802.1ag - Connectivity Fault Management Tutorial

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802.1ag - Connectivity Fault ManagementTutorial
Part 1

• Dinesh Mohan
• July 12, 2004

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802.1ag PAR Overview
3
802.1ag Scope

• This standard specifies protocols, procedures,
  and managed objects to support transport fault
  management. These allow discovery and
  verification of the path, through bridges and
  LANs, taken for frames addressed to and from
  specified network users, detection, and isolation
  of a connectivity fault to a specific bridge or
  LAN

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802.1ag Purpose

• Bridges are increasingly used in networks
  operated by multiple independent organizations,
  each with restricted management access to each
  others equipment. This standard will provide
  capabilities for detecting, verifying and
  isolating connectivity failures in such networks

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802.1ag Reason for Standardization

• Growing interest in the use of Fault Management
  tools within enterprise and provider networks
• Such tool needed for established operational
  practices
• Existence of similar tools e.g.
• ATMs continuity check, Loopback and
  multiple Loopback and
• IPs ping and traceroute
• Interest and activities within ITU-T and MEF have
  further highlighted the need for these fault
  management tool

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OAM Framework
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Ethernet OAM Layering
Customer
Customer
Service Provider
Eth Access
MPLS Core
MPLS Access
Device View
CE
U-PE
U-PE
N-PE
N-PE
CE
B
B
P
P
P
P

• Example network/service with Ethernet other
  technologies
• The Ethernet Layer implies the visibility to
  Ethernet frames
• BUT Flat! Difficult to manage and identify
  accountability

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OAM Domain Service/Network
Customer
Customer
Service Provider
Eth Access
MPLS Core
MPLS Access
Customer Domain
Provider Domain
Operator Domain
Operator Domain
Operator Domain

• Solution OAM Domains
• Domains necessary to bound OAM Flows OAM
  responsibilities

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Maintenance Entity Points (MEP) Maintenance
Intermediate Points (MIP)
Customer
Customer
Service Provider
Eth Access
MPLS Core
MPLS Access
Service OAM
Customer Domain
Provider Domain
Network OAM
Operator Domain
Operator Domain
Operator Domain
PW/MPLS OAM
MPLS Domain
MPLS Domain

• MEPs initiate/terminate/react to all OAM flows
• MIPs react to some OAM flows Optional
• MEPs MIPs dependent on Business Models
  Deployment Scenarios

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Ethernet MEPs MIPs
1
2
3
4
5
6
7
8
9
ETH

• Another representation for positioning of MEPs
  and MIPs on devices with consideration for
  ingress and egress.

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Maintenance Entities Mapped

• Example MEs identified
• 2 Service Providers (SP1 SP2)
• SP2 has two domains (operators)
• MEs 1,2,3,4 are required for Business
  relationship
• MEs 5,6 are required for convenience

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End-to-end OAM 2 Models

• Provider End-to-end OAM? CE-CE (terminating UNIs)
• 2 Possible Models
• Strong-Trust E-NNI
• ME (3) ME (2) ME (3)
• Weak-Trust E-NNI
• ME (3) ME (6) ME (4) ME (5) ME(3) or
• ME (3) ME (6) ME (4) ME (6) ME(3)

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Maintenance Entities P2P Case

• MEPs realize Maintenance Entities (MEs)

• All MEs may not be needed always

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Maintenance Entities MP2MP Case

• MEPs realize Maintenance Entities (MEs)

• All MEs may not be needed always

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Maintenance Entities CPE based Network
Demarcation Access

• All MEs may not be needed always

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Maintenance Entities CPE based Network
Demarcation Access

• All MEs may not be needed always

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Service/Network OAM How does it come together?

• OAM Interworking possible to utilize OAM across
  Layers
• However, each layer must support OAM capabilities
  independently

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Connectivity Fault Management Functions
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CFM Functionality

• a) CC Continuity Check
• Multicast unidirectional heartbeat
• Use Fault Detection
• b) Loopback
• Unicast bi-directional request/response
• Use Fault detection, verification
• c) Traceroute
• Multicast request/unicast responses
• Use Fault Isolation

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Other OAM Functionality (out of scope for .1ag)

• d) Discovery
• i) Service
• e.g. discover all PEs supporting common service
  instance
• ii) Network
• e.g. discover all devices (PE and P) common to a
  domain
• e) AIS/RDI
• Use Elt-gtW Fault propagation, Alarm Suppression
• f) Performance Management

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CFM Functions mapped to MEs
Customer
Customer
Service Provider
SP 1
SP 2
SP 2
1. a, b, c
2. a, b, c
3. a, b, c, e
3. a, b, c
4. a, b, c
5. a, b, c
6. a, b, c
6. a, b, c
6. a, b, c

• Note Specifically for ME (3) and ME (4)
• IEEE 802.3ah OAM can be used for network/link OAM
  when UNI/E-NNI is an Ethernet link
• When single service carried across a link,
  network OAM can map to service OAM

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Summary

• Ethernet moving into Provider Networks
• Providers require fault management tools to
  manage their networks
• High Industry interest in Ethernet connectivity
  fault management tools