDLC Payload CRC
CRC
PW Solutions Advanced TS2007 Slide 7
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 bytes
according 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)
ETHETH
IPIP
UDPUDP
CWCW
TDM/HDLC PayloadTDM/HDLC Payload
CRCCRC
PW Solutions Advanced TS2007 Slide 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
ATMoPSN GW ATMoPSN GW
PSN
RNCn × E1 IMA/
STM-1
Node B
Node B
ATM
PW Solutions Advanced TS2007 Slide 9
ATMoPSN
• Overhead size:
• IP: 45 bytes
• MPLS: 29 bytes
ETH(12)MPLS Type(2)
TunnelLabel(4)
PW Label (4)
ATM* CW (3)
Cell Header* ATM Payload CRC
(4)
ETH(12)IP
Type(2)IP
Header(20)PW
Label(4)ATM*
CW(3) CellHeader* ATM Payload CRC
(4)
*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)
PW Solutions Advanced TS2007 Slide 10
Multiple Cells Concatenation Format
ATM Payload size
• Up to 29 cells in a single frame
• Cell concatenation reduces overhead
ETHMPLS Type
TunnelLabel
PW Label
ATM CW Cell
Header*
Cell Header*
ATM Payload
ATM CW
Cell Header
Cell Header ATM Payload Cell
Header
Cell Header ATM Payload Cell
Header
Cell Header ATM Payload
CRC
PW Solutions Advanced TS2007 Slide 11
Pseudowire Standards
Application Standard IETF Product
TDM PW
TDMoIP Ietf-pwe3-tdmoip
IPmux-11IPmux-14IPmux-8/16Gmux-2000LA-110
CESoPSN Ietf-pwe3-cesopsnACE-3xxxLA-110LA-130
SAToP draft-ietf-pwe3-satopACE-3xxxLA-110LA-130
ATMoPSN ATM service transport ietf-pwe3-atm-encapACE-3xxxLA-110LA-130
HDLCoPSN HDLC transport RFC 4618 LA-110
PW Solutions Advanced TS2007 Slide 12
PW Solutions Advanced TS2007 Slide 13
PW Solutions Advanced TS2007 Slide 14
E1
VCC
VCCCBR
UBR
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
PSN GW
PW Solutions Advanced TS2007 Slide 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
PW Solutions Advanced TS2007 Slide 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
PW Solutions Advanced TS2007 Slide 17
PW Solutions Advanced TS2007 Slide 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
PW Solutions Advanced TS2007 Slide 19
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.
PW Frame
PW Frame
PayloadPayload
HeaderHeader
HeaderHeader
PW Frame
PayloadPayload
HeaderHeader
Payload Payload
PW Solutions Advanced TS2007 Slide 20
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
PW Frame
PW Frame
PayloadPayload
PayloadPayload
OverheadOverhead
OverheadOverhead
PW Solutions Advanced TS2007 Slide 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 Sec)
• Detection of AAL5 SDU bit=1 triggers packet transmission
PW Solutions Advanced TS2007 Slide 23
TDMoIP Calculator
RAD Technical Support - Broadband Access Solutions Best viewed at 1024x768 resulotion
Product:
Required TDMoIP BW: 2,624,171 [bps]
I nterface:
Required TDMoMPLS BW: 2,454,869 [bps]
Line Type:
Frames per second: 1,058 [fps]
Number of Time-Slots in the bundle:
Packetization Delay: 0.95 [ms]
TDM Byte/Frame size:
E2E Delay (w/o network): 33.95 [ms]
TDMoIP Version:
Max reordered packets Not supported [packets]
Ethernet utilization:
N/A
VLAN Tagging:
Error messages:
J itter Buffer size [ms]: (Allowed range:2.5-200)
None
Visit our eSupport system at:www.rad.com/ techsup.htm
TDMoIP/ MPLS Calculator
None
None
Fractional CAS Disabled
Full
No
II
IPmux- 14
E1
5x48
31
32
PW Solutions Advanced TS2007 Slide 24
CESoPSN & SAToP Calculator
TDMoPSN Calculator (Ver 1.2)
PSN Type TDM Payload size 40
VLAN TDM Rate 640 kbps
Interface type Packetization Delay 500 usec
Line type Actual Jitter Delay 2000 usec
Number of Time Slots (N) 10 [1-31] End-to-End Delay 2500 usec
Multiplier (M) 4 [4-51] Total Overhead 30
Jitter Buffer Delay(usec) 2000 [500-32000] Total Frame Length 70
Ethernet Utilization Overhead Precentage 42.86%
Required Bandwidth [pps] 2000 pps
Required Bandwidth [kbps] 1440 kbps
Disable
MPLS
E1
Framed
Preamble+Interframe Gap
PW Solutions Advanced TS2007 Slide 25
ATMoPSN Calculator
PSN Type VLAN mode Type
Insert number of concatenated cells 1Total overhead 46Total frame length 94Overhead compare to total frame length 48.9%Overload in percentage 77.4%
Insert input ATM in CPS 1000ATM input in Kbits 424.0PSN output in Kbits 912.0Total bandwidth over ETH 0.9%Total bandwidth over GBE 0.1%
Insert number of peers 1PSN output in Kbits 114.4Total clock bandwidth over ETH 0.1%Total clock bandwidth over GBE 0.0%
IP Disable VC
Instructions:1. Select the desired PSN type (MPLS/IP), the VLAN mode (Disable/Enable) , and the Connection type (VP/VC)2. Enter the number of cells which will be concatenated into a single frame; the total overhead, total frame length and overload in percentage fields are updated accordingly.3. Enter the input ATM stream in CPS (Cells per second); the total bandwidth over ETH/GBE fields are updated accordingly. 4. Enter the number of peers towards which clock stream is distributed; the total clock bandwidth over ETH/GBE fields are updated accordingly.
Note:Calculation for PSN output in Kbits include the preamble and inter frame gap.
PW Solutions Advanced TS2007 Slide 26
PW Solutions Advanced TS2007 Slide 27
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
PW Solutions Advanced TS2007 Slide 28
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
* TDMoIP OAM – RAD’s proprietary Operation Administration and Maintenance protocol* TDMoIP OAM – RAD’s proprietary Operation Administration and Maintenance protocol
PW
Wait 10 sec
5 OAM messages
Failure
PW-GW PW-GW
PSN
Wait 2 sec for an answer
and then stop transmission
PW Solutions Advanced TS2007 Slide 29
PW
ATM PWs
PW
Declares state= down Declares state=down
state = down
BFD BFD
PW-GW PW-GW
PSN
• 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)*
* Complies with draft-ietf-pwe3-vccv
PW Solutions Advanced TS2007 Slide 30
Help!!!
Help!!!
PW Solutions Advanced TS2007 Slide 31
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.
PW Solutions Advanced TS2007 Slide 32
TDM/ATM CE
Trunk condition/ AIS
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
PW-GW 2
PSN
PW-GW 1
TDM/ATM CE
PW Solutions Advanced TS2007 Slide 33
TDM/ATM failure
State
Generate Failure
Condition
Report on local TDM/ATM Failure
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
TDM/ATM CE
PW-GW 2
PSN
PW-GW 1
TDM/ATM CE
PW Solutions Advanced TS2007 Slide 34
PW Solutions Advanced TS2007 Slide 35
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.
3G RNC
2G BSCTDM
ETH ETHPacket
SwitchedNetwork
PSN-GWPSN-GW
RadioStations
ATMATM
TDM
PW Solutions Advanced TS2007 Slide 36
Synchronization and Clock Distribution
• 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
Clock distributed over the PSN
Node B
BTS
E1/T1
FE
C.STM-1ATM
2G BSC
TDM E1/T1
Clock
PSN-GW
PSN-GW
E1/T1
GbE
3G RNC
Packet SwitchedNetwork
PW Solutions Advanced TS2007 Slide 37
www.rad.com
thank youfor your attention
Merav ShenkarBroadBand Access teamEmail: [email protected]