Ethernet Packet Transport

2/1551-14/CSH 109 32/1 Uen Rev F

MINI-LINK TN ETSIEthernet Packet Transport

Technical Reference

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Copyright

Ericsson AB 2008

Disclaimer

No part of this document may be reproduced in any form without the written permission of the copyright owner.

The contents of this document are subject to revision without notice due to continued progress in methodology, design and manufacturing. Ericsson shall have no liability for any error or damage of any kind resulting from the use of this document.

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Copyright ii

Disclaimerii

1 Preface....................................................................................3

2 Acronyms and Glossary.......................................................3

3 Transport network evolution................................................33.1 Market trends/drivers...............................................................33.2 New packet based transport networks.....................................33.3 Packet transport in Microwave networks.................................33.4 Standards update....................................................................3

4 Packet support in MINI-LINK TN...........................................34.1 Target market segments..........................................................34.2 Multi service architecture.........................................................34.2.1 Backplane busses....................................................................34.2.2 Ethernet centric view...............................................................34.3 Network use cases..................................................................34.3.1 Ethernet connection services...................................................34.4 Product offering.......................................................................34.5 Ethernet features and characteristics......................................34.5.1 Functional model.....................................................................34.5.2 Frame size...............................................................................34.5.3 Security/admission control.......................................................34.5.4 Bridging/switching....................................................................34.5.5 Class of Service (CoS)............................................................34.5.6 Inverse Multiplexing (IM)..........................................................34.5.7 Generic Framing Protocol (GFP).............................................34.5.8 Link Loss Forwarding (LLF).....................................................34.5.9 Protection mechanisms...........................................................34.6 Ethernet feature matrix............................................................3

5 Appendix A: Standards update............................................35.1 Institute of Electrical and Electronics Engineers (IEEE)..........35.2 ITU-T Standards......................................................................35.3 Metro Ethernet Forum (MEF) Standards.................................35.4 Internet Engineering Task Force (IETF)..................................35.5 Relationship between IEEE, ITU-T, IETF and MEF.................3

6 Appendix B: Packet transport over a microwave link........36.1 Microwave Planning.................................................................36.2 BER and delay impact on TCP................................................36.3 BER impact on Real Time data...............................................3

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7 References...............................................................................3

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MINI-LINK TN ETSI

1 PrefaceThe main objective of this document is to present a technical overview of the Ethernet support in MINI-LINK TN R4.0 and to describe how MINI-LINK TN is a cost effective and flexible alternative for mobile RAN and broadband access backhaul networks.

To put the discussion into the proper context, a high level introduction to Ethernet transport in general and the dominant standardization efforts are provided.

This document is intended to give the reader a short insight into the ongoing packet evolution in transport networks and describe how MINI-LINK TN fits into this paradigm shift.

The target audience for this document is internal Ericsson personnel that seek technical information and understanding on how and what Ethernet capabilities are implemented in MINI-LINK TN. The information provided in this document is intended as background for RFx responses and customer meetings.

The initial sections of this document are describing the general packet architecture in MINI-LINK TN and are in some places referring to functionality not yet available. This is done to provide the reader with the complete scope of the planned packet capabilities in MINI-LINK TN and to put the current offering in the proper context of the future evolution. The current packet offering is briefly presented in chapter 4.4 and further described in the product catalogue.

2/1551-14/CSH 109 32/1 Uen Rev F 2008-08-08 Ericsson AB 2008 5 (61)Ericsson Internal

MINI-LINK TN ETSI

2 Acronyms and GlossaryEthernet related abbreviations that are extensively used in this document are listed below.

APU Application Plug-in Unit

BE Best Effort

E-LAN ETH LAN Service

E-LINE ETH Line Service

E-TREE ETH Tree Service

E-NNI External Network-Network Interface

EVC Ethernet Virtual Connection

FE Fast Ethernet

GE Gigabit Ethernet

HSU High Speed Unit

IM Inverse Multiplexer

IMS IP Multimedia Subsystem

I-NNI Internal Network-Network Interface

MAN Metropolitan Area Network

MEF Metro Ethernet Forum

MEN Metro EtherNet

NNI Network-Network Interface

OAM Operations And Maintenance

QoS Quality of Service

RSTP Rapid Spanning Tree Protocol

TCP Transport Control Protocol

UDP User Datagram Protocol

UNI User-Network Interface

VID VLAN Identifier

VLAN Virtual LAN

VPN Virtual Private Network


MINI-LINK TN ETSI

3 Transport network evolution

3.1 Market trends/drivers

In recent years we have experienced an explosion of new applications and products being launched on a daily basis. New applications for gaming, streaming of music/TV, positioning services, file sharing etc, are being adopted by all ages in our media driven society. Good examples of these new products are YouTube and MSN that for the young and upcoming generation are a main source of communication.

The traditional mobile phone is also changing its place in the communication food chain and is becoming increasingly more of a portable entertainment device in addition to the existing communication capabilities. Future mobile phones will most likely be a dominant portal for all kinds of media experiences for people on the move.

The new media/communication products and services represent huge new business opportunities not only for the traditional operators but also for the new players in the business value chain, e.g. content providers. However, the increased traffic and the new traffic types are putting pressure on the capacity in the existing transport networks. Operators are therefore constantly looking for new ways to both improve the efficiency in their existing infrastructure but also ways to evolve their legacy networks to more a cost efficient technology.

Traditionally, communication services have been quite simple and distributed in separated networks (e.g. TV, telephone). Today the scene has shifted completely and there is a clear trend towards convergence in what is often referred to as Multi Service Access Networks (MSAN).

The networks of the future will most likely share a common service layer (e.g. IMS) where services are offered to subscribers independent of location and user interface. Network data, i.e. digital media stored on centralized servers, as music/TV is becoming the dominant payload in the transport networks. Subscribers are expecting to access this payload on multiple devices through fixed as well as handheld devices. The common service layer must therefore be integrated with multiple different access technologies like, Public WiFi, GSM, UMTS and xDSL.

In the remaining parts of this document we will discuss how the operators can create new revenue streams from the new media explosion by evolving their transport networks using packet transport and MINI-LINK TN.


MINI-LINK TN ETSI

3.2 New packet based transport networks

To meet the challenges from the new services and applications described in the previous chapter, the transport networks must be upgraded to handle the increased traffic. The upgrade path must be a stepwise evolution to avoid any “big-bang” scenarios.

A fundamental concern for operators in this process is CAPEX and OPEX savings. To keep the competitive edge it is important that the new transport networks facilitate improved bits/dollar and at the same time are user friendly to improve operational efficiency.

A strong argument for packet based networks is the fact that many new applications are IP based. This means that the transport networks must be able to efficiently transport IP between the endpoints.

In the industry today there is also a strong drive towards packet based networks as it is commonly believed to be the answer to the increased bandwidth demands. The assumption is that a packet based network will provide better bandwidth efficiency compared to traditional circuit switched alternatives. This is based on the fact that a packet based network will better utilize the transport infrastructure through mechanisms like aggregation of traffic (i.e. statistical gain).

To facilitate a cost effective migration to the new packet based paradigm it is important to preserve the investments in existing circuit based infrastructure. This means that packet transport over a circuit switched infrastructure must be supported. For many operators this will be the starting point for the transition. In many products this is already supported today.

In this document we will describe how MINI-LINK TN fits into the new world of packet transport. We will describe how MINI-LINK TN can be used together with legacy circuit switched infrastructures as well as for Ethernet transport. Important features like QoS are also discussed to provide a comprehensive overview of the packet capabilities in MINI-LINK TN.


MINI-LINK TN ETSI

3.3 Packet transport in Microwave networks

This chapter discusses the unique challenges and opportunities when a microwave network is used for packet transport. Additional information is provided in appendix B.

Compared to other transmission technologies, a microwave link can be characterized as a limited bandwidth connection. This implies that microwave equipment must be designed to enable maximum packet payload throughput in the available bandwidth over the radio interface. The following features will improve the link efficiency.

Carrier class equipment

Carrier class equipment with high availability and multiple protection schemes will secure high link utilization. MINI-LINK TN can be regarded as a true carrier class device. The MINI-LINK product family has for many years proven itself as a carrier class product.

Congestion handling/priority queues

For connections with limited bandwidth it is important to support a mechanism that prioritizes high priority packets when a connection is congested. This feature is currently supported in MINI-LINK TN.

Aggregation of packet flows

Packet transport with shared bandwidth opens up possibilities for statistical gain with aggregation of traffic. Packet aggregation will potentially reduce bandwidth requirements and better utilize the available transmission capacity. This feature is supported for ATM and is for Ethernet included as a part of the MINI-LINK TN R4.0 release (mid 2008).

Adaptive modulation

The adaptive modulation mechanism seeks continuously to utilize the modulation alternative that will maximize the throughput under different conditions. Adaptive modulation is planned in R4.x releases (2009).

Low residual BER

Microwave links operates with large fade margins and forward error correction resulting in very low residual BER level, typically 10-12.


MINI-LINK TN ETSI

3.4 Standards update

Ethernet technologies and standards have traditionally been developed and deployed for the enterprise/residential market segment. These products have typically been characterized by low cost and limited capacity. IEEE has been driving the standardization in this area.

Driven by promises like reduced equipment and operational cost, Ethernet has also become a focus area for MAN/WAN networks and new standardization bodies like Metro Ethernet Forum (MEF).

In this chapter we will provide a short summary of the ongoing standardization activities that contributes to deployment of Ethernet in the MAN/WAN domain. Additional information is provided in appendix A. The following standardization bodies take an active interest in the standardization of Ethernet.

IEEE

The Institute of Electrical and Electronics Engineers (IEEE) has primarily focused on the Ethernet control and data planes in the IEEE 802.x standardization series.

ITU-T

The International Telecommunication Union (ITU) has focused on standardizing management aspects of an Ethernet based network to provide traditional telecom OAM functionality (e.g. ITU-T Y.1731). They are also looking into other aspects such as protection schemes.

ITU-T is cooperating with IEEE in the standardization of OAM functionality. IEEE actually has their own emerging standard in this area (802.1ag). One can suspect that these parallel standards might be merged in the future.

IETF

The Ethernet standardization work within the Internet Engineering Task Force (IETF) has traditionally focused on functions and protocols to manage and configure individual network elements (e.g. SNMP MIB). IETF has now stopped this development. New MIBs will be developed within the IEEE 802 working groups.

MEF

The Metro Ethernet Forum (MEF) has an ambition to build consensus and unite service providers, equipment vendors and end-customers on Ethernet service definition, technical specifications and interoperability.

MEF mainly reference existing IEEE, ITU-T and IETF standards but do also produce own standards in order to fill gaps left open by the other bodies.


MINI-LINK TN ETSI

4 Packet support in MINI-LINK TNThis chapter provides an overview of the packet transport capabilities in MINI-LINK TN.

4.1 Target market segments

Ethernet is rapidly becoming the dominating transport technology not only in a closed enterprise environment but also in carrier class fixed and mobile networks.

Ericsson is following this evolution closely and is aggressively pursuing both the mobile RAN and fixed broadband access market segments with the MINI-LINK TN product. The remaining parts of this section are briefly discussing how to use the MINI-LINK TN Ethernet transport capabilities in these two network environments.

Radio Access Networks

Historically, MINI-LINK TN has been widely used to build both 2G and 3G Radio Access Networks (RAN). The microwave radio and leased line interfaces combined with the embedded traffic routing capabilities has proven to be a highly competitive product to build radio backhaul networks. The Ethernet feature set in MINI-LINK TN is built on the same successful philosophy and is a complement to the existing circuit switch capabilities, i.e. the legacy circuit switched PDH/SDH capabilities are supported in parallel with the new Ethernet feature set.

There are currently multiple radio access technologies that are more or less competing in the same mobile market place. Industry and standardization initiatives like WiMAX, WiFi as well as 2G/3G are coming from slightly different starting points but are more and more pursuing business opportunities in the Metro Ethernet domain. From a traffic backhaul point of view there are many similarities which means that the combined packet and circuit capabilities in MINI-LINK TN are well suited to be used with multiple radio access technologies. The figure below illustrates how MINI-LINK TN can be used for different radio access alternatives.

Figure 1: MINI-LINK TN in a multi access radio backhaul network

More information can be found in the Mobile Backhaul section of the product catalogue.


WiFi

WCDMA

GSM

WiMAX

MINI-LINK TN

BackboneMINI-LINK TN

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Broadband access networks

The promise of high speed internet connectivity and new multimedia IP applications has been driving the deployment of broadband access technologies in the residential market. Due to the massive broadband access roll out, the private households now have high speed data connectivity that only a few years back were fiction.

Currently the first mile access is still utilizing the copper wire with xDSL modulation. However in the access backhaul and backbone networks the operators are upgrading from traditional circuit switched networks to packet based networks that more cost efficiently can transport the new packet based multimedia streams.

Other segments of the broadband access market are Business Access and Wholesale.

In a broadband access network, MINI-LINK TN is typically used at the edge of an access backhaul network. The combined radio and leased line interfaces as well as the circuit and packet capabilities provide in many cases a cost effective way of deploying a backhaul network. The figure below illustrates the use case.

Figure 2: MINI-LINK TN in a 2nd mile broadband access network

For an operator that offers both fixed and mobile services a site might contain access to both residential and business customers as well as mobile customers. All traffic can be backhauled through the same network with MINI-LINK TN.

4.2 Multi service architecture

As previously discussed, transport networks are currently being upgraded with packet transport capabilities to meet the increased demand for higher bandwidth.


Backbone

First mile Second mile

MINI-LINK TN

MINI-LINK TN

MINI-LINK TN

Residential

Business

Access Transport Network

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It is anticipated that in the long term, transport networks will be mainly packet based (i.e. all IP paradigm). However, in an interim period there will be need for network elements that can handle multiple technologies. MINI-LINK TN is well prepared for this scenario and supports both PDH/SDH as well as ATM/Ethernet transport technologies.

MINI-LINK TN offers a wide range of plug-in units that support different interface types (e.g. PDH/SDH radio modem). The different plug-in units are connected in the backplane with a redundant bus structure for transport of circuit and packet based traffic.

The traditional circuit switched traffic is transported over a TDM bus. The packet based traffic is transported both on high speed point-to-point connections and on the TDM bus by using a mapping function (i.e. IM). More information on the mapping function and other technical details is provided in chapter 4.5. The figure below shows a high level overview of the MINI-LINK TN architecture and the different Ethernet connection alternatives.

Figure 3: High level MINI-LINK TN architecture

4.2.1 Backplane busses

The MINI-LINK TN consists of multiple busses in the backplane that are used for different tasks. Some of the buses are used for internal housekeeping and management operations (e.g. PCI). For traffic payload, the TDM bus and the high speed connections are the main transport mechanisms.

TDM bus


Ethernet over PDH

TDM bus

Ethernetline i/f

Ethernetline i/f

PDHline i/fPDH

line i/f

CentralEthernet switch

CentralEthernet switch

Ethernetradio i/f

Ethernetradio i/f

PDHradio i/f

PDHradio i/f

High Speed connections

Native Ethernet ETH/SDH ETH/SDH

SDHradio i/f

SDHradio i/f

IM

GFP

Ethernet over SDH

MINI-LINK TN ETSI

A redundant 800Mbps TDM bus is interfacing all the different slot positions in an AMM chassis. The TDM bus is used to connect the different E1 ports.

High speed connections

The backplane in a MINI-LINK TN chassis provides multiple redundant high speed connections between the different slot positions. The high speed connections enable high speed communication between the central slot positions and the other Application Plug-in Unit (APU)1 slots in an AMM chassis.

The central slot positions in an AMM chassis are typically deployed with NPU and optional High Speed Unit (HSU)2 boards that contain for example SDH ADM or an Ethernet switching unit. In the figure below a conceptual view of the high speed connection structure is presented.

Figure 4: High speed connections

More details regarding the high speed connections in MINI-LINK TN are provided in chapter 4.4.

1 APU is a plug in unit in MINI-LINK TN typically providing a specific line interface type (e.g. MMU2 D)2 HSU is a central board that requires high speed communication with other APU boards (e.g. SXU3 B)


NPU HSU

APU

APU

APU

APU

APU

APU

MINI-LINK TN ETSI

4.2.2 Ethernet centric view

MINI-LINK TN supports a number of different Ethernet interfaces that can be used together in different combinations. This provides the customer with a flexibility to use the MINI-LINK TN for Ethernet transport in a large variety of topology and configurations.

Native Ethernet fixed line i/f (FE/GE)

Multiple electrical and optical FE and GE interfaces are supported in MINI-LINK TN. These interfaces are available on both the NPU and ETU boards.

Native Ethernet packet radio i/f 3

Native Ethernet traffic can be transported over a packet radio hop by using the packet enabled modem boards. The throughput is only limited by the bandwidth of the modem. Offered throughput for different modem boards will be provided in chapter 4.4. Capacity not used for packet transport can be used for PDH traffic.

This configuration requires that the other end of the radio hop also has a packet enabled modem and an Ethernet plug-in unit supporting the native packet radio interface.

Multiple packet radios can be grouped together in one logical connection to increase capacity.

Ethernet over SDH radio i/f with GFP mapping protocol

Ethernet frames can be transported over STM-1 radio connections with a total capacity up to 600Mbps. A GFP (LCAS/VCAT) module located on the SDH ADM plug-in unit is enabling the packet transport through the SDH network. One GFP connection can utilize one to four STM-1 links on multiple SDH modem plug-in units.

Ethernet over PDH radio/line i/f with IM mapping protocol

Ethernet frames can be transported over a PDH radio and/or line connection with a capacity up to 95Mbps4 per IM connection. A proprietary IM mapping module (see figure below) is enabling the packet transport through the PDH network. One IM connection can utilize multiple plug-in units and radio/line interfaces in any combination. MINI-LINK TN is required in both terminating ends of the IM connection.

3 Only Ethernet packet radio HW is currently released (i.e. MMU2 D)4 Only ETU2/ETU3.


MINI-LINK TN ETSI

All interfaces capable of carrying Ethernet traffic can be connected to the central Ethernet switching architecture in MINI-LINK TN either through the TDM bus, using a mapping protocol, or the high speed connections. The central Ethernet switch is implemented on the Node Processor Unit (NPU).

The figure below outlines the Ethernet architecture in MINI-LINK TN with the central Ethernet switch and multiple Ethernet interfaces.

Figure 5: Ethernet architecture with central switch

Not all items in the figure above are currently supported. The current product offering are presented in chapter 4.4.


Ethernet Line i/f

Ethernet Line i/f

ADMADM

SDH Radio i/f

SDH Radio i/f

SDH Radio i/fSDH

Radio i/f

PDH Radio i/f

PDH Radio i/f

PDH Line i/f

PDH Line i/f

NPU

FE/GE

FE/GE

TDM bus

High Speed connections

MINI-LINK TN

GFP

Single IM connection: 95Mbps (n*E1)


Single GFP connection: 600Mbps (n*STM-1)

Ethernet Radio i/fEthernet Radio i/f

Ethernet/ PDH

Ethernet/ PDH

IM

MINI-LINK TN ETSI

In some configurations there is no need for a central switch. This is typical at sites at the network edge. This configuration scenario is handled cost effectively with a NPU variant that doesn’t have the embedded Ethernet switch. The alternative is presented in the picture below.

Figure 6: Ethernet architecture with no embedded switch

For the Ethernet WAN configuration in the picture above, the NPU can be configured to either use the Ethernet over PDH mapping (i.e. IM) or a high speed connection towards the Ethernet radio5.

A third variant of the Ethernet architecture in MINI-LINK TN is a configuration with no NPU involvement. The Ethernet connectivity is handled by a separate plug-in board (i.e. ETU in stand alone mode).

Figure 7: Ethernet architecture with no NPU

5 The high speed connection interface is planned for future release


PDH Radio i/f

PDH Radio i/f

PDH Line i/f

PDH Line i/f

NPU

FE/GE

TDM bus



IM

MINI-LINK TN

Ethernet Radio i/fEthernet Radio i/f

PDH Radio i/f

PDH Radio i/f

PDH Line i/f

PDH Line i/f

TDM bus



MINI-LINK TN Ethernet

Line i/f Ethernet

Line i/f

FE/GE

Ethernet/ PDH

Ethernet/ PDH

IM

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4.3 Network use cases

This chapter describes different network scenarios and connection services for MINI-LINK TN.

4.3.1 Ethernet connection services

MINI-LINK TN support the following Ethernet connection services

Point to point scenario

In the point to point scenario, a customer typically has multiple not directly connected Ethernet clusters. By utilizing the point to point Ethernet connection service in MINI-LINK TN, the customers have an efficient and flexible way to combine the clusters into one network. The point to point connection service can operate over both a PDH and SDH transport network. The figure below illustrates the customer scenario.

Figure 8: Point to point Ethernet connection service

The main purpose of the point to point connection service offered by MINI-LINK TN is to provide a direct connection between two termination points. This means that the point to point service type in MINI-LINK TN provides no switching between the endpoints and is totally transparent to any additional Ethernet header item (e.g. Q-tag). For clusters with multiple directions an Ethernet switch would be needed to connect the different directions.

To support a multi-service environment, the point to point connection offered by MINI-LINK TN provides priority awareness and multiple priority egress queues. In congestion situations this means that frames with highest priority will typically be transmitted first. This functionality is crucial to support both data and voice/video traffic over a point to point Ethernet connection. More information on this topic is provided in chapter 4.5.5.


Ethernet cluster

Ethernet clusterEthernet

cluster

Ethernet cluster

Transport Network

Poit to point connection

Ethernet switch

MINI-LINK TN ETSI

The interface for a point to point Ethernet connection in MINI-LINK TN is a 10/100/1000 BASE-T or 1000 BASE-LX/ZX port. The figure below illustrates the basic set up.

Figure 9: Interfaces in point to point connection service

Multipoint to multipoint scenario

Using the MINI-LINK TN product family to build your Ethernet network means that you have a broad range of alternatives to choose from. Within the MINI-LINK TN product offering there is support for Ethernet transport with different bandwidth/capacity options over both radio as well as fixed connections. MINI-LINK TN supports Ethernet transport over PDH/SDH networks with the IM/GFP mapping protocols as well as packet radio.

Even if MINI-LINK TN provides a comprehensive product offering that can be used to build a complete network, a real customer deployment might also include 3rd party Ethernet devices. MINI-LINK TN is standards compliant and will work in a multi vendor environment.

Depending on where you are in a network, there are different characteristics and requirements a network element must comply with. The MINI-LINK TN product family offers Ethernet products in different sizes and capacities to meet the requirements for both an end site as well as an aggregation site. The end site offering is typically a low capacity node with few interfaces. The aggregation site node contains embedded Ethernet switching capabilities and multiple high capacity interfaces.


Transport Network

Ethernet Ethernet

MINI-LINK TN MINI-LINK TN

FE/GEFE/GE

Ethernet ptp connection

MINI-LINK TN ETSI

Figure 10: Mobile backhaul network scenario

In the figure above a broad specter of products in the MINI-LINK TN product family are used in a typical backhaul network scenario. The network could backhaul WiMax, DSL, 2G and/or 3G traffic.

In the end sites a single port NPU3 in an AMM2p B chassis is in most cases used to provide Ethernet connectivity. The end sites are connected to the aggregation points with an Ethernet over PDH connection using the IM protocol with a capacity up to 30Mbps. If multiple Ethernet LAN ports are required on the end site, the NPU3 B/ETU3 boards with up to 6 LAN ports can be used instead of the NPU3 board.

The aggregation sites contain an AMM6p or AMM20p magazine and an Ethernet switch capable NPU. The embedded Ethernet switch on the NPU will aggregate all the southbound traffic into a higher capacity northbound connection. The ETU boards with a capacity up to 95Mbps per IM connection or the SXU board with a capacity up to 600Mbps per GFP connection can be used to interconnect the aggregation sites.

At the feeder site an AMM20p is connected to a backbone fiber network through a 3rd party product. An SFP based optical Gbps Ethernet interface is typically used to connect MINI-LINK TN with the optical network.


End site with NPU3 and AMM2pB

Aggregation nodes with embedded switch

Backbone

Optical equipment

MINI-LINK TN ETSI

Currently, backhaul networks are in most cases also required to transport TDM circuits. Since MINI-LINK TN supports both TDM and packet simultaneously in the same chassis, covering this scenario is just a matter of configuration. By adapting the configuration over time, a customer can achieve a seamless migration from a traditional TDM based transport to the future all packet paradigm.

The scenario in the figure below is describing a broadband access network, where Ethernet connectivity is offered to a large number of customers. The Ethernet traffic that flows from the different connected customer devices are typically separated in different VLANs. Each of the customer interfaces represents an UNI as described in chapter 5.3.

Internally in the operator’s network the metro Ethernet can be deployed in ring, star or tree configurations. RSTP and/or other protection mechanisms described in chapter 4.5.7 are often used to improve availability in the network.


MINI-LINK TN ETSI

Figure 11: Broadband access network scenario


Ethernet switch point

Customer Ethernet device

3rd party Ethernet

3rd party Ethernet

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4.4 Product offering

Up to this point, this document has primarily focused on the conceptual aspects of the packet capabilities in MINI-LINK TN. In this chapter though, more details on the actual product offerings are provided.

MINI-LINK TN offer Ethernet connection services on the following products.

NPU3 B

NPU3 B is a half height processor board that contains an embedded Ethernet switch. NPU3 B fits in the AMM2p B, AMM6p C/D magazines.

Figure 12: NPU3 B board

The embedded MAC (IEEE802.1D-2004) and VLAN (IEEE802.1Q-2005) bridge/switch capabilities make NPU3 B an ideal component at an aggregation site. The following list is some of the switching capabilities:

Store and forward

MAC address table (16.000 entries)

Self learning with aging of MAC addresses

Static unicast/multicast routes

RSTP

Port based VLAN with up to 4094 VLANs

NPU3 B has two electrical LAN 10/100/1000BASE-T Ethernet interfaces. One of the Ethernet ports can be configured as a site LAN port.

The usage of the embedded switch on NPU3 B is regulated by a license. Without the license only one front Ethernet LAN port and one high speed connection towards the backplane can be used.


MINI-LINK TN ETSI

NPU3 B has support for high speed connections with the other slots in the chassis. A physical high speed connection can be split in multiple logical channels where one logical channel is associated with one LAN or WAN port (i.e. IM connection or a LAN port on the ETU3).

The high speed connections and the LAN ports enable NPU3 B to groom traffic from multiple directions as well as dropping Ethernet traffic locally at the site. In total the Ethernet switch on NPU3 B can handle seven logical high speed connections in addition to the two local LAN ports on the board.

For more technical details on the different features on the NPU3 B board see chapter 4.5

NPU3 board

The NPU3 board is a half height processor board that fits in the AMM2p B, AMM6p C and AMM 6pD magazines. NPU3 provides an Ethernet end site offering with support for one Ethernet direction.

Figure 13: NPU3/AMM2p B Ethernet offering

NPU3 supports one 10/100BASE-T interface for DCN site LAN and one 10/100BASE-T interface for Ethernet traffic.

The Ethernet traffic port is directly associated with one IM group and can be configured with up to 16*E1.

NPU3 supports 1-8 Traffic Classes/egress buffers per port.


MINI-LINK TN ETSI

ETU3 board

The ETU3 board is a half height plug in unit that fits in the AMM2p B, AMM6p C/D magazines. The ETU3 board is used together with the NPU3 B board (i.e. interworking mode) as a pair to provide additional LAN ports on the site as well as IM connectivity in a chassis. Future releases will upgrade ETU3 to support standalone mode in the same way as ETU2.

The ETU3 board supports two 10/100/1000BASE-T and two SFP cages on the front in addition to six IM groups towards the TDM bus in the backplane. The SFP cage can only be equipped with Ericsson approved SFP modules, which currently means electrical 1000BASE-T and optical 1000BASE-LX/ZX variants.

One IM connection can be configured with up to 48*E1. In total 96 E1s can be used for IM connections towards one ETU3 board. One half can be used freely on IM groups 1,2,6 and the other half on the IM groups 3,4,5. See chapter 4.5.6 for more information on the IM groups.

Traffic from all LAN and WAN ports on the ETU3 board are directed to the NPU3 B board using the high speed connections in the backplane.

Figure 14: ETU3 used in interworking mode together with NPU3 B

Due to bandwidth restrictions, not all interfaces can be utilized at the same time. A resource control function is supported to secure that the total interface throughput from ETU3 is equal or less than the throughput of the available high speed connection (i.e. 2Gbps).

A license key regulates the usage of additional IM groups in interworking mode. Without the license key all front LAN ports in addition to one 16*E1 IM group can be utilized.


FE/GE

FE/GE

TDM bus

ETU3ETU3IM

Plug in Units

Plug in Units

Plug in Units

Plug in UnitsNPU3 BNPU3 B

High speed connection

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ETU2 board

ETU2 is used for Ethernet point to point connection services and is typically deployed at a hub site where multiple Ethernet connections are distributed in different directions. An optional external switch is connected to the front Ethernet ports on the ETU2 board to switch the traffic.

ETU2 has no support for high speed connections or direct interaction with the embedded switch on the NPU. ETU2 operate in what is called stand alone mode.

Figure 15: ETU2 board

The ETU2 board is a full size APU that fits in all AMMs and supports five10/100BASE-T and one 10/100/1000BASE-T front Ethernet ports in addition to six IM groups.

A front Ethernet port is directly associated with one IM group. One IM connection can be configured with up to 48*E1. In total 96 E1s can be used for IM connections towards one ETU2 board. One half can be used freely on front Ethernet ports 1,2,6 and the other half on front Ethernet ports 3,4,5. See chapter 4.5.6 for more information on the IM groups.

ETU2 contains a license that regulates the usage of the front Ethernet LAN ports. Without the license only one front Ethernet port can be used with a capacity up to max 16*E1.


MINI-LINK TN ETSI

SXU3 B board

The SXU3 B board is a half height plug in unit that fits in the AMM2p B and AMM6p C/D magazines. The SXU3 B is primarily an ADM, but does also contain a GFP module that enables Ethernet transport over multiple STM-1 radio connections. One to four STM-1 links with up to 63xVC-12, 3xVC-3 or 1xVC-4 per link can be concatenated in a SXU3 B board. One SXU3 B can terminate up to seven GFP instances with a total capacity of 600Mbps.

Figure 16: SXU3 B board

The SXU3 B board supports four E1s on the front.

SXU3 B uses the high speed connections to communicate with the STM-1 interfaces and the Ethernet switch on the NPU.

Figure 17: SXU3 B and NPU3 B boards used as a pair



FE/GE

STM-1 radio

STM-1 radio

STM-1 radio

STM-1 radio

NPU3 BNPU3 BSXU3 BSXU3 B

GFP

ADM

MINI-LINK TN ETSI

AMM chassis

As described in chapter 4.2.1, the high speed connections in the backplane of MINI-LINK TN is used for packet transport between the interface boards, HSU boards and NPU board with the central Ethernet switch. The AMM chassis defines the following slot types:

NPU – Node Processor Unit

The NPU board is a central processing unit that contains a control system for supervision of node operations and optionally an Ethernet switch. The figures below in this chapter show the possibility for two NPU boards in one chassis to indicate the support for a redundant Ethernet switch on a second NPU board.

HSU – High Speed Unit

The HSU board (e.g. SXU3 B) is a central plug-in unit that requires high capacity communication (i.e. high speed connections) with other APU boards.

APU – Application Plug-in Unit

The APU boards are regular interface boards (e.g. MMU/LTU)

The AMM 2p B, AMM 6p C/D and AMM 20p B chassis have full flexibility with high speed connectivity between the HSU/NPU slots and from all HSU/NPU slots to each APU slot. The bandwidth is 2Gbps payload throughput between the NPU/HSU slots (e.g. NPU) and 1Gbps payload throughput between the NPU/HSU slots and the full size APU slots (e.g. MMU2 D).

Figure 18: High speed connections for AMM 2p B, AMM 6p C/D and AMM 20p B


AMM 6p D

APU

NPU

HSU/APU HSU/APU

NPU/HSU/APU

AMM 2p B

APU

NPU

NPU/HSU/APU

2Gbps ptp

1Gbps ptp

APU APU

AMM 20p B

HSU

/APUH

SU/APU

NPU

/HSU

/APU N

PU

AMM 6p C

APU

NPU/HSU/APU

HSU/APU

NPU

MINI-LINK TN ETSI

The AMM 6p, AMM 6p B and AMM 20p chassis types all have high speed connections from the central NPU/HSU slots to the other APU slots. The high speed connection to an APU is shared between the central NPU/HSU boards, but can only be configured for one of the HSU/NPU boards at a time. The capacity for a high speed connection is 500Mbps.

Figure 19: High speed connections for AMM 6p, AMM 6p B and AMM 20p

Network examples

This chapter describes typical configuration examples using the different Ethernet capable boards in MINI-LINK TN.

Point to multipoint point connection scenario

The NPU3 and ETU2 boards can be used to offer multiple point to point connections from a hub site to multiple remote sites. The Ethernet traffic will be mapped to the PDH structure using the IM protocol. The MMU2 board can be any PDH capable modem board (e.g. MMU2 B/C/D)

Figure 20: Network example with NPU3 and ETU2

If the traffic is aggregated and relayed in the hub site, the ETU2 board should be replaced with NPU3 B and ETU3 boards. Depending of the capacity requirement the Ethernet traffic can be mapped over PDH/SDH using IM/GFP protocols. In the figure below the IM alternative with ETU3 is shown.


AMM 6p/AMM 6p B

NPU/HSU/APU

APU

NPU

500 Mbps ptp

APU APU

AMM 20p

NPU

HSU

/APUH

SU/APU

NPU

/HSU

/APU

ETU2ETU2

NPU3NPU3

MMU2 MMU2

MMU2 MMU2

NPU3NPU3

MMU2 MMU2

NPU3NPU3

MMU2 MMU2

NPU3NPU3

MMU2 MMU2

MMU2 MMU2

MINI-LINK TN ETSI

Figure 21: Aggregation of traffic with NPU3 B and ETU3

In the coming releases, the aggregated northbound radio connection can utilize the native Ethernet capabilities in the MMU2 D hardware.

Using NPU3 B in end site

In most cases NPU3 will be used in the end site at the edge of the network. However, if more than one Ethernet LAN port is required in the end site, NPU3 B should be used instead. Since NPU3 B doesn’t support Ethernet over PDH/SDH mapping with IM/GFP the ETU3 board is also required.

.

Figure 22: Using NPU3 B in end site

Future enhancements and migration alternatives

This chapter describes how investments in the current Ethernet offering can be preserved going forward.


NPU3 BNPU3 B

ETU3ETU3

NPU3 BNPU3 B

MMU2 DMMU2 D

MMU2 MMU2

NPU3NPU3

MMU2 MMU2

NPU3NPU3

MMU2 MMU2

NPU3NPU3

MMU2 DMMU2 D

MMU2MMU2

MMU2MMU2

MMU2MMU2

ETU3ETU3

NPU3 BNPU3 B

NPU3 BNPU3 B

MMU2MMU2

NPU3 BNPU3 B

ETU3ETU3

MMU2MMU2

ETU3ETU3

MMU2MMU2

ETU3ETU3

MMU2MMU2

MINI-LINK TN ETSI

Co-existence and reuse of the current Ethernet products in MINI-LINK TN was crucial when planning the next generation Ethernet offering. Our ambition is that an existing customer with the current Ethernet offering shall be able to reuse this investment when the new products are deployed. The amount of required replacements will off course differ from case to case.

MINI-LINK TN provides the operator with the opportunity to use the same infrastructure for both circuit switched PDH/SDH traffic and Ethernet traffic. This is a cost effective solution and will most likely be an attractive option in the coming years as well. Especially out at the end sites, where the packet bandwidth demand is limited, this combo solution is cost effective. The current end site offering with NPU3, using Ethernet over PDH will therefore most likely be an important component in future packet based networks as well.

As described earlier in this document, a central Ethernet switch on the NPU3 B board is supported in AMM2p B, AMM6p C/D. NPU1 C with similar capabilities, is planned for the AMM20p chassis.

For packet transport, the Ethernet switch on the new NPU boards will communicate with the MMU2 D/H modem using the high speed connections. The MMU2 D and future MMU2 H boards will also be capable of carrying PDH traffic and will therefore also have an interface to the TDM bus. The capacity split between packet and circuit transport is configured individually per MMU2 D/H board.

Figure 23: Introducing the native Ethernet modem


MMU2 D/HMMU2 D/H

NPU3 B/ NPU1C

NPU3 B/ NPU1C

TDM bus


RadioRadio

MMU2 D/HMMU2 D/H

MINI-LINK TN ETSI

The deployment of the new native Ethernet modems in MINI-LINK TN will probably be driven by the demand for higher bandwidth. This will most likely happen first at the hub sites. The figure below illustrates how the new MMU2 D modem can be used at a hub site. The MMU2 D takes full advantage of the higher radio hop capacities introduced with the Ethernet modems.

Figure 24: Migration scenario

In the figure above the northbound connection is aggregated into one native Ethernet radio connection using the NPU3 B and MMU2 D boards. The key enabler in this configuration is the ETU3 board. The ETU3 board will connect the southbound IM links, transported on the TDM bus, with the high speed connections and the central Ethernet switch on the NPU3 B board.


NPU3NPU3

30Mbps

180Mbps

Southbound (Ethernet over PDH)

Northbound (native Ethernet radio)

AMM 6p C

PF

U

FAU

NPU3NPU3

NPU3NPU3

NPU3 BNPU3 B

AMM 2p B155Mbps ++

Packet Backbone

Eth. cluster

Eth. cluster

Eth. cluster

NPU3 BNPU3 BETU3ETU3

MMU2 D

MMU2 B/C

MMU2 B/C

MMU2 B/C

MMU2 D

MINI-LINK TN ETSI

4.5 Ethernet features and characteristics

MINI-LINK TN is targeting multiple applications and network environments with the embedded Ethernet capabilities. To be a competitive alternative, MINI-LINK TN therefore provides a great deal of flexibility and supports a large number of Ethernet services and features. The rest of this chapter describes the supported Ethernet functionality.

4.5.1 Functional model

When an Ethernet frame is forwarded through MINI-LINK TN, there are multiple functional steps the frame has to go through. The different functional steps will differ based upon where in the network the node is located. The figure below illustrates the functions from ingress to egress. More details of the different functions are provided later in this chapter.

Figure 25: Ethernet Functional flow

4.5.2 Frame size

In a real network there will often be Ethernet frames of different sizes. The size of a frame is often related to the application. A real time application (e.g. voice, video) that requires minimum latency typically uses small Ethernet frames, while a data application with non real-time characteristics uses the maximum frame size. MINI-LINK TN is well equipped to handle both small and large Ethernet frames as well as a mix.


Admission controlFrame type controlWhite list control (Source

MAC address)

Classification/taggingSet VLAN ID (VID)Set CoS

Policing*Per port Per port per VLANPer port per VLAN per CoSColoring

ess

ForwardingBased on VID and destination

MAC addressPort blocking

TC queue mapppingBased on CoS bits1-8 TC queues RED/WRED*

Scheduling/shaping*Strict priorityWFQ*

* = currently not released

INGRESS EGRESS

MINI-LINK TN ETSI

The maximum Ethernet frame size supported by MINI-LINK TN is 2000Byte according to IEEE 802.3as. This is more than sufficient to process the 1518Byte standard Ethernet frame size with additional header extensions (e.g. Q-tag).

Future enhancements of MINI-LINK TN will also support what is referred to as jumbo frames (9-13kByte). However this frame size is currently not embraced by the standardization organizations and is also not recommended to be used for low capacity links with jitter and latency limitations.

4.5.3 Security/admission control

MINI-LINK TN supports multiple security and admission control mechanisms to enable the operator to control the traffic flow into the network.

White lists

Individual white lists can be created per port to specify which source MAC addresses that can send traffic on a port. Frames with a source MAC address not on the list will be discarded.

Storm Protection

Filters can be created per port to prevent broadcast and multicast storms. Individual filters are used for broadcast and multicast traffic. The filter is specified as frames per second. When the limit is reached, additional frames will be discarded until the frame rate is below the specified threshold.

Port blocking

With the port blocking feature it is possible to prevent forwarding of frames from a given ingress port to one or more egress ports.

MAC address limiting per port

If MAC learning is activated on the node it is possible, from one interface, to flood the learning table. A flooded learning table will prevent learning on all other ports. To prevent the MAC address flooding it is possible to limit the MAC address table per port.


MINI-LINK TN ETSI

Frame admittance

At the network edge it is possible, with the frame admittance feature, to select by frame type which frames to admit and which frames to block. The following frame type options are available:

Q-Tagged (priority bits/VID set in Q-tag)

Priority tagged (only priority bits set in Q-tag)

Untagged (no Q-tag)

All other or unrecognized frame types (e.g. S-tags) are treated as untagged at the network edge.

4.5.4 Bridging/switching

MINI-LINK TN supports both a MAC bridge/switch according to IEEE802.1D-2004 and VLAN bridge/switch according to IEEE802.1Q-2005. The following features are supported:

Store and forward

MAC address table (16.000 entries)

Self learning with aging of MAC addresses

Static unicast routes

Static multicast routes

Head of line blocking prevention (HOLB)

Rapid Spanning Tree Protocol (RSTP)

SNMP based management interface

VLAN ID and priority tagging

Port based VLAN (up to 4094 VLANs)

Prepared for logical grouping of packet radios

Prepared for provider bridge (IEEE 802.1ad)


MINI-LINK TN ETSI

In a VLAN bridged/switched network, the VLAN ID (VID) is set at the edge of the network. The VID is often classified together with the CoS (see next section).

The following VID classification rules apply:

Untagged frames

A Q-tag will be applied/removed at the entry/exit of the customer network.

The VID is set based on the port.

Q-Tagged frames

The existing outermost Q-tag is reused for trusted frames.

For un-trusted frames the VID is set based on port default value.

Priority tagged frames

The VID is set based on the port.

L2 control protocol frames from connected networks can be tunneled through the operator’s network. The L2 control protocol tunneling feature enables transparent transport of a customers L2 protocol signaling (e.g. RSTP)

4.5.5 Class of Service (CoS)

To provide a predictable Class of Service (CoS) in an Ethernet based network, it is necessary to perform a number of operations such as classification, traffic conditioning, policing and congestion handling.

CoS types

The associated CoS value for a frame is a representation of the end user application (e.g. voice, best effort data etc) and is used to differentiate behavior of different frames in the node. An Ethernet frame’s CoS value indicates what type of behavior it expects from the network and how it shall be prioritized versus the other Ethernet frames in an interim network element.


MINI-LINK TN ETSI

The CoS definitions are standardized by IEEE in IEEE802.1Q-2005 and IEEE802.1D-2004. MINI-LINK TN supports both these alternatives in addition to a customized variant where the customer can use its own values freely. The figure below describes the priority definition standardized in IEEE 802.1D-2004.

CoS type Acronym Priority

Background BK 1

Spare - 2

Best Effort BE 0 (Default)

Excellent Effort EE 3

Controlled Load CL 4

Video<100ms latency and jitter VI 5

Voice<10ms latency and jitter VO 6

Network control NC 7

Figure 26: CoS definition in IEEE 802.1D-2004

Each CoS type is associated with a priority to indicate the relative importance of that CoS type. Highest number equals highest priority.

In a network, it is important that only one set of priority definitions is used (e.g. IEEE 802.1D-2004). Otherwise, the handling of Ethernet frames and the mapping to egress queues can differ between network elements. The outcome of this scenario is a non predictable behavior for the different traffic types (e.g. voice).

CoS classification

Going into an operator’s network, a frame’s CoS value is established at the network edge. We say that the frame is classified. In MINI-LINK TN there are different criteria that come into play when a frame is classified. First of all the operator must decide whether the connected clients that sends frames to the network is trusted or not. Being a trusted client means that the operator can reuse CoS information in a frame that is set by the client. For un-trusted clients all CoS information from the connected clients are discarded. The operator selects per port whether an interface is trusted or not.


MINI-LINK TN ETSI

On trusted interfaces, the CoS information set by the connected clients is used by the classification process. A connected client can set a CoS value in both the L2 Ethernet header and the DSCP/TOS Byte in the L3 IP header. The following flow chart is used to establish the CoS value for a frame.

Figure 27: CoS classification process

As an outcome of the classification process the appropriate CoS value is set in what is often called the priority or PCP bits in the L2 header. Internally in the operators network these priority/PCP bits will be used as CoS information field in the frame.

When the DSCP/TOS field in the IP header on a trusted port is used to establish the CoS, the L3 priority information is mapped to the L2 priority bits/PCP bits. The mapping is customized by the operator.

For un-trusted frames the CoS is set based on a default value. The default value is set by the operator per port.


Is the port trusted PCP?

Is the port trusted DSCP/

TOS?

Assign default CoS

Set CoS value based on DSCP/TOS

N

N

Y

Is frame tagged with

CoS?

Keep CoS value in C-tag

Y

Y

Y

IP packet?

Y

N

N

N

Is the port un-trusted?

MINI-LINK TN ETSI

Traffic class mapping

MINI-LINK TN supports from one to eight traffic classes or priority queues for each egress Ethernet port. Default, eight traffic classes are used but this value can be changed by the customer.

The Ethernet frames are mapped to the different traffic classes based on the priority/PCP bits in the Ethernet header. The mapping can be done according to IEEE 802.1D-2004 or IEEE802.1Q-2005 or customized.

Number of TC

CoS mapping to TC

1 BK,BE,EE,CL,VI,VO,NC

2

3

4

5

6

7

8

Figure 28: Mapping frames to traffic class based on IEEE 802.1D-2004

Ethernet frames with no CoS information are default given the Best Effort traffic class behavior, i.e. priority level 0. The default queue mapping for Ethernet frames with no priority marking can be altered from the management terminal.


BK,BE,EE

CL,VI

BE,EE

EE

EE

BE EE

BE,EE

BE

BE

-

BK

BK

BK

BK

BK

BK,BE,EE

CL,VI,VO

VO,NC

VO,NC

VO,NC

VO,NC

VO

VO

NC

NC

CL

CL

CL

VI

VI

CL,VI

CL

VI

VI

MINI-LINK TN ETSI

Egress buffers

Each Ethernet interface has a separate egress buffer to handle temporary link congestion. The egress buffers enable MINI-LINK TN to handle short bursts without packet loss. The buffer is organized in different priority queues or traffic classes. The buffer capacity is shared between the different egress priority queues for an Ethernet port.

NPU3 B and ETU3 LAN ports have a minimum buffering capacity of 100KByte memory space. In addition, a NPU3 B/ETU3 LAN port is allocated buffer capacity from a 1MByte shared memory. A NPU3 B/ETU3 LAN port’s actual buffer capacity is then calculated form the formula below:

LAN port buffer = 100kByte + (1MByte – number of LAN ports*100kByte)

Please note that the LAN egress buffer is limited upwards to 1024 frames per port.

For WAN ports, NPU3 B and ETU3 have a buffering capacity of 16MByte per port.

ETU2 has a buffer capacity of 1024 frames per LAN/WAN port for all frame sizes.

The buffer capacity for NPU3 B, ETU2 and ETU3 is shared between the traffic classes/priority queues. E.g. if an Ethernet interface is configured with four traffic classes, the buffer capacity is shared equally between the traffic classes. The figure below illustrates how the buffering capacity is divided between the different traffic classes/priority queues in a network that uses the IEEE 802.1 D-2004 definitions.

Number of TC

Buffer allocation to TC

1 100%

2 50% 50%

3 33% 33% 33%

4 25% 25% 25% 25%

5 20% 20% 20% 20% 20%

6 16% 16% 16% 16% 16% 16%

7 14% 14% 14% 14% 14% 14% 14%

8 12% 12% 12% 12% 12% 12% 12% 12%

Figure 29: Egress buffer allocation to TC for NPU3 B and ETU2/ETU3


MINI-LINK TN ETSI

NPU3 has a buffer capacity of 400kByte per LAN/WAN port. The Ethernet egress buffer on NPU3 is implemented as a dynamically allocated shared resource between the different priority queues.

The different priority queues for the NPU3 are implemented as linked lists in a ring buffer. The figure below illustrates an example where the egress buffer is configured with two priority queues.

1 2 2 2 1 1 2 2 1 2 2

Figure 30: NPU3 Ethernet egress buffer

Scheduling

MINI-LINK TN supports, individually per Ethernet port, a strict priority based scheduling of the Ethernet frames in the egress buffers. This means that Ethernet frames with the highest priority number are always scheduled first, e.g. all Ethernet frames with priority level 7 are scheduled before Ethernet frames with priority level 6.

Figure 31: Strict priority based scheduling


Highest priority

Lowest priority

Ethernet Egress portPCP

detection

Sched

uler

Ethernet Ingress port

MINI-LINK TN ETSI

Flow control

MINI-LINK TN supports the IEEE 802.3x standard to handle temporary congestion in a network element.

When a congestion threshold is reached in MINI-LINK TN a PAUSE signal is broadcasted to all connected devices to trigger a temporarily halt in the transmission of Ethernet frames.

Please note that the IEEE 802.3x based congestion handling mechanism doesn’t take into account the usage of different priority levels. The reception of a PAUSE message will trigger a network element to halt all Ethernet frames. This means that IEEE 802.3x based congestion handling is not suitable for networks configured for different priority levels and transmission of real time traffic.

4.5.6 Inverse Multiplexing (IM)

The IM function block in MINI-LINK TN is used to enable transportation of Ethernet frames through a PDH network. By utilizing the IM capabilities, MINI-LINK TN can set up a direct Ethernet connection between two end points in a circuit switched network using multiple E1s.

The IM protocol layer is inserted by the transmitting node and removed on the receiving end of the Ethernet IM connection. The figure below illustrates the simplified protocol stack.

Figure 32: IM protocol layer

The SA bits in TS0 are used as communication channel for the IM protocol between the peers. Thus, the IM connection can not traverse a cross connect where the E1 is “broken”, i.e. the E1s must be kept intact.


Inverse Multiplexer

G.703/ G.704

Ethernet frames

MINI-LINK TN

802.3

Ethernet frames

Inverse Multiplexer

G.703/ G.704

Ethernet frames

MINI-LINK TN

802.3

Ethernet frames

PDH

MINI-LINK TN ETSI

An IM connection can be configured to use any E1 in MINI-LINK TN for Ethernet transport. One IM connection can utilize either one interface on one board or be distributed to multiple interfaces on different boards. For an IM connection with multiple directions, the latency variation between the different directions must be less than 2ms.

The IM function block encapsulates an Ethernet frame, coming in on one Ethernet port, into one HDLC frame, i.e. 1:1. The HDLC frame is transmitted in parallel on the multiple E1 interfaces associated with the IM connection.

MINI-LINK TN contains buffers on the Ethernet egress interfaces to handle bursts. For an IM connection there are separate egress buffers towards the physical LAN Ethernet port and the IM WAN interface (Ethernet/PDH). In addition, on the IM interface side, Rx buffers are used to compensate for delay variations in the incoming traffic. The figure below illustrates the IM function blocks.

Figure 33: IM block diagram

4.5.7 Generic Framing Protocol (GFP)

tba


FE/GE

Egress buffer Rx buffers

Inverse Multiplexer

MINI-LINK TN

Egress buffer

Inverse Multiplexer

MINI-LINK TN

PDHFE/GE

Internal processing

Internal processing

Egress buffer

n*E1 Egress buffer

Rx buffers

MINI-LINK TN ETSI

4.5.8 Link Loss Forwarding (LLF)

The LLF feature improves the protection switching time for the point to point connection scenario by propagating connectivity loss information to both connection end points.

The LLF feature is implemented according to Ericsson specifications but is primarily used between MINI-LINK TN nodes. However, interoperability is verified for some AXX and OMS products. A list will be provided in a later version of this document.

LLF can be split in two scenarios, broken WAN or LAN links.

WAN link broken

When the terminating end points of the point to point connection detects that the WAN connection is lost (1), the Ethernet ports on both sides (2) will be taken down (i.e. disable line carrier) after a configurable hold off time

Figure 34: LLF, broken WAN link

LAN link broken

When a terminating end point of the point to point connection detects that the LAN connection is lost (1), the corresponding WAN port (2) will be taken down after a configurable hold off time. On the remote end, the disconnected WAN link is detected and the corresponding LAN port (3) will be taken down after a hold off time.

Figure 35: LLF, broken LAN link


MINI-LINK TN

WAN

MINI-LINK TN

LANLAN(2) (2)

(1)

MINI-LINK TN

WAN

MINI-LINK TN

LANLAN(1) (3)

(2)

MINI-LINK TN ETSI

4.5.9 Protection mechanisms

To meet the customer expectations for a carrier class product, MINI-LINK TN offers multiple redundancy features. The redundancy features are fulfilling different needs and operate both on plug-in unit and connection level.

In this chapter we will not present the complete redundancy capabilities but focus on the relevant redundancy features for the packet transport. The following redundancy features are supported:

Redundant central Ethernet switch 6

The central redundant Ethernet switch on the NPU plug-in unit can work in a redundant hot standby mode with an Ethernet switch on a second NPU board. A high speed connection in the backplane connects the Ethernet switches. A switch-over will take approximately 2s.

NOTE! It is only the Ethernet switching function that is redundant in this set-up, the NPU functions only run on the ordinary NPU board.

RSTP

The RSTP protocol offers redundancy and re-routing of traffic if a node is out of service. The Ethernet transport network is typically partitioned into multiple RSTP domains. Within one RSTP domain a reconfiguration of the active Ethernet connections will take less than 50ms and does not impact the service.

IM protocol redundancy

The IM protocol enable packet transport over multiple E1 connections with a built in redundancy mechanism. If one of the E1 links are down the IM group connection are still operational, but with reduced bandwidth. The bandwidth change takes less than 50 ms and does not impact the service.

GFP protocol redundancy

tba

1+1 SNCP E1

For an IM connection (Ethernet/PDH) it is possible to establish a 1+1 SNCP E1 protection between the two termination points. This scenario is especially valid for ring configurations. The change from active to passive path takes less than 50 ms and does not impact the service.

6 Currently not supported


MINI-LINK TN ETSI

MSP 1+1 protection

For a GFP connection (Ethernet/SDH) it is possible to establish a 1+1 MSP protection. For a link failure the switch from active to passive path board takes less than 50 ms and does not impact the service. For a board failure the switch from active to passive board takes less than 2s and will potentially impact the service.

1+1 modem protection

Both the packet radio and PDH/SDH modem plug-in units can be configured in a 1+1 configuration. For a link failure the switch from active to passive path takes less than 200 ms and does not impact the service. For a board failure the switch from active to passive board takes less than 2s and will potentially impact the service.

Link Aggregation Group7

Multiple LAN connections between two nodes can be grouped in a logical bundle. When a link fails the traffic will be switched to one of the operational links. For a link failure the switch from active to passive path takes less than 50 ms and does not impact the service. For a board failure the switch from active to passive board takes less than 2s and will potentially impact the service.

7 Currently not supported


MINI-LINK TN ETSI

4.6 Ethernet feature matrix

This chapter maps the different Ethernet features to specific hardware

Feature NPU3 NPU3 B ETU3 Interworking

mode

ETU2 SXU3 B

Ethernet LAN/WAN interfaces

10/100 Base T X X X X

1000 Base T X X X

1000 Base LX X

High speed connections8 X X X

Bridging/Switching

IEEE 802.1D switching X

IEEE 802 1Q switching X

Priority/PCP and VID-tagging (Q-tag) X

L2CP tunneling/discard (3) X (2) (3)

Ethernet over PDH/SDH

Ethernet over SDH using GFP mapping (4) X

Ethernet over PDH using IM mapping X (5) X X

CoS/Congestion handling

1-8 Priority queues/Traffic class mapping X X X X (2)

IEEE 802.3x flow control X X (2) X

Security

Frame admission X (2) (2)

White lists X (2) (2)

Storm protection X (2) (2)

Port blocking X (2) (2)

MAC address limiting per port X (2) (2)

Protection

Link Loss Forwarding (1) X (2) (1) (2)

RSTP X

8 This row shows only which products that have high speed connections towards the backplane, not how they can be combined in a chassis. The configuration restrictions are provided by other chapters in this document.


MINI-LINK TN ETSI

Management

Port mirroring X (2) (2)

Embedded VLAN based management X

Performance management X X X X (2)

(1) - LLF only for Ethernet/PDH (IM). Not remote LAN(2) - Feature provided by NPU3 B through high speed connections(3) - Only tunneling no discard(4) - Feature available on NPU3 B via SXU3B connected through high speed connections(5) - Feature available on NPU3 B via ETU3 connected through high speed connections


MINI-LINK TN ETSI

5 Appendix A: Standards updateIn this section we provide an overview of the standards bodies that are relevant for a MINI-LINK Ethernet network and their relation.

5.1 Institute of Electrical and Electronics Engineers (IEEE)

In the context of the MINI-LINK Ethernet traffic network, the IEEE has a set of active standards and a number of relevant ongoing standards development projects. They cover issues ranging from the attachment to and transmission over different physical media up to methods for operation and management of network elements.

The IEEE standards of interest for the MINI-LINK Ethernet traffic network are organized within IEEE’s 802 Standards Committee (802SC) for Local Area Networks (LAN) and Metropolitan Area Networks (MAN).

The relationship between the 802SC’s standardization activities (Figure 36) can be mapped against the OSI Layered Reference Model as shown in Figure 37. As seen in the figure the scope of the 802SC’s standardization activities as well as the scope of their existing standards covers layers 1 (Physical) and 2 (Data Link) of the OSI Reference Model.

Commonly, the use of 802SC protocols is combined with the use of IETF (Internet Engineering Task Force, see section 5.4) protocols at layer 3 (Network layer) and above. In the figure, the two most common combinations are shown, using the Internet Protocol (IP) at the Network layer in combination with either the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP) at the Transport layer.


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Figure 36 Relationship between the OSI Layered Reference Model and the TCP/IP Stack using Ethernet at the DataLink (and Physical) Layer(s).

Originally, 802SC’s emphasis was on LAN standards only (e.g. 802.3 CSMA/CD Ethernet and 802.5 Token Ring). However, in recent years, the group has taken responsibility for developing standards covering networks ranging from PAN (Personal Area Network) to WAN (Wide Area Networks) Networks. The committee develops standards for wireline (copper and fibre optics) as well as wireless communications. The figure below shows an overview of 802SC’s standards and activities.

Figure 37 Overview of IEEE 802 LAN/MAN Standards Committee Standards and Standardization Activities.


Data Link(MAC/LLC)

IP

TCP/UDP

IETF Scope

IEEE802 Scope

OthersPhysical

Data Link

Network

Transport

Session

Application

Presentation

Physical(PHYs/Media)

TCP/IP Stack

OSI LayeredReference Model

.3Ethernet

CSMA/CD

.16BWA

.22WRAN

.1 Bridging

.2 Logical Link Control

DataLink

Layer

PhysicalLayer

.17RPR

.11WLAN

.15WPAN

Overview

and Architecture

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During the lifetime of the 802SC, a number of standards have been developed for MAC methods with support for specific physical media. Typically, when a MAC standard is developed, initially it supports one or more physical media. If the MAC proves to be popular, standards amendments for additional PHYs may be developed at a later stage.

While each MAC method specified by the 802SC provides specific means for accessing network resources, the 802.1 working group specifies standards methods for interconnection/bridging of 802 network elements. The 802.1 working group also propose standards for operations such as Connectivity Fault Management and Access Control.

It is important to note that each working group of the 802SC usually maintains several standardization activities in parallel. Thus when making equipment according to 802SC standards (this also applies to ITU-T, IETF and MEF standards), we are chasing a moving and growing target. Thus, the challenge is to identify the relevant standards that may be either completed or under development.

5.2 ITU-T Standards

In the context of the MINI-LINK Ethernet traffic network, the ITU-T has a set of active standards and a number of relevant ongoing standards development projects. They cover definitions and services for use in Ethernet based transport networks. While the basic Ethernet functionality is specified by the previously mentioned IEEE 802 Ethernet standards, ITU specifies how to use (and extend) on these standards for use in a (packet based) transport network.

ITU-T standardization activities are conducted in cooperation with many other standards development organizations, e.g. IEEE.

The ITU-T standards of interest for the MINI-LINK Ethernet traffic network are organized within Study group 13 and 15.

The following Ethernet ITU standards are useful additional reading:

ITU-T Y.1730 (Ethernet OAM)

ITU-T G.8010/Y.1306 (Architecture of the Ethernet Layer Network)

ITU-T G.8011/Y.1307 (Ethernet Service Framework)

ITU-T G.8012/Y.1308 (Ethernet over Transport Architecture)

ITU-T G.8021/Y.1341 (Characteristics of Eth. Transport Network equipment functional blocks)


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5.3 Metro Ethernet Forum (MEF) Standards

Recently, standardization organizations are making a major effort to adapt Ethernet to metropolitan networks and further to backbone networks. The key issue is the ability to be able to guarantee service levels, why the term carrier class Ethernet is often used. The customer must be able to lease Ethernet Virtual Connections (EVC’s) from the provider of the network with a Service Level Agreement, see figure below.

Figure 38: Ethernet Service model.

Ethernet is thus no longer only a transport layer and connectivity layer, but also a service layer, see figure below.

Figure 39: The Ethernet service, connectivity and physical layers (PHY)

The Ethernet service layer is defined by the Metro Ethernet Forum (MEF). The mission of the Metro Ethernet Forum is to “accelerate Worldwide Adoption of Carrier-class Ethernet Networks and Services”.

The objectives of the MEF are to:


Ethernet service layer

AdaptationEthernet PHY

Ethernet connectivity layer

Ethernet PHY(IEEE 802.3)(UNI/E-NNI/I-NNI)

AdaptationRadio Link PHY

Radio Link PHY(I-NNI)

AdaptationPDH PHY

PDH PHY(I-NNI)

SDH PHY(UNI, I-NNI)

Ethernet Virtual Connection

(EVC)

Service Level Agreement (SLA)

User Network Interface

(UNI)

User Network Interface

(UNI)

Customer Edge(CE)

Customer Edge(CE)

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Build consensus and unite service providers, equipment vendors and end-customers on Ethernet service definition, technical specifications and interoperability.

Facilitate implementation of existing/new standards, Ethernet service definition, test procedures and technical specifications of the MEF to allow delivery of Ethernet services and make Ethernet-based metro networks carrier class.

Enhance worldwide awareness of the benefits of Ethernet services and Ethernet-based metro transport networks.

The primary priorities of the MEF are to define:

Ethernet Services for metro transport networks. Such services shall be delivered over native Ethernet-based Metro networks and could also be supported by other transport technologies.

Carrier-class Ethernet-based metro transport technologies by specifying architecture, protocols and management for Ethernet-based metro transport networks and supporting such Ethernet Services.

MEF standards offer a comprehensive service framework that supports different Ethernet service types and interfaces. The different Ethernet service types are addressing different topology and connectivity demands and enables the operators to offer both point-to-point and point-to-multipoint connections. MEF specifies the following service types:

E-Line service type

Any Ethernet service that is based on a point-to-point Ethernet Virtual Connection (EVC) is designated as an Ethernet Line Service (E-Line) type. The E-Line Service is illustrated in the figure below.

Figure 40: E-Line Service type using Point-to-Point EVC

An E-Line service type is typically used to connect two customer locations through an operator’s Metro Ethernet Network.

E-LAN service type

Any Ethernet Service that is based upon a multipoint-to-multipoint EVC is designated as an Ethernet LAN (E-LAN) Service type. The E-LAN service type is illustrated in the figure below.


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Figure 41: E-LAN Service type using Multipoint-to-Multipoint EVC

An E-LAN service type is typically used to connect multiple customer locations through an operator’s Metro Ethernet Network.

E-Tree service type

Any Ethernet Service that is based upon a rooted multipoint Ethernet Virtual Connection is designated as an Ethernet Tree (E-Tree) Service type. The E-Tree service type is illustrated in the figure below.

Figure 42: E-Tree Service type using Rooted Multipoint EVC

An E-Tree service type is typically used to connect multiple remote customer locations to one central site through an operator’s Metro Ethernet Network.

Service attributes

Potentially, any end user service (e.g. e-mail, web browsing) can be used for the different service types. To restrict the usage of an Ethernet connection the operator must configure the different attributes that is associated with each service type. The following service attribute categories are specified:

Ethernet physical interface

Bandwidth profile


Leaf UNI

Rooted Multipoint EVC

Metro Ethernet Network

Root UNI

Leaf UNILeaf

UNI

Leaf UNI

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Performance parameters

Class of Service identifiers

Service Frame delivery

VLAN Tag support

Service multiplexing

Bundling

Security filters

For further details see the following MEF standards:

MEF 10.1 (Ethernet Service Attributes)

MEF 12 (Metro Ethernet Network Architecture Framework)

MEF 6 (Metro Ethernet Service Definitions)

5.4 Internet Engineering Task Force (IETF)

In the context of the MINI-LINK Ethernet traffic network, the Internet Engineering Task Force (IETF) has a set of active standards and a number of relevant ongoing standards development projects. They are mainly related to management of Ethernet data and control plane functions of network elements of a MINI-LINK Ethernet traffic network.

The following Ethernet IETF standard is useful additional reading:

IETF RFC 2819 (Remote Network Monitoring Management)


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5.5 Relationship between IEEE, ITU-T, IETF and MEF

IEEE owns the Ethernet standard(s) defining the Ethernet frame format(s) for data-link layer communication between Ethernet-enabled end-nodes as well as Ethernet aware intermediate network elements. IEEE also defines a multitude of physical layers (PHYs) for transporting the individual bits of an Ethernet frame over a physical medium between the sender and (each intermediate) receiver(s). These PHYs covers transmission for mediums like coaxial cables, shielded and unshielded twisted pairs, optical fibers and wireless media.

Provisions are also made for transporting Ethernet frames over PHYs defined by other standardization organizations (e.g. Ethernet transported over a SDH/SONET infrastructure) like ITU-T.

Recently, the 802SC has initiated work for standardizing methods for OAM operations on an Ethernet based network infrastructure. This has traditionally been handled in foras like ITU-T for network elements in traditional telecom operators’ networks. However, with the growing success of Ethernet used for such networks, this has led to an effort by the 802SC to define such services for Ethernet based networks.

ITU-T is working in close cooperation with IEEE to ensure that the OAM functionality defined within the scope of the 802SC standardization project addresses the correct issues. Furthermore, functionality excluded from the scope of such projects which are considered important by ITU-T is a candidate for further standardization within the ITU-T, e.g. ITU-T standards that can be considered amendments to 802SC standards.

While the 802SC and ITU-T have had a focus on control and data plane functionality of (Ethernet) networks, the IETF has a set of standards that support functions to manage and configure individual network elements. By definition of protocols and standardized configuration databases (i.e. MIBs), provisions are made for supporting network management systems that allows remote operation and configuration of individual network elements as well as the complete network.

Such MIBs are often developed in close cooperation between the 802SC standardization project and an assigned project team within the IETF. Note however that this has recently changed. In RFC 4663, published September 2006, a plan to transition responsibility for bridging-related MIB modules from the IETF Bridge MIB Working Group to the IEEE 802.1 Working Group. Thus, in the future, the 802.1 related MIBs will be developed and standardized within the context of the 802.1 Working Group’s standardization project.


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Finally, the Metro Ethernet Forum has their objective of

Build consensus and unite service providers, equipment vendors and end-customers on Ethernet service definition, technical specifications and interoperability.

Facilitate implementation of existing and new standards, Ethernet service definition, test procedures and technical specifications of the MEF to allow delivery of Ethernet services and make Ethernet-based metro networks carrier class.

These objectives are achieved by uniting equipment vendors and service providers which work in technical (and marketing) committees, producing technical specifications, detailing different aspects of providing end-to-end Ethernet services. These specifications mostly reference standards produced by IEEE, ITU-T and IETF but in some cases original work is being done in order to fill gaps left open by the other bodies. In any case official liaison communication is set whenever the work touches issues that are being worked in a different standardization body.

The organization has been quite successful in its work and it currently has a great influence on how different equipment vendors and operators consider the provisioning of end-to-end Ethernet services.


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6 Appendix B: Packet transport over a microwave linkThis chapter describes the impact packet based traffic has on microwave transport media

6.1 Microwave Planning

This chapter doesn’t intend to describe the whole planning phase, just highlighting some of the criteria’s that has to be considered.

When planning a microwave hop you consider a certain quality standard as an input, normally we refer to G.826 but also to a certain BER like 10-6 and a percentage over the year: 99.999% BER 10-6 (means a quality worse than 10-6 in 0.001% which corresponds to about 5 minutes over a year)

The planning should consider all kinds of disturbance causes like rain, fading and interference. It is important also to consider unavailability due to hardware failures, as well as plan for a suitable spare part stock.

From the planning tools we get a fair figure on the quality and availability we will get and we will normally see disturbances lasting only a small number of minutes over the year.

6.2 BER and delay impact on TCP

In transmission networks, errors will be added over the complete chain, including all error adding products and media (microwave (equipment residual BER and path depending errors), fiber, coax….) gives a total end to end figure.

Ericsson MINI-LINK equipment has a residual BER of typical 10-12 which is practically no bit errors adding to the chain.

Typical latency figure for a hop is less than 1ms and in a typical microwave network the overall latency figure is less than 5ms (a microwave chain/cluster consisting of five hops in a row must be seen as a bigger sized cluster)

Delay Variation

The impact of jitter in a microwave network is negligible on TCP. Delay variation is caused by queuing of large packets that incurs delay on higher priority packets.


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Impact of errors on TCP

We can start with the observation that most analysis on TCP traffic calculates with packet loss indication of 1-5 %. Above that error ratio, TCP does not work efficiently.

Packet loss is typically due to congestion in some bottleneck link. Congestion is the nature of TCP, since that is how TCP senses the limit of available bandwidth. On wireless links, however, fading is the dominant source of packet loss through the increased bit-error ratio. If this loss is below 1 %, as a rule of thumb, then it won't cause trouble for the TCP connections.

Assuming that the maximum Ethernet frame size is 1500 bytes, i.e. 12000 bits, what is the bit-error ratio (BER) that causes a frame error ratio (FER) of 1 %?

BER = 1-(1-FER)(1/LEN) ; LEN = packet length in bits

The calculation gives a BER=8.4e-7.

A rough estimation shows that for BER below 10-6, the impact of bit errors on TCP can be disregarded.

The figure below shows the correlation between TCP throughput and BER for different round trip delays.

1

10

100

1000

1,E-14 1,E-12 1,E-10 1,E-08 1,E-06

RTT=1 ms

RTT=10 ms

RTT=100 ms

Bit error ratio

Max TCP throughput in a channel with unlimited bandwidth

Packet size 1500 bytes

RTT-round trip time

Figure 43: BER and Latency impact on TCP throughput


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6.3 BER impact on Real Time data

Ericsson MINI-LINK equipment has a residual BER of typical 10-12 which is practically no bit errors adding to the chain.

A critical aspect is the max tolerated and Packet Error Ratio (PER) without service impact, typically 10-4.

Since a faulty packet is a lost packet from RT services perspective, a relation between BER and Packet Error Ratio (PER) needs to be established to provide dimensioning guidelines for packet based microwave transmission. This relationship is:

PER = 1-(1-BER)LEN ; LEN = packet length in bits

and hence

BER = 1-(1-PER)(1/LEN) ; LEN = packet length in bits

Table below show the required BER for a given PER for typical RT packets, 75-100 octets.

PER 75 88 100

10-4 1.67*10-7 1.42*10-7 1.25*10-7

10-5 1.67*10-8 1.42*10-8 1.25*10-8

10-6 1.67*10-9 1.42*10-9 1.25*10-9

Figure 44: Calculated BER as function of desired PER and RT packet length in octets.

The limit for normal operation is PER value of 10-4. The BER value corresponding to a PER of 10-4 is approx. 10-7. This value can be considered the new availability design criteria.

Due to effective Forward Error Correction, modern microwave links act basically in a digital way between no bit errors and high bit error levels with no service as the BER is going extremely steep from 10-6 down to 10-9 with a small increase of receiver input power.

This means that the planning of the availability of the microwave link does not differ between using a BER threshold of e.g. 10-6 and e.g. 10-7.Practically speaking, the link will provide error free operation during the percentage of time it is designed for and will be close to unavailable during the rest of the time.


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7 References[1] MINI-LINK TN ETSI Ethernet Feature List - 3/1551-14/CSH 109 32 Uen


Documents

Ethernet Packet Transport