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Carrier-Grade Ethernet Technology

Based on the article:“Ethernet as a Carrier Grade Technology: Developments

and Innovations” by R. Sanchez, L. Raptis, K. Vaxenavakis

Raimena Veisllari TTM1 lecture 16.09.2011

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Outline

• Repetition of the main Ethernet characteristics

• Reasons/Challenges for the Carrier Ethernet development

• Standardizations/work in progress– Scalability through VLAN hierarchy– Traffic Engineering (TE)– Operation, Administration and Management (OAM)

• Deployment case study

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The native Ethernet frame

7 octets Preamble for synchronization SFD (10101011) start of MAC frames 48 bit DA/SA CSMA/CD (do we still need it in switched Ethernet?)

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Why did Ethernet “win” in the customer domain?• There are LOTS of LAN protocols

• Price!• Performance

• Availability

• Ease of use

• Scalability

• ….

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Main characteristics

Simplicity (plug n’play) and cost effective

The switching logic (self-configuration)

Listening, Learning and Forwarding

Redundancy through xSTP

VLAN known as a broadcast domain

Connection-less (single hop)

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Why Carrier Ethernet ?

• SP infrastrucure based on legacy circuit-switched

SDH/SONET, ATM, frame relay etc.

• Ethernet as the technology of choice in the customer

domain (85% of all networks and 95% of all LANs)

• Internet is packet-switched

• Eliminate potential internetworking problems

• High bandwidth with simplicity and low cost

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Carrier Ethernet Definition

The MEF1) has defined Carrier Ethernet as “an ubiquitous, standardized, carrier-class Service and Network defined by five attributes that distinguish Carrier Ethernet from familiar LAN based Ethernet”

Standardized services

Scalability

Reliability

QoS

Service Management

1) http://metroethernetforum.org/index.php

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Carrier Ethernet Challenges (1)

Moving Ethernet from the LAN to the carrier network brings out requirements/challenges:

1. Scalability– Support for 10exp6 customers of an SP– Evolving the VLAN-tagging standards

2. Protection (Reliability and Resiliency)– Achieve the required 50ms recovery time– Problems with xSTP recovery time– Other protocols required

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Carrier Ethernet Challenges (2)

3. Quality of Service– Hard QoS comparable with the guaranteed service from

existing leased lines

4. Service Management– Service provisioning based to SLAs– Service Monitoring– Troubleshooting

5. TDM support– Inter-working with existing technologies

(leverage the customer-driven investment)

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Ethernet Standardization Milestones

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Scalability through VLAN hierarchy(1)

Management, security and scalability reasons

4094 available VLANs not enough for an SP

Layer3 functions to communicate between VLANs

802.1Q

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Scalability(2)• Q-in-Q IEEE 802.1ad Provider Bridges adding a new S-VID to the frame, 4094 VLAN limitation for the provider!• A failure in the customer’s domain still affects the spanning-tree of the provider’s core (transport) network

http://en.wikipedia.org/wiki/IEEE_802.1ad

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Scalability (3)

• MAC-in-MAC IEEE 802.1ah Provider Backbone Bridges (PBB) adds a Backbone MAC header

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Scalability (4)

- MAC-in-MAC

header encapsulation

- 24 bit I-SID

~16 service instances

- Dedicated set of

MAC addresses

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Scalability through VLAN hierarchy(5)

PBB provides:

1. 24 bit I-SID identifying the service in the SP => 16exp6 services

2. Total separation of the customer and SP networks

The MAC header is added at the edge of the SP

The backbone B-VID used for traffic engineering,

”zone”separation

SP control frames are independent from the customer’s ones

3. Tunneling

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PBB-Traffic Engineering

PBB-TE 802.1Qay introduce connection-oriented forwarding

mode and Ethernet tunnels:

Deterministic service delivery, QoS

Resiliency

OAM requirements

Turning off xSTP

Forwarding is not based on the MAC learning

mechanism but provided by the OAM plane

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Ethernet Services

• MEF defines the services as Ethernet Virtual Connections (EVC):

– Point-to-point E-LINE

– Point-to-Multipoint E-Tree

– Multipoint-to-Multipoint E-LAN

• Private Leased Lines

– dedicated bandwidth

• Virtual Leased Lines

– shared bandwidth

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Carrier network with PBT

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Operation, Administration and Maintenance (OAM)

Important building block toward carrier services

Ethernet, multiple working/standardization bodies.

IEEE 802.1ag and ITU-T Y.1731:

Fault detection through Continuity Check Messages

Fault verification through Loopback and reply messages

Fault Isolation through Linktrace and reply messages

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Operation, Administration and Maintenance (OAM)

ITU-T Y.1731 Fault notification through Alarm Indication Signal

Performance monitoring

Frame Loss Ratio

Frame Delay

Frame Delay Variation

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OAM example

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Conclusions from the article

• Its simplicity and cost-effectiveness makes Ethernet a desirable technology for the NGN carrier networks– Can Ethernet still be considered ”simple” after the discussed changes???

• Native Ethernet is lacking capabilities for MAN and WAN environment.

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Conclusions from the article

• PBB, PBB-TE and OAM aim to enhance Ethernet and provide the required carrier-grade services as from SONET/SDH, ATM and MPLS.– The competing carrier technologies OTN and IP/MPLS will be discussed latter

in the course schedule!

• Resiliency?

• Work in progress!

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For further leisure reading

• Examples taken from “The road to Carrier-grade Ethernet” K. Fouli, M. Maier http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4804387

• Metro Ethernet Forum MEF http://metroethernetforum.org/index.php