MPLS-TP, PTN Transport


The MPLS-TP (Multiprotocol Label Switching - Transport Profile) is a variant of the IP-MPLS protocol issue in 2006 from Internet Engineering Task Force (IETF) together with International Telecommunication Union Telecommunication Standardization (ITU-T).

This PTN (Packet Transport Network) protocol is a simplified version of IP/MPLS which is easier to deploy and focuses on the Industries and Mission Critical Communication. This includes the Power industry as well as Teleprotection, Air Traffic Management, Railway-Mobility, Oil & Gas, Defense and Carriers, as well as other customers that require high level of bandwidth stability, latency and security to transport voice communication, SCADA, signalization, power control, etc.

The MPLS IP or TP applies a Label Switching Path (LSP) on packet from multiple protocols to accelerate the speed of their distribution in Mesh infrastructure or over VPN without packet analysis.

The MPLS-TP is the right evolution for TDM/SDH/SONET infrastructures to carry the Multiservice TDM together with high volume of packets ,and it is easier to deploy stable transport than IP/MPLS or IP and Carrier Ethernet for long distances, thanks to:

  • MPLS-TP is a Connection-Oriented protocol using LSP from edge to edge, where it is easy to deploy the circuits as PseudoWire
  • MPLS-TP has a static planning that is provided by a NMS for the Multiservice TDM access, SDH/SONET, PseudoWire and the creation of circuits over multiple transports,
  • MPLS-TP with bidirectional LSP supports determinist performance for bandwidth, latency, jitter, codirectional transport with synchronization and timing distribution,
  • Large and dynamic bandwidth IP/Ethernet in E-Line, E-LAN and E-Tree services are transported by MPLS-TP over VPWS, VPLS or H-VPLS in case of large number of instances,
  • Multiservice TDM (E1/T1, FE1/FT1, voice, serial…), SDH, SONET, low-rate Ethernet SCADA… are transported in PseudoWire end-to-end (PW) with their frequency and timing synchronization for symmetric and asymmetric traffics
  • MPLS-TP networks support multiples protection based on PseudoWire on LSP/Tunnel as 1+1 or 1:1 to optimize the bandwidth utilization or recovery time, always less than 50ms,
  • MPLS-TP OAM verify the integrity of PW and LSP which is always more flexible than SDH/SONET,
  • Loop Telecom MPLS-TP switches support together GE/10GE MPLS-TP for aggregation and core network, and GE/10GE Carrier Ethernet 2.0 interfaces for access services,
  • Loop Telecom MPLS-TP switches PTN10G/G7820 support also Layer 3 routing services: RIP, OSPF, VRRP, VFR. Some IP/MPLS protocols are in development* as LDP, OSPF routing, PHP termination, Ping, Route and RSVP-TE.
Easy to deploy

TDM are carried in point-to-point PW, switched Ethernet is connected in VPWS for point-to-point or VPLS to support Mesh multipoint. The MPLS-TP is a connection-oriented packed switched profile, the administrator will implement PW and LSP like the circuits for SDH/SONET infrastructure.

herefore, MPLS-TP features the OAM functions for the Alarm Monitoring and Alarm Signaling, Traffic Diagnosis and Circuit Performance Monitoring at every layer (Section, LSP, PW). In addition, this layer 2.5 protocol optimizes the transport over PTN infrastructure with enhanced carrier-grade protection switching, OAM and clock synchronization SyncE and PTP 1588v2.

Fast transport of the MPLS

Based on transmission between 2 LER (Label Edge Router) crossing several LSR (Label Switch Router), the LSP (Label Switching Path) is created by adding/changing a label for fast switching over the path. This bidirectional LSP can carry several PW(TDM) and VPWS/VPLS between two LERs.

The capacity to carry the IP/Ethernet in MPLS-TP over the GE/10GE interfaces is not limited by the intermediate switch LSR with 100G capacity instead of the EoS limitation of the SDH/SONET cross-connect.

Traffic Engineering algorithms guarantee and optimize bandwidth per service

The Traffic Engineering in QoS controls bandwidth of data flow with metering algorithms to reshape rate fluctuations by applying buffers to accommodate burst traffic metering algorithms using Token Bucket (TB): Single Rate Three Color (SRTC), Two Rate Three Color (TRTC) and Hierarchical QoS (H-QoS).

The administrator can define per PW Service, LSP and/or Tunnel:

  • the Traffic rate CIR (Committed Info. Rate) and PIR (Peak Info. Rate)
  • moderate the traffic with CBS (Committed Burst Size) and PBS (Peak Burst Size).

Then OAM can guarantee a fixed bandwidth to TDM PW and SCADA Ethernet PW by Traffic Engineering engine.

Loop Telecom proposes a range of PTN equipment with the MPLS-TP and Carrier Ethernet support

Their access tributaries interfaces make the interest for the different end-user application, but all devices are using the same Loop-OS with Layer 2, 2.5, 3 and some IP/MPLS feature in development.

Model G7820-48T G7860A O9400R-PTN O9500R-PTN
Function PTN with MPLS/TP/CE
GE/10GE Switch
Layer 2/2.5/3

GE/10GE Switch
Layer 2/2.5

GE/10GE Switch
Layer 2/2.5/3
GE/10GE Switch
Layer 2/2.5/3
      PDH DACS Multiplexer
System Fixed 1U, 2 PSU Modular 1U, 2 PSU Modular 6U, 2 CPU, 2 PSU Modular 6U, 2 CPU, 2 PSU
Fixed GE/10GE SFP+ 8 GE/10GE NNI/UNI 6 GE/10GE NNI/UNI 2 x 3 GE/10GE NNI/UNI
GE SFP or Copper 48 GE NNI/UNI 4 GE NNI/UNI + 16  FE/GE 2 x 8 GE SFP NNI/UNI + 2 x 10 GE
Switching Capacity 120Gbps 81Gbps 100Gbps
Transport Protocols Layer 2.5 MPLS-TP and Carrier Ethernet 2.0*
Ethernet L2 Transport VLSP or H-VLSP Bridging, 2K VLSP instance per node
Ethernet L3 Transport RIP, OSPF, VRRP, VRF   RIP, OSPF, VRRP*, VRF*
OAM Section/LSP/PW TP-OAM using BFD (per IEEE8113.2)
Protection LSP 1+1 and 1:1 (RFC6378)
RSTP(802.1w), MSTP(802.1s) all <50ms
TDM Transport   PseudoWire Emulation End-to-End (PWE3) over LSP in CESoPSN, SAToP and CEP for SDH/SONET
SDH/SONET   Access only STM1/4 ADM/TM node: STM1/4/16 or OC3/12/48
Protection   MSP 1+1 MSP 1+1, SNCP, MESH SNCP MSP 1+1, SNCP, MESH SNCP
TDM   Access G.703 Cross-connect G.703 to VCxx Cross-connect G.703 &DS0
Maximum E1/T1 G.703   16 to 80 E1/T1 378 E1/T1 or 18 E3/DS3 126 E1/T1 or 6 E3/DS3
PDH DACS/DCS Multiservices       E1, T1, CD 64K, FXS, FXO, E&M, Magneto, VoIP, RS232, RS485, RS422, X.21, V.35, C37.94
TDM Encapsulation   PW/LSP (TDM over MPLS-TP), “Dry Martini”, MEF-8 (TDMoE), TDM over IP
Ethernet Any GE/10GE interface can be used as NNI network or UNI local LAN interface
Services   E-Line, E-LAN, E-Tree, E-Access according to MEF 9 & 14 over VPWS/VPLS, Native Ethernet, VLAN simple/double tagging Q-in-Q E-Line, E-LAN, E-Tree, E-Access* according to MEF 9 & 14 over VPWS/VPLS, Native Ethernet, VLAN simple/double tagging Q-in-Q
VPLS VPLS and H-VPLS bridging, 32K MAC addresses, 2K VPLS instance, Split horizon to prevent forwarding loops
EoSDH & EoPDH     EoS EoS & EoPDH
Synchronization SyncE on all GE/10GE ports with ESMC (Ethernet Synchronization Message Channel)
IEEE 1588v2 PTP clocks: Ordinary/Boundary/Transparent, ToD, 1 PPS output
TDM Clock   Clock Input/Output: 2Mbps/1Mbps, SSM, E1/T1 or STMx/OCx ports

*In developement

References and recommended literature: