PWE3 Introduction 20090724 A

8/11/2019 PWE3 Introduction 20090724 A

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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

PWE3 Introduction


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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved. Page1

Objectives

Upon completion of this course, you will be able to:

Describe the basic concepts of PWE3

Outline the typical PWE3 encapsulation format

Outline the PWE3 application scenarios


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Contents

1. PWE3 Overview

2. TDM to PWE3

3. ATM to PWE3

4. ETH to PWE3

5. PWE3 Application Scenarios


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Contents

1. PWE3 Overview

1.1 Basic Concepts

1.2 Reference Model of PWE3

1.3 Reference Model of PWE3 Protocol Stack


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What Is PWE3?

Pseudo-Wire Emulation Edge to Edge (PWE3)

Concept of PW

The Mechanism that bears the simulated services between

PEs on the PSN.

PE

PE

PE

CECE

CE

AC

PW1

PW2

PW3


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Functions of PW

Functions of PW

Encapsulate the protocol data units (PDUs) specified by the service

from the logical or physical port on the PE side.

Carry the encapsulated packets to the transmit tunnel.

Set up PW at the tunnel end, including the exchanging and distribution

of PW IDs.

Perform the traffic monitoring in the ingress direction and traffic

shaping in the egress direction.

Manage signals, timing and sequence at the PW edge.

Manage the status specified by the service and alarms.


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Why PWE3?

Generic label, which provides a uniform multi-service

network data transport platform and reduces the operating

cost

Investment protection, which provides the backward andforward compatibility of network services

Private line emulation, which provides operators with

network services of great return.


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PWE3-Related Concepts

L1/2 service: Ethernet, ATM and TDM

PSN: MPLS and IP

AC: Physical or logical CE-PE connection

Tunnel: Carries one or multiple pseudo wires (PW)

PWs are transparently transmitted in the core network

PWs are created through signaling (LDP)


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PWE3-Related Concepts (Cont.)

PW control plane: Create and remove PWs and monitor the

status

PW forwarding plane: Convert the L1/2 header information

and transmit PDUs in sequence

MIB: Management Information Base, storage configuration

information.


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Reference Model of PWE3

Network

PE1

CE1 Tunnel CE2

Emulated Service

Pseudo Wire

PSN Tunnel

PE2

Native

Service

Native

Service

Custom

Edge 1

Custom

Edge 2

Provider

Edge 2

Provider

Edge 1

AC AC

AC: Attachment Circuit


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Payload

Encapsulation

Emulated

Service

(TDM, ATM,

Ethernet, etc)

PW

Demultiplexer

PSN Tunnel,

PSN &

Physical

Layers

Emulated Service

Pseudo Wire

PSN Tunnel

Payload

Encapsulation

Emulated

Service

(TDM, ATM,

Ethernet, etc)

PW

Demultiplexer

PSN Tunnel,

PSN &

Physical

Layers

PSN

RTP

Sequence Number

PW Label

LenFragFlags

Outer Label or MPLS-in-IP encapsulation

RTP

Sequence Number

PW Label (L2TP/MPLS)

LenFragFlags

IP

MAC

Reference Model of PWE3 Protocol Stack


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Contents

1. PWE3 Overview

2. TDM to PWE3

3. ATM to PWE3

4. ETH to PWE3



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PE2PE1

CE1 CE2

Phy Dec Phy

S1

Phy Enc Phy

S2

Phy Enc Phy

Phy Dec Phy

CE1 and CE2 terminate the TDM circuit

PE1 and PE2 adapts the services to PWs

S1 and S2 are core routers

PHY is the physical interface that terminates the TDM circuit

Enc is the PSN-bundling interface for PW, which has a jitter buffer

Dec is the CE-bundling interface for PW, which has a jitter buffer

Reference Model of TDM PWE3


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Reference Standards of TDM

PWE3 MEF

MEF3

Circuit Emulation Service Definitions, Framework and Requirements in Metro Ethernet

Networks

MEF8

Implementation Agreement for the Emulation of PDH Circuits over Metro Ethernet Networks

IETF

RFC4197

Requirements for Edge-to-Edge Emulation of Time Division Multiplexed (TDM) Circuits over

Packet Switching Networks

RFC4553

Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)

Structure-aware TDM Circuit Emulation Service over Packet Switched Network (CESoPSN)

draft-ietf-pwe3-tdmoip-06: TDM over IP

ITU-T

G.8261


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Byte m

Byte m+1

Byte m+nx32-1

Tunnel Label

PW Label

Control Word

Payload

4 bytes

4 bytes

4 bytes

payload

ETH header

CRC

payload

PPP header

FCS

SAToP

Principle

The SAToP mode does not detect any structure in the TDM circuit. It treats the

TDM circuit as a bit stream of a constant rate. One unit contains 8 bits. Cut a

certain length (reflected as loading time for the customer) from the TDM bit

stream and then load it to the emulation packet. The framing information and

channel information are not considered. Hence, the TDM service is

transparently transmitted.

Frame format


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CESoPSN

Principle

The CESoPSN mode detects the frame structure, framing mode,

timeslot information in the TDM circuit. The payload of the TDM frame

is extracted first and the timeslot of each channel is added into the

packet payload according to a certain sequence.

Frame format

Tunnel Label

PW Label

Control Word

Payload

#1 E1 Frame

#2 E1 Frame

#n E1 Frame

32 bytes

32 bytes

32 bytes

n = 124

4 bytes

4 bytes

4 bytes

payload

ETH header

CRC

payload

PPP header

FCS


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Contents

1. PWE3 Overview

2. TDM to PWE3

3. ATM to PWE3

4. ETH to PWE3



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Reference Standards of ATM

PWE3 IETF

RFC4717: Encapsulation Methods for Transport of Asynchronous

Transfer Mode (ATM) over MPLS Networks

RFC4816: Pseudo wire Emulation Edge-to-Edge (PWE3)

Asynchronous Transfer Mode (ATM) Transparent Cell TransportService

RFC4454: Asynchronous Transfer Mode (ATM) over Layer 2

Tunneling Protocol Version 3 (L2TPv3)

ITU-T

Y.1411: ATM-MPLS network interworking Cell mode user plane

interworking


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Encapsulation Format of ATM Service

No. PW Type Indication

3 0x0003 ATM transparent cell transport (V1R2)

9 0x0009 ATM n-to-one VCC cell transport

10 0x000A ATM n-to-one VPC cell transport

12 0x000C ATM one-to-one VCC Cell Mode

13 0x000D ATM one-to-one VPC Cell Mode

0 1 2 3

PSN Transport Header

Pseudo Wire Header

ATM Control Word

ATM Service Payload

The types of encapsulation supported by the OptiXPTN product:


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PSN Transport Header

It depends on the used tunnel technology and performs the packet

switching in the PSN network.

Pseudo Wire Header

It identifies the ATM service in a tunnel and it is the bottom of the label

stack in the MPLS.

ATM Control Word

It can be a length or sequence number and it is the control bit of the

transmitted service.

Encapsulation Format of ATM Service

(Cont.)


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0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

PSN Transport Header PWE3

Pseudo Wire Header in PWE3

0 0 0 0 Flags Res Length Sequence Number

VPI VCI PTI C

Payload (48 octets)

VPI VCI PTI C

Payload (48 octets)

N-to-One Cell ATM Mode

The encapsulation format of a single cell is required (fast encapsulation), the

encapsulation format of multiple cells is optional.

The number of cells can be encapsulated is restrained by the management

capability of MTU and Egress PE (router).

VPI/VCI: The value of Ingress PE can not be changed, but the value of Egress PE

can be changed into a new value.

PTI/CLP: Retain the original cell value.


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N-to-One Cell ATM Mode Description

One PW can carry one or more VPCs/VCCs. The format can be the single cellformat, or multiple cell encapsulation, which can enhance the bandwidth utilization.

The multiple cell encapsulation can enhance the bandwidth utilization, but it

causes network delay variation. In addition, the number of cells to be encapsulated

is determined by the MTU and CTD and CDV requirements of the ATM

connections multiplexed into the PW. Hence, the network environment and service

customization should be considered together.

The multiple VPCs/VCCs encapsulated in the PW may of different service types,

which are of different QoS requirements. Hence, the PSN packets should support

the highest level of the ATM service carried. To ensure the QoS of the PW, it isrecommended that one PW carry one VPC/VCC, or one PW carry the VPCs/VCCs

of the same QoS requirement.


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0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

PSN Transport Header in PWE3


0 0 0 0 Resvd Sequence Number M V RES PTI C

Payload

48 octets

M V RES PTI C

Payload

48 octets

CV PTIRESM VCI

Payload

48 octets

Payload

48 octets

VCI

VCI

Sequence Number CPTIRESVMResvd0 0 0 0



10987654321098765432109876543210

3210

VCC VPC

One-to-One ATM Cell Mode

One PW can carry one VPC/VCC

The format can be the single cell format or multiple cells encapsulation.


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One-to-One Cell ATM Mode

Description

The multiple cell encapsulation can enhance the bandwidth

utilization, but it causes network delay variation.

The number of cells to be encapsulated is determined by

the MTU and CTD and CDV requirements of the ATMconnections multiplexed into the PW.


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Contents

1. PWE3 Overview

2. TDM to PWE3

3. ATM to PWE3

4. ETH to PWE3



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ETH PWE3 Encapsulation Format

0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1



0 0 0 0 Reserved Sequence Number

ETH Payload

Control words, which are only sorted (165535).

The equipment support the modes without control words or with control

words.

The control words can be set at the PEs on the two ends through

signaling or manual configuration.


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Contents

1. PWE3 Overview

2. TDM to PWE3

3. ATM to PWE3

4. ETH to PWE3



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E1

CESoPSN

SAToP

Abis

TDM

PWE3

MPLS

PPP/

ML-PPP

HDLC

POS/E1

PSN

Abis

TDM

E1

STM-1

Abis

TDM

E1/ch

STM-1

Abis

TDM

PWE3

Tunnel

Line Interface Line InterfaceNetwork Interface

E1

E1

MAC

GE

TS# 1-9

Idle TS suppression

--

TS# 1-6

Idle TS suppression

TS# 1-8

Idle TS suppression

--

--

--

--

--

1+1/1:1 APS

E1/POS/GE/ch

STM1

MSPPoC3 PoC1

--

--

--

idle timeslot

regenerated

2G BTS

BSC

Multi-Service over PW: TDM Solution


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E1

E1

E1

E1

lub UP

AAL2

ATM

PWE3

MPLS

---

Line Interface Line InterfaceNetwork Interface

E1

E1

PoC3

lub UP

AAL2

ATM

IMA

E1

lub UP

AAL2

ATM

PWE3 N:1 ATM PWE3

Encapsulation

lub UP

AAL2

ATM

STM-1

PSN

STM-1

EF

AF3

BE

Legend

1+1/1:1 APS

Tunnel

PoC1

E1/POS/GE

3G Node B

RNC

3G Node B

Multi-Service over PW: ATM/IMA

Solution


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lub UP

802.1Q

Eth

PWE3

MPLS

---

Line Interface Line InterfaceNetwork Interfacelub UP

802.1Q

Eth

N:1 Eth PWE3

Encapsulation

PSN

EF

AF3

BE

Legend

1+1/1:1 APS

Tunnel

lub UP

802.1Q

Eth

PWE3

GE/FE

lub UP

802.1Q

Eth

GE

PoC3 PoC1

E1/POS/GE

3G Node B

RNC

Multi-Service over PW: IP/Eth Traffic

Solution

Offload Scenario 1 : ADSL Network


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Cased on ATM Forwarding (LSP

Tunnel)


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Cased on ATM Forwarding (IP Tunnel)


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Cased on MPLS Forwarding


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Cased on IP Forwarding (IP tunnel)


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Cased on IP Forwarding (GRE tunnel)


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Summary

PWE3 Overview

TDM to PWE3

ATM to PWE3

ETH to PWE3

PWE3 Application Scenarios

TDM

IMA

Ethernet

Offload


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PWE3 Introduction 20090724 A

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