Metro Ethernet Forum Layer 2 Services

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Metro Ethernet Forum Layer 2 Services

• Bob Klessig
• Member of the Board and Co-Chair of the Technical
  Committee
• Director of Engineering, Cisco Systemsbklessig_at_ci
  sco.com

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Agenda

• MEF Specifications Roadmap
• Services Model
• Traffic Management

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MEF Services Technical Specifications
MEF 1.0Ethernet Services Model,
Phase1 Technical descriptions of service features
MEF x.0Traffic Management Specification,
Phase1 Fractional Bandwidth and Performance
MEF x.0Ethernet Services Definitions,
Phase1 Specific service instances
http//www.metroethernetforum.org/PDFs/Standards/
MEF-1.0.doc
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Agenda

• MEF Specifications Roadmap
• Services Model
• Traffic Management

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Services Model
CustomerEdge (e.g., router) (CE)
CustomerEdge (CE)
MetroEthernetNetwork
ServiceAttributes
A service is what the CE sees. The technology
used inside the MEN is not visible.
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User Network Interface
The demarcation point between Service Provider
and Subscriber Responsibilities
CE
CE
MetroEthernetNetwork
UNI
UNI

• Dedicated to a single Subscriber
• Based on Standard Ethernet PHYs for Phase 1,
  e.g.,
• RJ45 Socket on Service Provider owned Ethernet
  switch
• RJ45 plug on Service Provider owned cable

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Service Frame

• The Layer 2 protocol data unit exchanged between
  the CE and the MEN at the UNI
• Standard Ethernet
• With IEEE 802.1Q tag (up to 1522 bytes)
• Without IEEE 802.1Q tag (up to 1518 bytes)
• Includes everything but the preamble
• More than 100 Million devices exist that are
  potential Customer Edge devices

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Service Frame Transparency
Service Frames must be delivered from ingress UNI
to egress UNI(s) transparently except possibly as
follows
Ingress Service Frame Egress Service Frame
Untagged Tagged
Tagged Untagged
Tagged Tagged w/ different value
Frame Check Sequence recalculated
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Each Service Instance is a Layer 2 VPN
Example showing a green serviceand a blue
service.
ServiceMultiplexed UNI

• Service Frames cannot leak in or out of a Service
  Instance
• Multiple Service instances can exist at a UNI,
  called Service Multiplexing

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Formal Service Instance Definition
Ethernet Virtual Connection (EVC)

• Association of two or more UNIs
• Service Frames can only be exchanged among the
  associated UNIs
• A Service Frame sent into the MEN via a
  particular UNI MUST NOT be delivered out of the
  MEN via that UNI

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Point-to-Point EVC
Exactly two UNIs are associated.
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Multipoint-to-Multipoint EVC

• Two or more UNIs are associated
• A broadcast or multicast ingress frame is
  typically replicated and delivered to all of the
  other UNIs

A MP2MP EVC with two UNIs is different than a
P2P EVC since additional UNIs can be added at any
time.
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Identifying an EVC at a UNI
CE-VLAN ID/EVC Map
Service Frame Format UntaggedPriority
TaggedTagged, VID 1Tagged, VID
2...Tagged, VID 4094Tagged, VID 4095
CE-VLAN ID 12...40944095
EVC RedGreen...Blue
CE-VLAN ID/EVC Map
Untagged and Priority Tagged Service Frames have
the same CE-VLAN ID and that value is
configurable at each UNI. This is the behavior
expected by an IEEE 802.1Q CE.
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CE-VLAN ID Preservation
CE-VLAN ID37
EVCBlue
CE-VLAN ID37
EVCBlue

• CE-VLAN ID/EVC Map for EVC must be identical at
  all UNIs in the EVC and
• Priority Tagged in must be priority tagged out
• Untagged in must be untagged out

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All to One Bundling (Map)
UntaggedPriority TaggedTagged, VID
1Tagged, VID 2...Tagged, VID
4094Tagged, VID 4095
CE-VLAN ID 12...40944095
EVC Red
CE-VLAN ID/EVC Map

• Only one EVC at the UNI (no service multiplexing)
• All CE-VLAN IDs map to this EVC no need for
  coordination of CE-VLAN ID/EVC Map between
  Subscriber and Service Provider
• EVC must have CE-VLAN ID Preservation

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Using All to One Bundling
Disaster RecoveryService Provider
Branch
HQ
Branch
Bridgeor Router
Private LineReplacement
LANExtension
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One to One Map
UntaggedPriority TaggedTagged, VID 1Tagged,
VID 2...Tagged, VID 4094Tagged, VID
4095
CE-VLAN ID 12...40944095
EVC RedBlue
CE-VLAN ID/EVC Map

• No more than one CE-VLAN ID is mapped to each EVC
  at the UNI
• If CE-VLAN ID not mapped to EVC, ingress Service
  Frames with that CE-VLAN ID are discarded
• Service Multiplexing possible
• CE-VLAN ID Preservation not required
• Subscriber and Service Provider must coordinate
  CE-VLAN ID/EVC Map

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CE-VLAN ID Translation
CE-VLAN ID37
EVCBlue
CE-VLAN ID156
EVCBlue

• CE-VLAN ID/EVC Map can be different at different
  UNIs in an EVC
• Fine for CE routers
• Problematic for CE bridges

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Using One to One Map
InternetService Provider
CE-VLAN ID Preservationwould constrain ISP
178 ? Blue179 ? Yellow180 ? Green
2000 ? Green
ISPCustomer 3
2000 ? Blue
2000 ? Yellow
ISPCustomer 1
ISPCustomer 2
Frame Relay PVCReplacement
Router
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Bundling (Map)
UntaggedPriority TaggedTagged, VID
1Tagged, VID 2...Tagged, VID
4094Tagged, VID 4095
CE-VLAN ID 123..40944095
EVC RedBlue
CE-VLAN ID/EVC Map

• More than one CE-VLAN ID is mapped to an EVC at
  the UNI
• Service Multiplexing possible
• CE-VLAN ID Preservation is required for EVC if
  multiple CE-VLAN IDs mapped to it
• Subscriber and Service Provider must coordinate
  CE-VLAN ID/EVC Map

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Feature Combinations and Uses
CE-VLAN ID/EVC Map Characteristic EVC Type EVC Type
CE-VLAN ID/EVC Map Characteristic Point-to-Point Multipoint-to-Multipoint
All to One Bundling Private Line replacement with Router or Bridge LAN Extension with Router or Bridge
One to One Map Frame Relay replacement with Router Uses TBD
Bundling Uses TBD Uses TBD
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Delivery of Service Frames

• Broadcast
• Deliver to all UNIs in the EVC but the ingress
  UNI
• Multicast
• Typically delivered to all UNIs in the EVC but
  the ingress UNI
• Unicast
• Typically delivered to all UNIs in the EVC but
  the ingress UNI if not learned
• Otherwise, deliver to the UNI learned for the
  destination MAC address
• Learning is important for Multipoint-to-Multipoint
  EVCs
• Type of Service Frame determined from the
  destination MAC address

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Handling Layer 2 Control Protocols
Need to worry about Layer 2 Control Protocols
Bridge
BridgingExample
Bridge
Bridge

• Bridges will try to run Spanning Tree Protocol by
  exchanging Bridge Protocol Data Units (BPDUs)
• If BPDUs are blocked, loop will result and
  Ethernet Service will be unusable
• Solutions Use routers or deliver Subscriber BPDUs

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Options for Layer 2 Control Protocols

• Discard
• PDU from CE discarded by MEN
• PDU never egresses from MEN
• Peer
• MEN peers with CE to run protocol
• Tunnel
• PDUs carried across MEN as if they were normal
  data
• EVC is that associated with the CE-VLAN ID of the
  PDU, e.g., the Untagged CE-VLAN ID for most
  standard Layer 2 Control Protocols defined by
  IEEE 802

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Agenda

• Specifications Roadmap
• Services Model
• Traffic Management

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Caveat
MEF Traffic Management work is still evolving and
likely to change significantly.
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Two Areas Covered by Traffic Management

• Bandwidth Profile
• How to buy just the bandwidth you need and have a
  predictable bill
• Class of Service
• Identifying the CoS for a Service Frame
• Performance parameters that define a CoS

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Bandwidth Profile Overview

• Similar in concept to the traffic policing of
  Frame Relay
• Bandwidth Profile is a characterization of the
  lengths and arrival times of Service Frames at
  the UNI
• The level of compliance with the Bandwidth
  Profile is assessed for each ingress Service
  Frame
• Green full compliance
• Yellow partial compliance
• Red non-compliance
• Delivery performance then based on compliance
  level

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Bandwidth Profile Defined by Token Bucket
Algorithm
CommittedInformationRate
ExcessInformationRate
GreenTokens
YellowTokens
Overflow
Overflow
CommittedBurst Size
ExcessBurst Size
C-Bucket
E-Bucket
If (Service Frame length less than C-Bucket
tokens) declare green and remove tokens from
C-Bucket else if (Service Frame length less than
E-Bucket tokens) declare yellow and remove
tokens from E-Bucket else declare red
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Two Options for Algorithm
Option 1 Decoupled
Option 2 Coupled
GreenTokens
GreenTokens
Overflow
Overflow
C-Bucket
C-Bucket
YellowTokens
YellowTokens
Overflow
Overflow
E-Bucket
E-Bucket
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Bandwidth Profile Parameters

• Committed Information Rate (CIR) expressed as
  bits per second. CIR ? 0.
• Committed Burst Size (CBS) expressed as bytes.
  CBS ? 0.
• Excess Information Rate (EIR) expressed as bits
  per second. EIR ? 0
• Excess Burst Size (EBS) expressed as bytes. EBS ?
  0.
• Coupling Flag (S). S 0 or 1.

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Detailed Algorithm (Extension of RFC 2697)
Frame of length lj arrives at tj
Bc(tj) minCBS, Bc(tj-1) CIR?(tj tj-1)
Be(tj) minEBS, Be(tj-1) EIR?(tj tj-1)
S?max0, Bc(tj-1) CIR?(tj tj-1) CBS
Yes
Declare frame greenBc(tj) Bc(tj) - lj
lj Bc(tj)
No
Yes
Declare frame yellowBe(tj) Be(tj) - lj
lj Be(tj)
No
Declare frame red
Algorithm for color blind mode. A color
aware version exists but requires some way to
identify the color of the ingress Service Frame.
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Three Ways to Apply Bandwidth Profile to a
Service Frame

• Per ingress UNI
• Per EVC at the ingress UNI
• Per CoS instance at the ingress UNI (see below
  for CoS identification)
• Multiple methods can apply at a UNI but
  configuration must be such that only one
  Bandwidth Profile is applied to each ingress
  Service Frame

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Bandwidth Profile Policing

• Green
• Deliver Service Frame with performance levels as
  per the Service Level Agreement for the CoS
  instance
• Yellow
• Deliver Service Frame but Service Level Agreement
  for the CoS instance does not apply
• Red
• Discard

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Two Ways to Identify CoS Instance

• EVC
• All Service Frames mapped to the same EVC receive
  the same CoS
• ltEVC,set of user_priority valuesgt
• All Service Frames mapped to an EVC with one of a
  set of user_priority values receive the same CoS

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Class of Service

• A Class of Service is defined by three
  performance objectives
• Frame Delay P percentile of delay d msec
• Frame Jitter Definition TBD
• Frame Loss Percent of frames lost p
• Phase 1 will cover only Point-to-Point EVCs

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