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Carrier-Grade Ethernet
Technology
Reading material: “Ethernet as a Carrier Grade Technology:
Developments and Innovations” by R. Sanchez, L. Raptis, K. Vaxenavakis
Raimena Veisllari
TTM1 lecture 13.09.2012
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Outline
• A short history of Ethernet
• Reasons and Challenges for the Carrier Ethernet development
• Carrier Ethernet characteristics
– Scalability through VLAN hierarchy
– Traffic Engineering (TE)
– Operation, Administration and Management (OAM)
• Deployment case study
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The native Ethernet

1973 - Metcalfe and Boggs (Xerox)

Shared medium access protocol


CSMA/CD, IEEE 802.3 (1980)
Coaxial Cable (”Ether”) based network

Thick Ethernet (10Base5)

Thin Ethernet (10Base2)

Twisted Pair (full-duplex communication, Base-T), Fiber (Base-X)

Repeaters and Hubs – one collision domain

Bridges and Switches – one broadcast domain
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The native Ethernet

7 octets Preamble for synchronization
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Indication of SFD (10101011) start of MAC frames

48 bit destination and source addresses
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EtherType (upper layer protocol, e.g. IP)
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Main characteristics

CSMA/CD (Do we still need it in switched Ethernet?)

Simplicity (plug n’play) and cost effective
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The switching logic (self-configuration)
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Listen, Learn and Forward
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Redundancy through xSTP

VLAN known as a broadcast domain
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Connection-less (single hop)
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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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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
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)
–
–
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Achieve the required 50ms recovery time
Problems with xSTP recovery time
Other protocols required
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Carrier Ethernet Challenges
3. Quality of Service
–
Hard QoS comparable with the guaranteed service from existing
leased lines
4. Service Management
–
–
–
Service provisioning based on SLAs
Service Monitoring
Troubleshooting
5. TDM support
–
Inter-working with existing technologies
(leverage the customer-driven investment)
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Standardization Milestones
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Scalability: Virtual LANs
• IEEE 802.1Q Virtual LAN:
•
•
•
•
•
Management, security and scalability reasons. Layer3 between VLANs
4094 available VLANs not enough for an SP!
Transparency problem within the SP backbone network!
A failure in the customer’s domain still affects the spanning-tree
of the provider’s core (transport) network
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Q-in-Q Virtual LAN
• IEEE 802.1ad Provider Bridges
• Add a new S-VID to the frame (VLAN stacking)
• Use the same MAC addresses through all the networks
• A maximum of 4094 VLANs is a limitation for the provider!
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MAC-in-MAC Virtual LAN
• IEEE 802.1ah Provider Backbone Bridges (PBB)
• Add a backbone MAC header (encapsulate the customers frame)
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VLAN hierarchy evolution
- MAC-in-MAC
header encapsulation
- 24 bit I-SID
- Dedicated set of
MAC addresses
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IEEE 802.1ah (PBB)
Provider Backbone Bridges 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
Ref: «IEEE 802.1ah Update” Paul Bottorff, Editor 802.1ah
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IEEE 802.1ah (PBB)
Ref: «IEEE 802.1ah Update” Paul Bottorff, Editor 802.1ah
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IEEE 802.1ah (PBB)
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An I-SID uniquely identifies an S-VLAN with the Backbone
The I-SID to/from S-VID mapping is provisioned when a new service
instance is created
B-VID : Separate the providers ID space : Many S-VLANs carried in a
single B-VLAN
Ref: «IEEE 802.1ah Update” Paul Bottorff, Editor 802.1ah
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Ethernet Services
• MEF defines the services as Ethernet Virtual Connections
(EVC):
1. Point-to-point E-LINE
2. Point-to-Multipoint E-Tree
3. Multipoint-to-Multipoint E-LAN
1.1 Ethernet Private Leased Lines (EPL)
–
dedicated bandwidth
1.2 Ethernet Virtual Leased Lines (EVPL)
–
shared bandwidth
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PBB-Traffic Engineering
PBB-TE 802.1Qay introduced connection-oriented forwarding mode and
Ethernet tunnels:
 Forwarding is not based on the MAC learning mechanism but
provided by the OAM plane
 Turning off xSTP
 Deterministic service delivery, QoS
 Resiliency
 OAM requirements
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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:
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Fault detection : Continuity Check Messages
Fault verification : Loopback and reply messages
Fault Isolation : Linktrace and Reply messages
ITU-T Y.1731
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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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Carrier Ethernet: What we
looked into?
Traffic Engineering
OAM
VLAN standards
1) http://metroethernetforum.org/index.php
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Conclusions
• 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.
• 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 in the course as well!
• 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
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IP over Optical (1)
Basic requirements:
• High capacity optical layer network
• Support high utilization of resources
• Support high granularity
• Support quality needed for strict real-time services
• Support variable length packets
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IP over Optical (2)
• Legacy technology, e.g. SDH/SONET network infrastructures have
provided a guaranteed level of performance and reliability for voice
calls and leased lines.
• Existing networks have been designed for telephony : static traffic
patterns
• Inefficient in handling the new traffic patterns that are dominated by
data services.
Increased traffic demands (e.g. from broadband home users/businesses
and new services) => Fat pipes needed.
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IP over Optical (3)
”IP everywhere” and development in optical technology => Focus on
simplifications:
What does the network look like?
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IP over Optical (4)
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IP over Optical (5)
• Traffic bypassing intermediate IP routers == Less load on routers
– smaller and cheaper
• In meshed networks:
Used to directly connect node pairs with high traffic load between
them.
Ref [1]
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Optical cross-connect example
• Wavelength switching done
all-optically e.g.
(transit traffic)
• Locally destined wavelengths
dropped/added
(processed electronically)