Tài liệu Ethernet over VDSL docx

Introduction VDSL Very high data rate Digital Subscriber Line is a broadband transport technology for twisted copper pairs operating at data rates of up to 52.8 Mbit/s with correspondin

Ethernet over VDSL

White Paper

1 Introduction

VDSL (Very high data rate Digital Subscriber Line) is a broadband transport technology for

twisted copper pairs operating at data rates of up to 52.8 Mbit/s with corresponding maximum reach ranging from 1000 feet (300 meters) to 4500 feet (1500 meters) of 24 gauge wire VDSL offers tremendous promise as a means to provide the next generation of high-speed networking technology over copper telephone lines

VDSL is referred to as a last-mile technology, as it is used for inter-connections between a

telephone switching station and a home or office, and is not used for interconnecting switching stations

2 VDSL Benefits

• Highest-rate DSL technology available

• Support for Symmetric and Asymmetric modes of operation

• Up to 52 Mbit/s downstream over single copper twisted-pair loop

• Coexistence with Voice

• Home networking or LAN over regular telephone lines

• The dominant physical access medium based on copper loop for MTU (Multi Tenant Unit) and residential applications

3 VDSL Applications

• Digital Video broadcast

• Video-on-demand

• Video conferencing and Voice over IP

• LAN to LAN connection over the existing telephone wires

4 VDSL Deployment Scenarios

• Possible deployment scenarios for VDSL are Fiber to the Exchange (FTTEX), Fiber to the

Neighborhood (FTTN), Fiber to the Cabinet (FTTCab) and Fiber to the Building (FTTB) In FTTEX, all subscribers are within close range of the Central Office (CO) FTTN and FTTCab are appropriate for VDSL termination in DLCs and NGDLCs FTTB can bring fiber directly into buildings, such as MDU and MTU, where VDSL is terminated

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• Ethernet over VDSL

Figure 1 VDSL Deployment Scenario

As demonstrated in Figure 1, VDSL technology enables transmission of high-speed traffic between the Network, the ONU, and end user premises over the existing telephone lines

The VDSL CPE on the user side is connected to VDSL ONU over a twisted copper pair

The connection of the the user’s home network to the public network is smoothly achieved by a native Ethernet interface between the VDSL CPE interface and the LAN

on the user’s side

5 Ethernet Over VDSL Technology

Using Ethernet Over VDSL technology enables the existing public copper network and the user LAN networks to be used for migration to new emerging services It also has

the following advantages:

• No need for new wiring

• Meeting consumer price and performance needs

• Cost effective high speed access - up to 20 Mbit/s or more

• Simple, easy to install; true plug-and-play

• Near-zero configuration

• Enables simultaneous delivery of additional services such as voice Ethernet framing ensures compatibility with existing Ethernet LAN

• MAN/WAN compatible

• Eliminates protocol conversions

Figure 2 describes the components involved in the connection between user premises equipment and the Ethernet core

• Ethernet over VDSL

Figure 2 VDSL Deployment Scenario

In Figure 2, the traffic from the user equipment to the CPE is transmitted over LAN

media using a native Ethernet frame

The Ethernet frame is transmitted from the CPE to the IMAP or DSLAM over VDSL

using a twisted copper pair The connection between the IMAP or DSLAM and the

Ethernet core can be applied over any transmission media, and the Ethernet frame

can be mapped to any destination over the public network using standard layer 2

MAC algorithms

6 Ethernet over VDSL (EoVDSL) Frame Encapsulation

6.1 VDSL Frame Format

The Ethernet frame is encapsulated in the following VDSL frame format:

• Ethernet over VDSL

Figure 3 VDSL Ethernet Frame

The payload is divided into two equal parts: fast channel for latency sensitive services, and slow

channel (mandatory) The slow and fast channel alternate as shown in Figure 3

To apply the mandatory Transport Class 1 (single latency) the values F=0, S=200 should be set

to remove the fast channel fields from the transmitted frame

6.1.1 Fast Channel

Figure 4 Fast Channel

Fast channel is optional, and defined for latency-sensitivity applicationssuch as

Voice The Fast Codeword should be <= 180 octets

6.1.2 Slow Channel

• Ethernet over VDSL

Figure 5 Slow Channel

The Slow channel is mandatory and defined for data transmission

The Slow codeword consists of 3-octet Operation Channel (OC) field, a Slow Payload field and a slow FEC field of 16 octets The length of the Slow Codeword is ≤ 200 octets

The slow codewords are protected by an Interleaver before transmission into the lines; it carries both payload and in-band control channel

6.1.2.1 Operational Channel

Figure 6 Operational Channel

The Operational Channel contains 3 octets per frame: one Op-code octet and two

data octets It is used as transport media for VOC (VDSL Overhead Control) and EOC (Embedded Operation Channel), while VOC used for control of the modem layers (VDSL chipset), and EOC is used for management applications

6.2 Ethernet Frame

• Ethernet over VDSL

Figure 7 Ethernet Frame

• The Ethernet frame must be transferred transparently, without manipulating the frame content

• The encapsulation method is a store & forward mechanism It is not data

dependant (no bit stuffing)

• EoVDSL is a PHY

• Prioritization is performed by higher layer devices and packets are transferred in the order they are received

• The Ethernet packet is preceded by an IPG of 9.6 usec/0.96 usec for

10/100Mbit/s links

• The preamble (0x55) is not used by MAC The SFD (0x5D) is required by the MAC layer

The Data in Figure 7 refers to the Ethernet frame from the destination address to the FCS, Destination Address, Source Address ,Type/ Length, DATA, FCS

6.3 EoVDSL Encapsulation

• Ethernet over VDSL

Figure 8 EoVDSL Encapsulation

The Ethernet frame (without preamble, SFD and EFD {Ethernet frame data}) is encapsulated by a new preamble Idle bytes are filled with flags

• The preamble includes a length field

• Ethernet Frame Data from destination address to FCS

7 Conclusion

Ethernet over VDSL is an excellent solution for high speed applications The media is highly available, and cheap compared to other solutions It is also simple to connect to, from any type of equipment supporting Ethernet LAN, and no protocol conversion is required