CarrierEthernetDefined EMEA

8/9/2019 CarrierEthernetDefined EMEA

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Describing each methods capabilitiesand how they support the end-user network

Carrier Ethernet Defined

This white paper addresses:

Benefits of three primary Carrier Ethernet services

A comparison of Ethernet features important to enterprises

Appropriate applications for each Carrier Ethernet service

A comparison of the key WAN transportmethods now available for deliveringhigh-value Ethernet services


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Carrier Ethernet Evolves as a Wide Area Network Service....................3

Ethernet-over-Fiber-MPLS Enhances Carrier Ethernet Services..............6

Ethernet-over-SDH Expands Across Networks .....................................7

Ultra-High Bandwidth of Ethernet-over-WDMAttracts Data Center Use....................................................................8

Choose Service Based On Application Requirements...........................8

Carrier Ethernet Service Capabilities Encourage Widespread Use ........9

Glossary ...........................................................................................11

Contents


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Carrier Ethernet Evolves as a Wide Area Network Service

Initially developed by carriers to deliver Ethernet to enterprise customers

at bandwidth levels previously unavailable (10 Mbps, 100 Mbps and

1Gbps), Carrier Ethernet services are becoming prevalent across leading

European metropolitan centers. Some services are available across

national boundaries. Carrier Ethernet services offer enterprises an

alternative WAN transport service to augment and replace existing leased

line and data services.

Carrier Ethernet has been developed from Ethernet for local area

networks with modifications to enable its use in the wide area. These

modifications include:

Enhanced equipment redundancy in hardware and software to make

them carrier class.

Traffic engineering techniques, such as Multiprotocol Label Switching

(MPLS) to scale network services with consistently high resiliency and

Quality of Service (QoS). MPLS provides a target of 50 ms restoration for

network services.

Implementation of Virtual Private LAN Services (VPLS) to provide

multipoint Ethernet for a single company across geographic locations.

VPLS overcomes the inherent limitations of Ethernet VLANs by adopting

MPLS for multipoint applications, using a defined encapsulation scheme

for Ethernet traffic.

Enhancement of SDH technology, to transport efficiently Ethernet traffic

across optical networks, through the Generic Framing Procedure (GFP)

and Link Capacity Adjustment Scheme (LCAS).

These enhancements give the carrier a data service that enables service

level agreements (SLAs) for business customers. These SLAs establish

metrics for guaranteed data delivery over a specified timeframe, with

defined refunds or credits when these metrics are not met.

The very top level guarantees little or no time lag for data packets, which

is suitable for MPEG 2 video traffic. The lowest level provides only best

efforts delivery of traffic, with no guarantees. Because the highest quality

Carrier Ethernet is now capable of providing compressed MPEG 2 video

quality transport that eliminates freeze frames, several carriers are

deploying Carrier Ethernet for aggregation and backhaul of video, voice

and Internet services over DSL, commonly referred to as the Triple Play.


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There are three types of Carrier Ethernet:

Ethernet-over-SDH (EoS)

Ethernet-over-Fiber (EoF)

Ethernet-over-WDM (EoW)

Since each is supported by a separate network infrastructure using

different optical transport technology, they differ in terms of resiliency,

bandwidth-level offered and available footprint.

Incumbent national carriers and leading alternative carriers are the

primary providers of Ethernet Wide Area Network (WAN) transport

services. Ethernet-over-Fiber was the first deployed by alternative carriers

to attract enterprises away from the leased line, Frame Relay and ATM

services of incumbent national carriers. EoF services have continued to

improve through traffic engineering techniques, specifically MPLS. Since

national carriers widely deployed SDH for ultra-reliable E1, E3, STM-1,

STM-4 and STM-16 transport, Ethernet-over-SDH has become one of the

preferred technologies for these carriers. Ethernet-over-WDM has been

proven inside core networks and in ultra-high bandwidth applicationsthat require n x 100 Mbps, 1 Gbps or 10 Gbps throughput, such as real-

time disk mirroring between dispersed data centers. While point-to-

multipoint services are becoming available in all these cases, most services

today are still point-to-point.

Enterprises are generally uninterested in underlying network technology.

But they do care about application-sensitive service attributes like

bandwidth, quality of service, restoration and resiliency, latency and

future enhancement of existing network assets to support Carrier

Ethernet. EoS, EoF and EoW differ considerably in these service

attributes, as shown in Table 1 on the next page.


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Ethernet-over-Fiber-MPLSEnhances Carrier Ethernet Services

Carriers initially deployed EoF services to connect enterprise LANs across

metro regions over fiber, and several carriers have active EoF services

today. Enterprise customers generally use the service as a replacement or

addition to a lower-speed ATM or Frame Relay data service for Internetaccess or site-to-site connections. EoF service is usually available as

point-to-point or multipoint-to-multipoint at the following bandwidth

levels: 10 to 100 Mbps and 1 Gbps.

The foundation of an EoF network is either a point-to-point Ethernet

connection through carrier-grade Ethernet switches or a mesh network of

Ethernet switches. Enterprises connect to the Ethernet core network at

the central office through a fiber interface powered by an optical device

that drops an Ethernet connection to the user, and an enterprise

connection may have two diverse routes from the enterprise site to the

central office or POP.

Enterprises need to be cautious, because some EoF network services offerbest efforts only. Where service providers do not provide SLAs, packet

transport performance is limited by subscription levels. When these

networks are oversubscribed, latency and jitter across paths increase. As a

result, enterprises can see a marked decrease in network performance,

which affects applications that use the EoF link.

Newer EoF networks are addressing latency and restoration time issues

found in earlier networks. Carriers now use MPLS traffic engineering

capability inside the core of an EoF network to offer point-to-point

services, along with multipoint-to-multipoint services enabled by VPLS, a

new standard that uses MPLS and the Martini encapsulation scheme.

VPLS gives carriers a way to deliver virtual private network services,commonly referred to as E-LANs by the Metro Ethernet Forum. Local

area specifications for Ethernet do not scale in the wide area because the

number of VLAN tags is limited by specification. VPLS overcomes this

problem and provides additional resiliency. Some carriers have adopted

VPLS in their networks, while others plan to deploy the technology to

offer robust VPN, multipoint services. These point-to-point and

multipoint-to-multipoint services can provide reduced latency and

decreased restoration time of less than 50 ms, equal to the restoration

time of EoS or EoW. These EoF-MPLS networks are being adopted by

enterprises because they offer SLAs that are similar to those available

through ATM and Frame Relay.

The key advantages of EoF-MPLS are competitive pricing and availability.

The key disadvantage of EoF-MPLS is its higher latency caused by

buffering of traffic as it traverses multiple Ethernet switches.

In addition to MPLS, another solution is to use Ethernet-over-SDH at the

core to take advantage of SDHs proven reliability. This has the important

added advantage of facilitating handoffs to the installed base of legacy

infrastructure found in carrier networks today. EoF with MPLS or SDH at

its core will become more attractive to business users who may move

away from their existing lower-speed Frame Relay and ATM services.


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Ethernet-over-SDH Expands Across Networks

Ethernet-over-SDH emerged as carriers and system vendors developed

specifications to extend the functionality of SDH networks to support

Ethernet traffic at bandwidth levels that are friendly to enterprise

applications. To ensure consistent deployment across SDH networks, rapid

adoption, and eventual ubiquity, Ethernet-over-SDH is anchored by a set

of standards developed by leading SDH vendors.

There are two types of EoS services:

EoS Leased line (EoS LL) uses a dedicated SDH channel per customer.

Essentially, EoS LL is a Leased Line service with a native Ethernet interface.

Switched EoS (Sw EoS) shares an SDH connection among several

enterprises. To ensure service quality, each enterprise is assigned a VLAN

tag and specific QoS through a committed information rate (CIR) for

guaranteed bandwidth and a peak information rate (PIR) for traffic bursts.

Effectively, Sw EoS offers a bandwidth-guaranteed Ethernet service that

takes advantage of the low latency and minimal jitter of SDH at a lower

price than EoS LL.

EoS Leased Line and Switched EoS are the premier Ethernet WAN

transport services and offer the following advantages:

Very low latency, since buffering is administered only on the ingress and

egress switches and not across intermediate switches

Very high resiliency and restoration. EoS LL as a TDM service takes

advantage of SDHs 50 ms restoration, while Sw EoS can use SDH or

LCAS for 50 ms restoration and Rapid Spanning Tree Protocol which

restores from 50 ms to seconds

Low jitter

Guaranteed quality for EoS LL, since it is a TDM service, and high QoS forSw EoS since it offers CIR and PIR on VLAN-designated traffic

Resilient transport across multiple sites for TDM, voice (packet and TDM)

and data services with ring technology

EoS LL is well suited to augment or replace an existing leased line service

like E1, E3 or STM-1, while Sw EoS is better suited to augment or replace

Frame Relay or ATM connections. Together, EoS LL and Sw EoS can

support all business Ethernet WAN transport needs.

National carriers are significant providers of EoS services with services

available in leading metropolitan centers in Europe. Carriers deploy EoS

using new multiservice provisioning platforms (MSPPs) or existing SDHequipment, coupled with EoS line cards or external devices that map

native Ethernet traffic to SDH frames. Service providers have also adapted

service management systems to support Ethernet. They currently offer

point-to-point services through EoS LL and may offer multipoint-to-

multipoint service through Sw EoS.


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Ultra-High Bandwidth of Ethernet-over-WDMAttracts Data Center Use

Ethernet-over-WDM emerged as carriers wanted to offer ultra-high

bandwidth services (GigE level) to connect customers data centers and

meet the needs of other specialized, bandwidth-hungry applications, such

as video transport. In addition, EoW also supports storage networktransport and large file transfers between corporate sites or data centers.

EoW is deployed using either Dense Wavelength Division Multiplexer

(DWDM) or Coarse Wavelength Division Multiplexer (CWDM)

technology. Generally, carriers use less-expensive CWDM to connect the

customer site to the service provider POP and DWDM between POPs to

transport site-to-site traffic. However, some carriers may use DWDM

across the entire network from customer site to POP. EoW offers high

potential resiliency through optical protection at 50 ms or less and very

low latency. Protected and unprotected links are available.

Service providers offer Ethernet-over-WDM services at 1 Gbps and 10

Gbps. In addition to Ethernet, many wavelength services offer support for

multiple protocols, such as ESCON, FICON and Fibre Channel. EoWsprimary strength is augmenting leased line data connections to support

storage and ultra-high speed data transport.

Choose Service Based On Application Requirements

According to a recent survey by International Orange Strategies, a leading

telecommunications analyst firm, file transfer, Internet access, LAN-to-

LAN and e-mail communications are the dominant applications for many

medium to large enterprises with at least 3 E1s of bandwidth, while VoIP

and storage transport applications also feature prominently.

In order to support these services through Carrier Ethernet, enterprises

need to weigh their bandwidth requirements and the latency and

resiliency characteristics of the various Ethernet services. EoS and EoW

have low latency because they require minimal packet buffering across

nodes. With EoF-MPLS, latency is greater and degrades per node and does

not compare to the levels offered by EoS or EoW. Graph 1 compares

relative latency among EoF-MPLS, EoS and EoW.

Graph 1. Normalized End-to-End Latency*

Latency End-to-End

0

0.5

1

1.5

2

2.5

3.0

EoW EoS EoF- MPLS

Normalized

Latency

* Normalized latency with EoS = 1 per

node. The lower the number the better

the latency.


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Common enterprise applications like traditional LAN-to-LAN transport,

email, Internet access and latency-dependent applications such as VoIP,

storage networking, imaging and video can be transported through MPLS-

engineered EoF services, EoS or EoW.

Network resiliency and restoration time can be different across EoS, EoF-

MPLS and EoW. EoS Leased line offers failover within 50 ms. Switched

EoS can provide failover to 50 ms depending on the restoration scheme,and EoW provides failover as quickly as EoS. EoF-MPLS networks has

restoration goals of within 50 ms.

According to a leading market research firm*, medium and large

enterprises give high priority to reliability, redundant connections, service

level agreements and low latency. Table 2 summarizes how each Carrier

Ethernet service measures up to these concerns.

Table 2. Comparison of Ethernet Features Important To Enterprises

Carrier Ethernet Service CapabilitiesEncourage Widespread Use

Enterprise customers have a number of options for Ethernet services

across the WAN.

Many enterprise applications such as e-mail, Web access, VoIP and file

transfer can be adequately served by EoF-MPLS and services from such

networks will attract more ATM and Frame Relay users for common

enterprise application demands.

Multipoint applications such as VPNs can be served through EoF-MPLS

networks by using VPLS as the enabling technology

EoS LL and Sw EoS are premier Ethernet services offering high resiliencyand low latency at a variety of bandwidth levels. This makes them

appropriate for most, if not all, enterprise business applications, including

e-mail, file transfer, VoIP, storage transport, imaging and Internet access.

As a ring-based service, EoS is highly suitable for connections with

multiple sites and for transport of TDM voice and data services.

ServiceAttribute EoS LL Sw EoS EoF EoW

Reliability andrestoration

High with50 ms

restorationtime

Medium to high with50 ms restoration time

available through SDHor LCAS or greater ifRSTP is used

Medium to high,with target of

50 ms

High with50 ms

restorationtime

RedundantConnections

Available Available Available, butnot-standard

Available

SLAs Guaranteed CIR, PIR, with PIR > CIR CIR, PIR, with PIR= CIR generally

Guaranteed

Latency Low Low Medium Low

* International Orange Strategies


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Glossary

Committed Information Rate (CIR) The throughput rate provided a service

provider guarantees for a network service.

Ethernet-over-SDH Leased Line (EoS LL) A service that allows enterprises

to connect multiple locations using Ethernet as an end-to-end protocol

over a SDH ring. EoS LL uses a dedicated SDH channel to transport the

Ethernet traffic end-to-end. EoS LL corresponds to the Metro Ethernet

Forums E-Line service.

Generic Framing Procedure (GFP) GFP provides a bandwidth efficient way

to map multiple protocols (eg., Etherent) onto packets for transport over

an optical network such as SDH.

Link Capacity Adjustment Scheme (LCAS) A signaling protocol used in

relation to the hitless increase and decrease of SDH bandwidth.

Multiprotocol Label Switching (MPLS) MPLS is a set of standards that

bridges the gap between connectionless IP networks, where routing

decisions are made at every hop, and connection-oriented networks that

deliver point-to-point services such as ATM and Frame Relay. MPLS uses

pre-determined data connections, known as Label Switched Paths (LSPs),

to transport traffic through core networks. Like ATM virtual circuits, these

MPLS LSPs have defined properties such as bandwidth availability,

bandwidth utilization and a QoS level. MPLS standards define Fast

Reroute recovery mechanisms to survive link or nodal failures with the

goal of a 50 ms restoration.

Packet Buffering Memory deployed in networking equipment to manage

the flow of packets in and out of line cards, and thus in and out of

networking nodes. They are used in conjunction with packet classification

and processing functions performed by the switch or router. Packet

buffers add some latency in the transmission of packets through a

networking node, however.

Peak Information Rate (PIR) Defines an upper limit to the throughput rate

a service provider allows for a network service. Traffic can burst beyond

the CIR up to the PIR in cases where the PIR > CIR.

Rapid Spanning Tree Protocol (RSTP) A standard to detect loops and

activate redundant paths to enable an Ethernet network to reconverge

and transmit traffic in event of a failure. Rapid Spanning Tree Protocol

improves upon Spanning Tree Protocol by speeding up reconvergence

time. It specifies all links as point-to-point rather than LAN connections

and eliminates the long timeouts before reconvergence.

Switched Ethernet-over-SDH (Sw EoS) A service that allows enterprises to

share an SDH connection among multiple locations using Ethernet as anend-to-end protocol. Sw EoS enables a multipoint service that can be

compared to the Metro Ethernet Forums E-LAN service.

Synchronous Digital Hierarchy (SDH) The standard for transmission on

optical fiber used by telecommunication operators for more than 10 years.

Time Division Multiplexing (TDM) A traditional multiplexing solution

where each signal is assigned to a time slot, classically used to carry PCM

voice, n x 64 Kbps leased lines or ISDN.

Wavelength Division Multiplexing (WDM) A solution to multiplex optical

signals on the same fiber using a set of different wavelengths.


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contact your Lucent Technologies Sales Representative or visitour web site at http://www.lucent.com.

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Information and/or technical specifications supplied within this

document does not waive (directly or indirectly) any rights or

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Copyright 2005

Lucent Technologies Inc.All rights reserved

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